[
https://issues.apache.org/jira/browse/HDFS-17543?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17859580#comment-17859580
]
ASF GitHub Bot commented on HDFS-17543:
---------------------------------------
hfutatzhanghb commented on code in PR #6868:
URL: https://github.com/apache/hadoop/pull/6868#discussion_r1650406400
##########
hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/async/AsyncForEachRun.java:
##########
@@ -0,0 +1,185 @@
+/**
+ * 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.hdfs.server.federation.router.async;
+
+import java.io.IOException;
+import java.util.Iterator;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+
+/**
+ * The AsyncForEachRun class is part of the asynchronous operation utilities
+ * within the Hadoop Distributed File System (HDFS) Federation router.
+ * It provides the functionality to perform asynchronous operations on each
+ * element of an Iterator, applying a given async function and then applying
+ * a final transformation function to the results.
+ *
+ * <p>This class is designed to work with other asynchronous interfaces and
+ * utility classes to enable complex asynchronous workflows. It allows for
+ * non-blocking execution of tasks, which can improve the performance and
+ * responsiveness of HDFS operations.</p>
+ *
+ * <p>The class implements the AsyncRun interface, which means it can be used
+ * in asynchronous task chains. It maintains an Iterator of elements to
+ * process, an asyncFunction to apply to each element, and a final
+ * transformation function (thenApply) to produce the final result.</p>
+ *
+ * <p>The run method initiates the asynchronous operation, and the doOnce
+ * method recursively applies the asyncFunction to each element and handles
+ * the results. If the satisfy flag is set, the operation is completed
+ * with the current result.</p>
+ *
+ * <p>AsyncForEachRun is used to implement the following semantics:</p>
+ * <pre>
+ * {@code
+ * for (I element : elements) {
+ * T res = asyncFunction(element);
+ * R result = thenApply(element, res);
+ * if (satisfyCondition(res, result)) {
+ * break;
+ * }
+ * }
+ * return result;
+ * }
+ * </pre>
+ *
+ * @param <I> the type of the elements being iterated over
+ * @param <T> the type of the intermediate result from the asyncFunction
+ * @param <R> the type of the final result after applying the thenApply
function
+ * @see AsyncRun
+ * @see AsyncApplyFunction
+ * @see BiFunction
+ */
+public class AsyncForEachRun<I, T, R> implements AsyncRun<R> {
+
+ private boolean satisfy = false;
+ private Iterator<I> iterator;
+ private I now;
+ private final CompletableFuture<R> result = new CompletableFuture<>();
+ private AsyncApplyFunction<I, T> asyncFunction;
+ private BiFunction<AsyncForEachRun<I, T, R>, T, R> thenApply;
Review Comment:
@KeeProMise Sir, do we need to support multiple thenApply here? for
example, `.then(then1).then(then2)`
> [ARR] AsyncUtil makes asynchronous code more concise and easier.
> ----------------------------------------------------------------
>
> Key: HDFS-17543
> URL: https://issues.apache.org/jira/browse/HDFS-17543
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Jian Zhang
> Assignee: Jian Zhang
> Priority: Major
> Labels: pull-request-available
> Attachments: HDFS-17543.001.patch
>
>
> *Describe*
> Using the original Java CompletableFuture to implement an asynchronous router
> is not conducive to the development of the open source community due to poor
> code readability and maintainability. Therefore, I have implemented a
> lightweight tool that encapsulates CompletableFuture.
> By using this AsyncUtil, it is easy to write readable asynchronous code,
> which is easy for everyone to understand. I have provided an example of this
> tool class in UT, demonstrating how to change synchronous methods to
> asynchronous code.
>
> *Examples and tests*
> SyncClass provides some common synchronization methods
> AsyncClass is the corresponding asynchronous implementation
> Use TestAsyncUtil to simultaneously test the methods corresponding to
> SyncClass and AsyncClass, ensuring that both asynchronous and synchronous
> methods return the same results
>
> {*}NOTE{*}: In HDFS-17545, I used this tool to implement RouterAsyncRpcClient
> which extends RouterRpcClient. You can also view RouterAsyncRpcClient to
> understand the use of this tool.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org
For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
