org.apache.hadoop.net.ServerSocketUtil.java Source code

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Here is the source code for org.apache.hadoop.net.ServerSocketUtil.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.hadoop.net;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.net.ServerSocket;
import java.util.Random;

public class ServerSocketUtil {

    private static final Logger LOG = LoggerFactory.getLogger(ServerSocketUtil.class);
    private static Random rand = new Random();

    /**
     * Port scan & allocate is how most other apps find ports
     * 
     * @param port given port
     * @param retries number of retries
     * @return
     * @throws IOException
     */
    public static int getPort(int port, int retries) throws IOException {
        int tryPort = port;
        int tries = 0;
        while (true) {
            if (tries > 0 || tryPort == 0) {
                tryPort = port + rand.nextInt(65535 - port);
            }
            if (tryPort == 0) {
                continue;
            }
            try (ServerSocket s = new ServerSocket(tryPort)) {
                LOG.info("Using port " + tryPort);
                return tryPort;
            } catch (IOException e) {
                tries++;
                if (tries >= retries) {
                    LOG.info("Port is already in use; giving up");
                    throw e;
                } else {
                    LOG.info("Port is already in use; trying again");
                }
            }
        }
    }

    /**
     * Check whether port is available or not.
     *
     * @param port given port
     * @return
     */
    private static boolean isPortAvailable(int port) {
        try (ServerSocket s = new ServerSocket(port)) {
            return true;
        } catch (IOException e) {
            return false;
        }
    }

    /**
     * Wait till the port available.
     *
     * @param port given port
     * @param retries number of retries for given port
     * @return
     * @throws InterruptedException
     * @throws IOException
     */
    public static int waitForPort(int port, int retries) throws InterruptedException, IOException {
        int tries = 0;
        while (true) {
            if (isPortAvailable(port)) {
                return port;
            } else {
                tries++;
                if (tries >= retries) {
                    throw new IOException("Port is already in use; giving up after " + tries + " times.");
                }
                Thread.sleep(1000);
            }
        }
    }

    /**
     * Find the specified number of unique ports available.
     * The ports are all closed afterwards,
     * so other network services started may grab those same ports.
     *
     * @param numPorts number of required port nubmers
     * @return array of available port numbers
     * @throws IOException
     */
    public static int[] getPorts(int numPorts) throws IOException {
        ServerSocket[] sockets = new ServerSocket[numPorts];
        int[] ports = new int[numPorts];
        for (int i = 0; i < numPorts; i++) {
            ServerSocket sock = new ServerSocket(0);
            sockets[i] = sock;
            ports[i] = sock.getLocalPort();
        }
        for (ServerSocket sock : sockets) {
            sock.close();
        }
        return ports;
    }
}