Pubsub emulator memory leak

[atillay]

Environment info

firebase-tools: 15.3.0

Platform: macOS

Test case

Since firebase-tools version 15.2.0, where pubsub emulator v0.8.25 was introduced, we encounter 100% cpu usage on the Java process on Mac os M1/M2 when we initiate our pubsub queues. The CPU usage never drops, it's like an infinite loop is going on.

We tried with Java 22 and Java 25 and the same problem occurs (on 3 different machines).
We tried to downgrade firebase-tools to 15.1.0 (which bundles with pubsub emulator v0.8.17) and it worked again like before.
On Linux it works perfectly.
So there must be a bug in the latest release of pubsub.

Steps to reproduce

To reproduce you need a Macbook with firebase-tools > 15.1.0, launch the pubsub emulator and create some queues.
Then watch the cpu usage with the mac monitor tool, you should see the Java process taking all the available cpu.
If you are not able to reproduce I can provide more context on how we initiate our queues.

Thanks in advance for your help !
For now we have downgraded firebase-emulators version to 15.1.0.

Expected behavior

We expect pubsub emulator to not cause full cpu usage.

Actual behavior

The pubsub java process is taking all the cpu available.

[aalej]

Hey @atillay, thanks for reporting this. I'm currently working on reproducing this, but so far I haven't seen the PubSub emulator java process use a lot CPU. Checking the Activity monitor, the CPU usage rises whenever a PubSub event is triggered, but after that it goes down again.

I tried publishing 100 message and saw the CPU usage spike to ~14%

However, after a while the CPU usage goes back down to ~0.6% and stays that level while idle

Here's my mcve - https://github.com/aalej/issues-9744. I'm not sure sure if I may be missing anything here, if I am, please let me know. Also, by any chance, would you be able to provide code snippets to help us reproduce this?

[atillay]

Hello @aalej , sorry for response delay, I have setup a repository and I am able to reproduce the issue : https://github.com/atillay/pubsub-emulator-issue

[aalej]

Thank you @atillay for the mcve, I really appreciate it! I was able to reproduce the issue, and it does look like it's only occurring on the newer version of the PubSub emulator(v0.8.25). Got CPU usage to go to 100% which was pretty surprising, it also seems to stay at that level. Will raise this to our engineering team and will mark this as reproducible

[atillay]

Hello @aalej , do you have any updates on this one ? I installed the newest version of pubsub but I still reproduce the issue.

[aalej]

At the moment we don't have a fix for this yet, but the PubSub team is aware of the issue, we were also able to reproduce this using the latest version.

While waiting for the fix, we added a feature that should allow you to choose which emulator version to use by setting an environment variable #9960. For example export PUBSUB_EMULATOR_VERSION=0.8.17

[google-oss-bot]

Hey @atillay. We need more information to resolve this issue but there hasn't been an update in 7 weekdays. I'm marking the issue as stale and if there are no new updates in the next 3 days I will close it automatically.

If you have more information that will help us get to the bottom of this, just add a comment!