tachyon.metrics.sink.MetricsServlet.java Source code

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Here is the source code for tachyon.metrics.sink.MetricsServlet.java

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/*
 * Licensed to the University of California, Berkeley under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The ASF licenses this file to You 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 tachyon.metrics.sink;

import java.io.IOException;
import java.util.Properties;
import java.util.concurrent.TimeUnit;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;

import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.json.MetricsModule;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * A sink that exposes metrics data in JSON format by HTTP.
 */
public class MetricsServlet implements Sink {
    private static final String SERVLET_KEY_PATH = "path";

    private Properties mProperties;
    private MetricRegistry mMetricsRegistry;
    private ObjectMapper mObjectMapper;

    /**
     * Creates a MetricsServlet with a Properties and MetricRegistry.
     *
     * @param properties the properties which may contain path property.
     * @param registry the metric registry to register.
     */
    public MetricsServlet(Properties properties, MetricRegistry registry) {
        mProperties = properties;
        mMetricsRegistry = registry;
        mObjectMapper = new ObjectMapper()
                .registerModule(new MetricsModule(TimeUnit.SECONDS, TimeUnit.MILLISECONDS, false));
    }

    private HttpServlet createServlet() {
        return new HttpServlet() {
            @Override
            protected void doGet(HttpServletRequest request, HttpServletResponse response)
                    throws ServletException, IOException {
                response.setContentType(String.format("text/json;charset=utf-8"));
                response.setStatus(HttpServletResponse.SC_OK);
                response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
                String result = mObjectMapper.writeValueAsString(mMetricsRegistry);
                response.getWriter().println(result);
            }
        };
    }

    /***
     * Get the ServletContextHandler of the metrics servlet.
     *
     * @return the ServletContextHandler object.
     */
    public ServletContextHandler getHandler() {
        ServletContextHandler contextHandler = new ServletContextHandler();
        String servletPath = mProperties.getProperty(SERVLET_KEY_PATH);
        contextHandler.setContextPath(servletPath);
        contextHandler.addServlet(new ServletHolder(createServlet()), "/");
        return contextHandler;
    }

    @Override
    public void start() {
    }

    @Override
    public void stop() {
    }

    @Override
    public void report() {
    }
}