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From mattf-horton <...@git.apache.org>
Subject [GitHub] metron pull request #530: METRON-777 Metron Extension System and Parser Exte...
Date Tue, 08 Aug 2017 16:40:29 GMT
Github user mattf-horton commented on a diff in the pull request:

    https://github.com/apache/metron/pull/530#discussion_r131966450
  
    --- Diff: bundles-lib/src/main/java/org/apache/metron/bundles/BundleClassLoaders.java
---
    @@ -0,0 +1,353 @@
    +/*
    + * 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.metron.bundles;
    +
    +import java.net.URISyntaxException;
    +import java.util.*;
    +
    +import org.apache.commons.collections.CollectionUtils;
    +import org.apache.commons.vfs2.FileObject;
    +import org.apache.commons.vfs2.FileSystemException;
    +import org.apache.commons.vfs2.FileSystemManager;
    +import org.apache.metron.bundles.bundle.Bundle;
    +import org.apache.metron.bundles.bundle.BundleCoordinate;
    +import org.apache.metron.bundles.bundle.BundleDetails;
    +import org.apache.metron.bundles.util.BundleProperties;
    +import org.apache.metron.bundles.util.BundleSelector;
    +import org.apache.metron.bundles.util.FileUtils;
    +import org.apache.metron.bundles.util.BundleUtil;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +/**
    + * A singleton class used to initialize the extension and framework classloaders.
    + */
    +public final class BundleClassLoaders {
    +
    +  private static volatile BundleClassLoaders bundleClassLoaders;
    +  private volatile InitContext initContext;
    +  private static final Logger logger = LoggerFactory.getLogger(BundleClassLoaders.class);
    +
    +  private final static class InitContext {
    +
    +    private final List<FileObject> extensionDirs;
    +    private final Map<String, Bundle> bundles;
    +
    +    private InitContext(
    +        final List<FileObject> extensionDirs,
    +        final Map<String, Bundle> bundles) {
    +      this.extensionDirs = extensionDirs;
    +      this.bundles = bundles;
    +    }
    +  }
    +
    +  private BundleClassLoaders() {
    +  }
    +
    +  /**
    +   * @return The singleton instance of the BundleClassLoaders
    +   */
    +  public static BundleClassLoaders getInstance() {
    +    BundleClassLoaders result = bundleClassLoaders;
    +    if (result == null) {
    +      synchronized (BundleClassLoaders.class) {
    +        result = bundleClassLoaders;
    +        if (result == null) {
    +          bundleClassLoaders = result = new BundleClassLoaders();
    +        }
    +      }
    +    }
    +    return result;
    +  }
    +
    +  public static void reset() {
    +    getInstance().unInit();
    +  }
    +
    +  private void unInit() {
    +    synchronized (this) {
    +      initContext = null;
    +    }
    +  }
    +
    +  /**
    +   * Initializes and loads the BundleClassLoaders. This method must be called before
the rest of the
    +   * methods to access the classloaders are called and it can be safely called any number
of times
    +   * provided the same framework and extension working dirs are used.
    --- End diff --
    
    I don't understand.  I'm pretty sure that all Storm bolts on the same physical host run
in the same JVM.  At least all bolts in the same Supervisor do; I'm not sure if you can run
multiple supers on a single host.  So any single-node cluster is going to have the potential
to run multiple parser plugins in the same JVM, but even multi-node clusters might -- it's
up to the  Master.


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