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XCOMMONS-3330: Job groups with several threads may not return a current job #1329

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XCOMMONS-3330: Job groups with several threads may not return a current job #1329

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ef19fc1
XCOMMONS-3330: Job groups with several threads may not return a curre…
michitux May 9, 2025
a6ce3ef
XCOMMONS-3330: Job groups with several threads may not return a curre…
michitux May 9, 2025
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19 changes: 19 additions & 0 deletions ...core/xwiki-commons-job/xwiki-commons-job-api/src/main/java/org/xwiki/job/JobExecutor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,9 +19,12 @@
*/
package org.xwiki.job;

import java.util.Collection;
import java.util.Collections;
import java.util.List;

import org.xwiki.component.annotation.Role;
import org.xwiki.stability.Unstable;

/**
* By default Jobs are either executed asynchronously whenever there is a free thread in the pool. Jobs can implement
Expand All @@ -40,9 +43,25 @@ public interface JobExecutor
*
* @param groupPath the group path
* @return the currently running job in the passed group
* @deprecated Use {@link #getCurrentJobs(JobGroupPath)} instead.
*/
@Deprecated(since = "17.4.0RC1")
Job getCurrentJob(JobGroupPath groupPath);

/**
* The set of jobs running within the specified job group.
*
* @param groupPath the path of the job group for which the current jobs should be retrieved
* @return a collection containing the currently running jobs in the provided group
* @since 17.4.0RC1
*/
@Unstable
default Collection<Job> getCurrentJobs(JobGroupPath groupPath)
{
// Not really accurate, but better than nothing.
return Collections.singleton(getCurrentJob(groupPath));
}

/**
* Return job corresponding to the provided id from the current executed or waiting jobs.
*
Expand Down
103 changes: 60 additions & 43 deletions ...ob/xwiki-commons-job-default/src/main/java/org/xwiki/job/internal/DefaultJobExecutor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,9 +19,15 @@
*/
package org.xwiki.job.internal;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedQueue;
Expand Down Expand Up @@ -72,11 +78,12 @@ private class JobGroupExecutor extends JobThreadExecutor implements ThreadFactor

private final JobGroupPath path;

private Job currentJob;
private final Set<Job> currentJobs =
Collections.synchronizedSet(Collections.newSetFromMap(new IdentityHashMap<>()));

private String groupThreadName;
private final String groupThreadName;

private GroupedJobInitializer initializer;
private final GroupedJobInitializer initializer;

JobGroupExecutor(JobGroupPath path, GroupedJobInitializer initializer)
{
Expand All @@ -96,7 +103,7 @@ private class JobGroupExecutor extends JobThreadExecutor implements ThreadFactor
@Override
protected String getThreadName(Runnable r)
{
return this.groupThreadName + " - " + this.currentJob;
return this.groupThreadName + " - " + r;
}

@Override
Expand All @@ -110,7 +117,7 @@ protected void beforeExecute(Thread t, Runnable r)
{
DefaultJobExecutor.this.lockTree.lock(this.path);

this.currentJob = (Job) r;
this.currentJobs.add((Job) r);

super.beforeExecute(t, r);
}
Expand All @@ -120,22 +127,26 @@ protected void afterExecute(Runnable r, Throwable t)
{
DefaultJobExecutor.this.lockTree.unlock(this.path);

this.currentJob = null;
Job job = (Job) r;

super.afterExecute(r, t);
this.currentJobs.remove(job);

Job job = (Job) r;
super.afterExecute(r, t);

List<String> jobId = job.getRequest().getId();
if (jobId != null) {
synchronized (DefaultJobExecutor.this.groupedJobs) {
Queue<Job> jobQueue = DefaultJobExecutor.this.groupedJobs.get(jobId);
if (jobQueue != null) {
if (jobQueue.peek() == job) {
jobQueue.poll();
}
// Use compute() to synchronize on the job ID to avoid concurrent insertion/deletion by other threads.
DefaultJobExecutor.this.groupedJobs.compute(jobId, (k, v) -> {
if (v != null && v.peek() == job) {
v.poll();
}
}

if (v == null || v.isEmpty()) {
return null;
}

return v;
});
}
}

Expand Down Expand Up @@ -187,12 +198,13 @@ protected void afterExecute(Runnable r, Throwable t)

List<String> jobId = job.getRequest().getId();
if (jobId != null) {
synchronized (DefaultJobExecutor.this.jobs) {
Job storedJob = DefaultJobExecutor.this.jobs.get(jobId);
if (storedJob == job) {
DefaultJobExecutor.this.jobs.remove(jobId);
DefaultJobExecutor.this.jobs.computeIfPresent(jobId, (k, v) -> {
if (v == job) {
return null;
}
}

return v;
});
}

// Reset thread name since it's not used anymore
Expand Down Expand Up @@ -262,11 +274,23 @@ public void dispose() throws ComponentLifecycleException
// JobManager

@Override
public Job getCurrentJob(JobGroupPath path)
public Job getCurrentJob(JobGroupPath groupPath)
{
// Provide a default implementation so implementors of this interface can stop implementing this method.
return getCurrentJobs(groupPath).stream().findFirst().orElse(null);
}

@Override
public Collection<Job> getCurrentJobs(JobGroupPath path)
{
JobGroupExecutor executor = this.groupExecutors.get(path);

return executor != null ? executor.currentJob : null;
if (executor != null) {
// Return an unmodifiable copy of the set of currently running jobs.
return Collections.unmodifiableCollection(new ArrayList<>(executor.currentJobs));
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It's not clear to me why you create an ArrayList. Isn't Collections.unmodifiableCollection enough to make the set readonly ?

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I want to avoid that the collection updates when jobs are started or stopped. I would expect that we expose this method in a script service and I don't want to let the author of a Velocity script deal with the fact that directly after isEmpty() returns false, there might not be any elements anymore in the collection.

We could also let this return a List, this might make things more explicit what to expect in terms of the different operations?

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I want to avoid that the collection updates when jobs are started or stopped.

Very good point indeed.

We could also let this return a List, this might make things more explicit what to expect in terms of the different operations?

Why not.

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Done. I also found and fixed some issues in the implementations for constructing the list both in the default and in the actual implementation.

}

return Collections.emptyList();
}

@Override
Expand All @@ -281,10 +305,7 @@ public Job getJob(List<String> id)
// Is it in a group
Queue<Job> jobQueue = this.groupedJobs.get(id);
if (jobQueue != null) {
job = jobQueue.peek();
if (job != null) {
return job;
}
return jobQueue.peek();
}

return null;
Expand Down Expand Up @@ -324,8 +345,8 @@ public Job execute(String jobType, Request request) throws JobException
public void execute(Job job)
{
if (!this.disposed) {
if (job instanceof GroupedJob) {
executeGroupedJob((GroupedJob) job);
if (job instanceof GroupedJob groupedJob) {
executeGroupedJob(groupedJob);
} else {
executeSingleJob(job);
}
Expand All @@ -348,6 +369,8 @@ private void executeSingleJob(Job job)

private void executeGroupedJob(GroupedJob job)
{
// While synchronization isn't necessary for the insertion in the group executors, this ensures that jobs in
// the "groupedJobs" queues have the same order as in the executor's queue.
synchronized (this.groupExecutors) {
JobGroupPath path = job.getGroupPath();

Expand All @@ -358,26 +381,20 @@ private void executeGroupedJob(GroupedJob job)
return;
}

JobGroupExecutor groupExecutor = this.groupExecutors.get(path);

if (groupExecutor == null) {
groupExecutor =
new JobGroupExecutor(path, this.groupedJobInitializerManager.getGroupedJobInitializer(path));
this.groupExecutors.put(path, groupExecutor);
}
JobGroupExecutor groupExecutor = this.groupExecutors.computeIfAbsent(path,
p -> new JobGroupExecutor(p, this.groupedJobInitializerManager.getGroupedJobInitializer(p)));

groupExecutor.execute(job);

List<String> jobId = job.getRequest().getId();
if (jobId != null) {
synchronized (this.groupedJobs) {
Queue<Job> jobQueue = this.groupedJobs.get(jobId);
if (jobQueue == null) {
jobQueue = new ConcurrentLinkedQueue<>();
this.groupedJobs.put(jobId, jobQueue);
}
jobQueue.offer(job);
}
// Use compute() to synchronize on the job ID to prevent that another thread would remove the empty
// queue again.
this.groupedJobs.compute(jobId, (k, v) -> {
Queue<Job> queue = Objects.requireNonNullElseGet(v, ConcurrentLinkedQueue::new);
queue.offer(job);
return queue;
});
}
}
}
Expand Down