ratpack.dropwizard.metrics.MetricsPrometheusHandler.java Source code

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Here is the source code for ratpack.dropwizard.metrics.MetricsPrometheusHandler.java

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/*
 * Copyright 2017 the original author or authors.
 *
 * 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 ratpack.dropwizard.metrics;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.buffer.ByteBufOutputStream;
import io.prometheus.client.CollectorRegistry;
import io.prometheus.client.exporter.common.TextFormat;
import ratpack.handling.Context;
import ratpack.handling.Handler;

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;

/**
 * A Handler that exposes metric reports in Prometheus format.
 * <p>
 * This handler should be bound to an application path, and most likely only for the GET method
 * <pre class="java-chain-dsl">
 * import ratpack.dropwizard.metrics.MetricsPrometheusHandler;
 * import static org.junit.Assert.*;
 *
 * assertTrue(chain instanceof ratpack.handling.Chain);
 * chain.get("admin/metrics", new MetricsPrometheusHandler());
 * </pre>
 *
 * @since 1.6
 */
public class MetricsPrometheusHandler implements Handler {

    @Override
    public void handle(Context ctx) throws Exception {
        final ByteBufAllocator byteBufAllocator = ctx.get(ByteBufAllocator.class);

        ByteBuf buf = byteBufAllocator.ioBuffer();
        try (Writer w = new OutputStreamWriter(new ByteBufOutputStream(buf))) {
            TextFormat.write004(w, ctx.get(CollectorRegistry.class).metricFamilySamples());

        } catch (IOException e) {
            buf.release();
            throw e;
        }
        ctx.getResponse().contentType(TextFormat.CONTENT_TYPE_004).status(200).send(buf);
    }
}