Add TimerContext to wrap timer metrics

TimerContext wraps the context used in Timer{0|1|2|3} and allows to
get the start time and elapsed time.

Update the replication plugin to use it.

Change-Id: I194b9a7bd6a00bc2841ac37ca8654f0b4a2dda00

gerrit-server/src/main/java/com/google/gerrit/metrics/Timer0.java

@@ -31,22 +31,22 @@ import java.util.concurrent.TimeUnit;
  * </pre>
  */
 public abstract class Timer0 implements RegistrationHandle {
-  public class Context implements AutoCloseable {
-    private final long startNanos;
+  public static class Context extends TimerContext {
+    private final Timer0 timer;
 
-    Context() {
-      this.startNanos = System.nanoTime();
+    Context(Timer0 timer) {
+      this.timer = timer;
     }
 
     @Override
-    public void close() {
-      record(System.nanoTime() - startNanos, NANOSECONDS);
+    public void record(long elapsed) {
+      timer.record(elapsed, NANOSECONDS);
     }
   }
 
   /** Begin a timer for the current block, value will be recorded when closed. */
   public Context start() {
-    return new Context();
+    return new Context(this);
   }
 
   /** Record a value in the distribution. */

gerrit-server/src/main/java/com/google/gerrit/metrics/Timer1.java

@@ -33,21 +33,19 @@ import java.util.concurrent.TimeUnit;
  * @param <F1> type of the field.
  */
 public abstract class Timer1<F1> implements RegistrationHandle {
-  public static class Context implements AutoCloseable {
+  public static class Context extends TimerContext {
     private final Timer1<Object> timer;
     private final Object field1;
-    private final long startNanos;
 
     @SuppressWarnings("unchecked")
     <F1> Context(Timer1<F1> timer, F1 field1) {
       this.timer = (Timer1<Object>) timer;
       this.field1 = field1;
-      this.startNanos = System.nanoTime();
     }
 
     @Override
-    public void close() {
-      timer.record(field1, System.nanoTime() - startNanos, NANOSECONDS);
+    public void record(long elapsed) {
+      timer.record(field1, elapsed, NANOSECONDS);
     }
   }
 

gerrit-server/src/main/java/com/google/gerrit/metrics/Timer2.java

@@ -34,23 +34,21 @@ import java.util.concurrent.TimeUnit;
  * @param <F2> type of the field.
  */
 public abstract class Timer2<F1, F2> implements RegistrationHandle {
-  public static class Context implements AutoCloseable {
+  public static class Context extends TimerContext {
     private final Timer2<Object, Object> timer;
     private final Object field1;
     private final Object field2;
-    private final long startNanos;
 
     @SuppressWarnings("unchecked")
     <F1, F2> Context(Timer2<F1, F2> timer, F1 field1, F2 field2) {
       this.timer = (Timer2<Object, Object>) timer;
       this.field1 = field1;
       this.field2 = field2;
-      this.startNanos = System.nanoTime();
     }
 
     @Override
-    public void close() {
-      timer.record(field1, field2, System.nanoTime() - startNanos, NANOSECONDS);
+    public void record(long elapsed) {
+      timer.record(field1, field2, elapsed, NANOSECONDS);
     }
   }
 

gerrit-server/src/main/java/com/google/gerrit/metrics/Timer3.java

@@ -35,12 +35,11 @@ import java.util.concurrent.TimeUnit;
  * @param <F3> type of the field.
  */
 public abstract class Timer3<F1, F2, F3> implements RegistrationHandle {
-  public static class Context implements AutoCloseable {
+  public static class Context extends TimerContext {
     private final Timer3<Object, Object, Object> timer;
     private final Object field1;
     private final Object field2;
     private final Object field3;
-    private final long startNanos;
 
     @SuppressWarnings("unchecked")
     <F1, F2, F3> Context(Timer3<F1, F2, F3> timer, F1 f1, F2 f2, F3 f3) {
@@ -48,13 +47,11 @@ public abstract class Timer3<F1, F2, F3> implements RegistrationHandle {
       this.field1 = f1;
       this.field2 = f2;
       this.field3 = f3;
-      this.startNanos = System.nanoTime();
     }
 
     @Override
-    public void close() {
-      timer.record(field1, field2, field3,
-          System.nanoTime() - startNanos, NANOSECONDS);
+    public void record(long elapsed) {
+      timer.record(field1, field2, field3, elapsed, NANOSECONDS);
     }
   }
 

gerrit-server/src/main/java/com/google/gerrit/metrics/TimerContext.java

@@ -0,0 +1,59 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// 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 com.google.gerrit.metrics;
+
+abstract class TimerContext implements AutoCloseable {
+  private final long startNanos;
+  private boolean stopped;
+
+  TimerContext() {
+    this.startNanos = System.nanoTime();
+  }
+
+  /**
+   * Record the elapsed time to the timer.
+   *
+   * @param elapsed Elapsed time in nanoseconds.
+   */
+  public abstract void record(long elapsed);
+
+  /** Get the start time in system time nanoseconds. */
+  public long getStartTime() {
+    return startNanos;
+  }
+
+  /**
+   * Stop the timer and record the elapsed time.
+   *
+   * @return the elapsed time in nanoseconds.
+   * @throws IllegalStateException if the timer is already stopped.
+   */
+  public long stop() {
+    if (!stopped) {
+      stopped = true;
+      long elapsed = System.nanoTime() - startNanos;
+      record(elapsed);
+      return elapsed;
+    }
+    throw new IllegalStateException("Already stopped");
+  }
+
+  @Override
+  public void close() {
+    if (!stopped) {
+      stop();
+    }
+  }
+}

plugins/replication

@@ -1 +1 @@
-Subproject commit 168032cb1efadb83db5da4fd0060c94c9e05ccfa
+Subproject commit 4ab29b755a147a69d88bf000e276a7a2eaa6403b