jena-fuseki2/jena-fuseki-core/src/main/java/org/apache/jena/fuseki/ctl/ActionPing.java

/**
 * Licensed to the Apache Software Foundation (ASF) 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 org.apache.jena.fuseki.ctl;

import static org.apache.jena.riot.WebContent.charsetUTF8;
import static org.apache.jena.riot.WebContent.contentTypeTextPlain;

import java.io.IOException;

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

import org.apache.jena.atlas.lib.DateTimeUtils;
import org.apache.jena.fuseki.Fuseki;
import org.apache.jena.fuseki.servlets.ServletOps;
import org.apache.jena.web.HttpSC;

/** The ping servlet provides a low cost, uncached endpoint that can be used
 * to determine if this component is running and responding.  For example,
 * a nagios check should use this endpoint.
 */
public class ActionPing extends HttpServlet
{
    // Ping is special.
    // To avoid excessive logging and id allocation for a "noise" operation,
    // this is a raw servlet.
    public ActionPing() { super(); }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
        doCommon(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
        doCommon(req, resp);
    }


    @Override
    protected void doHead(HttpServletRequest req, HttpServletResponse resp) {
        doCommon(req, resp);
    }

    protected void doCommon(HttpServletRequest request, HttpServletResponse response) {
        try {
            ServletOps.setNoCache(response);
            response.setContentType(contentTypeTextPlain);
            response.setCharacterEncoding(charsetUTF8);
            response.setStatus(HttpSC.OK_200);
            ServletOutputStream out = response.getOutputStream();
            out.println(DateTimeUtils.nowAsXSDDateTimeString());
        } catch (IOException ex) {
            Fuseki.serverLog.warn("ping :: IOException :: "+ex.getMessage());
        }
    }
}