Ensure child worker processes are monitored after specialization #7974
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
mathewc
commented
Dec 9, 2021
| @@ -69,7 +69,7 @@ public void Configure(string name, ScriptApplicationHostOptions options) | |||
| options.IsStandbyConfiguration = true; | |||
| } | |||
|
|
|||
| options.IsFileSystemReadOnly = IsZipDeployment(out bool isScmRunFromPackage); | |||
| options.IsFileSystemReadOnly |= IsZipDeployment(out bool isScmRunFromPackage); | |||
There was a problem hiding this comment.
To test this fix, I had to simulate specialization locally. That requires configuration that ensures placeholder channels are used. For this specific change, the check here requires a RO file system. So I'm making this change to facilitate testability, however it's a logical change to make regardless.
mathewc
commented
Dec 9, 2021
| await _hostService.StartAsync(CancellationToken.None); | ||
|
|
||
| // add general post startup validations here | ||
| mockEventManager.Verify(_ => _.Publish(It.IsAny<HostStartEvent>()), Times.Once()); |
There was a problem hiding this comment.
Added this StartAsync test so I had a place to add verification for the new event
mathewc
force-pushed
the
oop-proc-mon-fix
branch
from
5377844 to
92b8b1e
Compare
mathewc
force-pushed
the
oop-proc-mon-fix
branch
from
92b8b1e to
b5eecfa
Compare
pragnagopa
approved these changes
Dec 10, 2021
7 tasks
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Currently, child worker processes are only registered for monitoring when the process is started. That's a problem if the host is started in placeholder mode and later specialized. In that case, the worker channels are NOT restarted, and the child processes are not registered for monitoring by the new specialized host instance.
For testing, I've configured my local functions host to start in placeholder mode. I can see that placeholder worker channels are used. After triggering specialization, I can see the worker channels are specialized. Previously before my fix, the newly restarted/specialized host wouldn't be monitoring the child processes, because the were only registered on process start before. Now the worker process instance handles the HostStartEvent and registers.
Caught this issue in production testing. For a Python Consumption app, after specialization only the main host process is being monitored, not the worker process. That impacts DynamicConcurrency - it's unable to make correct concurrency decisions because it doesn't have a full view of CPU usage. In previous rounds of testing, I was testing with private site extensions, with placeholders disabled.
Will send a PR backporting to v3 as well, once this one is signed off on.
Pull request checklist
release_notes.md