keith-turner commented on a change in pull request #969: [WIP] Issue-967 URL: https://github.com/apache/fluo/pull/969#discussion_r152160862
########## File path: modules/core/src/main/java/org/apache/fluo/core/impl/AsyncReader.java ########## @@ -0,0 +1,101 @@ +/* + * 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.ArrayList; +import java.util.Collection; +import java.util.List; +import java.util.Map; +import java.util.concurrent.BlockingQueue; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; +import java.util.concurrent.LinkedBlockingQueue; + +import com.google.common.collect.Collections2; +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 BlockingQueue<AsyncGet> asyncGetsQueue; + private ExecutorService executorService; + private TransactionImpl tx; + + public AsyncReader(TransactionImpl tx) { + this.tx = tx; + asyncGetsQueue = new LinkedBlockingQueue<>(); + executorService = Executors.newSingleThreadExecutor(); + } + + public CompletableFuture<Bytes> get(Bytes row, Column column) { + return get(row, column, null); + } + + public CompletableFuture<Bytes> get(Bytes row, Column column, Bytes defaultValue) { + AsyncGet curAsyncGet = new AsyncGet(row, column, defaultValue); + asyncGetsQueue.add(curAsyncGet); + + executorService.submit(() -> { + List<AsyncGet> getsList = new ArrayList<>(); + asyncGetsQueue.drainTo(getsList); + + try { + Collection<RowColumn> rowColumns = Collections2.transform(getsList, ag -> ag.rc); + + Map<RowColumn, Bytes> getsMap = tx.get(rowColumns); + + for (AsyncGet asyncGet : getsList) { + Bytes result = getsMap.get(asyncGet.rc); + asyncGet.res.complete(result == null ? defaultValue : result); + getsList.remove(asyncGet); Review comment: The following comments are moot because I don't think things needs to be removed based on earlier comment. Just sharing some knowledge in following comments. This could cause a concurrent modification exception. The foreach has a hidden iterator. In java, many iterators will throw a concurrent modification exception if the collection is modified during iteration. Using a while loop with an explicit iterator and calling remove on the iterator is the best way to remove while iterating. Also removing items from an arraylist could be an O(N^2) operation. In the situation of removing from the middle of a list a linked list may be better. ---------------------------------------------------------------- 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: [email protected] With regards, Apache Git Services
