ejabberd - Comments for "[solved] ejabberdctl causes epmd messages to syslog"

solved!

arkhelion — Wed, 04 Aug 2010 19:08:45 +0000

badlop wrote:

Right, ejabberdctl starts an erlang node that connects to the main node.

This sentence answers clearly my issue, thanks a lot for pointing it to me :)

The question is then solved ^^
Thanks badlop!

Related email in the Erlang

mfoss — Tue, 03 Aug 2010 18:55:00 +0000

Related threads in the Erlang mailing lists:

http://www.erlang.org/cgi-bin/ezmlm-cgi?2:sss:1934:201008:ebleannceopgag...
http://www.erlang.org/cgi-bin/ezmlm-cgi?3:sss:1292:201008:imbaddedlflkhf...

All seems correct, try the tests yourself

mfoss — Tue, 03 Aug 2010 18:54:47 +0000

arkhelion wrote:

Is ejabberdctl creating his own node to get messages about the ejabberd node?

Right, ejabberdctl starts an erlang node that connects to the main node.

arkhelion wrote:

the fact that any command involving ejabberdctl triggers that line is more puzzling.

Does it mean that ejabberdctl makes the node crash? even with a simple "ejabberdctl status"?

epmd prints the debug line even when the erlang node is stopped correctly:

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l
47

$ erl -sname abcde
Erlang R14A (erts-5.8) [source] [smp:2:2] [rq:2] [async-threads:0] [kernel-poll:false]

Eshell V5.8  (abort with ^G)
(abcde@localhost)1> init:stop().
ok

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l
48

Even more: the line is printed when the erlang node is started, when it is still running, not when it is stopped, see:

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l
48

$ erl -sname aaa -detached

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l
49

$ epmd -names
epmd: up and running on port 4369 with data:
name aaa at port 34740
name ejabberd at port 35178

arkhelion wrote:

What I really mean is "is this the consequence of a wanted behavior of ejabberdctl?"

Yes, all that I could see until now in your comments and my tests is normal operation of ejabberd.

Is this a wanted behavior of ejabberdctl?

arkhelion — Mon, 02 Aug 2010 22:46:47 +0000

badlop wrote:

This line is added by epmd when epmd is started, or when an erlang node starts and connects to epmd. Notice that ejabberd starts an erlang node, and connects to epmd.

See how the line IS added even when ejabberd isn't involved; and see that the line ISN'T added even in case of a crash in the erlang node:

<...>

Looking at the epmd source code ( http://github.com/erlang/otp/blob/dev/erts/epmd/src/epmd.c#L239), the log line is written by this code:

dbg_printf(g,0,"epmd running - daemon = %d",g->is_daemon);

You can download the minimum erlang source code files required to compile that file, delete that line, compile epmd.c, install epmd and restart it.

Thanks for your answer, so I understand that epmd is writing a line when a node connects to the daemon. The fact that I have this line when starting, restarting ejabberd is not a matter to me. But the fact that any command involving ejabberdctl triggers that line is more puzzling.

Does it mean that ejabberdctl makes the node crash? even with a simple "ejabberdctl status"? Is ejabberdctl creating his own node to get messages about the ejabberd node?

What I really mean is "is this the consequence of a wanted behavior of ejabberdctl?"

Thanks a lot for pointing me out the line in epmd.c to recompile erlang without this (debug) message, but it may also be a good thing to check if it's ok for ejabberdctl to trigger this line.

arkhelion wrote: I found a

mfoss — Mon, 02 Aug 2010 11:55:00 +0000

arkhelion wrote:

I found a special event in my syslog:

epmd: epmd: epmd running - daemon = 1

Everytime I launch ejabberdctl it writes a line in the log.
So I'd like to find what triggers this message.

There seems to be no crash from any component :

So the questions are:
1. Do anyone know if this message is usual, or is there an underlying error or warning behind this (quite unclear) log message?
2. Is there a way to disable it or change ejabberdctl behavior so that it doesn't trigger it?

This line is added by epmd when epmd is started, or when an erlang node starts and connects to epmd. Notice that ejabberd starts an erlang node, and connects to epmd.

See how the line IS added even when ejabberd isn't involved; and see that the line ISN'T added even in case of a crash in the erlang node:

$ epmd -kill                                                                                            
epmd: Cannot connect to local epmd                                                                      

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l                                        
8                                                                                                       

$ epmd -daemon                                                                                          

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l                                        
9                                                                                                       

$ epmd -names                                                                                           
epmd: up and running on port 4369 with data:                                                            

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l                                        
9                                                                                                       

$ epmd -help
...

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l
9

$ erl -s testnode -s halt
Erlang R13B04 (erts-5.7.5) [source] [smp:2:2] [rq:2] [async-threads:0] [kernel-poll:false]

{"init terminating in do_boot",{undef,[{testnode,start,[]},{init,start_it,1},{init,start_em,1}]}}

Crash dump was written to: erl_crash.dump
init terminating in do_boot ()

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l
9

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l
9

$ erl -sname abcde -s testnode -s halt
Erlang R13B04 (erts-5.7.5) [source] [smp:2:2] [rq:2] [async-threads:0] [kernel-poll:false]

{"init terminating in do_boot",{undef,[{testnode,start,[]},{init,start_it,1},{init,start_em,1}]}}

Crash dump was written to: erl_crash.dump
init terminating in do_boot ()

$ sudo tail -n 500 /var/log/syslog | grep "epmd running" | wc -l
10

Looking at the epmd source code ( http://github.com/erlang/otp/blob/dev/erts/epmd/src/epmd.c#L239), the log line is written by this code:

dbg_printf(g,0,"epmd running - daemon = %d",g->is_daemon);

You can download the minimum erlang source code files required to compile that file, delete that line, compile epmd.c, install epmd and restart it.