package org.jgroups.protocols.pbcast;
import org.jgroups.*;
import org.jgroups.annotations.GuardedBy;
import org.jgroups.annotations.MBean;
import org.jgroups.annotations.ManagedAttribute;
import org.jgroups.annotations.ManagedOperation;
import org.jgroups.stack.Protocol;
import org.jgroups.stack.StateTransferInfo;
import org.jgroups.util.Digest;
import org.jgroups.util.StateTransferResult;
import org.jgroups.util.Util;
import java.io.*;
import java.util.*;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
/**
* STATE_TRANSFER protocol based on byte array transfer. 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
* @see STATE
* @see STATE_SOCK
*/
@MBean(description="State transfer protocol based on byte array transfer")
public class STATE_TRANSFER extends Protocol {
/* --------------------------------------------- JMX statistics --------------------------------------------- */
private long start, stop; // to measure state transfer time
private final AtomicInteger num_state_reqs=new AtomicInteger(0);
private final AtomicLong num_bytes_sent=new AtomicLong(0);
private double avg_state_size=0;
/* --------------------------------------------- Fields ------------------------------------------------------ */
private Address local_addr=null;
@GuardedBy("members")
private final List<Address> members=new ArrayList<Address>();
/**
* Set of state requesters
*/
private final Set<Address> state_requesters=new HashSet<Address>();
/** set to true while waiting for a STATE_RSP */
private volatile boolean waiting_for_state_response=false;
private boolean flushProtocolInStack=false;
/** Used to prevent spurious open and close barrier calls */
@ManagedAttribute(description="whether or not the barrier is closed")
protected AtomicBoolean barrier_closed=new AtomicBoolean(false);
@ManagedAttribute
public int getNumberOfStateRequests() {
return num_state_reqs.get();
}
@ManagedAttribute
public long getNumberOfStateBytesSent() {
return num_bytes_sent.get();
}
@ManagedAttribute
public double getAverageStateSize() {
return avg_state_size;
}
public List<Integer> requiredDownServices() {
List<Integer> retval=new ArrayList<Integer>();
retval.add(Event.GET_DIGEST);
retval.add(Event.OVERWRITE_DIGEST);
return retval;
}
public void resetStats() {
super.resetStats();
num_state_reqs.set(0);
num_bytes_sent.set(0);
avg_state_size=0;
}
public void init() throws Exception {}
public void start() throws Exception {
Map<String,Object> map=new HashMap<String,Object>();
map.put("state_transfer", Boolean.TRUE);
map.put("protocol_class", getClass().getName());
up_prot.up(new Event(Event.CONFIG, map));
}
public void stop() {
super.stop();
waiting_for_state_response=false;
}
@ManagedOperation(description="Closes BARRIER and suspends STABLE")
public void closeBarrierAndSuspendStable() {
if(!isDigestNeeded() || !barrier_closed.compareAndSet(false, true))
return;
if(log.isTraceEnabled())
log.trace(local_addr + ": sending down CLOSE_BARRIER and SUSPEND_STABLE");
down_prot.down(new Event(Event.CLOSE_BARRIER));
down_prot.down(new Event(Event.SUSPEND_STABLE));
}
@ManagedOperation(description="Opens BARRIER and resumes STABLE")
public void openBarrierAndResumeStable() {
if(!isDigestNeeded() || !barrier_closed.compareAndSet(true, false))
return;
if(log.isTraceEnabled())
log.trace(local_addr + ": sending down OPEN_BARRIER and RESUME_STABLE");
down_prot.down(new Event(Event.OPEN_BARRIER));
down_prot.down(new Event(Event.RESUME_STABLE));
}
public Object up(Event evt) {
switch(evt.getType()) {
case Event.MSG:
Message msg=(Message)evt.getArg();
StateHeader hdr=(StateHeader)msg.getHeader(this.id);
if(hdr == null)
break;
switch(hdr.type) {
case StateHeader.STATE_REQ:
handleStateReq(msg.getSrc());
break;
case StateHeader.STATE_RSP:
closeBarrierAndSuspendStable(); // fix for https://jira.jboss.org/jira/browse/JGRP-1013
try {
handleStateRsp(hdr, msg.getBuffer());
}
catch(Throwable t) {
handleException(t);
}
finally {
openBarrierAndResumeStable();
}
break;
case StateHeader.STATE_EX:
handleException((Throwable)msg.getObject());
break;
default:
if(log.isErrorEnabled())
log.error("type " + hdr.type + " not known in StateHeader");
break;
}
return null;
case Event.TMP_VIEW:
case Event.VIEW_CHANGE:
handleViewChange((View)evt.getArg());
break;
case Event.CONFIG:
Map<String,Object> config=(Map<String,Object>)evt.getArg();
if(config != null && config.containsKey("state_transfer")) {
log.error("Protocol stack cannot contain two state transfer protocols. Remove either one of them");
}
break;
}
return up_prot.up(evt);
}
public Object down(Event evt) {
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:
Address target;
StateTransferInfo info=(StateTransferInfo)evt.getArg();
if(info.target == null) {
target=determineCoordinator();
}
else {
target=info.target;
if(target.equals(local_addr)) {
if(log.isErrorEnabled())
log.error(local_addr + ": cannot fetch state from myself !");
target=null;
}
}
if(target == null) {
if(log.isDebugEnabled())
log.debug(local_addr + ": first member (no state)");
up_prot.up(new Event(Event.GET_STATE_OK, new StateTransferInfo()));
}
else {
Message state_req=new Message(target, null, null);
state_req.putHeader(this.id, new StateHeader(StateHeader.STATE_REQ));
if(log.isDebugEnabled())
log.debug(local_addr + ": asking " + target + " for state");
// suspend sending and handling of message 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");
down_prot.down(new Event(Event.SUSPEND_STABLE, new Long(info.timeout)));*/
waiting_for_state_response=true;
start=System.currentTimeMillis();
down_prot.down(new Event(Event.MSG, state_req));
}
return null; // don't pass down any further !
case Event.CONFIG:
Map<String,Object> config=(Map<String,Object>)evt.getArg();
if(config != null && config.containsKey("flush_supported")) {
flushProtocolInStack=true;
}
break;
case Event.SET_LOCAL_ADDRESS:
local_addr=(Address)evt.getArg();
break;
}
return down_prot.down(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
*
* @return true if use of digests is required, false otherwise
*/
private boolean isDigestNeeded() {
return !flushProtocolInStack;
}
/**
* Return the first element of members which is not me. Otherwise return null.
*/
private Address determineCoordinator() {
synchronized(members) {
for(Address member:members) {
if(!local_addr.equals(member)) {
return member;
}
}
}
return null;
}
private void handleViewChange(View v) {
Address old_coord;
List<Address> new_members=v.getMembers();
boolean send_up_exception=false;
synchronized(members) {
old_coord=(!members.isEmpty()? members.get(0) : null);
members.clear();
members.addAll(new_members);
// this handles the case where a coord dies during a state transfer; prevents clients from hanging forever
// Note this only takes a coordinator crash into account, a getState(target, timeout), where target is not
// null is not handled ! (Usually we get the state from the coordinator)
// http://jira.jboss.com/jira/browse/JGRP-148
if(waiting_for_state_response && old_coord != null && !members.contains(old_coord))
send_up_exception=true;
}
if(send_up_exception) {
if(log.isWarnEnabled())
log.warn(local_addr + ": discovered that the state provider (" + old_coord + ") left");
waiting_for_state_response=false;
Exception ex=new EOFException("state provider " + old_coord + " left");
up_prot.up(new Event(Event.GET_STATE_OK, new StateTransferResult(ex)));
openBarrierAndResumeStable();
}
synchronized(state_requesters) {
boolean was_empty=state_requesters.isEmpty();
state_requesters.removeAll(new_members);
if(!was_empty && state_requesters.isEmpty())
openBarrierAndResumeStable();
}
}
protected void handleException(Throwable exception) {
openBarrierAndResumeStable();
up_prot.up(new Event(Event.GET_STATE_OK, new StateTransferResult(exception)));
}
private void handleStateReq(Address requester) {
if(requester == null)
return;
if(log.isDebugEnabled())
log.debug(local_addr + ": received state request from " + requester);
synchronized(state_requesters) {
if(state_requesters.isEmpty())
closeBarrierAndSuspendStable();
state_requesters.add(requester);
Digest digest=null;
try {
if(isDigestNeeded())
digest=(Digest)down_prot.down(new Event(Event.GET_DIGEST));
getStateFromApplication(requester, digest);
}
catch(Throwable t) {
sendException(requester, t);
}
finally {
if(state_requesters.remove(requester) && state_requesters.isEmpty())
openBarrierAndResumeStable();
}
}
}
protected void getStateFromApplication(Address requester, Digest digest) {
StateTransferInfo rsp=(StateTransferInfo)up_prot.up(new Event(Event.GET_APPLSTATE));
byte[] state=rsp.state;
if(stats) {
num_state_reqs.incrementAndGet();
if(state != null)
num_bytes_sent.addAndGet(state.length);
avg_state_size=num_bytes_sent.doubleValue() / num_state_reqs.doubleValue();
}
Message state_rsp=new Message(requester, null, state);
state_rsp.putHeader(this.id, new StateHeader(StateHeader.STATE_RSP, digest));
if(log.isTraceEnabled()) {
int length=state != null? state.length : 0;
if(log.isTraceEnabled())
log.trace(local_addr + ": sending state to " + state_rsp.getDest() + " (size=" + Util.printBytes(length) + ")");
}
down_prot.down(new Event(Event.MSG, state_rsp));
}
protected void sendException(Address requester, Throwable exception) {
try {
Message ex_msg=new Message(requester, null, exception);
ex_msg.putHeader(getId(), new StateHeader(StateHeader.STATE_EX));
down(new Event(Event.MSG, ex_msg));
}
catch(Throwable t) {
log.error(local_addr + ": failed sending exception " + exception.toString() + " to " + requester);
}
}
/** Set the digest and the send the state up to the application */
private void handleStateRsp(StateHeader hdr, byte[] state) {
Digest tmp_digest=hdr.my_digest;
boolean digest_needed=isDigestNeeded();
waiting_for_state_response=false;
if(digest_needed && tmp_digest != null)
down_prot.down(new Event(Event.OVERWRITE_DIGEST, tmp_digest)); // set the digest (e.g. in NAKACK)
stop=System.currentTimeMillis();
log.debug(local_addr + ": received state, size=" + (state == null? "0" : Util.printBytes(state.length)) +
", time=" + (stop - start) + " milliseconds");
StateTransferResult result=new StateTransferResult(state);
up_prot.up(new Event(Event.GET_STATE_OK, result));
}
/* ------------------------ End of Private Methods ------------------------------ */
/**
* Wraps data for a state request/response. Note that for a state response
* the actual state will <em>not</em
* be stored in the header itself, but in the message's buffer.
*
*/
public static class StateHeader extends Header {
public static final byte STATE_REQ = 1;
public static final byte STATE_RSP = 2;
public static final byte STATE_EX = 3;
protected byte type=0;
protected Digest my_digest; // digest of sender (if type is STATE_RSP)
public StateHeader() { // for externalization
}
public StateHeader(byte type) {
this.type=type;
}
public StateHeader(byte type, Digest digest) {
this.type=type;
this.my_digest=digest;
}
public int getType() {
return type;
}
public Digest getDigest() {
return my_digest;
}
public String toString() {
StringBuilder sb=new StringBuilder();
sb.append("type=").append(type2Str(type));
if(my_digest != null)
sb.append(", digest=").append(my_digest);
return sb.toString();
}
static String type2Str(int t) {
switch(t) {
case STATE_REQ: return "STATE_REQ";
case STATE_RSP: return "STATE_RSP";
case STATE_EX: return "STATE_EX";
default: return "<unknown>";
}
}
public void writeTo(DataOutput out) throws Exception {
out.writeByte(type);
Util.writeStreamable(my_digest, out);
}
public void readFrom(DataInput in) throws Exception {
type=in.readByte();
my_digest=(Digest)Util.readStreamable(Digest.class, in);
}
public int size() {
int retval=Global.BYTE_SIZE; // type
retval+=Global.BYTE_SIZE; // presence byte for my_digest
if(my_digest != null)
retval+=my_digest.serializedSize();
return retval;
}
}
}