com.google.gerrit.metrics.dropwizard.BucketedCallback.java Source code

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Here is the source code for com.google.gerrit.metrics.dropwizard.BucketedCallback.java

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// 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.dropwizard;

import com.codahale.metrics.Gauge;
import com.codahale.metrics.Metric;
import com.codahale.metrics.MetricRegistry;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Maps;
import com.google.gerrit.metrics.Description;
import com.google.gerrit.metrics.Field;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/** Abstract callback metric broken down into buckets. */
abstract class BucketedCallback<V> implements BucketedMetric {
    private final DropWizardMetricMaker metrics;
    private final MetricRegistry registry;
    private final String name;
    private final Description.FieldOrdering ordering;
    protected final Field<?>[] fields;
    private final V zero;
    private final Map<Object, ValueGauge> cells;
    protected volatile Runnable trigger;
    private final Object lock = new Object();

    BucketedCallback(DropWizardMetricMaker metrics, MetricRegistry registry, String name, Class<V> valueType,
            Description desc, Field<?>... fields) {
        this.metrics = metrics;
        this.registry = registry;
        this.name = name;
        this.ordering = desc.getFieldOrdering();
        this.fields = fields;
        this.zero = CallbackMetricImpl0.zeroFor(valueType);
        this.cells = new ConcurrentHashMap<>();
    }

    void doRemove() {
        for (Object key : cells.keySet()) {
            registry.remove(submetric(key));
        }
        metrics.remove(name);
    }

    void doBeginSet() {
        for (ValueGauge g : cells.values()) {
            g.set = false;
        }
    }

    void doPrune() {
        Iterator<Map.Entry<Object, ValueGauge>> i = cells.entrySet().iterator();
        while (i.hasNext()) {
            if (!i.next().getValue().set) {
                i.remove();
            }
        }
    }

    void doEndSet() {
        for (ValueGauge g : cells.values()) {
            if (!g.set) {
                g.value = zero;
            }
        }
    }

    ValueGauge getOrCreate(Object f1, Object f2) {
        return getOrCreate(ImmutableList.of(f1, f2));
    }

    ValueGauge getOrCreate(Object f1, Object f2, Object f3) {
        return getOrCreate(ImmutableList.of(f1, f2, f3));
    }

    ValueGauge getOrCreate(Object key) {
        ValueGauge c = cells.get(key);
        if (c != null) {
            return c;
        }

        synchronized (lock) {
            c = cells.get(key);
            if (c == null) {
                c = new ValueGauge();
                registry.register(submetric(key), c);
                cells.put(key, c);
            }
            return c;
        }
    }

    private String submetric(Object key) {
        return DropWizardMetricMaker.name(ordering, name, name(key));
    }

    abstract String name(Object key);

    @Override
    public Metric getTotal() {
        return null;
    }

    @Override
    public Field<?>[] getFields() {
        return fields;
    }

    @Override
    public Map<Object, Metric> getCells() {
        return Maps.transformValues(cells, in -> (Metric) in);
    }

    final class ValueGauge implements Gauge<V> {
        volatile V value = zero;
        boolean set;

        @Override
        public V getValue() {
            Runnable t = trigger;
            if (t != null) {
                t.run();
            }
            return value;
        }
    }
}