Squashed 'src/rocksdb/' content from commit 78b8a7d

git-subtree-dir: src/rocksdb
git-subtree-split: 78b8a7d908d7e67cc6664398e39560b76c965773

java/org/rocksdb/StatisticsCollector.java

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+// Copyright (c) 2014, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+
+package org.rocksdb;
+
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * Helper class to collect DB statistics periodically at a period specified in
+ * constructor. Callback function (provided in constructor) is called with
+ * every statistics collection.
+ *
+ * Caller should call start() to start statistics collection. Shutdown() should
+ * be called to stop stats collection and should be called before statistics (
+ * provided in constructor) reference has been disposed.
+ */
+public class StatisticsCollector {
+  private final Statistics _statistics;
+  private final ThreadPoolExecutor _threadPoolExecutor;
+  private final int _statsCollectionInterval;
+  private final StatisticsCollectorCallback _statsCallback;
+  private volatile boolean _isRunning = true;
+
+  /**
+   * Constructor for statistics collector.
+   * @param statistics Reference of DB statistics.
+   * @param statsCollectionIntervalInMilliSeconds Statistics collection time 
+   *        period (specified in milliseconds) 
+   * @param statsCallback Reference of statistics callback interface.
+   */
+  public StatisticsCollector(Statistics statistics,
+      int statsCollectionIntervalInMilliSeconds,
+      StatisticsCollectorCallback statsCallback) {
+    _statistics = statistics;
+    _statsCollectionInterval = statsCollectionIntervalInMilliSeconds;
+    _statsCallback = statsCallback;
+
+    _threadPoolExecutor = new ThreadPoolExecutor(1, 1, 0, TimeUnit.SECONDS,
+        new ArrayBlockingQueue<Runnable>(1));
+  }
+
+  public void start() {
+    _threadPoolExecutor.submit(collectStatistics());
+  }
+
+  public void shutDown() throws InterruptedException {
+    _isRunning = false;
+
+    _threadPoolExecutor.shutdown();
+    // Wait for collectStatistics runnable to finish so that disposal of
+    // statistics does not cause any exceptions to be thrown.
+    _threadPoolExecutor.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);
+  }
+
+  private Runnable collectStatistics() {
+    return new Runnable() {
+
+      @Override
+      public void run() {
+        while (_isRunning) {
+          try {
+            // Collect ticker data
+            for(TickerType ticker : TickerType.values()) {
+              long tickerValue = _statistics.getTickerCount(ticker);
+              _statsCallback.tickerCallback(ticker, tickerValue);
+            }
+
+            // Collect histogram data
+            for(HistogramType histogramType : HistogramType.values()) {
+              HistogramData histogramData =
+                  _statistics.geHistogramData(histogramType);
+              _statsCallback.histogramCallback(histogramType, histogramData);
+            }
+
+            Thread.sleep(_statsCollectionInterval);
+          }
+          catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            throw new RuntimeException("Thread got interrupted!", e);
+          }
+          catch (Exception e) {
+            throw new RuntimeException("Error while calculating statistics", e);
+          }
+        }
+      }
+    };
+  }
+}