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[server] make sure to release websocket clients #10193

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Merged
merged 1 commit into from
May 24, 2022
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AlexTugarev
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@AlexTugarev AlexTugarev commented May 23, 2022

What was initially introduces as some experimental try, seems to be a reasonable way to mitigate server leaks.

The way websocket connections are bounds to jsonrpc servers, which themselves integrate with the rest of the system, makes it necessary to have a circuit breaker in place to guarantee that stale client connections do not cause leakage of resource.

How to test

Unfortunately, it's hard to provoke the otherwise missing close event.

Fixing memory leak in server.

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AlexTugarev commented May 24, 2022

/werft run

👍 started the job as gitpod-build-at-release-ws.2
(with .werft/ from main)

@AlexTugarev AlexTugarev marked this pull request as ready for review May 24, 2022 08:50
@AlexTugarev AlexTugarev requested a review from a team May 24, 2022 08:50
@github-actions github-actions bot added the team: webapp Issue belongs to the WebApp team label May 24, 2022
this.clients.delete(ws);
emitClose();
log.warn(
"websocket in strange state. forcefully emitting a close event to release resources.",
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A metric would be better here than a log. Alternatively, enrich it with some data - ie Connection ID to make it useful for tracking down which connection.

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Reading on https://github.com/websockets/ws/blob/master/lib/websocket.js#L245-L259, we shouldn't even end up in this situation.

What kind of metric would you suggest? Assuming this is a bug, we want to log it. +1 for logging more details on the connection. Not sure which id is meant, I'll go with full ClientMetadata.

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done

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Basically it comes down to what is it you're trying to observe in the system. Presumably you're logging it so that you can get an idea that it is happening. For that use-case, a counter metric you add to a dashboard is a better choice - it's cheaper and doesn't require deep context.

If, however, this is just cleanup and we don't really care about how often, or details, of the problem, we might as well not log at all.

@roboquat roboquat merged commit f94bfa1 into main May 24, 2022
@roboquat roboquat deleted the at/release-ws branch May 24, 2022 10:55
@roboquat roboquat added deployed: webapp Meta team change is running in production deployed Change is completely running in production labels Jun 9, 2022
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3 participants