package org.jgroups.blocks;
import org.jgroups.Address;
import org.jgroups.Message;
import org.jgroups.Transport;
import org.jgroups.View;
import org.jgroups.annotations.GuardedBy;
import org.jgroups.util.Rsp;
import org.jgroups.util.RspList;
import java.util.*;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
/**
* Sends a message to all members of the group and waits for all responses (or
* timeout). Returns a boolean value (success or failure). Results (if any) can
* be retrieved when done.
* <p>
* The supported transport to send requests is currently either a
* RequestCorrelator or a generic Transport. One of them has to be given in the
* constructor. It will then be used to send a request. When a message is
* received by either one, the receiveResponse() of this class has to be called
* (this class does not actively receive requests/responses itself). Also, when
* a view change or suspicion is received, the methods viewChange() or suspect()
* of this class have to be called.
* <p>
* When started, an array of responses, correlating to the membership, is
* created. Each response is added to the corresponding field in the array. When
* all fields have been set, the algorithm terminates. This algorithm can
* optionally use a suspicion service (failure detector) to detect (and exclude
* from the membership) fauly members. If no suspicion service is available,
* timeouts can be used instead (see <code>execute()</code>). When done, a
* list of suspected members can be retrieved.
* <p>
* Because a channel might deliver requests, and responses to <em>different</em>
* requests, the <code>GroupRequest</code> class cannot itself receive and
* process requests/responses from the channel. A mechanism outside this class
* has to do this; it has to determine what the responses are for the message
* sent by the <code>execute()</code> method and call
* <code>receiveResponse()</code> to do so.
* <p>
* <b>Requirements</b>: lossless delivery, e.g. acknowledgment-based message
* confirmation.
*
* @author Bela Ban
*/
public class GroupRequest extends Request {
/** Correlates requests and responses */
@GuardedBy("lock")
private final Map<Address,Rsp> requests;
@GuardedBy("lock")
int num_received, num_not_received, num_suspected;
/**
* @param msg The message to be sent
* @param corr The request correlator to be used. A request correlator sends requests tagged with a unique ID and
* notifies the sender when matching responses are received. The reason <code>GroupRequest</code> uses
* it instead of a <code>Transport</code> is that multiple requests/responses might be sent/received concurrently
* @param targets The targets, which are supposed to receive the message. Any receiver not in this set will
* discard the message. Targets are always a subset of the current membership
* @param options The request options to be used for this call
*/
public GroupRequest(Message msg, RequestCorrelator corr, Collection<Address> targets, RequestOptions options) {
super(msg, corr, null, options);
int size=targets.size();
requests=new HashMap<Address,Rsp>(size);
setTargets(targets);
}
public GroupRequest(Message m, RequestCorrelator corr, Address target, RequestOptions options) {
super(m, corr, null, options);
requests=new HashMap<Address,Rsp>(1);
setTarget(target);
}
public GroupRequest(Message m, Transport transport, Collection<Address> mbrs, RequestOptions options) {
super(m, null, transport, options);
int size=mbrs.size();
requests=new HashMap<Address,Rsp>(size);
setTargets(mbrs);
}
public boolean getAnycasting() {
return options.getAnycasting();
}
public void setAnycasting(boolean anycasting) {
options.setAnycasting(anycasting);
}
public void sendRequest() throws Exception {
sendRequest(requests.keySet(), req_id);
}
/* ---------------------- Interface RspCollector -------------------------- */
/**
* <b>Callback</b> (called by RequestCorrelator or Transport).
* Adds a response to the response table. When all responses have been received,
* <code>execute()</code> returns.
*/
public void receiveResponse(Object response_value, Address sender) {
if(done)
return;
Rsp rsp=requests.get(sender);
if(rsp == null)
return;
RspFilter rsp_filter=options.getRspFilter();
boolean responseReceived=false;
lock.lock();
try {
if(!rsp.wasReceived()) {
if((responseReceived=(rsp_filter == null) || rsp_filter.isAcceptable(response_value, sender)))
rsp.setValue(response_value);
rsp.setReceived(responseReceived);
}
if(responseReceived)
num_received++;
done=rsp_filter == null? responsesComplete() : !rsp_filter.needMoreResponses();
if(responseReceived || done)
completed.signalAll(); // wakes up execute()
if(done && corr != null)
corr.done(req_id);
}
finally {
lock.unlock();
}
if(responseReceived || done)
checkCompletion(this);
}
/**
* <b>Callback</b> (called by RequestCorrelator or Transport).
* Report to <code>GroupRequest</code> that a member is reported as faulty (suspected).
* This method would probably be called when getting a suspect message from a failure detector
* (where available). It is used to exclude faulty members from the response list.
*/
public void suspect(Address suspected_member) {
if(suspected_member == null)
return;
boolean changed=false;
Rsp rsp=requests.get(suspected_member);
if(rsp != null) {
if(rsp.setSuspected(true)) {
rsp.setValue(null);
changed=true;
lock.lock();
try {
num_suspected++;
completed.signalAll();
}
finally {
lock.unlock();
}
}
}
if(changed)
checkCompletion(this);
}
/**
* Any member of 'membership' that is not in the new view is flagged as
* SUSPECTED. Any member in the new view that is <em>not</em> in the
* membership (ie, the set of responses expected for the current RPC) will
* <em>not</em> be added to it. If we did this we might run into the
* following problem:
* <ul>
* <li>Membership is {A,B}
* <li>A sends a synchronous group RPC (which sleeps for 60 secs in the
* invocation handler)
* <li>C joins while A waits for responses from A and B
* <li>If this would generate a new view {A,B,C} and if this expanded the
* response set to {A,B,C}, A would wait forever on C's response because C
* never received the request in the first place, therefore won't send a
* response.
* </ul>
*/
public void viewChange(View new_view) {
Vector<Address> mbrs=new_view != null? new_view.getMembers() : null;
if(mbrs == null)
return;
boolean changed=false;
if(requests == null || requests.isEmpty())
return;
lock.lock();
try {
for(Map.Entry<Address,Rsp> entry: requests.entrySet()) {
Address mbr=entry.getKey();
if(!mbrs.contains(mbr)) {
Rsp rsp=entry.getValue();
rsp.setValue(null);
if(rsp.setSuspected(true)) {
num_suspected++;
changed=true;
}
}
}
if(changed)
completed.signalAll();
}
finally {
lock.unlock();
}
if(changed)
checkCompletion(this);
}
/* -------------------- End of Interface RspCollector ----------------------------------- */
/** Returns the results as a RspList */
public RspList getResults() {
Collection<Rsp> rsps=requests.values();
return new RspList(rsps);
}
public RspList get() throws InterruptedException, ExecutionException {
lock.lock();
try {
waitForResults(0);
}
finally {
lock.unlock();
}
return getResults();
}
public RspList get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
boolean ok;
lock.lock();
try {
ok=waitForResults(unit.toMillis(timeout));
}
finally {
lock.unlock();
}
if(!ok)
throw new TimeoutException();
return getResults();
}
public String toString() {
StringBuilder ret=new StringBuilder(128);
ret.append(super.toString());
if(!requests.isEmpty()) {
ret.append(", entries:\n");
for(Map.Entry<Address,Rsp> entry: requests.entrySet()) {
Address mbr=entry.getKey();
Rsp rsp=entry.getValue();
ret.append(mbr).append(": ").append(rsp).append("\n");
}
}
return ret.toString();
}
/* --------------------------------- Private Methods -------------------------------------*/
private void setTarget(Address mbr) {
requests.put(mbr, new Rsp(mbr));
num_not_received=1;
}
private void setTargets(Collection<Address> mbrs) {
for(Address mbr: mbrs)
requests.put(mbr, new Rsp(mbr));
num_not_received=requests.size();
}
private static int determineMajority(int i) {
return i < 2? i : (i / 2) + 1;
}
private void sendRequest(final Collection<Address> targetMembers, long requestId) throws Exception {
try {
if(corr != null) {
corr.sendRequest(requestId, targetMembers, request_msg, options.getMode() == GET_NONE? null : this, options);
}
else {
if(options.getAnycasting()) {
for(Address mbr: targetMembers) {
Message copy=request_msg.copy(true);
copy.setDest(mbr);
transport.send(copy);
}
}
else {
transport.send(request_msg);
}
}
}
catch(Exception ex) {
if(corr != null)
corr.done(requestId);
throw ex;
}
}
@GuardedBy("lock")
protected boolean responsesComplete() {
if(done)
return true;
final int num_total=requests.size();
switch(options.getMode()) {
case GET_FIRST:
if(num_received > 0)
return true;
if(num_suspected >= num_total)
// e.g. 2 members, and both suspected
return true;
break;
case GET_ALL:
return num_received + num_suspected >= num_total;
case GET_MAJORITY:
int majority=determineMajority(num_total);
if(num_received + num_suspected >= majority)
return true;
break;
case GET_ABS_MAJORITY:
majority=determineMajority(num_total);
if(num_received >= majority)
return true;
break;
case GET_N:
return true;
case GET_NONE:
return true;
default :
if(log.isErrorEnabled()) log.error("rsp_mode " + options.getMode() + " unknown !");
break;
}
return false;
}
}