core.async

Exceptions cannot be captured by default uncaught exception handler

Details

  • Type: Defect Defect
  • Status: Open Open
  • Priority: Major Major
  • Resolution: Unresolved
  • Affects Version/s: None
  • Fix Version/s: None
  • Component/s: None
  • Labels:
    None
  • Patch:
    Code and Test

Description

Both core.async thread pools have a try/catch which catches and prints exceptions thrown in callbacks. This prevents application code from using the built-in mechanisms of the JVM to handle exceptions on arbitrary threads, namely Thread.setDefaultUncaughtExceptionHandler

In addition, the pool for 'thread' and 'thread-call' does not close the channel when an exception is thrown, which may lead to deadlocks.

Current Patch: 0002-ASYNC-76-propagate-exceptions-with-tests.patch

Approach: For the callback/go thread pool, do not catch exceptions at all. For the 'thread' pool, remove the 'catch' and close the channel in a 'finally'.

Background: Printing exceptions was added shortly after changing the arity to the 'put!' callback, to aid in debugging, see commit 9fcae995. Prior to this, the 'thread-call' function has always dropped exceptions silently; see commit 0b8e6171.

Duplicate of ASYNC-71 and similar to ASYNC-61, both of which request that the thread pools dispatch errors to a handler function Var which application code can alter.

An earlier issue (no JIRA ticket) occurred when tasks were submitted to the ThreadPoolExecutor with .submit, which returns a Future, instead of .execute.

Activity

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Stuart Sierra added a comment - - edited

No, the default uncaught exception handler is global for the whole JVM. Thread.setDefaultUncaughtExceptionHandler is static.

The exception handler can be overridden on a per-thread or per-thread-group basis.

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Stuart Sierra added a comment - - edited No, the default uncaught exception handler is global for the whole JVM. Thread.setDefaultUncaughtExceptionHandler is static. The exception handler can be overridden on a per-thread or per-thread-group basis.
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Timothy Baldridge added a comment -

These threads are created in a fixed size thread pool. Won't you need to set the exception handler on the Executor constructor instead of on the thread itself?

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Timothy Baldridge added a comment - These threads are created in a fixed size thread pool. Won't you need to set the exception handler on the Executor constructor instead of on the thread itself?

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Dates

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    Updated: