Squashed 'src/rocksdb/' content from commit 224932d

git-subtree-dir: src/rocksdb
git-subtree-split: 224932d4d0b561712107d747c662df181c39644d

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.List;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ExecutorService;
+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 List<StatsCollectorInput> _statsCollectorInputList;
+  private final ExecutorService _executorService;
+  private final int _statsCollectionInterval;
+  private volatile boolean _isRunning = true;
+
+  /**
+   * Constructor for statistics collector.
+   * 
+   * @param statsCollectorInputList List of statistics collector input.
+   * @param statsCollectionIntervalInMilliSeconds Statistics collection time 
+   *        period (specified in milliseconds).
+   */
+  public StatisticsCollector(List<StatsCollectorInput> statsCollectorInputList,
+      int statsCollectionIntervalInMilliSeconds) {
+    _statsCollectorInputList = statsCollectorInputList;
+    _statsCollectionInterval = statsCollectionIntervalInMilliSeconds;
+
+    _executorService = Executors.newSingleThreadExecutor();
+  }
+
+  public void start() {
+    _executorService.submit(collectStatistics());
+  }
+
+  /**
+   * Shuts down statistics collector.
+   * 
+   * @param shutdownTimeout Time in milli-seconds to wait for shutdown before
+   *        killing the collection process.
+   */
+  public void shutDown(int shutdownTimeout) throws InterruptedException {
+    _isRunning = false;
+
+    _executorService.shutdownNow();
+    // Wait for collectStatistics runnable to finish so that disposal of
+    // statistics does not cause any exceptions to be thrown.
+    _executorService.awaitTermination(shutdownTimeout, TimeUnit.MILLISECONDS);
+  }
+
+  private Runnable collectStatistics() {
+    return new Runnable() {
+
+      @Override
+      public void run() {
+        while (_isRunning) {
+          try {
+            if(Thread.currentThread().isInterrupted()) {
+              break;
+            }  
+            for(StatsCollectorInput statsCollectorInput :
+                _statsCollectorInputList) {
+              Statistics statistics = statsCollectorInput.getStatistics();
+              StatisticsCollectorCallback statsCallback =
+                  statsCollectorInput.getCallback();
+              
+                // 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();
+            break;
+          }
+          catch (Exception e) {
+            throw new RuntimeException("Error while calculating statistics", e);
+          }
+        }
+      }
+    };
+  }
+}