[PROTON-1964] [c] pn_proactor_wait() can return empty event batches.

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: proton-c
• Assignee: Unassigned
• Reporter: Alan Conway
• Created: 14/Nov/18 21:59
• Updated: 17/Jun/20 21:39

Description

The bug PROTON-1586  had events returned after a connection was TRANSPORT_CLOSED and no longer existed (original reproducer below) The bug still exists in a more subtle form - the proactor can return an empty event batch after TRANSPORT_CLOSED. This does not cause segfaults but is incorrect behavior according to the proactor documentation.

To reproduce the problem see the comments in c/tests/pn_test_proactor.cpp in function proactor::wait_next().

The fix to PROTON-1586 was to have the connection_driver batch to hide events after TRANSPORT_CLOSE by returning NULL as if the batch were empty. However, that is too late to prevent the batch being returned by the proactor - from the proactors perspective it is not empty, it contains  CONNECTION_LOCAL_CLOSE but it looks empty to the user.

This is really a bug in the pn_connection_driver, not the proactor, and it should be fixed there so that all proactors and non-proactor applications will benefit.

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Original reproducer: 

Run the send examples code with an invalid hostname like shown in the following -

[gmurthy@localhost build]$ pwd
/home/gmurthy/opensource/qpid-proton/build
[gmurthy@localhost build]$ 
[gmurthy@localhost build]$ 
[gmurthy@localhost build]$ examples/c/send nosuchhost
PN_TRANSPORT_CLOSED: proton:io: No address associated with hostname - connect to  nosuchhost:5672
epoll proactor failure in /home/gmurthy/opensource/qpid-proton/proton-c/src/proactor/epoll.c:648: "arming polled file descriptor": No such file or directory
Aborted (core dumped)
[gmurthy@localhost build]$ 

The proactor code coredumps.

Issue Links

• is a clone of: PROTON-1586 [proton-c] examples send core dumps on specifying invalid host