/*
 * 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.catalina.ha.session;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;

import org.apache.catalina.Container;
import org.apache.catalina.Context;
import org.apache.catalina.Engine;
import org.apache.catalina.Globals;
import org.apache.catalina.Host;
import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleListener;
import org.apache.catalina.Manager;
import org.apache.catalina.Session;
import org.apache.catalina.ha.CatalinaCluster;
import org.apache.catalina.ha.ClusterManager;
import org.apache.catalina.ha.ClusterMessage;
import org.apache.catalina.ha.ClusterValve;
import org.apache.catalina.ha.session.DeltaSession;
import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.catalina.session.ManagerBase;
import org.apache.catalina.session.PersistentManager;
import org.apache.catalina.util.LifecycleSupport;
import org.apache.catalina.util.StringManager;
import org.apache.catalina.valves.ValveBase;

/**
 * Valve to handle Tomcat jvmRoute takeover using mod_jk module after node
 * failure. After a node crashes, subsequent requests go to other cluster nodes.
 * That incurs a drop in performance. When this Valve is enabled on a backup
 * node and sees a request, which was intended for another (thus failed) node,
 * it will rewrite the cookie jsessionid information to use the route to this
 * backup cluster node, that answered the request. After the response is
 * delivered to the client, all subsequent client requests will go directly to
 * the backup node. The change of sessionid is also sent to all other cluster
 * nodes. After all that, the session stickyness will work directly to the
 * backup node and the traffic will not go back to the failed node after it is
 * restarted!
 * 
 * <p>
 * For this valve to function correctly, so that all nodes of the cluster
 * receive the sessionid change notifications that it generates, the following
 * ClusterListener MUST be configured at all nodes of the cluster:
 * {@link org.apache.catalina.ha.session.JvmRouteSessionIDBinderListener
 * JvmRouteSessionIDBinderListener} since Tomcat 5.5.10, and both
 * JvmRouteSessionIDBinderListener and JvmRouteSessionIDBinderLifecycleListener
 * for earlier versions of Tomcat.
 * 
 * <p>
 * Add this Valve to your host definition at conf/server.xml .
 * 
 * Since 5.5.10 as direct cluster valve:<br/>
 * 
 * <pre>
 *  &lt;Cluster&gt;
 *  &lt;Valve className=&quot;org.apache.catalina.ha.session.JvmRouteBinderValve&quot; /&gt;  
 *  &lt;/Cluster&gt;
 * </pre>
 * 
 * <br />
 * Before 5.5.10 as Host element:<br/>
 * 
 * <pre>
 *  &lt;Host&gt;
 *  &lt;Valve className=&quot;org.apache.catalina.ha.session.JvmRouteBinderValve&quot; /&gt;  
 *  &lt;/Host&gt;
 * </pre>
 * 
 * <em>A Trick:</em><br/>
 * You can enable this mod_jk turnover mode via JMX before you drop a node to
 * all backup nodes! Set enable true on all JvmRouteBinderValve backups, disable
 * worker at mod_jk and then drop node and restart it! Then enable mod_jk worker
 * and disable JvmRouteBinderValves again. This use case means that only
 * requested sessions are migrated.
 * 
 * @author Peter Rossbach
 * @version $Revision: 892545 $ $Date: 2009-12-20 02:04:17 +0100 (Sun, 20 Dec 2009) $
 */
public class JvmRouteBinderValve extends ValveBase implements ClusterValve, Lifecycle {

    /*--Static Variables----------------------------------------*/
    public static org.apache.juli.logging.Log log = org.apache.juli.logging.LogFactory
            .getLog(JvmRouteBinderValve.class);

    /**
     * The descriptive information about this implementation.
     */
    protected static final String info = "org.apache.catalina.ha.session.JvmRouteBinderValve/1.2";

    /*--Instance Variables--------------------------------------*/

    /**
     * the cluster
     */
    protected CatalinaCluster cluster;

    /**
     * The string manager for this package.
     */
    protected StringManager sm = StringManager.getManager(Constants.Package);

    /**
     * Has this component been started yet?
     */
    protected boolean started = false;

    /**
     * enabled this component
     */
    protected boolean enabled = true;

    /**
     * number of session that no at this tomcat instanz hosted
     */
    protected long numberOfSessions = 0;

    protected String sessionIdAttribute = "org.apache.catalina.ha.session.JvmRouteOrignalSessionID";

    /**
     * The lifecycle event support for this component.
     */
    protected LifecycleSupport lifecycle = new LifecycleSupport(this);

    /*--Logic---------------------------------------------------*/

    /**
     * Return descriptive information about this implementation.
     */
    public String getInfo() {

        return (info);

    }

    /**
     * set session id attribute to failed node for request.
     * 
     * @return Returns the sessionIdAttribute.
     */
    public String getSessionIdAttribute() {
        return sessionIdAttribute;
    }

    /**
     * get name of failed reqeust session attribute
     * 
     * @param sessionIdAttribute
     *            The sessionIdAttribute to set.
     */
    public void setSessionIdAttribute(String sessionIdAttribute) {
        this.sessionIdAttribute = sessionIdAttribute;
    }

    /**
     * @return Returns the number of migrated sessions.
     */
    public long getNumberOfSessions() {
        return numberOfSessions;
    }

    /**
     * @return Returns the enabled.
     */
    public boolean getEnabled() {
        return enabled;
    }

    /**
     * @param enabled
     *            The enabled to set.
     */
    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    /**
     * Detect possible the JVMRoute change at cluster backup node..
     * 
     * @param request
     *            tomcat request being processed
     * @param response
     *            tomcat response being processed
     * @exception IOException
     *                if an input/output error has occurred
     * @exception ServletException
     *                if a servlet error has occurred
     */
    public void invoke(Request request, Response response) throws IOException,
            ServletException {

         if (getEnabled() 
             && request.getContext() != null
             && request.getContext().getDistributable() ) {
             // valve cluster can access manager - other cluster handle turnover 
             // at host level - hopefully!
             Manager manager = request.getContext().getManager();

             if (manager != null && (
                     (manager instanceof ClusterManager
                       && getCluster() != null
                       && getCluster().getManager(((ClusterManager)manager).getName()) != null)
                     ||
                     (manager instanceof PersistentManager)))
                 handlePossibleTurnover(request, response);
        }
        // Pass this request on to the next valve in our pipeline
        getNext().invoke(request, response);
    }

    /**
     * handle possible session turn over.
     * 
     * @see JvmRouteBinderValve#handleJvmRoute(Request, Response, String, String)
     * @param request current request
     * @param response current response
     */
    protected void handlePossibleTurnover(Request request, Response response) {
        String sessionID = request.getRequestedSessionId() ;
        if (sessionID != null) {
            long t1 = System.currentTimeMillis();
            String jvmRoute = getLocalJvmRoute(request);
            if (jvmRoute == null) {
                if (log.isDebugEnabled())
                    log.debug(sm.getString("jvmRoute.missingJvmRouteAttribute"));
                return;
            }
            handleJvmRoute( request, response, sessionID, jvmRoute);
            if (log.isDebugEnabled()) {
                long t2 = System.currentTimeMillis();
                long time = t2 - t1;
                log.debug(sm.getString("jvmRoute.turnoverInfo", new Long(time)));
            }
        }
    }

    /**
     * get jvmroute from engine
     * 
     * @param request current request
     * @return return jvmRoute from ManagerBase or null
     */
    protected String getLocalJvmRoute(Request request) {
        Manager manager = getManager(request);
        if(manager instanceof ManagerBase)
            return ((ManagerBase) manager).getJvmRoute();
        return null ;
    }

    /**
     * get Cluster DeltaManager
     * 
     * @param request current request
     * @return manager or null
     */
    protected Manager getManager(Request request) {
        Manager manager = request.getContext().getManager();
        if (log.isDebugEnabled()) {
            if(manager != null)
                log.debug(sm.getString("jvmRoute.foundManager", manager,  request.getContext().getName()));
            else 
                log.debug(sm.getString("jvmRoute.notFoundManager", manager,  request.getContext().getName()));
        }
        return manager;
    }

    /**
     * @return Returns the cluster.
     */
    public CatalinaCluster getCluster() {
        return cluster;
    }
    
    /**
     * @param cluster The cluster to set.
     */
    public void setCluster(CatalinaCluster cluster) {
        this.cluster = cluster;
    }
    
    /**
     * Handle jvmRoute stickyness after tomcat instance failed. After this
     * correction a new Cookie send to client with new jvmRoute and the
     * SessionID change propage to the other cluster nodes.
     * 
     * @param request current request
     * @param response
     *            Tomcat Response
     * @param sessionId
     *            request SessionID from Cookie
     * @param localJvmRoute
     *            local jvmRoute
     */
    protected void handleJvmRoute(
            Request request, Response response,String sessionId, String localJvmRoute) {
        // get requested jvmRoute.
        String requestJvmRoute = null;
        int index = sessionId.indexOf(".");
        if (index > 0) {
            requestJvmRoute = sessionId
                    .substring(index + 1, sessionId.length());
        }
        if (requestJvmRoute != null && !requestJvmRoute.equals(localJvmRoute)) {
            if (log.isDebugEnabled()) {
                log.debug(sm.getString("jvmRoute.failover", requestJvmRoute,
                        localJvmRoute, sessionId));
            }
            Session catalinaSession = null;
            try {
                catalinaSession = getManager(request).findSession(sessionId);
            } catch (IOException e) {
                // Hups!
            }
            String id = sessionId.substring(0, index);
            String newSessionID = id + "." + localJvmRoute;
            // OK - turnover the session and inform other cluster nodes
            if (catalinaSession != null) {
                changeSessionID(request, response, sessionId, newSessionID,
                        catalinaSession);
                numberOfSessions++;
            } else {
                try {
                    catalinaSession = getManager(request).findSession(newSessionID);
                } catch (IOException e) {
                    // Hups!
                }
                if (catalinaSession != null) {
                    // session is rewrite at other request, rewrite this also
                    changeRequestSessionID(request, response, sessionId, newSessionID);
                } else {
                    if (log.isDebugEnabled()) {
                        log.debug(sm.getString("jvmRoute.cannotFindSession",sessionId));
                    }
                }
            }
        }
    }

    /**
     * change session id and send to all cluster nodes
     * 
     * @param request current request
     * @param response current response
     * @param sessionId
     *            original session id
     * @param newSessionID
     *            new session id for node migration
     * @param catalinaSession
     *            current session with original session id
     */
    protected void changeSessionID(Request request,
            Response response, String sessionId, String newSessionID, Session catalinaSession) {
        lifecycle.fireLifecycleEvent("Before session migration",
                catalinaSession);
        // FIXME: setId trigger session Listener, but only chance to registiert manager with correct id!
        catalinaSession.setId(newSessionID);
        // FIXME: Why we remove change data from other running request?
        // setId also trigger resetDeltaRequest!!
        if (catalinaSession instanceof DeltaSession)
            ((DeltaSession) catalinaSession).resetDeltaRequest();
        changeRequestSessionID(request, response, sessionId, newSessionID);

        if (getCluster() != null) {
            // now sending the change to all other clusternode!
            ClusterManager manager = (ClusterManager)catalinaSession.getManager();
            sendSessionIDClusterBackup(manager,request,sessionId, newSessionID);
        }

        lifecycle.fireLifecycleEvent("After session migration", catalinaSession);
        if (log.isDebugEnabled()) {
            log.debug(sm.getString("jvmRoute.changeSession", sessionId,
                    newSessionID));
        }   
    }

    /**
     * Change Request Session id
     * @param request current request
     * @param response current response
     * @param sessionId
     *            original session id
     * @param newSessionID
     *            new session id for node migration
     */
    protected void changeRequestSessionID(Request request, Response response, String sessionId, String newSessionID) {
        request.changeSessionId(newSessionID);

        // set orginal sessionid at request, to allow application detect the
        // change
        if (sessionIdAttribute != null && !"".equals(sessionIdAttribute)) {
            if (log.isDebugEnabled()) {
                log.debug(sm.getString("jvmRoute.set.orignalsessionid",sessionIdAttribute,sessionId));
            }
            request.setAttribute(sessionIdAttribute, sessionId);
        }
    }
    
    /**
     * Send the changed Sessionid to all clusternodes.
     * 
     * @see JvmRouteSessionIDBinderListener#messageReceived(ClusterMessage)
     * @param manager
     *            ClusterManager
     * @param sessionId
     *            current failed sessionid
     * @param newSessionID
     *            new session id, bind to the new cluster node
     */
    protected void sendSessionIDClusterBackup(ClusterManager manager,Request request,String sessionId,
            String newSessionID) {
        SessionIDMessage msg = new SessionIDMessage();
        msg.setOrignalSessionID(sessionId);
        msg.setBackupSessionID(newSessionID);
        Context context = request.getContext();
        msg.setContextPath(context.getPath());
        msg.setHost(context.getParent().getName());
        if(manager.doDomainReplication())
            cluster.sendClusterDomain(msg);
        else
            cluster.send(msg);
    }

    /**
     * Sets a new cookie for the given session id and response and see
     * {@link org.apache.catalina.connector.Request#configureSessionCookie(javax.servlet.http.Cookie)}
     * 
     * @param request current request
     * @param response Tomcat Response
     * @param sessionId The session id
     * 
     * @deprecated Use {@link Request#changeSessionId(String)}
     */
    protected void setNewSessionCookie(Request request,
                                       Response response, String sessionId) {
        if (response != null) {
            Context context = request.getContext();
            if (context.getCookies()) {
                // set a new session cookie
                Cookie newCookie = new Cookie(Globals.SESSION_COOKIE_NAME,
                        sessionId);
                newCookie.setMaxAge(-1);
                String contextPath = null;
                if (!response.getConnector().getEmptySessionPath()
                        && (context != null)) {
                    contextPath = context.getEncodedPath();
                }
                if ((contextPath != null) && (contextPath.length() > 0)) {
                    newCookie.setPath(contextPath);
                } else {
                    newCookie.setPath("/");
                }
                if (request.isSecure()) {
                    newCookie.setSecure(true);
                }
                if (log.isDebugEnabled()) {
                    Object[] args = new Object[] {sessionId,
                            Globals.SESSION_COOKIE_NAME,
                            newCookie.getPath(),
                            new Boolean(newCookie.getSecure()),
                            new Boolean(context.getUseHttpOnly())};
                    log.debug(sm.getString("jvmRoute.newSessionCookie", args));
                }
                response.addCookieInternal(newCookie, context.getUseHttpOnly());
            }
        }
    }

    // ------------------------------------------------------ Lifecycle Methods

    /**
     * Add a lifecycle event listener to this component.
     * 
     * @param listener
     *            The listener to add
     */
    public void addLifecycleListener(LifecycleListener listener) {

        lifecycle.addLifecycleListener(listener);

    }

    /**
     * Get the lifecycle listeners associated with this lifecycle. If this
     * Lifecycle has no listeners registered, a zero-length array is returned.
     */
    public LifecycleListener[] findLifecycleListeners() {

        return lifecycle.findLifecycleListeners();

    }

    /**
     * Remove a lifecycle event listener from this component.
     * 
     * @param listener
     *            The listener to add
     */
    public void removeLifecycleListener(LifecycleListener listener) {

        lifecycle.removeLifecycleListener(listener);

    }

    /**
     * Prepare for the beginning of active use of the public methods of this
     * component. This method should be called after <code>configure()</code>,
     * and before any of the public methods of the component are utilized.
     * 
     * @exception LifecycleException
     *                if this component detects a fatal error that prevents this
     *                component from being used
     */
    public void start() throws LifecycleException {

        // Validate and update our current component state
        if (started)
            throw new LifecycleException(sm
                    .getString("jvmRoute.valve.alreadyStarted"));
        lifecycle.fireLifecycleEvent(START_EVENT, null);
        started = true;
        if (cluster == null) {
            Container hostContainer = getContainer();
            // compatibility with JvmRouteBinderValve version 1.1
            // ( setup at context.xml or context.xml.default )
            if (!(hostContainer instanceof Host)) {
                if (log.isWarnEnabled())
                    log.warn(sm.getString("jvmRoute.configure.warn"));
                hostContainer = hostContainer.getParent();
            }
            if (hostContainer instanceof Host
                    && ((Host) hostContainer).getCluster() != null) {
                cluster = (CatalinaCluster) ((Host) hostContainer).getCluster();
            } else {
                Container engine = hostContainer.getParent() ;
                if (engine instanceof Engine
                        && ((Engine) engine).getCluster() != null) {
                    cluster = (CatalinaCluster) ((Engine) engine).getCluster();
                }
            }
        }
        
        if (log.isInfoEnabled()) {
            log.info(sm.getString("jvmRoute.valve.started"));
            if (cluster == null)
                log.info(sm.getString("jvmRoute.noCluster"));
        }

    }

    /**
     * Gracefully terminate the active use of the public methods of this
     * component. This method should be the last one called on a given instance
     * of this component.
     * 
     * @exception LifecycleException
     *                if this component detects a fatal error that needs to be
     *                reported
     */
    public void stop() throws LifecycleException {

        // Validate and update our current component state
        if (!started)
            throw new LifecycleException(sm
                    .getString("jvmRoute.valve.notStarted"));
        lifecycle.fireLifecycleEvent(STOP_EVENT, null);
        started = false;
        cluster = null;
        numberOfSessions = 0;
        if (log.isInfoEnabled())
            log.info(sm.getString("jvmRoute.valve.stopped"));

    }

}
