03c15eb275
* Introducing MultiLangDaemon support for Enhanced Fan-Out. * MultiLangDaemon now supports the following command line options. * `--properties-file`: Properties file that the KCL should use to set up the Scheduler. * `--log-configuration`: logback.xml that the KCL should use for logging. * Updated AWS SDK dependency to 2.2.0. * MultiLangDaemon now uses logback for logging.
87 lines
3.2 KiB
Java
87 lines
3.2 KiB
Java
/*
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* Copyright 2018 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 software.amazon.kinesis.multilang;
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import java.io.BufferedReader;
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import java.io.IOException;
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import software.amazon.kinesis.multilang.messages.Message;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import lombok.extern.slf4j.Slf4j;
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/**
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* Gets the next message off the STDOUT of the child process. Throws an exception if a message is not found before the
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* end of the input stream is reached.
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*/
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@Slf4j
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class GetNextMessageTask extends LineReaderTask<Message> {
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private ObjectMapper objectMapper;
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private static final String EMPTY_LINE = "";
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/**
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* Constructor.
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*
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* @param objectMapper An object mapper for decoding json messages from the input stream.
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*/
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GetNextMessageTask(ObjectMapper objectMapper) {
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this.objectMapper = objectMapper;
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}
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/**
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* Checks if a line is an empty line.
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*
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* @param line A string
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* @return True if the line is an empty string, i.e. "", false otherwise.
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*/
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static boolean isEmptyLine(String line) {
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return EMPTY_LINE.equals(line);
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}
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@Override
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protected HandleLineResult<Message> handleLine(String line) {
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try {
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/*
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* If the line is an empty line we don't bother logging anything because we expect the child process to be
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* nesting its messages between new lines, e.g. "\n<JSON message>\n". If there are no other entities writing
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* to the child process's STDOUT then this behavior will result in patterns like
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* "...\n<JSON message>\n\n<JSON message>\n..." which contains empty lines.
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*/
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if (!isEmptyLine(line)) {
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return new HandleLineResult<Message>(objectMapper.readValue(line, Message.class));
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}
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} catch (IOException e) {
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log.info("Skipping unexpected line on STDOUT for shard {}: {}", getShardId(), line);
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}
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return new HandleLineResult<Message>();
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}
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@Override
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protected Message returnAfterException(Exception e) {
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throw new RuntimeException("Encountered an error while reading a line from STDIN for shard " + getShardId()
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+ " so won't be able to return a message.", e);
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}
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@Override
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protected Message returnAfterEndOfInput() {
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throw new RuntimeException("Reached end of STDIN of child process for shard " + getShardId()
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+ " so won't be able to return a message.");
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}
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public LineReaderTask<Message> initialize(BufferedReader reader, String shardId) {
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return initialize(reader, shardId, "Reading next message from STDIN for " + shardId);
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}
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}
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