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/*
* 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.opentable.metrics;
import java.util.Arrays;
import java.util.EventObject;
import java.util.Map;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.Supplier;
import com.codahale.metrics.Counter;
import com.codahale.metrics.ExponentiallyDecayingReservoir;
import com.codahale.metrics.Histogram;
import com.codahale.metrics.Meter;
import com.codahale.metrics.Metric;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.MetricSet;
import com.codahale.metrics.Reservoir;
import com.codahale.metrics.Timer;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
/**
* Builder style class for constructing {@link MetricSet}s that integrate
* with other platform components, such as Spring.
*
* Intended to be used standalone or as a prototype scope injected bean.
* In order to register by event, the built MetricSet must itself be registered
* as a bean in the Spring context.
*/
public class MetricSetBuilder {
private final ImmutableMap.Builder mapBuilder = ImmutableMap.builder();
private MetricRegistry registry;
private Class eventClass;
private String metricPrefix = "";
private MetricSet built;
/**
* Create a Metric Set Builder
*/
public MetricSetBuilder() { }
/**
* Create a Metric Set Builder
* @param registry the registry to register metrics on
*/
public MetricSetBuilder(MetricRegistry registry) {
this.registry = registry;
}
/**
* Set the metric registry. If set, the metric set will be registered on this metric set when built,
* or if an eventClassSet class is set once the event is fired
* @param registry the registry to register metrics on
* @return this
*/
public synchronized MetricSetBuilder setRegistry(MetricRegistry registry) {
this.registry = registry;
return this;
}
/**
* Delays Metric registration until the given event type fires in the Spring
* application context that created this builder.
*
*
* Automatic registration is implemented in the {@link DefaultMetricsConfiguration}, and thus requires
* instances of this class be acquired via injection from that configuration class.
*
* @param eventClass the event type to await
* @return this
*/
public MetricSetBuilder registerOnEvent(Class eventClass) {
this.eventClass = eventClass;
return this;
}
/**
* Set a metric prefix to prepend to all metrics created once the prefix is set
*
* @param metricPrefix a prefix to prepend to name for metrics created from this call forward;
* defaults to {@code ""} if this isn't called
* @return this
*/
public MetricSetBuilder setPrefix(String metricPrefix) {
Preconditions.checkArgument(!metricPrefix.endsWith("."),
String.format("prefix '%s' ends with '.'", metricPrefix));
if (!metricPrefix.isEmpty()) {
metricPrefix += ".";
}
this.metricPrefix = metricPrefix;
return this;
}
/**
* Create a counter
* @param name the name of the counter to create
* @return a new counter
*/
public Counter counter(String name) {
return create(name, Counter::new);
}
/**
* Create a meter
* @param name the name of the meter to create
* @return a new meter
*/
public Meter meter(String name) {
return create(name, Meter::new);
}
/**
* Create a timer
* @param name the name of the timer to create
* @return a new timer
*/
public Timer timer(String name) {
return create(name, Timer::new);
}
/**
* Create a long gauge
* @param name the name of the gauge to create
* @return a new {@link AtomicLongGauge}
*/
public AtomicLong longGauge(String name) {
return create(name, AtomicLongGauge::new);
}
/**
* Create a histogram using an {@link ExponentiallyDecayingReservoir}
* @param name the name of the histogram to create
* @return a new histogram
*/
public Histogram histogram(String name) {
return histogram(name, new ExponentiallyDecayingReservoir());
}
/**
* Create a histogram using with a specific reservoir
* @param name the name of the histogram to create
* @param reservoir the reservoir to use for collecting histogram data
* @return a new histogram
*/
public Histogram histogram(String name, Reservoir reservoir) {
return create(name, () -> new Histogram(reservoir));
}
/**
* Create a metric for every value of the gives enum.
* For each enum value a metric will be created with the name of (given name).(enum name).
* The metric will be created by the provided factory.
*
* @param name the base name for created metrics
* @param enumClass the enum type to key by
* @param factory a factory to create metrics
* @return a map of enum values to metrics
*/
public , M extends Metric> Map enumMetrics(String name, Class enumClass, Supplier factory) {
ImmutableMap.Builder builder = ImmutableMap.builder();
Arrays.stream(enumClass.getEnumConstants()).forEach(e ->
builder.put(e, create(name + "." + e, factory)));
return builder.build();
}
/**
* Create a metric
* @param name the name of the metric to create
* @param factory the factory for instances
* @return the created metric
*/
public T create(String name, Supplier factory) {
final T result = factory.get();
// NB: metricPrefix, if nonempty, will end with '.'.
mapBuilder.put(metricPrefix + name, result);
return result;
}
/**
* Produce the metric set; if registry is set, register its metrics
* either immediately or on the configured event trigger.
* @return the resulting metric set
*/
public synchronized MetricSet build() {
if (built != null) {
return built;
}
final BuiltMetricSet result = new BuiltMetricSet(this);
if (registry != null && eventClass == null) {
registry.registerAll(result);
// Otherwise, if there's still an event class, the machinery in DefaultMetricsConfiguration will
// govern registration and removal.
}
return built = result;
}
/**
* A Metric Set built by the Metric Set Builder
*/
public static class BuiltMetricSet implements MetricSet {
private final ImmutableMap map;
private final Class eventClass;
/**
* Create a built metric set
* @param builder the metric set builder
*/
BuiltMetricSet(MetricSetBuilder builder) {
map = builder.mapBuilder.build();
eventClass = builder.eventClass;
}
@Override
public Map getMetrics() {
return map;
}
/**
* Get the class of event that triggers the registration of this metric
* @return the event class
*/
public Class getEventClass() {
return eventClass;
}
@Override
public String toString() {
return "BuiltMetricSet" + getMetrics().keySet();
}
}
}