ape.NetworkDropPacketsCommand.java Source code

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Here is the source code for ape.NetworkDropPacketsCommand.java

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/**
  * Copyright (c) 2012 Yahoo! Inc. All rights reserved.
  * Licensed 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. See accompanying LICENSE file.
*/

package ape;

import java.io.IOException;

import org.apache.commons.cli.Option;
import org.apache.commons.cli.OptionBuilder;
import org.apache.commons.cli.ParseException;

/**
 * This command will drop a specified percentage of packets for a specified duration.
 * All inbound and outbound packets are affected by this.  This is achieved using
 * the netem (network emulation) module.
 * 
 *
 */
public class NetworkDropPacketsCommand extends ApeCommand {
    private Option option;

    /**
     * The constructor for this command simply creates its Option object (used by
     * the CLI parser)
     */
    public NetworkDropPacketsCommand() {
        option = OptionBuilder.withArgName("percentage> <duration").hasArgs(2).withValueSeparator().withDescription(
                "Drops a specified percentage of all inbound network packets for a duration specified in seconds.")
                .withLongOpt("network-drop").create("p");
    }

    public String getName() {
        return option.getLongOpt();
    }

    public Option getOption() {
        return option;
    }

    public boolean runImpl(String[] args) throws ParseException, IOException {
        String arg1, arg2 = null;
        arg1 = args[0];
        arg2 = args[1];

        double percent = Double.parseDouble(arg1);
        double period = Double.parseDouble(arg2);

        if (percent <= 0 || period <= 0) {
            System.err.println("Argument Not Positive");
            return false;
        }

        if (!executecommand(percent, period)) {
            System.err.println("Simulating Network Dropping Packets unsuccessful, turn on VERBOSE flag to check");
            return false;
        }

        return true;
    }

    /**
     * This method implement the event by using the netem module
     * @param percent The percentage of packets that are to be dropped
     * @param period The duration that the packet loss should last
     * @return True if the execution was successful, false if an error occurred 
     * @throws IOException
     */
    private boolean executecommand(double percent, double period) throws IOException {
        String cmd = "tc qdisc add dev eth0 root netem loss " + percent + "% && sleep " + period
                + " && tc qdisc del dev eth0 root netem";
        ProcessBuilder pb = new ProcessBuilder("bash", "-c", cmd);
        pb.redirectErrorStream(true);
        Process p = null;

        try {
            p = pb.start();
        } catch (IOException e) {
            System.err.println(
                    "Executing network connection simulation catches IOException, enter VERBOSE mode to see the Stack Trace");
            e.printStackTrace();
            return false;
        }

        try {
            if (p.waitFor() != 0) {
                System.err.println("Non-zero return code (" + p.exitValue() + ") when executing: '" + cmd + "'");

                ProcessBuilder tmp2 = new ProcessBuilder("bash", "-c", "tc qdisc del dev eth0 root netem");
                Process ptmp = tmp2.start();
                if (ptmp.waitFor() == 0)
                    System.out.println("Connection resumed");
                else {
                    System.out.println("Connection resumed failed");
                    return false;
                }

                return false;
            }
        } catch (InterruptedException e1) {
            e1.printStackTrace();
            return false;
        }

        return true;
    }
}