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Tomcat example source code file (Shm.java)

This example Tomcat source code file (Shm.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

c2bconverter, io, ioexception, ioexception, msg, msgcontext, msgcontext, no, shm, shm, shm_write_slot, string, string, tomcat, util, vector

The Tomcat Shm.java source code

/*
 *  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.jk.common;

import java.io.IOException;
import java.util.Vector;

import org.apache.jk.apr.AprImpl;
import org.apache.jk.core.Msg;
import org.apache.jk.core.MsgContext;
import org.apache.jk.core.WorkerEnv;
import org.apache.tomcat.util.IntrospectionUtils;
import org.apache.tomcat.util.buf.C2BConverter;

/* The code is a bit confusing at this moment - the class is used as
   a Bean, or ant Task, or CLI - i.e. you set properties and call execute.

   That's different from the rest of jk handlers wich are stateless ( but
   similar with Coyote-http ).
*/


/** Handle the shared memory objects.
 *
 * @author Costin Manolache
 */
public class Shm extends JniHandler {
    String file="/tmp/shm.file";
    int size;
    String host="localhost";
    int port=8009;
    String unixSocket;

    boolean help=false;
    boolean unregister=false;
    boolean reset=false;
    String dumpFile=null;

    Vector groups=new Vector();
    
    // Will be dynamic ( getMethodId() ) after things are stable 
    static final int SHM_WRITE_SLOT=2;
    static final int SHM_RESET=5;
    static final int SHM_DUMP=6;
    
    public Shm() {
    }

    /** Scoreboard location
     */
    public void setFile( String f ) {
        file=f;
    }

    /** Copy the scoreboard in a file for debugging
     *  Will also log a lot of information about what's in the scoreboard.
     */
    public void setDump( String dumpFile ) {
        this.dumpFile=dumpFile;
    }
    
    /** Size. Used only if the scoreboard is to be created.
     */
    public void setSize( int size ) {
        this.size=size;
    }

    /** Set this to get the scoreboard reset.
     *  The shm segment will be destroyed and a new one created,
     *  with the provided size.
     *
     *  Requires "file" and "size".
     */
    public void setReset(boolean b) {
        reset=true;
    }

    /** Ajp13 host
     */
    public void setHost( String host ) {
        this.host=host;
    }

    /** Mark this instance as belonging to a group
     */
    public void setGroup( String grp ) {
        groups.addElement( grp );
    }

    /** Ajp13 port
     */
    public void setPort( int port ) {
        this.port=port;
    }

    /** Unix socket where tomcat is listening.
     *  Use it only if tomcat is on the same host, of course
     */
    public void setUnixSocket( String unixSocket  ) {
        this.unixSocket=unixSocket;
    }

    /** Set this option to mark the tomcat instance as
        'down', so apache will no longer forward messages to it.
        Note that requests with a session will still try this
        host first.

        This can be used to implement gracefull shutdown.

        Host and port are still required, since they are used
        to identify tomcat.
    */
    public void setUnregister( boolean unregister  ) {
        this.unregister=true;
    }
    
    public void init() throws IOException {
        super.initNative( "shm" );
        if( apr==null ) return;
        if( file==null ) {
            log.error("No shm file, disabling shared memory");
            apr=null;
            return;
        }

        // Set properties and call init.
        setNativeAttribute( "file", file );
        if( size > 0 )
            setNativeAttribute( "size", Integer.toString( size ) );
        
        initJkComponent();
    }

    public void resetScoreboard() throws IOException {
        if( apr==null ) return;
        MsgContext mCtx=createMsgContext();
        Msg msg=(Msg)mCtx.getMsg(0);
        msg.reset();

        msg.appendByte( SHM_RESET );
        
        this.invoke( msg, mCtx );
    }

    public void dumpScoreboard(String fname) throws IOException {
        if( apr==null ) return;
        MsgContext mCtx=createMsgContext();
        Msg msg=(Msg)mCtx.getMsg(0);
        C2BConverter c2b=mCtx.getConverter();
        msg.reset();

        msg.appendByte( SHM_DUMP );

        appendString( msg, fname, c2b);
        
        this.invoke( msg, mCtx );
    }

    /** Register a tomcat instance
     *  XXX make it more flexible
     */
    public void registerTomcat(String host, int port, String unixDomain)
        throws IOException
    {
        String instanceId=host+":" + port;

        String slotName="TOMCAT:" + instanceId;
        MsgContext mCtx=createMsgContext();
        Msg msg=(Msg)mCtx.getMsg(0);
        msg.reset();
        C2BConverter c2b=mCtx.getConverter();
        
        msg.appendByte( SHM_WRITE_SLOT );
        appendString( msg, slotName, c2b );

        int channelCnt=1;
        if( unixDomain != null ) channelCnt++;

        // number of groups. 0 means the default lb.
        msg.appendInt( groups.size() );
        for( int i=0; i<groups.size(); i++ ) {
            appendString( msg, (String)groups.elementAt( i ), c2b);
            appendString( msg, instanceId, c2b);
        }
        
        // number of channels for this instance
        msg.appendInt( channelCnt );
        
        // The body:
        appendString(msg, "channel.socket:" + host + ":" + port, c2b );
        msg.appendInt( 1 );
        appendString(msg, "tomcatId", c2b);
        appendString(msg, instanceId, c2b);

        if( unixDomain != null ) {
            appendString(msg, "channel.apr:" + unixDomain, c2b );
            msg.appendInt(1);
            appendString(msg, "tomcatId", c2b);
            appendString(msg, instanceId, c2b);
        }

        if (log.isDebugEnabled())
            log.debug("Register " + instanceId );
        this.invoke( msg, mCtx );
    }

    public void unRegisterTomcat(String host, int port)
        throws IOException
    {
        String slotName="TOMCAT:" + host + ":" + port;
        MsgContext mCtx=createMsgContext();
        Msg msg=(Msg)mCtx.getMsg(0);
        msg.reset();
        C2BConverter c2b=mCtx.getConverter();
        
        msg.appendByte( SHM_WRITE_SLOT );
        appendString( msg, slotName, c2b );

        // number of channels for this instance
        msg.appendInt( 0 );
        msg.appendInt( 0 );
        
        if (log.isDebugEnabled())
            log.debug("UnRegister " + slotName );
        this.invoke( msg, mCtx );
    }

    public void destroy() throws IOException {
        destroyJkComponent();
    }

    
    public  int invoke(Msg msg, MsgContext ep )
        throws IOException
    {
        if( apr==null ) return 0;
        log.debug("ChannelShm.invoke: "  + ep );
        super.nativeDispatch( msg, ep, JK_HANDLE_SHM_DISPATCH, 0 );
        return 0;
    }    

    private static org.apache.juli.logging.Log log=
        org.apache.juli.logging.LogFactory.getLog( Shm.class );

    
    //-------------------- Main - use the shm functions from ant or CLI ------

    /** Local initialization - for standalone use
     */
    public void initCli() throws IOException {
        WorkerEnv wEnv=new WorkerEnv();
        AprImpl apr=new AprImpl();
        wEnv.addHandler( "apr", apr );
        wEnv.addHandler( "shm", this );
        apr.init();
        if( ! apr.isLoaded() ) {
            log.error( "No native support. " +
                       "Make sure libapr.so and libjkjni.so are available in LD_LIBRARY_PATH");
            return;
        }
    }
    
    public void execute() {
        try {
            if( help ) return;
            initCli();
            init();

            if( reset ) {
                resetScoreboard();
            } else if( dumpFile!=null ) {
                dumpScoreboard(dumpFile);
            } else if( unregister ) {
                unRegisterTomcat( host, port );
            } else {
                registerTomcat( host, port, unixSocket );
            }
        } catch (Exception ex ) {
            log.error( "Error executing Shm", ex);
        }
    }

    public void setHelp( boolean b ) {
        if (log.isDebugEnabled()) {
            log.debug("Usage: ");
            log.debug("  Shm [OPTIONS]");
            log.debug("");
            log.debug("  -file SHM_FILE");
            log.debug("  -group GROUP ( can be specified multiple times )");
            log.debug("  -host HOST");
            log.debug("  -port PORT");
            log.debug("  -unixSocket UNIX_FILE");
            //        log.debug("  -priority XXX");
            //        log.debug("  -lbFactor XXX");
        }
        help=true;
        return;
    }
    
    public static void main( String args[] ) {
        try {
            Shm shm=new Shm();

            if( args.length == 0 ||
                ( "-?".equals(args[0]) ) ) {
                shm.setHelp( true );
                return;
            }

            IntrospectionUtils.processArgs( shm, args);
            shm.execute();
        } catch( Exception ex ) {
            ex.printStackTrace();
        }
    }
}

Other Tomcat examples (source code examples)

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