Jiri Daněk created DISPATCH-2059:
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Summary: Support running router under rr during test execution
Key: DISPATCH-2059
URL: https://issues.apache.org/jira/browse/DISPATCH-2059
Project: Qpid Dispatch
Issue Type: Wish
Components: Tests
Affects Versions: 1.15.0
Reporter: Jiri Daněk
Dispatch has env variable {{QPID_DISPATCH_RUNNER}} which is (according to
comment) intended to be used for running tests under valgrind. That is outdated
comment, because the memory checking is currently solved in a different way, in
{{RuntimeChecks.cmake}}. One tool that would make sense to use to wrap dispatch
is rr, the record-replay debugger from Mozilla (https://rr-project.org/).
I've previously tried rr with (very) limited success in DISPATCH-782.
[~aconway] considered it while working on DISPATCH-902 and used it on other
issues.
There has been an attempt
https://issues.apache.org/jira/browse/DISPATCH-739?focusedCommentId=15983719&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-15983719
to use rr which however did not survive in the mainline to the present day.
I have two problems with rr:
# Dispatch system-tests send SIGTERM to the subprocess itself, which is rr.
What is necessary is to kill its children instead. Killing rr causes abrupt
termination of the recording. When I issue ^C to a {{rr record qdrouterd -c
...}} in the terminal, that signal goes correctly to the child. I am not sure
what's happening there in the test, where the difference comes from. Explicitly
killing only children in the system test does the right thing. Sadly doing that
requires hacks, python's subprocess does not allow to query children easily.
The os module has some ways; psutil is the easiest, but thats a 3rd party
dependency.
# CLion debugger disconnects during replay when qdrouterd gets SIGTERM, but the
router handles that signal and continues running (cleanup)
One awesome feature of rr is that the recording can be replayed many times,
backwards and forwards, and all memory addresses stay the same in the
recording, on every replay. Meaning that one can use {{watch -l *0x0000000}}
breakpoints to watch specific places of memory, and use {{reverse-cont}} gdb
command. (rr emulates the gdb UI, it's a wrapper over gdb, actually, if I
understand correctly.)
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