Add StackDriver implementation, in monitoring/metrics package

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=130287319

java/google/registry/monitoring/metrics/MetricReporter.java

@@ -0,0 +1,114 @@
+// Copyright 2016 The Domain Registry Authors. All Rights Reserved.
+//
+// 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 google.registry.monitoring.metrics;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Optional;
+import com.google.common.collect.ImmutableList;
+import com.google.common.util.concurrent.AbstractScheduledService;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.logging.Logger;
+
+/**
+ * Engine to write metrics to a {@link MetricWriter} on a regular periodic basis.
+ *
+ * <p>In the Producer/Consumer pattern, this class is the Producer and {@link MetricExporter} is the
+ * consumer.
+ */
+public class MetricReporter extends AbstractScheduledService {
+
+  private static final Logger logger = Logger.getLogger(MetricReporter.class.getName());
+
+  private final long writeInterval;
+  private final MetricRegistry metricRegistry;
+  private final BlockingQueue<Optional<ImmutableList<MetricPoint<?>>>> writeQueue;
+  private final MetricExporter metricExporter;
+
+  /**
+   * Returns a new MetricReporter.
+   *
+   * @param metricWriter {@link MetricWriter} implementation to write metrics to.
+   * @param writeInterval time period between metric writes, in seconds.
+   */
+  public MetricReporter(MetricWriter metricWriter, long writeInterval) {
+    this(
+        metricWriter,
+        writeInterval,
+        MetricRegistryImpl.getDefault(),
+        new ArrayBlockingQueue<Optional<ImmutableList<MetricPoint<?>>>>(1000));
+  }
+
+  @VisibleForTesting
+  MetricReporter(
+      MetricWriter metricWriter,
+      long writeInterval,
+      MetricRegistry metricRegistry,
+      BlockingQueue<Optional<ImmutableList<MetricPoint<?>>>> writeQueue) {
+    checkArgument(writeInterval > 0, "writeInterval must be greater than zero");
+
+    this.writeInterval = writeInterval;
+    this.metricRegistry = metricRegistry;
+    this.writeQueue = writeQueue;
+    this.metricExporter = new MetricExporter(writeQueue, metricWriter);
+  }
+
+  @Override
+  protected void runOneIteration() {
+    logger.info("Running background metric push");
+    ImmutableList.Builder<MetricPoint<?>> points = new ImmutableList.Builder<>();
+
+    /*
+    TODO(shikhman): Right now timestamps are recorded for each datapoint, which may use more storage
+    on the backend than if one timestamp were recorded for a batch. This should be configurable.
+     */
+    for (Metric<?> metric : metricRegistry.getRegisteredMetrics()) {
+      points.addAll(metric.getTimestampedValues());
+      logger.fine(String.format("Enqueued metric %s", metric));
+      MetricMetrics.pushedPoints.incrementBy(
+          1, metric.getMetricSchema().kind().name(), metric.getValueClass().toString());
+    }
+
+    if (!writeQueue.offer(Optional.of(points.build()))) {
+      logger.warning("writeQueue full, dropped a reporting interval of points");
+    }
+
+    MetricMetrics.pushIntervals.incrementBy(1);
+  }
+
+  @Override
+  protected void shutDown() {
+    // Make sure to run one iteration on shutdown so that short-lived programs still report at
+    // least once.
+    runOneIteration();
+
+    writeQueue.offer(Optional.<ImmutableList<MetricPoint<?>>>absent());
+    metricExporter.stopAsync().awaitTerminated();
+  }
+
+  @Override
+  protected void startUp() {
+    metricExporter.startAsync().awaitRunning();
+  }
+
+  @Override
+  protected Scheduler scheduler() {
+    // Start writing after waiting for one writeInterval.
+    return Scheduler.newFixedDelaySchedule(writeInterval, writeInterval, TimeUnit.SECONDS);
+  }
+}