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rpc doesn't handle disconnection gracefully (or something) #1016

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opened 2025-10-18 20:57:27 +00:00 by pennae · 3 comments
pennae commented 2025-10-18 20:57:27 +00:00
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a recent ci failure looks a lot like either disconnection not being handled properly or lifetimes being wrong.

a [recent ci failure](https://buildkite.com/lix-project/lix/builds/5259#0199e27a-7937-4593-844b-dee89bdc6e50/27-2836) looks a lot like either disconnection not being handled properly or lifetimes being wrong.
commentatorforall commented 2025-10-18 20:58:46 +00:00
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was "reproduced" on the same chain in testAsan too: https://buildkite.com/lix-project/lix/builds/5259#0199e27a-7963-4e51-87aa-c1bc182f3adb/27-2931

was "reproduced" on the same chain in testAsan too: https://buildkite.com/lix-project/lix/builds/5259#0199e27a-7963-4e51-87aa-c1bc182f3adb/27-2931
commentatorforall commented 2025-10-18 21:05:45 +00:00
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found another one
https://buildkite.com/lix-project/lix/builds/5255#0199e238-e14f-4f46-ba04-efb6a865d09f/27-2866

found another one https://buildkite.com/lix-project/lix/builds/5255#0199e238-e14f-4f46-ba04-efb6a865d09f/27-2866
pennae commented 2025-10-19 15:24:27 +00:00
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we've managed to reproduce this on the cl the ci run was testing by running the failing test at a 40x oversubscription factor.

this happened because timeout handling killed the build hook while rpc calls were still in progress.
error (ignored): error: resetBlockingState: Bad file descriptor happens because killing the hook closes the log pipe while the reader is still active, Exception: std::__exception_ptr::exception_ptr: capnp/rpc.c++:3561: disconnected: RpcSystem was destroyed. happens because the rpc calls that are still running have their connections ripped out from underneath them. this is fundamentally a hook lifetime issue that is no longer reproducible in cl/4443, but we should still refactor the code to make these lifetime problems impossible.

we've managed to reproduce this on the cl the ci run was testing by running the failing test at a 40x oversubscription factor. this happened because timeout handling killed the build hook while rpc calls were still in progress. `error (ignored): error: resetBlockingState: Bad file descriptor` happens because killing the hook closes the log pipe while the reader is still active, `Exception: std::__exception_ptr::exception_ptr: capnp/rpc.c++:3561: disconnected: RpcSystem was destroyed.` happens because the rpc calls that are still running have their connections ripped out from underneath them. this is fundamentally a hook lifetime issue that is no longer reproducible in cl/4443, but we should still refactor the code to make these lifetime problems impossible.
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