fluo-notifications mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From GitBox <...@apache.org>
Subject [GitHub] keith-turner commented on a change in pull request #969: [WIP] Issue-967
Date Thu, 01 Jan 1970 00:00:00 GMT
keith-turner commented on a change in pull request #969: [WIP] Issue-967
URL: https://github.com/apache/fluo/pull/969#discussion_r150892232
 
 

 ##########
 File path: modules/core/src/main/java/org/apache/fluo/core/impl/AsyncReader.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.fluo.core.impl;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.PriorityQueue;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import org.apache.fluo.api.data.Bytes;
+import org.apache.fluo.api.data.Column;
+import org.apache.fluo.api.data.RowColumn;
+import org.apache.fluo.core.impl.TransactionImpl;
+
+public class AsyncReader {
+  private PriorityQueue<AsyncGet> getsQueue;
+  private ExecutorService executorService;
+  private TransactionImpl tx;
+
+  public AsyncReader(TransactionImpl tx) {
+    this.tx = tx;
+    getsQueue = new PriorityQueue<>();
+    executorService = Executors.newSingleThreadExecutor();
+  }
+
+  public CompletableFuture<String> gets(String row, Column column) {
+    return gets(row, column, null);
+  }
+
+  public CompletableFuture<String> gets(String row, Column column, String defaultValue)
{
+    AsyncGet curAsyncGet = new AsyncGet(row, column, defaultValue);
+    getsQueue.add(curAsyncGet);
+    executorService.submit(() -> {
+      int i = 0;
 
 Review comment:
   In the face of concurrency this lambda is not correct.  I would recommend something like
the following and I will try to explain why.
   
   ```java
   
     //use arraylist instead of hashset because it has better performance and no need for
unique
     List <AsyncGet> gets = new ArrayList();  
   
     asyncGets.drainTo(gets);
   
     //not sure if I have the syntax below correct, but I think Guava has this method
     Collection<RowColumn> rowColumns = Collections2.transform(gets, ag -> ag.rc);

     Map<RowColumn, Bytes> getsMap = tx.get(rowColumns);
   
     //process everything we drained off the queue... do not want to touch the queue as new
things may have been added.
     for(AsyncGet asynGet : gets) {
       Bytes result = getsMap.get(asyncGet);
       asyncGet.res.complete(result);  //TODO handle default value
     }
   
   ```
   
   With the current code if the execservice had multiple threads then multiple threads could
process the same AsyncGet request.   Using drainTo with LinkedBlockingQueue avoids this. 
This is not true for all collections, but this particular collection impl gets a lock in drainTo.
   

----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on GitHub and use the
URL above to go to the specific comment.
 
For queries about this service, please contact Infrastructure at:
users@infra.apache.org


With regards,
Apache Git Services

Mime
View raw message