@grpc/gprc-js: EventEmitter leak for drain/close/error

[schmidt-sebastian]

See googleapis/nodejs-firestore#661 (comment)

Firestore customers (on @grpc/grpc-js 0.4.3) are reporting that they are still seeing EventEmitter leak warnings, albeit not for connectivityStateChanged` listeners.

Instead, they see:

(node:48004) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 drain listeners added. Use emitter.setMaxListeners() to increase limit
(node:48004) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 error listeners added. Use emitter.setMaxListeners() to increase limit
(node:48004) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 close listeners added. Use emitter.setMaxListeners() to increase limit

[schmidt-sebastian]

@murgatroid99

[murgatroid99]

I'm really going to need a stack trace or reproduction code to track this down. We can get stack traces using this code snippet from #694:

process.on('warning', e => console.warn(e.stack));

[jmacedoit]

@murgatroid99 I'm trying to reproduce it again, it appears to be harder to do so than before. Will let you know when I have a stack trace for you.

[jmacedoit]

MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 drain listeners added. Use emitter.setMaxListeners() to increase limit
    at _addListener (events.js:251:17)
    at DestroyableTransform.addListener (events.js:267:10)
    at DestroyableTransform.Readable.on (/Users/xxx/Projects/yyy/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:786:33)
    at BunWrapper.Stream.pipe (internal/streams/legacy.js:28:8)
    at _firestore.readWriteStream.then.backendStream (/Users/xxx/Projects/yyy/node_modules/@google-cloud/firestore/build/src/watch.js:343:35)
(node:66877) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 error listeners added. Use emitter.setMaxListeners() to increase limit
MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 error listeners added. Use emitter.setMaxListeners() to increase limit
    at _addListener (events.js:251:17)
    at DestroyableTransform.addListener (events.js:267:10)
    at DestroyableTransform.Readable.on (/Users/xxx/Projects/yyy/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:786:33)
    at BunWrapper.Stream.pipe (internal/streams/legacy.js:62:8)
    at _firestore.readWriteStream.then.backendStream (/Users/xxx/Projects/yyy/node_modules/@google-cloud/firestore/build/src/watch.js:343:35)
(node:66877) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 close listeners added. Use emitter.setMaxListeners() to increase limit
MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 close listeners added. Use emitter.setMaxListeners() to increase limit
    at _addListener (events.js:251:17)
    at DestroyableTransform.addListener (events.js:267:10)
    at DestroyableTransform.Readable.on (/Users/xxx/Projects/yyy/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:786:33)
    at BunWrapper.Stream.pipe (internal/streams/legacy.js:84:8)
    at _firestore.readWriteStream.then.backendStream (/Users/xxx/Projects/yyy/node_modules/@google-cloud/firestore/build/src/watch.js:343:35)

There it is. I still need to run some extra tests to understand the conditions in which this happens. I'm not sure if this can happen in normal conditions or if it has anything to do with unreliable internet / suspending the machine.

[murgatroid99]

Those call stacks don't say grpc-js anywhere. I don't think this one is actually a grpc-js issue.

[schmidt-sebastian]

I'll see if I can repro this. This might be an issue in Firestore.

[schmidt-sebastian]

I am not able to come up with a test case, but this seems to be happening in our Watch code. On re-connect, we pipe back to the original stream. I suspect that this is happening when we have more than 10 reconnect attempts.

I am closing this issue for now - will resolve this as part of googleapis/nodejs-firestore#661