Fix Watcher blocking during slow pool termination#343
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The Watcher calls DynamicSupervisor.terminate_child/2 synchronously, blocking all other watch/terminate operations until the pool finishes shutting down. This test reproduces the issue with a slow disconnect.
v0idpwn
commented
Apr 20, 2026
| @impl true | ||
| def terminate(_, {_, started_refs}) do | ||
| for {_, {caller_pid, _}} <- started_refs do | ||
| for {_, {caller_pid, _}} when caller_pid != nil <- started_refs do |
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This was necessary because now we keep ref => {nil, nil} when a termination is on flight
v0idpwn
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josevalim
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Apr 20, 2026
josevalim
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Apr 20, 2026
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Thank you @josevalim! 💚 |
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The Watcher calls DynamicSupervisor.terminate_child/2 synchronously,
blocking all other watch/terminate operations until the pool finishes
shutting down.
This can cause applications running multiple pools to have degraded
performance when connections take long to terminate (observed in production
with Postgrex).
Added a test reproducing the issue, and a proposed fix via a Task calling
GenServer.stop/1.