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From aljoscha <...@git.apache.org>
Subject [GitHub] flink pull request: Refactoring the File Monitoring Source.
Date Wed, 27 Apr 2016 09:30:03 GMT
Github user aljoscha commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1929#discussion_r61228546
  
    --- Diff: flink-streaming-java/src/main/java/org/apache/flink/streaming/api/functions/source/FileSplitMonitoringFunction.java
---
    @@ -0,0 +1,234 @@
    +/*
    + * 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.flink.streaming.api.functions.source;
    +
    +import org.apache.flink.api.common.io.FileInputFormat;
    +import org.apache.flink.configuration.Configuration;
    +import org.apache.flink.core.fs.FileInputSplit;
    +import org.apache.flink.core.fs.FileStatus;
    +import org.apache.flink.core.fs.FileSystem;
    +import org.apache.flink.core.fs.Path;
    +import org.apache.flink.runtime.JobException;
    +import org.apache.flink.util.Preconditions;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import java.io.IOException;
    +import java.net.URI;
    +import java.util.ArrayList;
    +import java.util.HashSet;
    +import java.util.List;
    +import java.util.Set;
    +
    +/**
    + * This is the single (non-parallel) task which monitors a user-provided path and assigns
splits
    + * to downstream tasks for further reading and processing. Which splits will be further
processed
    + * depends on the user-provided {@link FileSplitMonitoringFunction.WatchType}.
    + */
    +public class FileSplitMonitoringFunction<OUT>
    +	extends RichSourceFunction<FileInputSplit> {
    +
    +	private static final long serialVersionUID = 1L;
    +
    +	private static final Logger LOG = LoggerFactory.getLogger(FileSplitMonitoringFunction.class);
    +
    +	/**
    +	 * Specifies when computation will be triggered.
    +	 */
    +	public enum WatchType {
    +		REPROCESS_WITH_APPENDED		// Reprocesses the whole file when new data is appended.
    +	}
    +
    +	/** The path to monitor. */
    +	private final String path;
    +
    +	/** The default parallelism for the job, as this is going to be the parallelism of the
downstream readers. */
    +	private final int readerParallelism;
    +
    +	/** The {@link FileInputFormat} to be read. */
    +	private FileInputFormat<OUT> format;
    +
    +	/** How often to monitor the state of the directory for new data. */
    +	private final long interval;
    +
    +	/** Which new data to process (see {@link WatchType}. */
    +	private final WatchType watchType;
    +
    +	private long globalModificationTime;
    +
    +	private FilePathFilter pathFilter;
    +
    +	private volatile boolean isRunning = false;
    +
    +	private Configuration configuration;
    +
    +	public FileSplitMonitoringFunction(
    +		FileInputFormat<OUT> format, String path, Configuration configuration,
    +		WatchType watchType, int readerParallelism, long interval) {
    +
    +		this(format, path, configuration, FilePathFilter.DefaultFilter.getInstance(), watchType,
readerParallelism, interval);
    +	}
    +
    +	public FileSplitMonitoringFunction(
    +		FileInputFormat<OUT> format, String path, Configuration configuration,
    +		FilePathFilter filter, WatchType watchType, int readerParallelism, long interval) {
    +
    +		this.format = Preconditions.checkNotNull(format);
    +		this.path = Preconditions.checkNotNull(path);
    +		this.configuration = Preconditions.checkNotNull(configuration);
    +
    +		Preconditions.checkArgument(interval >= 100,
    +			"The specified monitoring interval is smaller than the minimum allowed one (100 ms).");
    +		this.interval = interval;
    +
    +		this.watchType = watchType;
    +
    +		this.pathFilter = Preconditions.checkNotNull(filter);
    +
    +		this.readerParallelism = Math.max(readerParallelism, 1);
    +		this.globalModificationTime = Long.MIN_VALUE;
    +	}
    +
    +	@Override
    +	@SuppressWarnings("unchecked")
    +	public void open(Configuration parameters) throws Exception {
    +		super.open(parameters);
    +		format.configure(this.configuration);
    +	}
    +
    +	/**
    +	 * Creates the input splits for the path to be assigned to the downstream tasks.
    +	 * Those are going to read their contents for further processing.
    +	 */
    +	private FileInputSplit[] createInputSplits() throws JobException {
    +		FileInputSplit[] inputSplits;
    +		try {
    +			inputSplits = format.createInputSplits(readerParallelism);
    +		} catch (Throwable t) {
    +			throw new JobException("Creating the input splits caused an error: " + t.getMessage(),
t);
    +		}
    +		return inputSplits;
    +	}
    +
    +	@Override
    +	public void run(SourceFunction.SourceContext<FileInputSplit> context) throws Exception
{
    +		if(!isRunning) {
    --- End diff --
    
    We should not change this here. I think it can be problematic with race conditions. Just
initializing `isRunning` to `true` when declaring the field should do the trick. (This is
also how the Kafka Consumer does it and I think as this one as the reference consumer since
it's most widely used.)


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