state_transfer.java

JGRoups源码

package org.jgroups.protocols.pbcast;

import org.jgroups.*;
import org.jgroups.stack.Protocol;
import org.jgroups.stack.StateTransferInfo;
import org.jgroups.util.Promise;
import org.jgroups.util.Streamable;
import org.jgroups.util.Util;

import java.io.*;
import java.util.*;


/**
 * New STATE_TRANSFER protocol based on PBCAST. Compared to the one in ./protocols, it doesn't
 * need a QUEUE layer above it. A state request is sent to a chosen member (coordinator if
 * null). That member makes a copy D of its current digest and asks the application for a copy of
 * its current state S. Then the member returns both S and D to the requester. The requester
 * first sets its digest to D and then returns the state to the application.
 * @author Bela Ban
 * @version $Id: STATE_TRANSFER.java,v 1.44 2006/09/29 21:48:17 bstansberry Exp $
 */
public class STATE_TRANSFER extends Protocol {
    Address        local_addr=null;
    final Vector   members=new Vector();
    long           state_id=1;  // used to differentiate between state transfers (not currently used)

    // final Set      state_requesters=new HashSet(); // requesters of state (usually just 1, could be more)

    /** Map<String,Set> of state requesters. Keys are state IDs, values are Sets of Addresses (one for each requester) */
    final Map      state_requesters=new HashMap();

    /** set to true while waiting for a STATE_RSP */
    boolean        waiting_for_state_response=false;

    Digest         digest=null;
    final HashMap  map=new HashMap(); // to store configuration information
    long           start, stop; // to measure state transfer time
    int            num_state_reqs=0;
    long           num_bytes_sent=0;
    double         avg_state_size=0;
    final static   String name="STATE_TRANSFER";
    boolean        use_flush=false;
    long           flush_timeout=4000;
    Promise        flush_promise;


    /** All protocol names have to be unique ! */
    public String getName() {
        return name;
    }

    public int getNumberOfStateRequests() {return num_state_reqs;}
    public long getNumberOfStateBytesSent() {return num_bytes_sent;}
    public double getAverageStateSize() {return avg_state_size;}

    public Vector requiredDownServices() {
        Vector retval=new Vector();
        retval.addElement(new Integer(Event.GET_DIGEST_STATE));
        retval.addElement(new Integer(Event.SET_DIGEST));
        return retval;
    }

    public Vector requiredUpServices() {
        Vector retval=new Vector();
        if(use_flush) {
            retval.addElement(new Integer(Event.SUSPEND));
            retval.addElement(new Integer(Event.RESUME));
        }
        return retval;
    }

    public void resetStats() {
        super.resetStats();
        num_state_reqs=0;
        num_bytes_sent=0;
        avg_state_size=0;
    }


    public boolean setProperties(Properties props) {
        super.setProperties(props);

        use_flush=Util.parseBoolean(props, "use_flush", false);        
        flush_promise=new Promise();
        
        flush_timeout = Util.parseLong(props, "flush_timeout", flush_timeout);       
        if(props.size() > 0) {
            log.error("the following properties are not recognized: " + props);
            return false;
        }
        return true;
    }

    public void init() throws Exception {
        map.put("state_transfer", Boolean.TRUE);
        map.put("protocol_class", getClass().getName());
    }


    public void start() throws Exception {
        passUp(new Event(Event.CONFIG, map));
    }

    public void stop() {
        super.stop();
        waiting_for_state_response=false;
    }


    public void up(Event evt) {
        Message     msg;
        StateHeader hdr;

        switch(evt.getType()) {

        case Event.BECOME_SERVER:
            break;

        case Event.SET_LOCAL_ADDRESS:
            local_addr=(Address)evt.getArg();
            break;

        case Event.TMP_VIEW:
        case Event.VIEW_CHANGE:
            handleViewChange((View)evt.getArg());
            break;

        case Event.GET_DIGEST_STATE_OK:
            synchronized(state_requesters) {
                digest=(Digest)evt.getArg();
                if(log.isDebugEnabled())
                    log.debug("GET_DIGEST_STATE_OK: digest is " + digest + "\npassUp(GET_APPLSTATE)");

                requestApplicationStates();
            }
            return;

        case Event.MSG:
            msg=(Message)evt.getArg();
            if(!(msg.getHeader(name) instanceof StateHeader))
                break;

            hdr=(StateHeader)msg.removeHeader(name);
            switch(hdr.type) {
            case StateHeader.STATE_REQ:
                handleStateReq(hdr);
                break;
            case StateHeader.STATE_RSP:
                handleStateRsp(hdr, msg.getBuffer());
                if(use_flush) {
            		stopFlush();
            	}
                break;
            default:
                if(log.isErrorEnabled()) log.error("type " + hdr.type + " not known in StateHeader");
                break;
            }
            return;
        }
        passUp(evt);
    }



    public void down(Event evt) {
        byte[] state;
        Address target, requester;
        StateTransferInfo info;
        StateHeader hdr;

        switch(evt.getType()) {

            case Event.TMP_VIEW:
            case Event.VIEW_CHANGE:
                handleViewChange((View)evt.getArg());
                break;

            // generated by JChannel.getState(). currently, getting the state from more than 1 mbr is not implemented
            case Event.GET_STATE:
                info=(StateTransferInfo)evt.getArg();
                if(info.target == null) {
                    target=determineCoordinator();
                }
                else {
                    target=info.target;
                    if(target.equals(local_addr)) {
                        if(log.isErrorEnabled()) log.error("GET_STATE: cannot fetch state from myself !");
                        target=null;
                    }
                }
                if(target == null) {
                    if(log.isDebugEnabled()) log.debug("GET_STATE: first member (no state)");
                    passUp(new Event(Event.GET_STATE_OK, new StateTransferInfo()));
                }
                else {
                    if(use_flush) {
                        startFlush(flush_timeout);
                    }
                    Message state_req=new Message(target, null, null);
                    state_req.putHeader(name, new StateHeader(StateHeader.STATE_REQ, local_addr, state_id++, null, info.state_id));
                    if(log.isDebugEnabled()) log.debug("GET_STATE: asking " + target + " for state");

                    // suspend sending and handling of mesage garbage collection gossip messages,
                    // fixes bugs #943480 and #938584). Wake up when state has been received
                    if(log.isDebugEnabled())
                        log.debug("passing down a SUSPEND_STABLE event");
                    passDown(new Event(Event.SUSPEND_STABLE, new Long(info.timeout)));
                    waiting_for_state_response=true;
                    start=System.currentTimeMillis();
                    passDown(new Event(Event.MSG, state_req));
                }
                return;                 // don't pass down any further !

            case Event.GET_APPLSTATE_OK:
                info=(StateTransferInfo)evt.getArg();
                state=info.state;
                String id=info.state_id;
                synchronized(state_requesters) {
                    if(state_requesters.size() == 0) {
                        if(warn)
                            log.warn("GET_APPLSTATE_OK: received application state, but there are no requesters !");
                        return;
                    }
                    if(isDigestNeeded()){
	                    if(digest == null) {
	                        if(warn) log.warn("GET_APPLSTATE_OK: received application state, but there is no digest !");
                        }
	                    else {
	                        digest=digest.copy();
                        }
                    }
                    if(stats) {
                        num_state_reqs++;
                        if(state != null)
                            num_bytes_sent+=state.length;
                        avg_state_size=num_bytes_sent / num_state_reqs;
                    }

                    Set requesters=(Set)state_requesters.get(id);
                    if(requesters == null || requesters.size() == 0) {
                        log.warn("received state for id=" + id + ", but there are no requesters for this ID");
                    }
                    else {
                        for(Iterator it=requesters.iterator(); it.hasNext();) {
                            requester=(Address)it.next();
                            final Message state_rsp=new Message(requester, null, state);
                            hdr=new StateHeader(StateHeader.STATE_RSP, local_addr, 0, digest, id);
                            state_rsp.putHeader(name, hdr);
                            if(trace)
                                log.trace("sending state for ID=" + id + " to " + requester + " (" + state.length + " bytes)");

                            // This has to be done in a separate thread, so we don't block on FC
                            // (see http://jira.jboss.com/jira/browse/JGRP-225 for details). This will be reverted once
                            // we have the threadless stack  (http://jira.jboss.com/jira/browse/JGRP-181)
                            // and out-of-band messages (http://jira.jboss.com/jira/browse/JGRP-205)
                            new Thread() {
                                public void run() {
                                   passDown(new Event(Event.MSG, state_rsp));
                                }
                            }.start();
                            // passDown(new Event(Event.MSG, state_rsp));
                        }
                        state_requesters.remove(id);
                    }
                }
                return;             // don't pass down any further !
            case Event.SUSPEND_OK:
            	if(use_flush) {
            		flush_promise.setResult(Boolean.TRUE);
            	}
            	break;
                
            case Event.CONFIG :
               Map config = (Map) evt.getArg();               
               if(config != null && config.containsKey("flush_timeout")){
                  Long ftimeout = (Long) config.get("flush_timeout");
                  use_flush = true;                  
                  flush_timeout = ftimeout.longValue();                               
               }
               break;     

        }

        passDown(evt);              // pass on to the layer below us
    }









    /* --------------------------- Private Methods -------------------------------- */

    /**
	 * When FLUSH is used we do not need to pass digests between members
	 *
	 * see JGroups/doc/design/PartialStateTransfer.txt
	 * see JGroups/doc/design/FLUSH.txt