63 lines
2.3 KiB
Java
63 lines
2.3 KiB
Java
/*
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* Copyright 2019 Amazon.com, Inc. or its affiliates.
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* Licensed under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package software.amazon.kinesis.multilang;
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import java.io.BufferedReader;
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import lombok.extern.slf4j.Slf4j;
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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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@Slf4j
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class DrainChildSTDOUTTask extends LineReaderTask<Boolean> {
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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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