67 lines
2.4 KiB
Java
67 lines
2.4 KiB
Java
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/*
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* Copyright 2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* Licensed under the Amazon Software License (the "License").
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* You may not use this file except in compliance with the License.
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* A copy of the License is located at
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*
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* http://aws.amazon.com/asl/
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*
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* or in the "license" file accompanying this file. This file is distributed
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* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
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* express or implied. See the License for the specific language governing
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* permissions and limitations under the License.
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*/
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package com.amazonaws.services.kinesis.multilang;
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import java.io.BufferedReader;
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import org.apache.commons.logging.Log;
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import org.apache.commons.logging.LogFactory;
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/**
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* This class is used to drain the STDOUT of the child process. After the child process has been given a shutdown
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* message and responded indicating that it is shutdown, we attempt to close the input and outputs of that process so
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* that the process can exit.
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*
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* To understand why this is necessary, consider the following scenario:
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*
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* <ol>
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* <li>Child process responds that it is done with shutdown.</li>
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* <li>Child process prints debugging text to STDOUT that fills the pipe buffer so child becomes blocked.</li>
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* <li>Parent process doesn't drain child process's STDOUT.</li>
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* <li>Child process remains blocked.</li>
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* </ol>
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*
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* To prevent the child process from becoming blocked in this way, it is the responsibility of the parent process to
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* drain the child process's STDOUT. We reprint each drained line to our log to permit debugging.
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*/
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class DrainChildSTDOUTTask extends LineReaderTask<Boolean> {
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private static final Log LOG = LogFactory.getLog(DrainChildSTDOUTTask.class);
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DrainChildSTDOUTTask() {
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}
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@Override
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protected HandleLineResult<Boolean> handleLine(String line) {
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LOG.info("Drained line for shard " + getShardId() + ": " + line);
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return new HandleLineResult<Boolean>();
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}
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@Override
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protected Boolean returnAfterException(Exception e) {
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LOG.info("Encountered exception while draining STDOUT of child process for shard " + getShardId(), e);
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return false;
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}
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@Override
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protected Boolean returnAfterEndOfInput() {
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return true;
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}
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public LineReaderTask<Boolean> initialize(BufferedReader reader, String shardId) {
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return initialize(reader, shardId, "Draining STDOUT for " + shardId);
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}
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}
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