org.apache.ambari.servicemonitor.utils.FindAndPingPid.java Source code

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Here is the source code for org.apache.ambari.servicemonitor.utils.FindAndPingPid.java

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/*
 * 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.ambari.servicemonitor.utils;

import org.apache.commons.io.IOUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InterruptedIOException;

/**
 * Class to find and ping a process -designed for use outside a probe, which can
 * aid testing.
 *
 * The path/file is set up at create time but the file containing the pid must
 * be reloaded every ping(), so that after a service restart the new pid will 
 * be picked up.
 */
public class FindAndPingPid {
    private static final Log LOG = LogFactory.getLog(FindAndPingPid.class);

    private final String pidPath;
    private final File pidFile;

    public FindAndPingPid(File pidFile) {
        this.pidFile = pidFile;
        pidPath = pidFile.getAbsolutePath();
    }

    public String getPidPath() {
        return pidPath;
    }

    public File getPidFile() {
        return pidFile;
    }

    @Override
    public String toString() {
        return pidPath;
    }

    /**
     * Load the pid from a file
     * @return the trimmed string from the file
     * @throws IOException IO problems
     * @throws FileNotFoundException if the pid file is missing
     */
    public String loadPid() throws IOException {
        if (!pidFileExists()) {
            throw new FileNotFoundException(pidFile.toString());
        } else {
            if (LOG.isDebugEnabled()) {
                LOG.debug("Loading file " + pidFile);
            }
            FileInputStream inputStream = new FileInputStream(pidFile);
            try {
                String text = IOUtils.toString(inputStream);
                return text.trim();
            } finally {
                inputStream.close();
            }
        }
    }

    public boolean pidFileExists() {
        return pidFile.exists();
    }

    /**
     * Ping the process
     * @return true iff the pid file could be loaded, it contains a pid and that
     * pid responds to a signal request
     * @throws IOException on any execution problem.
     */
    public boolean ping() throws IOException {
        String pid = loadPid();
        if (LOG.isDebugEnabled()) {
            LOG.debug("Loaded pid \"" + pid + "\"");
        }
        if (pid.isEmpty()) {
            throw new IOException("No PID in the file");
        }
        int result = signalPid(pid, 0);
        if (LOG.isDebugEnabled()) {
            LOG.debug("return code \"" + result + "\"");
        }
        return result == 0;
    }

    /**
     * Signal the pid, block for completion
     * @param pid process to signal
     * @param signal signal to raise
     * @return the return code
     * @throws IOException any IO problem.
     * @throws InterruptedIOException if the thread was interrupted during execution.
     */
    int signalPid(String pid, int signal) throws IOException {
        String[] cmds = new String[3];
        int c = 0;
        cmds[c++] = "kill";
        cmds[c++] = "-" + signal;
        cmds[c] = pid;

        Process process = Runtime.getRuntime().exec(cmds);
        try {
            return process.waitFor();
        } catch (InterruptedException e) {
            throw new InterruptedIOException("While signalling " + pid);
        }

    }

}