Add stats collector

java/org/rocksdb/StatisticsCollector.java

@@ -0,0 +1,86 @@
+// 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;
+      
+  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);
+          }
+        }
+      }
+    };
+  }
+}

java/org/rocksdb/StatisticsCollectorCallback.java

@@ -0,0 +1,27 @@
+// 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;
+
+/**
+ * Callback interface provided to StatisticsCollector.
+ * @param tickerType
+ * @param tickerCount
+*/
+public interface StatisticsCollectorCallback {
+  /**
+   * Callback function to get ticker values.
+   * @param tickerType Ticker type.
+   * @param tickerCount Value of ticker type.
+  */
+  void tickerCallback(TickerType tickerType, long tickerCount);
+  
+  /**
+   * Callback function to get histogram values.
+   * @param histType Histogram type.
+   * @param histData Histogram data.
+  */
+  void histogramCallback(HistogramType histType, HistogramData histData);
+}

java/org/rocksdb/test/StatisticsCollectorTest.java

@@ -0,0 +1,39 @@
+// 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.test;
+
+import org.rocksdb.*;
+
+public class StatisticsCollectorTest {
+  static final String db_path = "/tmp/backupablejni_db";
+  static {
+    RocksDB.loadLibrary();
+  }
+  
+  public static void main(String[] args) throws InterruptedException, RocksDBException {
+    Options opt = new Options().createStatistics().setCreateIfMissing(true);
+    Statistics stats = opt.statisticsPtr();
+    
+    RocksDB db = RocksDB.open(db_path);
+   
+    StatsCallbackMock callback = new StatsCallbackMock();
+    StatisticsCollector statsCollector = new StatisticsCollector(stats, 100,  
+        callback);
+    statsCollector.start();
+    
+    Thread.sleep(1000);
+    
+    assert(callback.tickerCallbackCount > 0);
+    assert(callback.histCallbackCount > 0);
+    
+    statsCollector.shutDown();
+    
+    db.close();
+    opt.dispose();
+    
+    System.out.println("Stats collector test passed.!");
+  }
+}

java/org/rocksdb/test/StatsCallbackMock.java

@@ -0,0 +1,22 @@
+// 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.test;
+
+import org.rocksdb.*;
+
+public class StatsCallbackMock implements StatisticsCollectorCallback {
+  public int tickerCallbackCount = 0;
+  public int histCallbackCount = 0;
+        
+  public void tickerCallback(TickerType tickerType, long tickerCount) {
+    tickerCallbackCount++;
+  }
+    
+  public void histogramCallback(HistogramType histType,
+      HistogramData histData) {
+    histCallbackCount++;
+  }
+}