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Fix for handling empty response timer list#17

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debug-ito merged 1 commit intodebug-ito:masterfrom
catchvoid:bugfix/handle-empty-response-timer-list
Jan 27, 2025
Merged

Fix for handling empty response timer list#17
debug-ito merged 1 commit intodebug-ito:masterfrom
catchvoid:bugfix/handle-empty-response-timer-list

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@catchvoid catchvoid commented Jan 22, 2025

When running a simple greskell test command-line binary, the following error is encountered:

gr-test-exe: waitAnySTM: invalid argument: input list must be non-empty

Observations:

  • The code submits a basic query to a Gremlin Server (v3.7.3) and is expected to print a single response line.
  • The issue arises only in the compiled binary. Running the same code in GHCi works without any problems.
  • Same behaviour exists when connecting to a JanusGraphDB.

Issue:
The error can be traced to an unhandled empty list in the file:
greskell-websocket/src/Network/Greskell/WebSocket/Connection/Impl.hs

Environment Details:

  • Stack Version: 3.1.1
  • Stackage Snapshot: lts-22.39
  • Greskell Version: master branch
  • OS: Linux

Test code:

isMarko :: Walk Transform AVertex AVertex
isMarko = gHas2 "name" $ string "marko"

getMarkoAge :: Client -> IO (ResultHandle Integer)
getMarkoAge client = submit client (source "g" & sV [] &. isMarko &. gValues ["age"]) Nothing

submitExample :: IO ()
submitExample =
  bracket (connect "127.0.0.1" 8182) close $ \client -> do
    vs <- getMarkoAge client
    vectors <- slurpResults vs
    putStrLn $ "Marko's age is: " ++ show (Data.Vector.head vectors)

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debug-ito commented Jan 23, 2025 •
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Thanks!

Is it possible to write the test code in test/ServerTest/Connection.hs and reproduce the issue? Never mind.

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debug-ito commented Jan 23, 2025

I think this issue occurs on basically any operation on greskell-websocket if you use it with async-2.2.5 or newer.

async-2.2.5 includes async #132, which makes waitAnySTM immediately throw an exception if the input is an empty list. Before, it threw BlockedIndefinitelyOnSTM exception if there was no other STM event sources. In the case of greskell-websocket, however, there are a lot of other event sources, so waitAnySTM didn't need to throw BlockedIndefinitelyOnSTM in almost 100% cases, I think.

@catchvoid catchvoid force-pushed the bugfix/handle-empty-response-timer-list branch from be8d45d to f14306c Compare January 26, 2025 16:00
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catchvoid commented Jan 26, 2025

I conducted a test using ghc-9.0.2 with async version 2.2.4. I verified that this version was used by running stack exec -- ghc-pkg list async, and I can confirm that the issue no longer occurs. Your assessment was spot on!

@catchvoid catchvoid closed this Jan 26, 2025
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debug-ito commented Jan 26, 2025

Thanks for confirmation. However, you didn't need to close the pull-request. The problem is greskell's fault, and we need to fix it.

@debug-ito debug-ito reopened this Jan 26, 2025
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debug-ito commented Jan 26, 2025

Thanks for the force-push. I'll test the code and release the fixed version later.

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debug-ito commented Jan 27, 2025

I tested the code and confirmed that it resolved the issue. Thanks!

@debug-ito debug-ito merged commit 34992f6 into debug-ito:master Jan 27, 2025
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catchvoid commented Jan 27, 2025

Sorry I closed the PR a bit too early, I didn't fully understand the github workflow yet :-) Cool, you could merge it, Thanks!

@catchvoid catchvoid deleted the bugfix/handle-empty-response-timer-list branch January 27, 2025 21:24
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debug-ito commented Jan 30, 2025

I just released greskell-websocket-1.0.0.4, which includes this p-r.

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