Meaning of SMTP backtrace

[SzV]

Good morning!

You may remember #112.

Does this backtrace mean anything? This is v5.17.1 Thank you.

[UTC May 16 09:06:44] error    : 'courier-mta-msa' failed protocol test [SMTP] at [127.0.0.1]:587 [TCP/IP] -- Error receiving data from the mailserver -- Resource temporarily unavailable
[UTC May 16 09:06:44] debug    : -------------------------------------------------------------------------------
[UTC May 16 09:06:44] debug    :     /usr/bin/monit() [0x41e92b]
[UTC May 16 09:06:44] debug    :     /usr/bin/monit(LogError+0xb6) [0x41f2a6]
[UTC May 16 09:06:44] debug    :     /usr/bin/monit(Event_post+0x2e0) [0x41b1d0]
[UTC May 16 09:06:44] debug    :     /usr/bin/monit() [0x42e97b]
[UTC May 16 09:06:44] debug    :     /usr/bin/monit(check_process+0x123) [0x42f2f3]
[UTC May 16 09:06:44] debug    :     /usr/bin/monit(validate+0x2fe) [0x42f15e]
[UTC May 16 09:06:44] debug    :     /usr/bin/monit(main+0x4e8) [0x40c9c8]
[UTC May 16 09:06:44] debug    :     /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5) [0x7f7a0cc33b45]
[UTC May 16 09:06:44] debug    :     /usr/bin/monit() [0x40ce4e]
[UTC May 16 09:06:44] debug    : -------------------------------------------------------------------------------
[UTC May 16 09:06:44] debug    : Sending Connection failed notification to [e-mail]
[UTC May 16 09:06:44] debug    : Trying to send mail via localhost:25
[UTC May 16 09:06:44] info     : 'courier-mta-msa' trying to restart
[UTC May 16 09:06:44] info     : 'courier-mta-msa' stop: /etc/init.d/courier-mta
[UTC May 16 09:06:44] debug    : Stopping Courier SMTP MSA server: done.
Stopping Courier SMTP server: done.
Stopping Courier mail filter: done.
Stopping Courier mail server: done.
[UTC May 16 09:06:44] debug    : 'courier-mta-msa' stopped
[UTC May 16 09:06:44] debug    : 'courier-mta-msa' process test failed [pid=14158] -- No such process
[UTC May 16 09:06:44] info     : 'courier-mta-msa' start: /etc/init.d/courier-mta
[UTC May 16 09:06:44] debug    : Starting Courier mail server: done.
Starting Courier mail filter: done.
Starting Courier SMTP server: done.
Starting Courier SMTP MSA server: done.
[UTC May 16 09:06:44] debug    : 'courier-mta-msa' started

[Tildeslash]

The backtrace is showed for every error when you start monit with "-vv" option. It just shows a code path, which led to the error. If you don't want to see the stacktrace, remove the "-vv" option (single "-v" shows debug info without stacktrace).

It seems that the MTA didn't respond, i recommend to use for example wireshark/tcpdump to debug the network communication between MTA and monit (you can then observe the whole communication, including TCP handshake).

[SzV]

Thank you for the explanation and the advise.