[erlang-questions] crash dump at ejabberd startup

Wed Nov 17 02:12:25 CET 2010

Hello Michael,

another suggestion on what could have caused the issue and how to resolv it. 
The idea came into my mind while reading 
http://www.erlang.org/doc/apps/erts/inet_cfg.html
and when remembering there was another person having a similar problem, 
which that person could resolve by adding a proper hostname to it's FreeBSD 
jail.

Well, I of course HAVE a proper hostname configuration for this jail. But 
may be, epmd just cannot find the hostname as it - by default - does not use 
the regular methods ? 

This might be an explanation why the connection at first was established but 
then closed immediately.

if true, the issue almost probably can be resolved by just editing the 
inetrc file and make it use the correct methods for finding the hostname.

Ok, all this is wild speculation by a non erlang insider but however, here's  
the standard inetrc file as delivered by FreeBSD's Ports Collection:

# cat inetrc.example
{lookup,["file","native"]}.
{host,{127,0,0,1}, ["localhost","hostalias"]}.
{file, resolv, "/etc/resolv.conf"}.

This example-inetrc might be working for a standard FreeBSD host but may be 
needs to get adapted for a FreeBSD jail. I'm just unsure on how to change 
the values there (as I do not understand one word of Erlang and am not sure 
I got it right from your link).

kind regards
Tom

On Wednesday 17 November 2010 00:22:02 Michael Santos wrote:
> On Tue, Nov 16, 2010 at 09:36:49PM +0100, tom@REDACTED wrote:
> > I have a process running by unix user "ejabberd", yes:
> > # ps axu
> > ejabberd  2355  0.0  0.1  3448  1284  ??  SJ    5:54AM   0:00.14
> > /usr/local/lib/erlang/erts-5.8.1/bin/epmd -daemon
> > 
> > I guess, this process was started by the ejabberdctl skript when it
> > tried to launch ejabberd.
> > 
> > EPMD tries to connect to "localhost" ?
> 
> The Erlang node connects to epmd (on 127.0.0.1:4369). The TCP connection
> is working, but the socket is closed immmediately.
> 
> > Then we are on the right track now I
> > guess FreeBSD jails have only sort of a "half own localhost" and thus
> > one has to configure the Jails IP address instead of localhost /
> > 127.0.0.1 instead (what usually works for all other daemons).
> 
> Which version of Erlang are you using? R14B?
> 
> epmd in R14B was changed to allow some messages (like name registrations)
> only from 127/8.
> 
> > Where can I configure Erlang to use the Jails IP instead
> > localhost/127.0.0.1
> > 
> > ? In that mysterious "inetrc" config file ?
> 
> inetrc is used for hostname resolution. See:
> 
> http://www.erlang.org/doc/apps/erts/inet_cfg.html
> 
> > However, there must be a way as I earlier had it running already in
> > another test host (half a year ago). Just cannot remember the details
> > on how I did it.
> > 
> > > Check epmd is running and if the node is allowed to contact it from
> > > the jail. You can get debugging info by running epmd manually: epmd
> > > -d -d -d
> > 
> > Ok, did that as
> > # kill -9 2355
> > # /usr/local/lib/erlang/erts-5.8.1/bin/epmd -d -d -d
> > epmd: Tue Nov 16 20:29:59 2010: epmd running - daemon = 0
> > epmd: Tue Nov 16 20:29:59 2010: try to initiate listening port 4369
> > epmd: Tue Nov 16 20:29:59 2010: starting
> > epmd: Tue Nov 16 20:29:59 2010: entering the main select() loop
> > epmd: Tue Nov 16 20:30:04 2010: time in seconds: 1289939404
> > epmd: Tue Nov 16 20:30:09 2010: time in seconds: 1289939409
> > epmd: Tue Nov 16 20:30:14 2010: time in seconds: 1289939414
> > epmd: Tue Nov 16 20:30:20 2010: time in seconds: 1289939420
> > epmd: Tue Nov 16 20:30:25 2010: time in seconds: 1289939425
> > epmd: Tue Nov 16 20:30:30 2010: time in seconds: 1289939430
> > epmd: Tue Nov 16 20:30:35 2010: time in seconds: 1289939435
> > epmd: Tue Nov 16 20:30:40 2010: time in seconds: 1289939440
> > ...
> > ...
> > ^C
> 
> Was epmd started up inside the jail? Did you bring up ejabberd as well?
> I don't see any registration attempts.
> 
> > ["inet_tcp",{{badmatch,{error,epmd_close}},[{inet_tcp_dist,listen,1},
> > {'EXIT',nodistribution}},{offender,[{pid,undefined},{name,net_kernel},
> > 
> > is it sure the error message above means the connection between erlang
> > and localhost:4369 ?
> 
> Just a guess :)
> 
> Here is the error message:
> 
> {badmatch,{error,epmd_close}}
> 
> When the ejabberd node starts up, it connects to 127.0.0.1:4369 and sends
> a EPMD_ALIVE2_REQ message to register its name and distribution port (an
> ephemeral port).
> 
> The code that does this is in inet_tcp_dist:listen/1 which calls
> erl_epmd:register_node/2.
> 
> {ok, Creation} = erl_epmd:register_node(Name, Port)
> 
> epmd closes the connection immediately (possibly because the
> EPMD_ALIVE2_REQ message is not allowed) and register_node/2 returns
> {error, epmd_close}, causing the badmatch.
> 
> You can get the same error by starting up 2 erlang nodes (kill epmd if
> it is running):
> 
> $ erl
> Erlang R14B01 (erts-5.8.2) [source] [smp:2:2] [rq:2] [async-threads:0]
> [hipe] [kernel-poll:false]
> 
> Eshell V5.8.2  (abort with ^G)
> 1> {ok, L} = gen_tcp:listen(4369, [{active, false}]).
> 2> {ok, S} = gen_tcp:accept(L), ok = gen_tcp:close(S).
> 
> And in another shell:
> 
> $ erl -name test
> {error_logger,{{2010,11,16},{18,12,6}},"Protocol: ~p: register error:
> ~p~n",["inet_tcp",{{badmatch,{error,epmd_close}},[{inet_tcp_dist,listen,
> 1},{net_kernel,start_protos,4},{net_kernel,start_protos,3},{net_kernel,in
> it_node,2},{net_kernel,init,1},{gen_server,init_it,6},{proc_lib,init_p_do
> _apply,3}]}]}
> 
> 
> 
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