Add metrics for async batch operation processing

We want to know how long it's actually taking to process asynchronous
contact/host deletions and DNS refreshes on host renames. This adds
instrumentation. Five metrics are recorded as follows:

* An incrementable metric for each async task processed (split out by
  type of task and result).
* Two event metrics for processing time between when a task is enqueued
  and when it is processed -- tracked separately for contact/host
  deletion and DNS refresh on host rename.
* Two event metrics for batch size every time the two mapreduces are
  run (this is usually 0). Tracked separately for contact/host deletion
  and DNS refresh on host rename.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=157001310

javatests/google/registry/flows/async/AsyncFlowMetricsTest.java

@@ -0,0 +1,70 @@
+// Copyright 2017 The Nomulus 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.flows.async;
+
+import static google.registry.flows.async.AsyncFlowMetrics.OperationResult.SUCCESS;
+import static google.registry.flows.async.AsyncFlowMetrics.OperationType.CONTACT_AND_HOST_DELETE;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+
+import google.registry.monitoring.metrics.EventMetric;
+import google.registry.monitoring.metrics.IncrementableMetric;
+import google.registry.testing.FakeClock;
+import google.registry.testing.InjectRule;
+import google.registry.testing.ShardableTestCase;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link AsyncFlowMetrics}. */
+@RunWith(JUnit4.class)
+public class AsyncFlowMetricsTest extends ShardableTestCase {
+
+  @Rule public final InjectRule inject = new InjectRule();
+
+  private final IncrementableMetric asyncFlowOperationCounts = mock(IncrementableMetric.class);
+  private final EventMetric asyncFlowOperationProcessingTime = mock(EventMetric.class);
+  private final EventMetric asyncFlowBatchSize = mock(EventMetric.class);
+  private AsyncFlowMetrics asyncFlowMetrics;
+  private FakeClock clock;
+
+  @Before
+  public void setUp() {
+    clock = new FakeClock();
+    asyncFlowMetrics = new AsyncFlowMetrics(clock);
+    inject.setStaticField(
+        AsyncFlowMetrics.class, "asyncFlowOperationCounts", asyncFlowOperationCounts);
+    inject.setStaticField(
+        AsyncFlowMetrics.class,
+        "asyncFlowOperationProcessingTime",
+        asyncFlowOperationProcessingTime);
+    inject.setStaticField(AsyncFlowMetrics.class, "asyncFlowBatchSize", asyncFlowBatchSize);
+  }
+
+  @Test
+  public void testRecordAsyncFlowResult_calculatesDurationMillisCorrectly() {
+    asyncFlowMetrics.recordAsyncFlowResult(
+        CONTACT_AND_HOST_DELETE,
+        SUCCESS,
+        clock.nowUtc().minusMinutes(10).minusSeconds(5).minusMillis(566));
+    verify(asyncFlowOperationCounts).increment("contactAndHostDelete", "success");
+    verify(asyncFlowOperationProcessingTime).record(605566.0, "contactAndHostDelete", "success");
+    verifyNoMoreInteractions(asyncFlowOperationCounts);
+    verifyNoMoreInteractions(asyncFlowOperationProcessingTime);
+  }
+}