google-nomulus/java/google/registry/monitoring/metrics/VirtualMetric.java
shikhman 91f8b6da38 Change to metrics to keep track of when the metric value was first set
This CL also adds IncrementableMetric#reset() methods to allow resetting the
value and start timestamp of IncrementableMetrics.

This is necessary because some backends, like Stackdriver, use non-monotonic
changes in cumulative metric values to detect timeseries restarts. Tracking and
re-setting the start timestamp allows users to track mostly monotonic metrics
which may have non-monotonic discontinuities.

See https://cloud.google.com/monitoring/api/ref_v3/rest/v3/TimeSeries#Point for
more details.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=130795229
2016-08-22 14:44:28 -04:00

91 lines
3.2 KiB
Java

// 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 com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Supplier;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import google.registry.monitoring.metrics.MetricSchema.Kind;
import java.util.Map.Entry;
import javax.annotation.concurrent.ThreadSafe;
import org.joda.time.Instant;
/**
* A metric whose value is computed at sample-time.
*
* <p>This pattern works well for gauge-like metrics, such as CPU usage, memory usage, and file
* descriptor counts.
*
* <p>The {@link MetricPoint#interval()} of values of instances of this metric will always have a
* start time equal to the end time, since the metric value represents a point-in-time snapshot with
* no relationship to prior values.
*/
@ThreadSafe
public final class VirtualMetric<V> extends AbstractMetric<V> {
private final Supplier<ImmutableMap<ImmutableList<String>, V>> valuesSupplier;
/**
* Local cache of the count of values so that we don't have to evaluate the callback function to
* get the metric's cardinality.
*/
private volatile int cardinality;
VirtualMetric(
String name,
String description,
String valueDisplayName,
ImmutableSet<LabelDescriptor> labels,
Supplier<ImmutableMap<ImmutableList<String>, V>> valuesSupplier,
Class<V> valueClass) {
super(name, description, valueDisplayName, Kind.GAUGE, labels, valueClass);
this.valuesSupplier = valuesSupplier;
}
/**
* Returns a snapshot of the metric's values. This will evaluate the stored callback function. The
* timestamp for each MetricPoint will be the current time.
*/
@Override
public ImmutableList<MetricPoint<V>> getTimestampedValues() {
return getTimestampedValues(Instant.now());
}
/**
* Returns the cached value of the cardinality of this metric. The cardinality is computed when
* the metric is evaluated. If the metric has never been evaluated, the cardinality is zero.
*/
@Override
public int getCardinality() {
return cardinality;
}
@VisibleForTesting
ImmutableList<MetricPoint<V>> getTimestampedValues(Instant timestamp) {
ImmutableMap<ImmutableList<String>, V> values = valuesSupplier.get();
ImmutableList.Builder<MetricPoint<V>> metricPoints = ImmutableList.builder();
for (Entry<ImmutableList<String>, V> entry : values.entrySet()) {
metricPoints.add(
MetricPoint.create(this, entry.getKey(), timestamp, timestamp, entry.getValue()));
}
cardinality = values.size();
return metricPoints.build();
}
}