FileMetricObserver.java

/*
 * Copyright 2014 Netflix, Inc.
 *
 * Licensed 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 com.netflix.servo.publish;

import com.netflix.servo.Metric;
import com.netflix.servo.util.Clock;
import com.netflix.servo.util.ClockWithOffset;
import com.netflix.servo.util.Preconditions;
import com.netflix.servo.util.Throwables;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import java.util.TimeZone;
import java.util.zip.GZIPOutputStream;

/**
 * Writes observations to a file. The format is a basic text file with tabs
 * separating the fields.
 */
public final class FileMetricObserver extends BaseMetricObserver {

  private static final Logger LOGGER =
      LoggerFactory.getLogger(FileMetricObserver.class);

  private static final String FILE_DATE_FORMAT = "yyyy_MM_dd_HH_mm_ss_SSS";
  private final File dir;
  private final boolean compress;
  private final Clock clock;
  private final SimpleDateFormat fileFormat;

  /**
   * Creates a new instance that stores files in {@code dir} with a prefix of
   * {@code name} and a suffix of a timestamp in the format
   * {@code yyyy_MM_dd_HH_mm_ss_SSS}.
   *
   * @param name name to use as a prefix on files
   * @param dir  directory where observations will be stored
   */
  public FileMetricObserver(String name, File dir) {
    this(name, dir, false);
  }

  /**
   * Creates a new instance that stores files in {@code dir} with a prefix of
   * {@code name} and a suffix of a timestamp in the format
   * {@code yyyy_MM_dd_HH_mm_ss_SSS}.
   *
   * @param name     name to use as a prefix on files
   * @param dir      directory where observations will be stored
   * @param compress whether to compress our output
   */
  public FileMetricObserver(String name, File dir, boolean compress) {
    this(name,
        String.format("'%s'_%s", name, FILE_DATE_FORMAT) + (compress ? "'.log.gz'" : "'.log'"),
        dir,
        compress);
  }

  /**
   * Creates a new instance that stores files in {@code dir} with a name that
   * is created using {@code namePattern}.
   *
   * @param name        name of the observer
   * @param namePattern date format pattern used to create the file names
   * @param dir         directory where observations will be stored
   * @param compress    whether to compress our output
   */
  public FileMetricObserver(String name, String namePattern, File dir, boolean compress) {
    this(name, namePattern, dir, compress, ClockWithOffset.INSTANCE);
  }

  /**
   * Creates a new instance that stores files in {@code dir} with a name that
   * is created using {@code namePattern}.
   *
   * @param name        name of the observer
   * @param namePattern date format pattern used to create the file names
   * @param dir         directory where observations will be stored
   * @param compress    whether to compress our output
   * @param clock       clock instance to use for getting the time used in the filename
   */

  public FileMetricObserver(String name, String namePattern, File dir,
                            boolean compress, Clock clock) {
    super(name);
    this.dir = dir;
    this.compress = compress;
    this.clock = clock;
    fileFormat = new SimpleDateFormat(namePattern);
    fileFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
  }

  /**
   * {@inheritDoc}
   */
  public void updateImpl(List<Metric> metrics) {
    Preconditions.checkNotNull(metrics, "metrics");
    File file = new File(dir, fileFormat.format(new Date(clock.now())));
    Writer out = null;
    try {
      try {
        LOGGER.debug("writing {} metrics to file {}", metrics.size(), file);
        OutputStream fileOut = new FileOutputStream(file, true);
        if (compress) {
          fileOut = new GZIPOutputStream(fileOut);
        }
        out = new OutputStreamWriter(fileOut, "UTF-8");
        for (Metric m : metrics) {
          out.append(m.getConfig().getName()).append('\t')
              .append(m.getConfig().getTags().toString()).append('\t')
              .append(m.getValue().toString()).append('\n');
        }
      } catch (Throwable t) {
        if (out != null) {
          out.close();
          out = null;
        }
        throw Throwables.propagate(t);
      } finally {
        if (out != null) {
          out.close();
        }
      }
    } catch (IOException e) {
      incrementFailedCount();
      LOGGER.error("failed to write update to file " + file, e);
    }
  }
}