[exim] debugging problems with transport_filter

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Author: Ross Boylan
Date:  
To: exim
CC: ross
Subject: [exim] debugging problems with transport_filter
I spent yesterday getting a transport filter to work. Eventually it
did, but I don't understand why. Can anyone suggest some more effective
way to debug such problems?

I tried -d with various options, but the result was not illuminating
(see below for an excerpt). I tried to write to some files from the
filter, but that mostly didn't work (and in some cases may have been
responsible for the error). And I ran the filter standalone.

Observations on the trace below:
"R=filter_test T=easy_test defer (-24): transport filter process failed
(2) while writing to /home/ross/mailutil/mbox" made me think the issue
was actually in writing to the mbox. I think the actual error was in
running the filter. Is that correct?

"appendfile yields 10 with errno=-24 more_errno=2"? Could someone help
me interpret that? What do the 10, -24, and 2 mean in general--that is,
what kind of things do they indicate, and what do the specific values
mean in this case?

At one point I thought the problem was that the python process was
trying to write some temp files, even though the code did not appear to
be accessing the disk (i.e., no calls to open()).

I updated the configuration file but did not restart the daemon. I
thought since my tests were all using the command line (exim -bm) the
state of the daemon wouldn't matter, but perhaps it does. Should it?

I'm running exim 4.69 on Debian Lenny.

Thanks.
Ross Boylan

--------------------------- tracing output from transport -------------------------
20:49:28 changed uid/gid: local delivery to ross <ross@???> transport=easy_test
20:49:28   uid=1000 gid=1000 pid=19933
20:49:28   auxiliary group list: <none>
20:49:28   home=/home/ross/mailutil current=/home/ross/mailutil
20:49:28 set_process_info: 19933 delivering 1R82Bz-0005BJ-PB to ross using easy_test
20:49:28 direct command:
20:49:28   argv[0] = /usr/bin/python
20:49:28   argv[1] = /home/ross/mailutil/linefilter.py
20:49:28 direct command after expansion:
20:49:28   argv[0] = /usr/bin/python
20:49:28   argv[1] = /home/ross/mailutil/linefilter.py
20:49:28 T: easy_test
20:49:28 appendfile transport entered
20:49:28 appendfile: mode=660 notify_comsat=0 quota=0 warning=0
20:49:28   file=/home/ross/mailutil/mbox format=unix
20:49:28   message_prefix=From ${if def:return_path{$return_path}{MAILER-DAEMON}} ${tod_bsdinbox}\n
20:49:28   message_suffix=\n
20:49:28   maildir_use_size_file=no
20:49:28   locking by lockfile fcntl 
20:49:28 lock name: /home/ross/mailutil/mbox.lock
20:49:28 hitch name: /home/ross/mailutil/mbox.lock.corn.betterworld.us.4e7ff648.00004ddd
20:49:28 lock file created
20:49:28 mailbox /home/ross/mailutil/mbox is locked
20:49:28 writing to file /home/ross/mailutil/mbox
20:49:28 condition: def:return_path
20:49:28    result: true
20:49:28 expanding: $return_path
20:49:28    result: root@???
20:49:28 expanding: MAILER-DAEMON
20:49:28    result: MAILER-DAEMON
20:49:28 skipping: result is not used
20:49:28 expanding: From ${if def:return_path{$return_path}{MAILER-DAEMON}} ${tod_bsdinbox}
20:49:28 
20:49:28    result: From root@??? Sun Sep 25 20:49:28 2011
20:49:28 
20:49:28 writing data block fd=6 size=50 timeout=0
20:49:28 process 19934 running as transport filter: write=9 read=10
20:49:28 writing data block fd=9 size=993 timeout=0
20:49:28 process 19935 writing to transport filter
20:49:28 copying from the filter
20:49:28 waiting for filter process
20:49:28 filter process returned 2
20:49:28 waiting for writing process
20:49:28 end of filtering transport writing: yield=0
20:49:28 errno=-24 more_errno=2
20:49:28 appendfile yields 10 with errno=-24 more_errno=2
20:49:28 search_tidyup called
20:49:28 easy_test transport returned PANIC for ross@???
20:49:28 post-process ross@??? (10)
20:49:28 LOG: MAIN PANIC
20:49:28   == ross@??? R=filter_test T=easy_test defer (-24): transport filter process failed (2) while writing to /home/ross/mailutil/mbox
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