com.cloudera.gertrude.file.FileExperimentSpaceLoader.java Source code

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Here is the source code for com.cloudera.gertrude.file.FileExperimentSpaceLoader.java

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/**
 * Copyright (c) 2013, Cloudera, Inc. All Rights Reserved.
 *
 * Cloudera, Inc. 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
 *
 * This software 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 com.cloudera.gertrude.file;

import com.cloudera.gertrude.ExperimentSpace;
import com.cloudera.gertrude.ExperimentSpaceLoader;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.io.Files;
import org.apache.commons.io.monitor.FileAlterationListenerAdaptor;
import org.apache.commons.io.monitor.FileAlterationMonitor;
import org.apache.commons.io.monitor.FileAlterationObserver;

import java.io.File;
import java.io.FileFilter;

public final class FileExperimentSpaceLoader extends ExperimentSpaceLoader {
    private static final long DEFAULT_POLL_INTERVAL_MILLIS = 5 * 1000L;

    private final File dataFile;

    public FileExperimentSpaceLoader(File dataFile) throws Exception {
        this(dataFile, DEFAULT_POLL_INTERVAL_MILLIS);
    }

    public FileExperimentSpaceLoader(File dataFile, long pollIntervalMillis) throws Exception {
        Preconditions.checkArgument(!dataFile.isDirectory(), "Data file cannot be a directory");
        this.dataFile = dataFile;
        FileAlterationMonitor monitor = getMonitor(pollIntervalMillis);
        monitor.start();
    }

    private FileAlterationMonitor getMonitor(long pollIntervalMillis) {
        FileAlterationObserver observer = new FileAlterationObserver(dataFile.getParentFile(), new FileFilter() {
            @Override
            public boolean accept(File file) {
                return dataFile.equals(file);
            }
        });

        observer.addListener(new FileAlterationListenerAdaptor() {
            @Override
            public void onFileChange(File file) {
                file.setLastModified(System.currentTimeMillis());
                reload(false);
            }
        });
        FileAlterationMonitor m = new FileAlterationMonitor(pollIntervalMillis);
        m.addObserver(observer);
        return m;
    }

    @Override
    protected Optional<ExperimentSpace.Serialized> getSerialized() {
        return Optional.of(new ExperimentSpace.Serialized(String.valueOf(dataFile.lastModified()),
                Files.newInputStreamSupplier(dataFile)));
    }
}