[ASYNC-76] Exceptions cannot be captured by default uncaught exception handler Created: 02/Jul/14 Updated: 09/Jul/14
|Reporter:||Stuart Sierra||Assignee:||Stuart Sierra|
|Patch:||Code and Test|
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.
An earlier issue (no JIRA ticket) occurred when tasks were submitted to the ThreadPoolExecutor with .submit, which returns a Future, instead of .execute.
|Comment by Timothy Baldridge [ 03/Jul/14 8:13 AM ]|
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?
|Comment by Stuart Sierra [ 03/Jul/14 8:18 AM ]|
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.