ThreadQuota=1 not respected in TheadManager (leads to termination)

[hofst]

What version of gRPC and what language are you using?

1.62.1

What operating system (Linux, Windows,...) and version?

Linux

What runtime / compiler are you using (e.g. python version or version of gcc)

clang 17

What did you do?

Start a grpc callback server with SetResourceQuota(ResourceQuota().SetMaxThreads(1));
Put some load on the server so we hit the following code-path:

grpc/src/cpp/thread_manager/thread_manager.cc

Line 204 in 84ee28e

resource_exhausted = true;

This code path does not make sense to me: It first reduces the poller count by one and then checks } else if (num_pollers_ > 0) {. This way it will always ignore the own thread.
As far as I understand, the resource exhausted case should not occur when I have configured a thread limit of 1 and I have 1 thread worker (as expected). I'd rather expect the condition to be } else if ((num_pollers_+1) > 0) { since we already decremented the num_pollers and should not ignore our own thread.

What did you expect to see?

Start a grpc callback server with SetResourceQuota(ResourceQuota().SetMaxThreads(1)); should work even under load.

What did you see instead?

grpc server terminates.

[drfloob]

Please provide a minimum repro in the form of a runnable example in a github repo, or a gist. I'm not sure what you mean by termination here, and the ThreadManager is used for sync servers.

[hofst]

@drfloob

I'm not sure what you mean by termination here

Termination as in: The grpc server will shut down because it tries to spawn an additional thread but detects that this would violate the thread resource quota of one thread.

Did you have a look at the code that I referenced in thread_manager.cc ?
The MainWorkLoop is quite a simple function and I believe I already described coherently what's going wrong in that function.