Enforce monotonicity for IncrementableMetrics

This change enforces that IncrementableMetrics should only monotonically
increase in value, and adds a new increment() method to increment by one, which is slightly faster than incrementBy (due to a lack of non-negative checking) in the common case that the counter should only be incremented by one.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=130578421

java/google/registry/monitoring/metrics/Counter.java

@@ -49,17 +49,25 @@ public final class Counter extends AbstractMetric<Long>
   }
 
   @VisibleForTesting
-  void incrementBy(Number offset, ImmutableList<String> labelValues) {
-    values.addAndGet(labelValues, offset.longValue());
+  void incrementBy(long offset, ImmutableList<String> labelValues) {
+    values.addAndGet(labelValues, offset);
   }
 
   @Override
   public final void incrementBy(long offset, String... labelValues) {
     checkArgument(labelValues.length == this.getMetricSchema().labels().size(), LABEL_COUNT_ERROR);
+    checkArgument(offset >= 0, "The offset provided must be non-negative");
 
     incrementBy(offset, ImmutableList.copyOf(labelValues));
   }
 
+  @Override
+  public final void increment(String... labelValues) {
+    checkArgument(labelValues.length == this.getMetricSchema().labels().size(), LABEL_COUNT_ERROR);
+
+    incrementBy(1L, ImmutableList.copyOf(labelValues));
+  }
+
   /**
    * Returns a snapshot of the metric's values. The timestamp of each {@link MetricPoint} will be
    * the last modification time for that tuple of label values.

java/google/registry/monitoring/metrics/IncrementableMetric.java

@@ -17,19 +17,35 @@ package google.registry.monitoring.metrics;
 /**
  * A {@link Metric} which can be incremented.
  *
- * <p>This is a view into a {@link Counter} to provide compile-time checking to disallow re-setting
- * the metric, which is useful for metrics which should be monotonic.
+ * <p>This is a view into a {@link Counter} to provide compile-time checking to disallow arbitrarily
+ * setting the metric, which is useful for metrics which should be monotonically increasing.
  */
 public interface IncrementableMetric extends Metric<Long> {
 
   /**
-   * Increments a metric for a given set of label values.
+   * Increments a metric by 1 for the given set of label values.
    *
-   * <p>If the metric is undefined for given label values, it will first be set to zero.
+   * Use this method rather than {@link IncrementableMetric#incrementBy(long, String...)} if the
+   * increment value is zero, as it will be slightly more performant.
+   *
+   * <p>If the metric is undefined for given label values, it will be incremented from zero.
    *
    * <p>The metric's timestamp will be updated to the current time for the given label values.
    *
    * <p>The count of {@code labelValues} must be equal to the underlying metric's count of labels.
    */
+  void increment(String... labelValues);
+
+  /**
+   * Increments a metric by the given non-negative offset for the given set of label values.
+   *
+   * <p>If the metric is undefined for given label values, it will be incremented from zero.
+   *
+   * <p>The metric's timestamp will be updated to the current time for the given label values.
+   *
+   * <p>The count of {@code labelValues} must be equal to the underlying metric's count of labels.
+   *
+   * @throws IllegalArgumentException if the offset is negative.
+   */
   void incrementBy(long offset, String... labelValues);
 }

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

@@ -104,7 +104,7 @@ public class MetricReporter extends AbstractScheduledService {
     for (Metric<?> metric : metricRegistry.getRegisteredMetrics()) {
       points.addAll(metric.getTimestampedValues());
       logger.fine(String.format("Enqueued metric %s", metric));
-      MetricMetrics.pushedPoints.incrementBy(1,
+      MetricMetrics.pushedPoints.increment(
           metric.getMetricSchema().kind().name(), metric.getValueClass().toString());
     }
 
@@ -112,7 +112,7 @@ public class MetricReporter extends AbstractScheduledService {
       logger.severe("writeQueue full, dropped a reporting interval of points");
     }
 
-    MetricMetrics.pushIntervals.incrementBy(1);
+    MetricMetrics.pushIntervals.increment();
   }
 
   @Override

java/google/registry/monitoring/metrics/StackdriverWriter.java

@@ -195,7 +195,7 @@ public class StackdriverWriter implements MetricWriter {
     monitoringClient.projects().timeSeries().create(projectResource, request).execute();
 
     for (TimeSeries timeSeries : timeSeriesList) {
-      pushedPoints.incrementBy(1, timeSeries.getMetricKind(), timeSeries.getValueType());
+      pushedPoints.increment(timeSeries.getMetricKind(), timeSeries.getValueType());
     }
     logger.info(String.format("Flushed %d metrics to Stackdriver", timeSeriesList.size()));
   }