content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.metrics.sink;
  
  import com.codahale.metrics.MetricRegistry;
  import io.prometheus.client.CollectorRegistry;
  import io.prometheus.client.dropwizard.DropwizardExports;
  import io.prometheus.client.exporter.MetricsServlet;
  import org.eclipse.jetty.servlet.ServletContextHandler;
  import org.eclipse.jetty.servlet.ServletHolder;
  
  import java.util.Properties;
  import javax.annotation.concurrent.NotThreadSafe;
  
  /**
   * A sink that exposes metrics data in prometheus format by HTTP.
   * See https://github.com/prometheus/client_java/issues/101
   */
  @NotThreadSafe
  public class PrometheusMetricsServlet implements Sink {
  
    private static final String SERVLET_PATH = "/metrics/prometheus";
  
    private CollectorRegistry mCollectorRegistry;
  
    /**
     * Creates a new {@link alluxio.metrics.sink.PrometheusMetricsServlet} with a
     * {@link MetricRegistry}.
     *
     * @param registry the metric registry to register
     */
    public PrometheusMetricsServlet(MetricRegistry registry) {
      mCollectorRegistry = CollectorRegistry.defaultRegistry;
      mCollectorRegistry.register(new DropwizardExports(registry));
    }
  
    /**
     * Creates a new {@link alluxio.metrics.sink.PrometheusMetricsServlet} with a
     * {@link MetricRegistry}.
     *
     * @param properties the properties, not used for now
     * @param registry the metric registry to register
     */
    public PrometheusMetricsServlet(Properties properties, MetricRegistry registry) {
      this(registry);
    }
  
    /**
     * Gets the {@link ServletContextHandler} of the metrics servlet.
     *
     * @return the {@link ServletContextHandler} object
     */
    public ServletContextHandler getHandler() {
      ServletContextHandler contextHandler = new ServletContextHandler();
      contextHandler.setContextPath(SERVLET_PATH);
      contextHandler.addServlet(new ServletHolder(new MetricsServlet(mCollectorRegistry)), "/");
      return contextHandler;
    }
  
    @Override
    public void start() {
    }
  
    @Override
    public void stop() {
    }
  
    @Override
    public void report() {
    }
  }
  
  