org.jgroups.protocols.pbcast.ViewHandler Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
package org.jgroups.protocols.pbcast;
import org.jgroups.annotations.GuardedBy;
import org.jgroups.logging.Log;
import org.jgroups.util.BoundedList;
import org.jgroups.util.Util;
import java.util.*;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.BiPredicate;
import java.util.function.Consumer;
import java.util.stream.Collectors;
/**
* Responsible for dispatching JOIN/LEAVE/MERGE requests to the GMS protocol. Bundles multiple concurrent requests into
* a request list
* @param the type of the request
* @author Bela Ban
* @since 4.0.5
*/
public class ViewHandler {
protected final Collection requests=new ConcurrentLinkedQueue<>();
protected final Lock lock=new ReentrantLock();
protected final AtomicBoolean suspended=new AtomicBoolean(false);
@GuardedBy("lock")
protected final AtomicBoolean processing=new AtomicBoolean(false);
protected final Condition processing_done=lock.newCondition();
protected final GMS gms;
protected Consumer> req_processor;
protected BiPredicate req_matcher;
protected final BoundedList history=new BoundedList<>(20); // maintains a list of the last 20 requests
/**
* Constructor
* @param gms The ref to GMS
* @param req_processor A request processor which processes a list of requests
* @param req_matcher The matcher which determines whether any given 2 requests can be processed together
*/
public ViewHandler(GMS gms, Consumer> req_processor, BiPredicate req_matcher) {
if(req_processor == null)
throw new IllegalArgumentException("request processor cannot be null");
this.gms=gms;
this.req_processor=req_processor;
this.req_matcher=req_matcher != null? req_matcher : (a,b) -> true;
}
public boolean suspended() {return suspended.get();}
public boolean processing() {return processing.get();}
public int size() {return requests.size();}
public ViewHandler reqProcessor(Consumer> p) {req_processor=p; return this;}
public Consumer> reqProcessor() {return req_processor;}
public ViewHandler reqMatcher(BiPredicate m) {req_matcher=m; return this;}
public BiPredicate reqMatcher() {return req_matcher;}
public ViewHandler add(R req) {
if(_add(req))
process();
return this;
}
@SuppressWarnings("unchecked")
public ViewHandler add(R ... reqs) {
if(_add(reqs))
process();
return this;
}
public ViewHandler add(Collection reqs) {
if(_add(reqs))
process();
return this;
}
/** Clears the queue and discards new requests from now on */
public void suspend() {
if(suspended.compareAndSet(false, true)) {
lock.lock();
try {
requests.clear();
}
finally {
lock.unlock();
}
}
}
public void resume() {
suspended.compareAndSet(true, false);
}
/** Blocks the caller until the current set of requests being processed have been completed. Returns
* immediately if no requests are currently being processed */
public void waitUntilComplete() {
lock.lock();
try {
while(processing.get()) {
try {
processing_done.await();
}
catch(InterruptedException ignored) {
}
}
}
finally {
lock.unlock();
}
}
/** Blocks the caller until the current set of requests being processed have been completed, or the timeout
* elapsed.
* Returns immediately if no requests are currently being processed
* @param timeout Max time to wait in milliseconds
*/
public void waitUntilComplete(long timeout) {
long base=System.currentTimeMillis();
long now=0;
lock.lock();
try {
while(processing.get()) {
long delay=timeout-now;
if(delay <= 0)
break;
try {
processing_done.await(delay, TimeUnit.MILLISECONDS);
now=System.currentTimeMillis()-base;
}
catch(InterruptedException e) {
}
}
}
finally {
lock.unlock();
}
}
/** To be used by testing only! */
public > T processing(boolean flag) {
lock.lock();
try {
processing.set(flag);
if(flag == false)
processing_done.signalAll();
return (T)this;
}
finally {
lock.unlock();
}
}
public String dumpQueue() {
return requests.stream().map(Object::toString).collect(Collectors.joining("\n"));
}
public String dumpHistory() {
return String.join("\n", history);
}
public String toString() {
return Util.printListWithDelimiter(requests, ", ");
}
protected Log log() {return gms.getLog();}
protected boolean _add(R req) {
if(req == null)
return false;
if(suspended.get()) {
log().trace("%s: queue is suspended; request %s is discarded", gms.getAddress(), req);
return false;
}
String log= Util.utcNow() + ": " + req;
lock.lock();
try {
if(!requests.contains(req)) { // non-null check already performed (above)
requests.add(req);
history.add(log);
}
return processing.compareAndSet(false, true);
}
finally {
lock.unlock();
}
}
@SuppressWarnings("unchecked")
protected boolean _add(R ... reqs) {
if(reqs == null || reqs.length == 0)
return false;
return _add(Arrays.asList(reqs));
}
protected boolean _add(Collection reqs) {
if(reqs == null || reqs.isEmpty())
return false;
if(suspended.get()) {
log().trace("%s: queue is suspended; requests %s are discarded", gms.getAddress(), reqs);
return false;
}
lock.lock();
try {
for(R req: reqs) {
if(req != null && !requests.contains(req)) {
requests.add(req);
history.add(Util.utcNow() + ": " + req);
}
}
return processing.compareAndSet(false, true);
}
finally {
lock.unlock();
}
}
/** We're guaranteed that only one thread will be called with this method at any time */
protected void process() {
for(;;) {
while(!requests.isEmpty()) {
Collection reqs=null;
lock.lock();
try {
reqs=remove(requests); // remove matching requests
}
finally {
lock.unlock();
}
if(reqs != null && !reqs.isEmpty()) {
try {
req_processor.accept(reqs); // process outside of the lock scope
}
catch(Throwable t) {
log().error("%s: failed processsing requests: %s", gms.addr(), t);
lock.lock();
try {
if(processing.compareAndSet(true, false))
processing_done.signalAll();
throw t;
}
finally {
lock.unlock();
}
}
}
}
lock.lock();
try {
if(requests.isEmpty()) {
if(processing.compareAndSet(true, false))
processing_done.signalAll();
return;
}
}
finally {
lock.unlock();
}
}
}
/**
* Removes requests as long as they match - breaks at the first non-matching request or when requests is empty
* This method must catch all exceptions; or else process() might return without setting processing to true again!
*/
@GuardedBy("lock")
protected Collection remove(Collection requests) {
Collection removed=new ArrayList<>();
R first_req=null;
Iterator it=requests.iterator();
try {
if(it.hasNext()) { // safeguard to prevent https://issues.redhat.com/browse/JGRP-2718
first_req=it.next();
removed.add(first_req);
it.remove();
}
while(it.hasNext()) {
R next=it.next();
if(req_matcher.test(first_req, next)) {
removed.add(next);
it.remove();
}
else
break;
}
}
catch(Throwable t) {
log().error("failed processing requests", t);
}
return removed;
}
}