[undertow-dev] Dispatching to non IO threads

[Bill O'Neil]

I have come across a few Handlers that dispatch to a worker thread these
include blocking handler, resource handler and the form parsing handler.

My specific use case was with the form parsing handler.  I had a bunch of
handlers chained together basically as follows.

Blocking handler -> ExceptionHandler -> FormParsingHandler ->
MyBlockingHandler

The form parsing handler would cause the handler to be dispatched a second
time to a new executor.  This made me lose the stack trace, and the
Exception handler was not catching an exception being thrown inside of
MyBlockingHandler.

I resolved this by basically cloning the form parsing handler and calling
the parseBlocking() instead of the non blocking parse().  This is
acceptable because I already dispatched to a non IO thread.

Should any handler that attempts to dispatch first check if the exchange is
in an IO thread before dispatching or is there a specific use case for some
handlers to always dispatch?

Thanks,
Bill
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