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From lmc...@apache.org
Subject [08/37] knox git commit: KNOX-1014 - Service Discovery and Topology Generation Framework (Phil Zampino via lmccay)
Date Thu, 26 Oct 2017 14:22:44 GMT
http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorHandler.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorHandler.java b/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorHandler.java
new file mode 100644
index 0000000..fb563fa
--- /dev/null
+++ b/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorHandler.java
@@ -0,0 +1,186 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.simple;
+
+import org.apache.hadoop.gateway.i18n.messages.MessagesFactory;
+import org.apache.hadoop.gateway.services.Service;
+import org.apache.hadoop.gateway.topology.discovery.DefaultServiceDiscoveryConfig;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscovery;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryFactory;
+
+import java.io.*;
+import java.util.*;
+
+
+/**
+ * Processes simple topology descriptors, producing full topology files, which can subsequently be deployed to the
+ * gateway.
+ */
+public class SimpleDescriptorHandler {
+
+    private static final Service[] NO_GATEWAY_SERVICES = new Service[]{};
+
+    private static final SimpleDescriptorMessages log = MessagesFactory.get(SimpleDescriptorMessages.class);
+
+    public static Map<String, File> handle(File desc) throws IOException {
+        return handle(desc, NO_GATEWAY_SERVICES);
+    }
+
+    public static Map<String, File> handle(File desc, Service...gatewayServices) throws IOException {
+        return handle(desc, desc.getParentFile(), gatewayServices);
+    }
+
+    public static Map<String, File> handle(File desc, File destDirectory) throws IOException {
+        return handle(desc, destDirectory, NO_GATEWAY_SERVICES);
+    }
+
+    public static Map<String, File> handle(File desc, File destDirectory, Service...gatewayServices) throws IOException {
+        return handle(SimpleDescriptorFactory.parse(desc.getAbsolutePath()), desc.getParentFile(), destDirectory, gatewayServices);
+    }
+
+    public static Map<String, File> handle(SimpleDescriptor desc, File srcDirectory, File destDirectory) {
+        return handle(desc, srcDirectory, destDirectory, NO_GATEWAY_SERVICES);
+    }
+
+    public static Map<String, File> handle(SimpleDescriptor desc, File srcDirectory, File destDirectory, Service...gatewayServices) {
+        Map<String, File> result = new HashMap<>();
+
+        File topologyDescriptor;
+
+        DefaultServiceDiscoveryConfig sdc = new DefaultServiceDiscoveryConfig(desc.getDiscoveryAddress());
+        sdc.setUser(desc.getDiscoveryUser());
+        sdc.setPasswordAlias(desc.getDiscoveryPasswordAlias());
+        ServiceDiscovery sd = ServiceDiscoveryFactory.get(desc.getDiscoveryType(), gatewayServices);
+        ServiceDiscovery.Cluster cluster = sd.discover(sdc, desc.getClusterName());
+
+        Map<String, List<String>> serviceURLs = new HashMap<>();
+
+        if (cluster != null) {
+            for (SimpleDescriptor.Service descService : desc.getServices()) {
+                String serviceName = descService.getName();
+
+                List<String> descServiceURLs = descService.getURLs();
+                if (descServiceURLs == null || descServiceURLs.isEmpty()) {
+                    descServiceURLs = cluster.getServiceURLs(serviceName);
+                }
+
+                // If there is at least one URL associated with the service, then add it to the map
+                if (descServiceURLs != null && !descServiceURLs.isEmpty()) {
+                    serviceURLs.put(serviceName, descServiceURLs);
+                } else {
+                    log.failedToDiscoverClusterServiceURLs(serviceName, cluster.getName());
+                    throw new IllegalStateException("ServiceDiscovery failed to resolve any URLs for " + serviceName +
+                                                    ". Topology update aborted!");
+                }
+            }
+        } else {
+            log.failedToDiscoverClusterServices(desc.getClusterName());
+        }
+
+        topologyDescriptor = null;
+        File providerConfig = null;
+        try {
+            // Verify that the referenced provider configuration exists before attempting to reading it
+            providerConfig = resolveProviderConfigurationReference(desc.getProviderConfig(), srcDirectory);
+            if (providerConfig == null) {
+                log.failedToResolveProviderConfigRef(desc.getProviderConfig());
+                throw new IllegalArgumentException("Unresolved provider configuration reference: " +
+                                                   desc.getProviderConfig() + " ; Topology update aborted!");
+            }
+            result.put("reference", providerConfig);
+
+            // TODO: Should the contents of the provider config be validated before incorporating it into the topology?
+
+            String topologyFilename = desc.getName();
+            if (topologyFilename == null) {
+                topologyFilename = desc.getClusterName();
+            }
+            topologyDescriptor = new File(destDirectory, topologyFilename + ".xml");
+            FileWriter fw = new FileWriter(topologyDescriptor);
+
+            fw.write("<topology>\n");
+
+            // Copy the externalized provider configuration content into the topology descriptor in-line
+            InputStreamReader policyReader = new InputStreamReader(new FileInputStream(providerConfig));
+            char[] buffer = new char[1024];
+            int count;
+            while ((count = policyReader.read(buffer)) > 0) {
+                fw.write(buffer, 0, count);
+            }
+            policyReader.close();
+
+            // Write the service declarations
+            for (String serviceName : serviceURLs.keySet()) {
+                fw.write("    <service>\n");
+                fw.write("        <role>" + serviceName + "</role>\n");
+                for (String url : serviceURLs.get(serviceName)) {
+                    fw.write("        <url>" + url + "</url>\n");
+                }
+                fw.write("    </service>\n");
+            }
+
+            fw.write("</topology>\n");
+
+            fw.flush();
+            fw.close();
+        } catch (IOException e) {
+            log.failedToGenerateTopologyFromSimpleDescriptor(topologyDescriptor.getName(), e);
+            topologyDescriptor.delete();
+        }
+
+        result.put("topology", topologyDescriptor);
+        return result;
+    }
+
+
+    private static File resolveProviderConfigurationReference(String reference, File srcDirectory) {
+        File providerConfig;
+
+        // If the reference includes a path
+        if (reference.contains(File.separator)) {
+            // Check if it's an absolute path
+            providerConfig = new File(reference);
+            if (!providerConfig.exists()) {
+                // If it's not an absolute path, try treating it as a relative path
+                providerConfig = new File(srcDirectory, reference);
+                if (!providerConfig.exists()) {
+                    providerConfig = null;
+                }
+            }
+        } else { // No file path, just a name
+            // Check if it's co-located with the referencing descriptor
+            providerConfig = new File(srcDirectory, reference);
+            if (!providerConfig.exists()) {
+                // Check the shared-providers config location
+                File sharedProvidersDir = new File(srcDirectory, "../shared-providers");
+                if (sharedProvidersDir.exists()) {
+                    providerConfig = new File(sharedProvidersDir, reference);
+                    if (!providerConfig.exists()) {
+                        // Check if it's a valid name without the extension
+                        providerConfig = new File(sharedProvidersDir, reference + ".xml");
+                        if (!providerConfig.exists()) {
+                            providerConfig = null;
+                        }
+                    }
+                }
+            }
+        }
+
+        return providerConfig;
+    }
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorImpl.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorImpl.java b/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorImpl.java
new file mode 100644
index 0000000..32ceba9
--- /dev/null
+++ b/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorImpl.java
@@ -0,0 +1,111 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.gateway.topology.simple;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import java.util.ArrayList;
+import java.util.List;
+
+class SimpleDescriptorImpl implements SimpleDescriptor {
+
+    @JsonProperty("discovery-type")
+    private String discoveryType;
+
+    @JsonProperty("discovery-address")
+    private String discoveryAddress;
+
+    @JsonProperty("discovery-user")
+    private String discoveryUser;
+
+    @JsonProperty("discovery-pwd-alias")
+    private String discoveryPasswordAlias;
+
+    @JsonProperty("provider-config-ref")
+    private String providerConfig;
+
+    @JsonProperty("cluster")
+    private String cluster;
+
+    @JsonProperty("services")
+    private List<ServiceImpl> services;
+
+    private String name = null;
+
+    void setName(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public String getName() {
+        return name;
+    }
+
+    @Override
+    public String getDiscoveryType() {
+        return discoveryType;
+    }
+
+    @Override
+    public String getDiscoveryAddress() {
+        return discoveryAddress;
+    }
+
+    @Override
+    public String getDiscoveryUser() {
+        return discoveryUser;
+    }
+
+    @Override
+    public String getDiscoveryPasswordAlias() {
+        return discoveryPasswordAlias;
+    }
+
+    @Override
+    public String getClusterName() {
+        return cluster;
+    }
+
+    @Override
+    public String getProviderConfig() {
+        return providerConfig;
+    }
+
+    @Override
+    public List<Service> getServices() {
+        List<Service> result = new ArrayList<>();
+        result.addAll(services);
+        return result;
+    }
+
+    public static class ServiceImpl implements Service {
+        private String name;
+        private List<String> urls;
+
+        @Override
+        public String getName() {
+            return name;
+        }
+
+        @Override
+        public List<String> getURLs() {
+            return urls;
+        }
+    }
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorMessages.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorMessages.java b/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorMessages.java
new file mode 100644
index 0000000..cf9aa28
--- /dev/null
+++ b/gateway-server/src/main/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorMessages.java
@@ -0,0 +1,44 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.simple;
+
+import org.apache.hadoop.gateway.i18n.messages.Message;
+import org.apache.hadoop.gateway.i18n.messages.MessageLevel;
+import org.apache.hadoop.gateway.i18n.messages.Messages;
+import org.apache.hadoop.gateway.i18n.messages.StackTrace;
+
+@Messages(logger="org.apache.gateway.topology.simple")
+public interface SimpleDescriptorMessages {
+
+    @Message(level = MessageLevel.ERROR,
+            text = "Service discovery for cluster {0} failed.")
+    void failedToDiscoverClusterServices(final String cluster);
+
+    @Message(level = MessageLevel.ERROR,
+            text = "No URLs were discovered for {0} in the {1} cluster.")
+    void failedToDiscoverClusterServiceURLs(final String serviceName, final String clusterName);
+
+    @Message(level = MessageLevel.ERROR,
+            text = "Failed to resolve the referenced provider configuration {0}.")
+    void failedToResolveProviderConfigRef(final String providerConfigRef);
+
+    @Message(level = MessageLevel.ERROR,
+            text = "Error generating topology {0} from simple descriptor: {1}")
+    void failedToGenerateTopologyFromSimpleDescriptor(final String topologyFile,
+                                                      @StackTrace( level = MessageLevel.DEBUG ) Exception e );
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/services/topology/DefaultTopologyServiceTest.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/services/topology/DefaultTopologyServiceTest.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/services/topology/DefaultTopologyServiceTest.java
index 55cd5cc..498d750 100644
--- a/gateway-server/src/test/java/org/apache/hadoop/gateway/services/topology/DefaultTopologyServiceTest.java
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/services/topology/DefaultTopologyServiceTest.java
@@ -22,8 +22,12 @@ import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.monitor.FileAlterationMonitor;
 import org.apache.commons.io.monitor.FileAlterationObserver;
 import org.apache.hadoop.gateway.config.GatewayConfig;
+import org.apache.hadoop.gateway.services.security.AliasService;
 import org.apache.hadoop.gateway.services.topology.impl.DefaultTopologyService;
 import org.apache.hadoop.gateway.topology.*;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscovery;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryConfig;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryFactory;
 import org.apache.hadoop.test.TestUtils;
 import org.easymock.EasyMock;
 import org.junit.After;
@@ -36,6 +40,8 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.util.*;
 
+import static org.easymock.EasyMock.anyObject;
+import static org.easymock.EasyMock.isA;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.Matchers.hasItem;
 import static org.hamcrest.core.IsNull.notNullValue;
@@ -78,9 +84,17 @@ public class DefaultTopologyServiceTest {
   public void testGetTopologies() throws Exception {
 
     File dir = createDir();
-    long time = dir.lastModified();
+    File topologyDir = new File(dir, "topologies");
+
+    File descriptorsDir = new File(dir, "descriptors");
+    descriptorsDir.mkdirs();
+
+    File sharedProvidersDir = new File(dir, "shared-providers");
+    sharedProvidersDir.mkdirs();
+
+    long time = topologyDir.lastModified();
     try {
-      createFile(dir, "one.xml", "org/apache/hadoop/gateway/topology/file/topology-one.xml", time);
+      createFile(topologyDir, "one.xml", "org/apache/hadoop/gateway/topology/file/topology-one.xml", time);
 
       TestTopologyListener topoListener = new TestTopologyListener();
       FileAlterationMonitor monitor = new FileAlterationMonitor(Long.MAX_VALUE);
@@ -89,17 +103,16 @@ public class DefaultTopologyServiceTest {
       Map<String, String> c = new HashMap<>();
 
       GatewayConfig config = EasyMock.createNiceMock(GatewayConfig.class);
-      EasyMock.expect(config.getGatewayTopologyDir()).andReturn(dir.toString()).anyTimes();
+      EasyMock.expect(config.getGatewayTopologyDir()).andReturn(topologyDir.getAbsolutePath()).anyTimes();
+      EasyMock.expect(config.getGatewayConfDir()).andReturn(descriptorsDir.getParentFile().getAbsolutePath()).anyTimes();
       EasyMock.replay(config);
 
       provider.init(config, c);
 
-
       provider.addTopologyChangeListener(topoListener);
 
       provider.reloadTopologies();
 
-
       Collection<Topology> topologies = provider.getTopologies();
       assertThat(topologies, notNullValue());
       assertThat(topologies.size(), is(1));
@@ -110,7 +123,7 @@ public class DefaultTopologyServiceTest {
       topoListener.events.clear();
 
       // Add a file to the directory.
-      File two = createFile(dir, "two.xml", "org/apache/hadoop/gateway/topology/file/topology-two.xml", 1L);
+      File two = createFile(topologyDir, "two.xml", "org/apache/hadoop/gateway/topology/file/topology-two.xml", 1L);
       provider.reloadTopologies();
       topologies = provider.getTopologies();
       assertThat(topologies.size(), is(2));
@@ -131,7 +144,7 @@ public class DefaultTopologyServiceTest {
       assertThat(event.getTopology(), notNullValue());
 
       // Update a file in the directory.
-      two = createFile(dir, "two.xml", "org/apache/hadoop/gateway/topology/file/topology-three.xml", 2L);
+      two = createFile(topologyDir, "two.xml", "org/apache/hadoop/gateway/topology/file/topology-three.xml", 2L);
       provider.reloadTopologies();
       topologies = provider.getTopologies();
       assertThat(topologies.size(), is(2));
@@ -153,6 +166,49 @@ public class DefaultTopologyServiceTest {
       topology = topologies.iterator().next();
       assertThat(topology.getName(), is("one"));
       assertThat(topology.getTimestamp(), is(time));
+
+      // Add a simple descriptor to the descriptors dir to verify topology generation and loading (KNOX-1006)
+      // N.B. This part of the test depends on the DummyServiceDiscovery extension being configured:
+      //         org.apache.hadoop.gateway.topology.discovery.test.extension.DummyServiceDiscovery
+      AliasService aliasService = EasyMock.createNiceMock(AliasService.class);
+      EasyMock.expect(aliasService.getPasswordFromAliasForGateway(anyObject(String.class))).andReturn(null).anyTimes();
+      EasyMock.replay(aliasService);
+      DefaultTopologyService.DescriptorsMonitor dm =
+                                          new DefaultTopologyService.DescriptorsMonitor(topologyDir, aliasService);
+
+      // Write out the referenced provider config first
+      File provCfgFile = createFile(sharedProvidersDir,
+                                    "ambari-cluster-policy.xml",
+                                    "org/apache/hadoop/gateway/topology/file/ambari-cluster-policy.xml",
+                                    1L);
+      try {
+        // Create the simple descriptor in the descriptors dir
+        File simpleDesc =
+                createFile(descriptorsDir,
+                           "four.json",
+                           "org/apache/hadoop/gateway/topology/file/simple-topology-four.json",
+                           1L);
+
+        // Trigger the topology generation by noticing the simple descriptor
+        dm.onFileChange(simpleDesc);
+
+        // Load the generated topology
+        provider.reloadTopologies();
+        topologies = provider.getTopologies();
+        assertThat(topologies.size(), is(2));
+        names = new HashSet<>(Arrays.asList("one", "four"));
+        iterator = topologies.iterator();
+        topology = iterator.next();
+        assertThat(names, hasItem(topology.getName()));
+        names.remove(topology.getName());
+        topology = iterator.next();
+        assertThat(names, hasItem(topology.getName()));
+        names.remove(topology.getName());
+        assertThat(names.size(), is(0));
+      } finally {
+        provCfgFile.delete();
+
+      }
     } finally {
       FileUtils.deleteQuietly(dir);
     }

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/PropertiesFileServiceDiscoveryTest.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/PropertiesFileServiceDiscoveryTest.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/PropertiesFileServiceDiscoveryTest.java
new file mode 100644
index 0000000..269bed2
--- /dev/null
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/PropertiesFileServiceDiscoveryTest.java
@@ -0,0 +1,90 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery;
+
+import org.apache.hadoop.gateway.services.security.impl.DefaultAliasService;
+import org.apache.hadoop.gateway.topology.discovery.test.extension.PropertiesFileServiceDiscoveryType;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Properties;
+
+import static org.junit.Assert.*;
+
+
+public class PropertiesFileServiceDiscoveryTest {
+
+    private static final Map<String, String> clusterProperties = new HashMap<>();
+    static {
+        clusterProperties.put("mycluster.name", "mycluster");
+        clusterProperties.put("mycluster.NAMENODE", "hdfs://namenodehost:8020");
+        clusterProperties.put("mycluster.JOBTRACKER", "rpc://jobtrackerhostname:8050");
+        clusterProperties.put("mycluster.WEBHCAT", "http://webhcathost:50111/templeton");
+        clusterProperties.put("mycluster.OOZIE", "http://ooziehost:11000/oozie");
+        clusterProperties.put("mycluster.HIVE", "http://hivehostname:10001/clipath");
+        clusterProperties.put("mycluster.RESOURCEMANAGER", "http://remanhost:8088/ws");
+    }
+
+    private static final Properties config = new Properties();
+    static {
+        for (String name : clusterProperties.keySet()) {
+            config.setProperty(name, clusterProperties.get(name));
+        }
+    }
+
+
+    @Test
+    public void testPropertiesFileServiceDiscovery() throws Exception {
+        ServiceDiscovery sd = ServiceDiscoveryFactory.get("PROPERTIES_FILE");
+        assertNotNull(sd);
+
+        String discoveryAddress = this.getClass().getName() + "__test-discovery-source.properties";
+        File discoverySource = new File(discoveryAddress);
+        try {
+            config.store(new FileOutputStream(discoverySource), "Test discovery source for PropertiesFileServiceDiscovery");
+
+            ServiceDiscovery.Cluster c =
+                        sd.discover(new DefaultServiceDiscoveryConfig(discoverySource.getAbsolutePath()), "mycluster");
+            assertNotNull(c);
+            for (String name : clusterProperties.keySet()) {
+                assertEquals(clusterProperties.get(name), c.getServiceURLs(name.split("\\.")[1]).get(0));
+            }
+        } finally {
+            discoverySource.delete();
+        }
+    }
+
+
+    private void printServiceURLs(ServiceDiscovery.Cluster cluster, String...services) {
+        for (String name : services) {
+            String value = "";
+            List<String> urls = cluster.getServiceURLs(name);
+            if (urls != null && !urls.isEmpty()) {
+                for (String url : urls) {
+                    value += url + " ";
+                }
+            }
+            System.out.println(String.format("%18s: %s", name, value));
+        }
+    }
+
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryFactoryTest.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryFactoryTest.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryFactoryTest.java
new file mode 100644
index 0000000..d592ede
--- /dev/null
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryFactoryTest.java
@@ -0,0 +1,81 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery;
+
+import org.apache.hadoop.gateway.services.security.AliasService;
+import org.apache.hadoop.gateway.services.security.impl.DefaultAliasService;
+import org.apache.hadoop.gateway.topology.discovery.test.extension.PropertiesFileServiceDiscoveryType;
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+
+import static org.junit.Assert.*;
+
+
+public class ServiceDiscoveryFactoryTest {
+
+    @Test
+    public void testGetDummyImpl() throws Exception {
+        String TYPE = "DUMMY";
+        ServiceDiscovery sd = ServiceDiscoveryFactory.get(TYPE);
+        assertNotNull("Expected to get a ServiceDiscovery object.", sd);
+        assertEquals("Unexpected ServiceDiscovery type.", TYPE, sd.getType());
+    }
+
+
+    @Test
+    public void testGetDummyImplWithMismatchedCase() throws Exception {
+        String TYPE = "dUmmY";
+        ServiceDiscovery sd = ServiceDiscoveryFactory.get(TYPE);
+        assertNotNull("Expected to get a ServiceDiscovery object.", sd);
+        assertEquals("Unexpected ServiceDiscovery type.", TYPE.toUpperCase(), sd.getType());
+    }
+
+
+    @Test
+    public void testGetInvalidImpl() throws Exception {
+        String TYPE = "InValID";
+        ServiceDiscovery sd = ServiceDiscoveryFactory.get(TYPE);
+        assertNull("Unexpected ServiceDiscovery object.", sd);
+    }
+
+
+    @Test
+    public void testGetImplWithMismatchedType() throws Exception {
+        String TYPE = "DeclaredType";
+        ServiceDiscovery sd = ServiceDiscoveryFactory.get(TYPE);
+        assertNull("Unexpected ServiceDiscovery object.", sd);
+    }
+
+
+    @Test
+    public void testGetPropertiesFileImplWithAliasServiceInjection() throws Exception {
+        String TYPE = "PROPERTIES_FILE";
+        ServiceDiscovery sd = ServiceDiscoveryFactory.get(TYPE, new DefaultAliasService());
+        assertNotNull("Expected to get a ServiceDiscovery object.", sd);
+        assertEquals("Unexpected ServiceDiscovery type.", TYPE, sd.getType());
+
+        // Verify that the AliasService was injected as expected
+        Field aliasServiceField = sd.getClass().getDeclaredField("aliasService");
+        aliasServiceField.setAccessible(true);
+        Object fieldValue = aliasServiceField.get(sd);
+        assertNotNull(fieldValue);
+        assertTrue(AliasService.class.isAssignableFrom(fieldValue.getClass()));
+    }
+
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/DummyServiceDiscovery.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/DummyServiceDiscovery.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/DummyServiceDiscovery.java
new file mode 100644
index 0000000..4a5323e
--- /dev/null
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/DummyServiceDiscovery.java
@@ -0,0 +1,66 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery.test.extension;
+
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscovery;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryConfig;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * This implementation is intended to be used by tests for which the actual service URLs are of no importance, such that
+ * tests can be written without having a valid service registry (e.g., Ambari) available.
+ */
+public class DummyServiceDiscovery implements ServiceDiscovery {
+
+    static final String TYPE = "DUMMY";
+
+    private static final Cluster DUMMY = new Cluster() {
+        @Override
+        public String getName() {
+            return "dummy";
+        }
+
+        @Override
+        public List<String> getServiceURLs(String serviceName) {
+            return Collections.singletonList("http://servicehost:9999/dummy");
+        }
+    };
+
+    private static final Map<String, Cluster> CLUSTERS = new HashMap<>();
+    static {
+        CLUSTERS.put(DUMMY.getName(), DUMMY);
+    }
+
+    @Override
+    public String getType() {
+        return TYPE;
+    }
+
+    @Override
+    public Map<String, Cluster> discover(ServiceDiscoveryConfig config) {
+        return CLUSTERS;
+    }
+
+    @Override
+    public Cluster discover(ServiceDiscoveryConfig config, String clusterName) {
+        return DUMMY;
+    }
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/DummyServiceDiscoveryType.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/DummyServiceDiscoveryType.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/DummyServiceDiscoveryType.java
new file mode 100644
index 0000000..d47c38d
--- /dev/null
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/DummyServiceDiscoveryType.java
@@ -0,0 +1,32 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery.test.extension;
+
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscovery;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryType;
+
+public class DummyServiceDiscoveryType implements ServiceDiscoveryType {
+    @Override
+    public String getType() {
+        return DummyServiceDiscovery.TYPE;
+    }
+
+    @Override
+    public ServiceDiscovery newInstance() {
+        return new DummyServiceDiscovery();
+    }
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/PropertiesFileServiceDiscovery.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/PropertiesFileServiceDiscovery.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/PropertiesFileServiceDiscovery.java
new file mode 100644
index 0000000..a7fc34a
--- /dev/null
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/PropertiesFileServiceDiscovery.java
@@ -0,0 +1,108 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery.test.extension;
+
+import org.apache.hadoop.gateway.services.security.AliasService;
+import org.apache.hadoop.gateway.topology.discovery.GatewayService;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscovery;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryConfig;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.util.*;
+
+class PropertiesFileServiceDiscovery implements ServiceDiscovery {
+
+    static final String TYPE = "PROPERTIES_FILE";
+
+    @GatewayService
+    AliasService aliasService;
+
+    @Override
+    public String getType() {
+        return TYPE;
+    }
+
+    @Override
+    public Map<String, ServiceDiscovery.Cluster> discover(ServiceDiscoveryConfig config) {
+
+        Map<String, ServiceDiscovery.Cluster> result = new HashMap<>();
+
+        Properties p = new Properties();
+        try {
+            p.load(new FileInputStream(config.getAddress()));
+
+            Map<String, Map<String, List<String>>> clusters = new HashMap<>();
+            for (Object key : p.keySet()) {
+                String propertyKey = (String)key;
+                String[] parts = propertyKey.split("\\.");
+                if (parts.length == 2) {
+                    String clusterName = parts[0];
+                    String serviceName = parts[1];
+                    String serviceURL  = p.getProperty(propertyKey);
+                    if (!clusters.containsKey(clusterName)) {
+                        clusters.put(clusterName, new HashMap<String, List<String>>());
+                    }
+                    Map<String, List<String>> serviceURLs = clusters.get(clusterName);
+                    if (!serviceURLs.containsKey(serviceName)) {
+                        serviceURLs.put(serviceName, new ArrayList<String>());
+                    }
+                    serviceURLs.get(serviceName).add(serviceURL);
+                }
+            }
+
+            for (String clusterName : clusters.keySet()) {
+                result.put(clusterName,
+                        new PropertiesFileServiceDiscovery.Cluster(clusterName, clusters.get(clusterName)));
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+
+        return result;
+    }
+
+
+    @Override
+    public ServiceDiscovery.Cluster discover(ServiceDiscoveryConfig config, String clusterName) {
+        Map<String, ServiceDiscovery.Cluster> clusters = discover(config);
+        return clusters.get(clusterName);
+    }
+
+
+    static class Cluster implements ServiceDiscovery.Cluster {
+        private String name;
+        private Map<String, List<String>> serviceURLS = new HashMap<>();
+
+        Cluster(String name, Map<String, List<String>> serviceURLs) {
+            this.name = name;
+            this.serviceURLS.putAll(serviceURLs);
+        }
+
+        @Override
+        public String getName() {
+            return name;
+        }
+
+        @Override
+        public List<String> getServiceURLs(String serviceName) {
+            return serviceURLS.get(serviceName);
+        }
+    }
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/PropertiesFileServiceDiscoveryType.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/PropertiesFileServiceDiscoveryType.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/PropertiesFileServiceDiscoveryType.java
new file mode 100644
index 0000000..2cfd998
--- /dev/null
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/PropertiesFileServiceDiscoveryType.java
@@ -0,0 +1,35 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery.test.extension;
+
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscovery;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryType;
+
+public class PropertiesFileServiceDiscoveryType implements ServiceDiscoveryType {
+
+    @Override
+    public String getType() {
+        return PropertiesFileServiceDiscovery.TYPE;
+    }
+
+    @Override
+    public ServiceDiscovery newInstance() {
+        return new PropertiesFileServiceDiscovery();
+    }
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/SneakyServiceDiscoveryImpl.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/SneakyServiceDiscoveryImpl.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/SneakyServiceDiscoveryImpl.java
new file mode 100644
index 0000000..8f7b71a
--- /dev/null
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/SneakyServiceDiscoveryImpl.java
@@ -0,0 +1,40 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery.test.extension;
+
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscovery;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryConfig;
+
+import java.util.Map;
+
+public class SneakyServiceDiscoveryImpl implements ServiceDiscovery {
+    @Override
+    public String getType() {
+        return "ActualType";
+    }
+
+    @Override
+    public Map<String, Cluster> discover(ServiceDiscoveryConfig config) {
+        return null;
+    }
+
+    @Override
+    public Cluster discover(ServiceDiscoveryConfig config, String clusterName) {
+        return null;
+    }
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/SneakyServiceDiscoveryType.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/SneakyServiceDiscoveryType.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/SneakyServiceDiscoveryType.java
new file mode 100644
index 0000000..97665dc
--- /dev/null
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/discovery/test/extension/SneakyServiceDiscoveryType.java
@@ -0,0 +1,33 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery.test.extension;
+
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscovery;
+import org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryType;
+
+public class SneakyServiceDiscoveryType implements ServiceDiscoveryType {
+    @Override
+    public String getType() {
+        return "DeclaredType";
+    }
+
+    @Override
+    public ServiceDiscovery newInstance() {
+        return new SneakyServiceDiscoveryImpl();
+    }
+}
+

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorFactoryTest.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorFactoryTest.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorFactoryTest.java
new file mode 100644
index 0000000..3dac66a
--- /dev/null
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorFactoryTest.java
@@ -0,0 +1,218 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.simple;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.Writer;
+import java.util.*;
+
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+
+public class SimpleDescriptorFactoryTest {
+
+
+    @Test
+    public void testParseJSONSimpleDescriptor() throws Exception {
+
+        final String   discoveryType    = "AMBARI";
+        final String   discoveryAddress = "http://c6401.ambari.apache.org:8080";
+        final String   discoveryUser    = "admin";
+        final String   providerConfig   = "ambari-cluster-policy.xml";
+        final String   clusterName      = "myCluster";
+
+        final Map<String, List<String>> services = new HashMap<>();
+        services.put("NODEMANAGER", null);
+        services.put("JOBTRACKER", null);
+        services.put("RESOURCEMANAGER", null);
+        services.put("HIVE", Arrays.asList("http://c6401.ambari.apache.org", "http://c6402.ambari.apache.org", "http://c6403.ambari.apache.org"));
+        services.put("AMBARIUI", Arrays.asList("http://c6401.ambari.apache.org:8080"));
+
+        String fileName = "test-topology.json";
+        File testJSON = null;
+        try {
+            testJSON = writeJSON(fileName, discoveryType, discoveryAddress, discoveryUser, providerConfig, clusterName, services);
+            SimpleDescriptor sd = SimpleDescriptorFactory.parse(testJSON.getAbsolutePath());
+            validateSimpleDescriptor(sd, discoveryType, discoveryAddress, providerConfig, clusterName, services);
+        } catch (Exception e) {
+            e.printStackTrace();
+        } finally {
+            if (testJSON != null) {
+                try {
+                    testJSON.delete();
+                } catch (Exception e) {
+                    // Ignore
+                }
+            }
+        }
+    }
+
+    @Test
+    public void testParseYAMLSimpleDescriptor() throws Exception {
+
+        final String   discoveryType    = "AMBARI";
+        final String   discoveryAddress = "http://c6401.ambari.apache.org:8080";
+        final String   discoveryUser    = "joeblow";
+        final String   providerConfig   = "ambari-cluster-policy.xml";
+        final String   clusterName      = "myCluster";
+
+        final Map<String, List<String>> services = new HashMap<>();
+        services.put("NODEMANAGER", null);
+        services.put("JOBTRACKER", null);
+        services.put("RESOURCEMANAGER", null);
+        services.put("HIVE", Arrays.asList("http://c6401.ambari.apache.org", "http://c6402.ambari.apache.org", "http://c6403.ambari.apache.org"));
+        services.put("AMBARIUI", Arrays.asList("http://c6401.ambari.apache.org:8080"));
+
+        String fileName = "test-topology.yml";
+        File testYAML = null;
+        try {
+            testYAML = writeYAML(fileName, discoveryType, discoveryAddress, discoveryUser, providerConfig, clusterName, services);
+            SimpleDescriptor sd = SimpleDescriptorFactory.parse(testYAML.getAbsolutePath());
+            validateSimpleDescriptor(sd, discoveryType, discoveryAddress, providerConfig, clusterName, services);
+        } catch (Exception e) {
+            e.printStackTrace();
+        } finally {
+            if (testYAML != null) {
+                try {
+                    testYAML.delete();
+                } catch (Exception e) {
+                    // Ignore
+                }
+            }
+        }
+    }
+
+
+    private void validateSimpleDescriptor(SimpleDescriptor    sd,
+                                          String              discoveryType,
+                                          String              discoveryAddress,
+                                          String              providerConfig,
+                                          String              clusterName,
+                                          Map<String, List<String>> expectedServices) {
+        assertNotNull(sd);
+        assertEquals(discoveryType, sd.getDiscoveryType());
+        assertEquals(discoveryAddress, sd.getDiscoveryAddress());
+        assertEquals(providerConfig, sd.getProviderConfig());
+        assertEquals(clusterName, sd.getClusterName());
+
+        List<SimpleDescriptor.Service> actualServices = sd.getServices();
+
+        assertEquals(expectedServices.size(), actualServices.size());
+
+        for (SimpleDescriptor.Service actualService : actualServices) {
+            assertTrue(expectedServices.containsKey(actualService.getName()));
+            assertEquals(expectedServices.get(actualService.getName()), actualService.getURLs());
+        }
+    }
+
+
+    private File writeJSON(String path, String content) throws Exception {
+        File f = new File(path);
+
+        Writer fw = new FileWriter(f);
+        fw.write(content);
+        fw.flush();
+        fw.close();
+
+        return f;
+    }
+
+
+    private File writeJSON(String path,
+                           String discoveryType,
+                           String discoveryAddress,
+                           String discoveryUser,
+                           String providerConfig,
+                           String clusterName,
+                           Map<String, List<String>> services) throws Exception {
+        File f = new File(path);
+
+        Writer fw = new FileWriter(f);
+        fw.write("{" + "\n");
+        fw.write("\"discovery-type\":\"" + discoveryType + "\",\n");
+        fw.write("\"discovery-address\":\"" + discoveryAddress + "\",\n");
+        fw.write("\"discovery-user\":\"" + discoveryUser + "\",\n");
+        fw.write("\"provider-config-ref\":\"" + providerConfig + "\",\n");
+        fw.write("\"cluster\":\"" + clusterName + "\",\n");
+        fw.write("\"services\":[\n");
+
+        int i = 0;
+        for (String name : services.keySet()) {
+            fw.write("{\"name\":\"" + name + "\"");
+            List<String> urls = services.get(name);
+            if (urls != null) {
+                fw.write(", \"urls\":[");
+                Iterator<String> urlIter = urls.iterator();
+                while (urlIter.hasNext()) {
+                    fw.write("\"" + urlIter.next() + "\"");
+                    if (urlIter.hasNext()) {
+                        fw.write(", ");
+                    }
+                }
+                fw.write("]");
+            }
+            fw.write("}");
+            if (i++ < services.size() - 1) {
+                fw.write(",");
+            }
+            fw.write("\n");
+        }
+        fw.write("]\n");
+        fw.write("}\n");
+        fw.flush();
+        fw.close();
+
+        return f;
+    }
+
+    private File writeYAML(String path,
+                           String discoveryType,
+                           String discoveryAddress,
+                           String discoveryUser,
+                           String providerConfig,
+                           String clusterName,
+                           Map<String, List<String>> services) throws Exception {
+        File f = new File(path);
+
+        Writer fw = new FileWriter(f);
+        fw.write("---" + "\n");
+        fw.write("discovery-type: " + discoveryType + "\n");
+        fw.write("discovery-address: " + discoveryAddress + "\n");
+        fw.write("discovery-user: " + discoveryUser + "\n");
+        fw.write("provider-config-ref: " + providerConfig + "\n");
+        fw.write("cluster: " + clusterName+ "\n");
+        fw.write("services:\n");
+        for (String name : services.keySet()) {
+            fw.write("    - name: " + name + "\n");
+            List<String> urls = services.get(name);
+            if (urls != null) {
+                fw.write("      urls:\n");
+                for (String url : urls) {
+                    fw.write("          - " + url + "\n");
+                }
+            }
+        }
+        fw.flush();
+        fw.close();
+
+        return f;
+    }
+
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorHandlerTest.java
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorHandlerTest.java b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorHandlerTest.java
new file mode 100644
index 0000000..90c7146
--- /dev/null
+++ b/gateway-server/src/test/java/org/apache/hadoop/gateway/topology/simple/SimpleDescriptorHandlerTest.java
@@ -0,0 +1,239 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.gateway.topology.simple;
+
+import org.apache.hadoop.gateway.topology.validation.TopologyValidator;
+import org.apache.hadoop.gateway.util.XmlUtils;
+import org.easymock.EasyMock;
+import org.junit.Test;
+import org.w3c.dom.Document;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+import org.xml.sax.SAXException;
+
+import javax.xml.xpath.XPath;
+import javax.xml.xpath.XPathConstants;
+import javax.xml.xpath.XPathFactory;
+import java.io.*;
+import java.util.*;
+
+import static org.junit.Assert.*;
+
+
+public class SimpleDescriptorHandlerTest {
+
+    private static final String TEST_PROVIDER_CONFIG =
+            "    <gateway>\n" +
+                    "        <provider>\n" +
+                    "            <role>authentication</role>\n" +
+                    "            <name>ShiroProvider</name>\n" +
+                    "            <enabled>true</enabled>\n" +
+                    "            <param>\n" +
+                    "                <!-- \n" +
+                    "                session timeout in minutes,  this is really idle timeout,\n" +
+                    "                defaults to 30mins, if the property value is not defined,, \n" +
+                    "                current client authentication would expire if client idles contiuosly for more than this value\n" +
+                    "                -->\n" +
+                    "                <name>sessionTimeout</name>\n" +
+                    "                <value>30</value>\n" +
+                    "            </param>\n" +
+                    "            <param>\n" +
+                    "                <name>main.ldapRealm</name>\n" +
+                    "                <value>org.apache.hadoop.gateway.shirorealm.KnoxLdapRealm</value>\n" +
+                    "            </param>\n" +
+                    "            <param>\n" +
+                    "                <name>main.ldapContextFactory</name>\n" +
+                    "                <value>org.apache.hadoop.gateway.shirorealm.KnoxLdapContextFactory</value>\n" +
+                    "            </param>\n" +
+                    "            <param>\n" +
+                    "                <name>main.ldapRealm.contextFactory</name>\n" +
+                    "                <value>$ldapContextFactory</value>\n" +
+                    "            </param>\n" +
+                    "            <param>\n" +
+                    "                <name>main.ldapRealm.userDnTemplate</name>\n" +
+                    "                <value>uid={0},ou=people,dc=hadoop,dc=apache,dc=org</value>\n" +
+                    "            </param>\n" +
+                    "            <param>\n" +
+                    "                <name>main.ldapRealm.contextFactory.url</name>\n" +
+                    "                <value>ldap://localhost:33389</value>\n" +
+                    "            </param>\n" +
+                    "            <param>\n" +
+                    "                <name>main.ldapRealm.contextFactory.authenticationMechanism</name>\n" +
+                    "                <value>simple</value>\n" +
+                    "            </param>\n" +
+                    "            <param>\n" +
+                    "                <name>urls./**</name>\n" +
+                    "                <value>authcBasic</value>\n" +
+                    "            </param>\n" +
+                    "        </provider>\n" +
+                    "\n" +
+                    "        <provider>\n" +
+                    "            <role>identity-assertion</role>\n" +
+                    "            <name>Default</name>\n" +
+                    "            <enabled>true</enabled>\n" +
+                    "        </provider>\n" +
+                    "\n" +
+                    "        <!--\n" +
+                    "        Defines rules for mapping host names internal to a Hadoop cluster to externally accessible host names.\n" +
+                    "        For example, a hadoop service running in AWS may return a response that includes URLs containing the\n" +
+                    "        some AWS internal host name.  If the client needs to make a subsequent request to the host identified\n" +
+                    "        in those URLs they need to be mapped to external host names that the client Knox can use to connect.\n" +
+                    "\n" +
+                    "        If the external hostname and internal host names are same turn of this provider by setting the value of\n" +
+                    "        enabled parameter as false.\n" +
+                    "\n" +
+                    "        The name parameter specifies the external host names in a comma separated list.\n" +
+                    "        The value parameter specifies corresponding internal host names in a comma separated list.\n" +
+                    "\n" +
+                    "        Note that when you are using Sandbox, the external hostname needs to be localhost, as seen in out\n" +
+                    "        of box sandbox.xml.  This is because Sandbox uses port mapping to allow clients to connect to the\n" +
+                    "        Hadoop services using localhost.  In real clusters, external host names would almost never be localhost.\n" +
+                    "        -->\n" +
+                    "        <provider>\n" +
+                    "            <role>hostmap</role>\n" +
+                    "            <name>static</name>\n" +
+                    "            <enabled>true</enabled>\n" +
+                    "            <param><name>localhost</name><value>sandbox,sandbox.hortonworks.com</value></param>\n" +
+                    "        </provider>\n" +
+                    "    </gateway>\n";
+
+
+    /**
+     * KNOX-1006
+     *
+     * N.B. This test depends on the DummyServiceDiscovery extension being configured:
+     *             org.apache.hadoop.gateway.topology.discovery.test.extension.DummyServiceDiscovery
+     */
+    @Test
+    public void testSimpleDescriptorHandler() throws Exception {
+
+        final String type = "DUMMY";
+        final String address = "http://c6401.ambari.apache.org:8080";
+        final String clusterName = "dummy";
+        final Map<String, List<String>> serviceURLs = new HashMap<>();
+        serviceURLs.put("NAMENODE", null);
+        serviceURLs.put("JOBTRACKER", null);
+        serviceURLs.put("WEBHDFS", null);
+        serviceURLs.put("WEBHCAT", null);
+        serviceURLs.put("OOZIE", null);
+        serviceURLs.put("WEBHBASE", null);
+        serviceURLs.put("HIVE", null);
+        serviceURLs.put("RESOURCEMANAGER", null);
+        serviceURLs.put("AMBARIUI", Arrays.asList("http://c6401.ambari.apache.org:8080"));
+
+        // Write the externalized provider config to a temp file
+        File providerConfig = writeProviderConfig("ambari-cluster-policy.xml", TEST_PROVIDER_CONFIG);
+
+        File topologyFile = null;
+        try {
+            File destDir = (new File(".")).getCanonicalFile();
+
+            // Mock out the simple descriptor
+            SimpleDescriptor testDescriptor = EasyMock.createNiceMock(SimpleDescriptor.class);
+            EasyMock.expect(testDescriptor.getName()).andReturn("mysimpledescriptor").anyTimes();
+            EasyMock.expect(testDescriptor.getDiscoveryAddress()).andReturn(address).anyTimes();
+            EasyMock.expect(testDescriptor.getDiscoveryType()).andReturn(type).anyTimes();
+            EasyMock.expect(testDescriptor.getDiscoveryUser()).andReturn(null).anyTimes();
+            EasyMock.expect(testDescriptor.getProviderConfig()).andReturn(providerConfig.getAbsolutePath()).anyTimes();
+            EasyMock.expect(testDescriptor.getClusterName()).andReturn(clusterName).anyTimes();
+            List<SimpleDescriptor.Service> serviceMocks = new ArrayList<>();
+            for (String serviceName : serviceURLs.keySet()) {
+                SimpleDescriptor.Service svc = EasyMock.createNiceMock(SimpleDescriptor.Service.class);
+                EasyMock.expect(svc.getName()).andReturn(serviceName).anyTimes();
+                EasyMock.expect(svc.getURLs()).andReturn(serviceURLs.get(serviceName)).anyTimes();
+                EasyMock.replay(svc);
+                serviceMocks.add(svc);
+            }
+            EasyMock.expect(testDescriptor.getServices()).andReturn(serviceMocks).anyTimes();
+            EasyMock.replay(testDescriptor);
+
+            // Invoke the simple descriptor handler
+            Map<String, File> files =
+                           SimpleDescriptorHandler.handle(testDescriptor,
+                                                          providerConfig.getParentFile(), // simple desc co-located with provider config
+                                                          destDir);
+            topologyFile = files.get("topology");
+
+            // Validate the resulting topology descriptor
+            assertTrue(topologyFile.exists());
+
+            // Validate the topology descriptor's correctness
+            TopologyValidator validator = new TopologyValidator( topologyFile.getAbsolutePath() );
+            if( !validator.validateTopology() ){
+                throw new SAXException( validator.getErrorString() );
+            }
+
+            XPathFactory xPathfactory = XPathFactory.newInstance();
+            XPath xpath = xPathfactory.newXPath();
+
+            // Parse the topology descriptor
+            Document topologyXml = XmlUtils.readXml(topologyFile);
+
+            // Validate the provider configuration
+            Document extProviderConf = XmlUtils.readXml(new ByteArrayInputStream(TEST_PROVIDER_CONFIG.getBytes()));
+            Node gatewayNode = (Node) xpath.compile("/topology/gateway").evaluate(topologyXml, XPathConstants.NODE);
+            assertTrue("Resulting provider config should be identical to the referenced content.",
+                       extProviderConf.getDocumentElement().isEqualNode(gatewayNode));
+
+            // Validate the service declarations
+            Map<String, List<String>> topologyServiceURLs = new HashMap<>();
+            NodeList serviceNodes =
+                        (NodeList) xpath.compile("/topology/service").evaluate(topologyXml, XPathConstants.NODESET);
+            for (int serviceNodeIndex=0; serviceNodeIndex < serviceNodes.getLength(); serviceNodeIndex++) {
+                Node serviceNode = serviceNodes.item(serviceNodeIndex);
+                Node roleNode = (Node) xpath.compile("role/text()").evaluate(serviceNode, XPathConstants.NODE);
+                assertNotNull(roleNode);
+                String role = roleNode.getNodeValue();
+                NodeList urlNodes = (NodeList) xpath.compile("url/text()").evaluate(serviceNode, XPathConstants.NODESET);
+                for(int urlNodeIndex = 0 ; urlNodeIndex < urlNodes.getLength(); urlNodeIndex++) {
+                    Node urlNode = urlNodes.item(urlNodeIndex);
+                    assertNotNull(urlNode);
+                    String url = urlNode.getNodeValue();
+                    assertNotNull("Every declared service should have a URL.", url);
+                    if (!topologyServiceURLs.containsKey(role)) {
+                        topologyServiceURLs.put(role, new ArrayList<String>());
+                    }
+                    topologyServiceURLs.get(role).add(url);
+                }
+            }
+            assertEquals("Unexpected number of service declarations.", serviceURLs.size(), topologyServiceURLs.size());
+
+        } catch (Exception e) {
+            e.printStackTrace();
+            fail(e.getMessage());
+        } finally {
+            providerConfig.delete();
+            if (topologyFile != null) {
+                topologyFile.delete();
+            }
+        }
+    }
+
+
+    private File writeProviderConfig(String path, String content) throws IOException {
+        File f = new File(path);
+
+        Writer fw = new FileWriter(f);
+        fw.write(content);
+        fw.flush();
+        fw.close();
+
+        return f;
+    }
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/resources/META-INF/services/org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryType
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/resources/META-INF/services/org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryType b/gateway-server/src/test/resources/META-INF/services/org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryType
new file mode 100644
index 0000000..82a6f86
--- /dev/null
+++ b/gateway-server/src/test/resources/META-INF/services/org.apache.hadoop.gateway.topology.discovery.ServiceDiscoveryType
@@ -0,0 +1,21 @@
+##########################################################################
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+##########################################################################
+
+org.apache.hadoop.gateway.topology.discovery.test.extension.SneakyServiceDiscoveryType
+org.apache.hadoop.gateway.topology.discovery.test.extension.PropertiesFileServiceDiscoveryType
+org.apache.hadoop.gateway.topology.discovery.test.extension.DummyServiceDiscoveryType
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/resources/org/apache/hadoop/gateway/topology/file/ambari-cluster-policy.xml
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/resources/org/apache/hadoop/gateway/topology/file/ambari-cluster-policy.xml b/gateway-server/src/test/resources/org/apache/hadoop/gateway/topology/file/ambari-cluster-policy.xml
new file mode 100644
index 0000000..8223bea
--- /dev/null
+++ b/gateway-server/src/test/resources/org/apache/hadoop/gateway/topology/file/ambari-cluster-policy.xml
@@ -0,0 +1,74 @@
+<gateway>
+    <provider>
+        <role>authentication</role>
+        <name>ShiroProvider</name>
+        <enabled>true</enabled>
+        <param>
+            <!--
+            session timeout in minutes,  this is really idle timeout,
+            defaults to 30mins, if the property value is not defined,,
+            current client authentication would expire if client idles contiuosly for more than this value
+            -->
+            <name>sessionTimeout</name>
+            <value>30</value>
+        </param>
+        <param>
+            <name>main.ldapRealm</name>
+            <value>org.apache.hadoop.gateway.shirorealm.KnoxLdapRealm</value>
+        </param>
+        <param>
+            <name>main.ldapContextFactory</name>
+            <value>org.apache.hadoop.gateway.shirorealm.KnoxLdapContextFactory</value>
+        </param>
+        <param>
+            <name>main.ldapRealm.contextFactory</name>
+            <value>$ldapContextFactory</value>
+        </param>
+        <param>
+            <name>main.ldapRealm.userDnTemplate</name>
+            <value>uid={0},ou=people,dc=hadoop,dc=apache,dc=org</value>
+        </param>
+        <param>
+            <name>main.ldapRealm.contextFactory.url</name>
+            <value>ldap://localhost:33389</value>
+        </param>
+        <param>
+            <name>main.ldapRealm.contextFactory.authenticationMechanism</name>
+            <value>simple</value>
+        </param>
+        <param>
+            <name>urls./**</name>
+            <value>authcBasic</value>
+        </param>
+    </provider>
+
+    <provider>
+        <role>identity-assertion</role>
+        <name>Default</name>
+        <enabled>true</enabled>
+    </provider>
+
+    <!--
+    Defines rules for mapping host names internal to a Hadoop cluster to externally accessible host names.
+    For example, a hadoop service running in AWS may return a response that includes URLs containing the
+    some AWS internal host name.  If the client needs to make a subsequent request to the host identified
+    in those URLs they need to be mapped to external host names that the client Knox can use to connect.
+
+    If the external hostname and internal host names are same turn of this provider by setting the value of
+    enabled parameter as false.
+
+    The name parameter specifies the external host names in a comma separated list.
+    The value parameter specifies corresponding internal host names in a comma separated list.
+
+    Note that when you are using Sandbox, the external hostname needs to be localhost, as seen in out
+    of box sandbox.xml.  This is because Sandbox uses port mapping to allow clients to connect to the
+    Hadoop services using localhost.  In real clusters, external host names would almost never be localhost.
+    -->
+    <provider>
+        <role>hostmap</role>
+        <name>static</name>
+        <enabled>true</enabled>
+        <param><name>localhost</name><value>sandbox,sandbox.hortonworks.com</value></param>
+    </provider>
+
+</gateway>
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-server/src/test/resources/org/apache/hadoop/gateway/topology/file/simple-topology-four.json
----------------------------------------------------------------------
diff --git a/gateway-server/src/test/resources/org/apache/hadoop/gateway/topology/file/simple-topology-four.json b/gateway-server/src/test/resources/org/apache/hadoop/gateway/topology/file/simple-topology-four.json
new file mode 100644
index 0000000..45407a7
--- /dev/null
+++ b/gateway-server/src/test/resources/org/apache/hadoop/gateway/topology/file/simple-topology-four.json
@@ -0,0 +1,18 @@
+{
+  "discovery-type":"DUMMY",
+  "discovery-address":"http://c6401.ambari.apache.org:8080",
+  "provider-config-ref":"../shared-providers/ambari-cluster-policy.xml",
+  "cluster":"dummy",
+  "services":[
+    {"name":"NAMENODE"},
+    {"name":"JOBTRACKER"},
+    {"name":"WEBHDFS"},
+    {"name":"WEBHCAT"},
+    {"name":"OOZIE"},
+    {"name":"WEBHBASE"},
+    {"name":"HIVE"},
+    {"name":"RESOURCEMANAGER"},
+    {"name":"AMBARI", "urls":["http://c6401.ambari.apache.org:8080"]},
+    {"name":"AMBARIUI", "urls":["http://c6401.ambari.apache.org:8080"]}
+  ]
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/GatewayService.java
----------------------------------------------------------------------
diff --git a/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/GatewayService.java b/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/GatewayService.java
new file mode 100644
index 0000000..554ddbe
--- /dev/null
+++ b/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/GatewayService.java
@@ -0,0 +1,29 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery;
+
+import java.lang.annotation.*;
+
+/**
+ * This annotation can be used to inject gateway services into a ServiceDiscovery implementation.
+ */
+@Documented
+@Target(ElementType.FIELD)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface GatewayService {
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscovery.java
----------------------------------------------------------------------
diff --git a/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscovery.java b/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscovery.java
new file mode 100644
index 0000000..eefa30b
--- /dev/null
+++ b/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscovery.java
@@ -0,0 +1,76 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery;
+
+import java.util.List;
+import java.util.Map;
+
+
+/**
+ * Implementations provide the means by which Hadoop service endpoint URLs are discovered from a source with knowledge
+ * about the service topology of one or more clusters.
+ */
+public interface ServiceDiscovery {
+
+    /**
+     * This is the type specified in a simple descriptor to indicate which ServiceDiscovery implementation to employ.
+     *
+     * @return The identifier for the service discovery type.
+     */
+    String getType();
+
+
+    /**
+     * Discover details of all the clusters known to the target registry.
+     *
+     * @param config The configuration for the discovery invocation
+     *
+     * @return A Map of the discovered service data, keyed by the cluster name.
+     */
+    Map<String, Cluster> discover(ServiceDiscoveryConfig config);
+
+
+    /**
+     * Discover details for a single cluster.
+     *
+     * @param config The configuration for the discovery invocation
+     * @param clusterName The name of a particular cluster
+     *
+     * @return The discovered service data for the specified cluster
+     */
+    Cluster discover(ServiceDiscoveryConfig config, String clusterName);
+
+
+    /**
+     * A handle to the service discovery result.
+     */
+    interface Cluster {
+
+        /**
+         * @return The name of the cluster
+         */
+        String getName();
+
+        /**
+         * @param serviceName The name of the service
+         * @return The URLs for the specified service in this cluster.
+         */
+        List<String> getServiceURLs(String serviceName);
+    }
+
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryConfig.java
----------------------------------------------------------------------
diff --git a/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryConfig.java b/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryConfig.java
new file mode 100644
index 0000000..6b2e741
--- /dev/null
+++ b/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryConfig.java
@@ -0,0 +1,42 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery;
+
+/**
+ * ServiceDiscovery configuration details.
+ */
+public interface ServiceDiscoveryConfig {
+
+    /**
+     *
+     * @return The address of the discovery source.
+     */
+    String getAddress();
+
+    /**
+     *
+     * @return The username configured for interactions with the discovery source.
+     */
+    String getUser();
+
+    /**
+     *
+     * @return The alias for the password required for interactions with the discovery source.
+     */
+    String getPasswordAlias();
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryType.java
----------------------------------------------------------------------
diff --git a/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryType.java b/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryType.java
new file mode 100644
index 0000000..cddced1
--- /dev/null
+++ b/gateway-spi/src/main/java/org/apache/hadoop/gateway/topology/discovery/ServiceDiscoveryType.java
@@ -0,0 +1,40 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.hadoop.gateway.topology.discovery;
+
+/**
+ * ServiceDiscovery extensions must implement this interface to add support for a new discovery source.
+ *
+ * The ServiceLoader mechanism is used to include ServiceDiscovery extensions, and implementations of this interface
+ * are the providers.
+ */
+public interface ServiceDiscoveryType {
+
+    /**
+     *
+     * @return The identifier for the discovery type.
+     */
+    String getType();
+
+
+    /**
+     *
+     * @return A new instance of the ServiceDiscovery implementation provided by this type.
+     */
+    ServiceDiscovery newInstance();
+
+}

http://git-wip-us.apache.org/repos/asf/knox/blob/c2ca4432/pom.xml
----------------------------------------------------------------------
diff --git a/pom.xml b/pom.xml
index d2f4176..2708f6b 100644
--- a/pom.xml
+++ b/pom.xml
@@ -45,6 +45,7 @@
         <module>gateway-i18n-logging-log4j</module>
         <module>gateway-i18n-logging-sl4j</module>
         <module>gateway-spi</module>
+        <module>gateway-discovery-ambari</module>
         <module>gateway-server</module>
         <module>gateway-server-launcher</module>
         <module>gateway-server-xforwarded-filter</module>
@@ -684,6 +685,11 @@
             </dependency>
             <dependency>
                 <groupId>${gateway-group}</groupId>
+                <artifactId>gateway-discovery-ambari</artifactId>
+                <version>${gateway-version}</version>
+            </dependency>
+            <dependency>
+                <groupId>${gateway-group}</groupId>
                 <artifactId>gateway-release</artifactId>
                 <version>${gateway-version}</version>
             </dependency>
@@ -702,17 +708,16 @@
                 <artifactId>gateway-shell-samples</artifactId>
                 <version>${gateway-version}</version>
             </dependency>
-
-        <dependency>
-            <groupId>org.picketlink</groupId>
-            <artifactId>picketlink-federation</artifactId>
-            <version>2.7.0.CR3</version>
-        </dependency>
-        <dependency>
-            <groupId>org.jboss.logging</groupId>
-            <artifactId>jboss-logging</artifactId>
-            <version>3.2.0.Final</version>
-        </dependency>
+            <dependency>
+                <groupId>org.picketlink</groupId>
+                <artifactId>picketlink-federation</artifactId>
+                <version>2.7.0.CR3</version>
+            </dependency>
+            <dependency>
+                <groupId>org.jboss.logging</groupId>
+                <artifactId>jboss-logging</artifactId>
+                <version>3.2.0.Final</version>
+            </dependency>
             <dependency>
                 <groupId>org.glassfish.jersey.containers</groupId>
                 <artifactId>jersey-container-servlet</artifactId>


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