/*******************************************************************************
 *
 * Copyright (c) 2010, InfraDNA, Inc.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *
 *
 *
 *
 *******************************************************************************/ 

package hudson.util;

import hudson.ExtensionList;
import hudson.ExtensionPoint;
import hudson.model.Hudson;

import java.io.IOException;
import java.io.Serializable;

/**
 * Extension point that defines more elaborate way of killing processes, such as
 * sudo or pfexec, for {@link ProcessTree}.
 *
 * <h2>Lifecycle</h2> <p> Each implementation of {@link ProcessKiller} is
 * instantiated once on the master. Whenever a process needs to be killed, those
 * implementations are serialized and sent over to the appropriate slave, then
 * the {@link #kill(hudson.util.ProcessTree.OSProcess)} method is invoked to
 * attempt to kill the process.
 *
 * <p> One of the consequences of this design is that the implementation should
 * be stateless and concurrent-safe. That is, the
 * {@link #kill(hudson.util.ProcessTree.OSProcess)} method can be invoked by
 * multiple threads concurrently on the single instance.
 *
 * <p> Another consequence of this design is that if your {@link ProcessKiller}
 * requires configuration, it needs to be serializable, and configuration needs
 * to be updated atomically, as another thread may be calling into
 * {@link #kill(hudson.util.ProcessTree.OSProcess)} just when you are updating
 * your configuration.
 *
 * @author jpederzolli
 * @author Kohsuke Kawaguchi
 * @since 1.362
 */
public abstract class ProcessKiller implements ExtensionPoint, Serializable {

    /**
     * Returns all the registered {@link ProcessKiller} descriptors.
     */
    public static ExtensionList<ProcessKiller> all() {
        return Hudson.getInstance().getExtensionList(ProcessKiller.class);
    }

    /**
     * Attempts to kill the given process.
     *
     * @param process process to be killed. Always a
     * {@linkplain ProcessTree.Local local process}.
     * @return true if the killing was successful, and Hudson won't try to use
     * other {@link ProcessKiller} implementations to kill the process. false if
     * the killing failed or is unattempted, and Hudson will continue to use the
     * rest of the {@link ProcessKiller} implementations to try to kill the
     * process.
     * @throws IOException The caller will log this exception and otherwise
     * treat as if the method returned false, and moves on to the next killer.
     * @throws InterruptedException if the callee performs a time consuming
     * operation and if the thread is canceled, do not catch
     * {@link InterruptedException} and just let it thrown from the method.
     */
    public abstract boolean kill(ProcessTree.OSProcess process) throws IOException, InterruptedException;
    private static final long serialVersionUID = 1L;
}