com.github.rollingmetrics.dropwizard.adapter.TopMetricSet Maven / Gradle / Ivy

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/*
 *    Copyright 2017 Vladimir Bukhtoyarov
 *
 *      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.github.rollingmetrics.dropwizard.adapter;

import com.codahale.metrics.Gauge;
import com.codahale.metrics.Metric;
import com.codahale.metrics.MetricSet;
import com.github.rollingmetrics.top.Position;
import com.github.rollingmetrics.top.Top;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.TimeUnit;

/**
 * The adapter to use {@link Top} with {@link com.codahale.metrics.MetricRegistry}.
 * 
 * 
Sample Usage:
 * 
 {@code
 *
 *  Top top = Top.builder(3).resetAllPositionsOnSnapshot().build();
 *  MetricSet metricSet = new TopMetricSet("my-top", top, TimeUnit.MILLISECONDS, 5);
 *  registry.registerAll(metricSet);
 * }
 * The code above creates 7 gauges with following names:
 * 
 *   my-top.latencyUnit
 *   my-top.0.latency
 *   my-top.0.description
 *   my-top.1.latency
 *   my-top.1.description
 *   my-top.2.latency
 *   my-top.2.description
 * 
 * The "latency" gauges have {@link BigDecimal} type, the "latencyUnit" and "description" gauges have {@link String} type.
 * The number in the gauge name represents position in the top in descending order, the "0" is the slowest query.
 *
 */
class TopMetricSet implements MetricSet {

    private final BigDecimal zero;
    private final Map gauges;

    /**
     * Creates new collection of gauges which compatible with {@link com.codahale.metrics.MetricRegistry}.
     *
     * @param name the name prefix for each gauge
     * @param top the target {@link Top}
     * @param latencyUnit the time unit to convert latency
     * @param digitsAfterDecimalPoint the number of digits after decimal point
     */
    TopMetricSet(String name, Top top, TimeUnit latencyUnit, int digitsAfterDecimalPoint) {
        if (name == null) {
            throw new IllegalArgumentException("name should not be null");
        }
        if (name.isEmpty()) {
            throw new IllegalArgumentException("name should not be empty");
        }
        if (top == null) {
            throw new IllegalArgumentException("top should not be null");
        }
        if (latencyUnit == null) {
            throw new IllegalArgumentException("latencyUnit should not be null");
        }
        if (digitsAfterDecimalPoint < 0) {
            throw new IllegalArgumentException("digitsAfterDecimalPoint should not be negative");
        }

        gauges = new HashMap<>();
        gauges.put(name + ".latencyUnit", (Gauge) latencyUnit::toString);

        zero = BigDecimal.ZERO.setScale(digitsAfterDecimalPoint, RoundingMode.CEILING);

        int size = top.getSize();
        for (int i = 0; i < size; i++) {
            String latencyName = name + "." + i + "." + "latency";
            Gauge latencyGauge = createLatencyGauge(i, top, latencyUnit, digitsAfterDecimalPoint);
            gauges.put(latencyName, latencyGauge);

            String descriptionName = name + "." + i + "." + "description";
            Gauge descriptionGauge = createDescriptionGauge(i, top);
            gauges.put(descriptionName, descriptionGauge);
        }
    }

    @Override
    public Map getMetrics() {
        return gauges;
    }

    private Gauge createLatencyGauge(int i, Top top, TimeUnit latencyUnit, int digitsAfterDecimalPoint) {
        return () -> {
            List positions = top.getPositionsInDescendingOrder();
            if (positions.size() <= i) {
                return zero;
            }
            double latencyNanos = positions.get(i).getLatencyInNanoseconds();
            long scale = latencyUnit.toNanos(1);
            double result = latencyNanos/scale;

            return new BigDecimal(result).setScale(digitsAfterDecimalPoint, RoundingMode.CEILING);
        };
    }

    private Gauge createDescriptionGauge(int i, Top top) {
        return () -> {
            List positions = top.getPositionsInDescendingOrder();
            if (positions.size() <= i) {
                return "";
            }
            return positions.get(i).getQueryDescription();
        };
    }

}