FYI easy to trigger GHC bug with prometheus-client

fimad / prometheus-haskell

Haskell client library for exposing prometheus.io metrics.

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FYI easy to trigger GHC bug with prometheus-client #14

Open robinp opened 7 years ago

robinp commented 7 years ago

I encountered https://ghc.haskell.org/trac/ghc/ticket/13751 while using Prometheus, in case others would run into the bug. In the mean time, with using RTS option -N1 or -N2 the bug didn't reproduce. It doesn't mean it's not there of course.

fimad commented 7 years ago

Is there anything that can be done in the library to prevent users from running into this problem?

robinp commented 7 years ago

I noticed that making some fields stricter in the summary metric calculation, I couldn't reproduce. But that's still not a hard guarantee.

Note that the bug was fixed in the meantime, and will be released in GHC 8.2. If users experience the hanging (or even proactively), should consider limiting thread count to -N2.