Skip to content

[Broker] Fix possible data race in getFirstAvailableConsumerPermits #10831

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Merged
merlimat merged 2 commits into from
Jun 5, 2021
Merged

[Broker] Fix possible data race in getFirstAvailableConsumerPermits #10831

merlimat merged 2 commits into from
Jun 5, 2021

Conversation

@lhotari
Copy link
Member

@lhotari lhotari commented Jun 4, 2021

Motivation

  • there's a chance for a data race so that the consumer's available permits goes
    below zero after it has been checked in isConsumerAvailable

Modifications

  • check that availablePermits > 0 before returning

@lhotari
Fix possible race in getFirstAvailableConsumerPermits
c297074 
- there's a chance for a race so that the consumer's available permits goes
  below zero after it has been checked in "isConsumerAvailable"
@lhotari lhotari added the type/bug The PR fixed a bug or issue reported a bug label Jun 4, 2021
@lhotari lhotari added this to the 2.8.0 milestone Jun 4, 2021
@lhotari lhotari self-assigned this Jun 4, 2021
@michaeljmarshall
Copy link
Member

michaeljmarshall commented Jun 4, 2021 •
edited
Loading

@lhotari - in order to call get on the atomic wrapper just once, what if we added a new method that returns an Optional<Integer> that is a combination of the isConsumerAvailable and the getAvailablePermits methods? It would introduce additional overhead for the new objects, so perhaps it's an unnecessary change. Do you have a preference?

codelipenghui
codelipenghui reviewed Jun 5, 2021
View reviewed changes
.../java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherMultipleConsumers.java Outdated
Comment on lines 675 to 680
if (isConsumerAvailable(consumer)) {
return consumer.getAvailablePermits();
int availablePermits = consumer.getAvailablePermits();
if (availablePermits > 0) {
return availablePermits;
}
}
Copy link
Contributor

@codelipenghui codelipenghui Jun 5, 2021

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Is better to change to:

if (consumer != null && !consumer.isBlocked()) {
       return consumer.getAvailablePermits();
}

So that we don't need to check availablePermits twice

Copy link
Member Author

@lhotari lhotari Jun 5, 2021

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

@codelipenghui Done. PTAL

@codelipenghui codelipenghui modified the milestones: 2.8.0, 2.9.0 Jun 5, 2021
@lhotari
Copy link
Member Author

lhotari commented Jun 5, 2021

@lhotari - in order to call get on the atomic wrapper just once, what if we added a new method that returns an Optional<Integer> that is a combination of the isConsumerAvailable and the getAvailablePermits methods? It would introduce additional overhead for the new objects, so perhaps it's an unnecessary change. Do you have a preference?

In this part of code I believe that there's a goal of zero allocations since this is part of a hot code path. Therefore, omitting the usage of Optional is also desired.

michaeljmarshall
michaeljmarshall approved these changes Jun 5, 2021
View reviewed changes
Copy link
Member

@michaeljmarshall michaeljmarshall left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

LGTM

@merlimat merlimat merged commit bd568bc into apache:master Jun 5, 2021
@merlimat merlimat modified the milestones: 2.9.0, 2.8.0 Jun 5, 2021
eolivelli pushed a commit to datastax/pulsar that referenced this pull request Jun 7, 2021
@lhotari @eolivelli
[Broker] Fix possible data race in getFirstAvailableConsumerPermits (a…
9f30951 
…pache#10831)

* Fix possible race in getFirstAvailableConsumerPermits

- there's a chance for a race so that the consumer's available permits goes
  below zero after it has been checked in "isConsumerAvailable"

* Address review feedback

(cherry picked from commit bd568bc)
yangl pushed a commit to yangl/pulsar that referenced this pull request Jun 23, 2021
@lhotari @yangl
[Broker] Fix possible data race in getFirstAvailableConsumerPermits (a…
fbcfcf7 
…pache#10831)

* Fix possible race in getFirstAvailableConsumerPermits

- there's a chance for a race so that the consumer's available permits goes
  below zero after it has been checked in "isConsumerAvailable"

* Address review feedback
@codelipenghui codelipenghui added cherry-picked/branch-2.8 Archived: 2.8 is end of life and removed cherry-picked/branch-2.8 Archived: 2.8 is end of life release/2.8.1 release/2.7.3 labels Jun 25, 2021
@codelipenghui
Copy link
Contributor

codelipenghui commented Jun 27, 2021

This PR fixes the issues introduce by #10417, so don't need to cherry-pick to branch-2.7

bharanic-dev pushed a commit to bharanic-dev/pulsar that referenced this pull request Mar 18, 2022
@lhotari @splunk-xingw
[Broker] Fix possible data race in getFirstAvailableConsumerPermits (a…
45e997a 
…pache#10831)

* Fix possible race in getFirstAvailableConsumerPermits

- there's a chance for a race so that the consumer's available permits goes
  below zero after it has been checked in "isConsumerAvailable"

* Address review feedback
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@merlimat merlimat merlimat approved these changes

@codelipenghui codelipenghui codelipenghui approved these changes

@michaeljmarshall michaeljmarshall michaeljmarshall approved these changes

@rdhabalia rdhabalia Awaiting requested review from rdhabalia

@eolivelli eolivelli Awaiting requested review from eolivelli

Assignees

@lhotari lhotari

Labels

type/bug The PR fixed a bug or issue reported a bug

Projects

None yet

Milestone

2.8.0

Development

Successfully merging this pull request may close these issues.

4 participants

@lhotari @michaeljmarshall @codelipenghui @merlimat