no function clause matching lists:seq(1,unknown)

[Amolith]

I run ejabberd in LXC. After upgrading the host system this morning, I started encountering very odd errors that I didn't understand as I have no experience with erlang (yet). I talked with a few friends, though, and they suggested that this issue might be caused by LXC not providing a count of my CPU's logical cores?

I want to confirm that this is indeed an issue with LXC rather than ejabberd (or my ejabberd config) before popping into the LXC IRC channel and asking there. Any ideas or suggestions would be greatly appreciated!

2022-04-28 04:41:06.994538+00:00 [error] <0.181.0>@proc_lib:crash_report/4:525 CRASH REPORT:
  crasher:
    initial call: supervisor:eimp_sup/1
    pid: <0.181.0>
    registered_name: []
    exception error: no function clause matching lists:seq(1,unknown) (lists.erl, line 243)
      in function  eimp_sup:init/1 (eimp_sup.erl, line 45)
      in call from supervisor:init/1 (supervisor.erl, line 301)
      in call from gen_server:init_it/2 (gen_server.erl, line 417)
      in call from gen_server:init_it/6 (gen_server.erl, line 385)
    ancestors: [<0.180.0>]
    message_queue_len: 1
    messages: [{'EXIT',<0.180.0>,normal}]
    links: []
    dictionary: []
    trap_exit: true
    status: running
    heap_size: 610
    stack_size: 28
    reductions: 242
  neighbours:

2022-04-28 04:41:06.994512+00:00 [error] <0.179.0>@proc_lib:crash_report/4:525 CRASH REPORT:
  crasher:
    initial call: application_master:init/4
    pid: <0.179.0>
    registered_name: []
    exception exit: {{function_clause,
                         [{lists,seq,
                              [1,unknown],
                              [{file,"lists.erl"},{line,243}]},
                          {eimp_sup,init,1,[{file,"eimp_sup.erl"},{line,45}]},
                          {supervisor,init,1,
                              [{file,"supervisor.erl"},{line,301}]},
                          {gen_server,init_it,2,
                              [{file,"gen_server.erl"},{line,417}]},
                          {gen_server,init_it,6,
                              [{file,"gen_server.erl"},{line,385}]},
                          {proc_lib,init_p_do_apply,3,
                              [{file,"proc_lib.erl"},{line,226}]}]},
                     {eimp_app,start,[normal,[]]}}
      in function  application_master:init/4 (application_master.erl, line 138)
    ancestors: [<0.178.0>]
    message_queue_len: 1
    messages: [{'EXIT',<0.180.0>,normal}]
    links: [<0.178.0>,<0.44.0>]
    dictionary: []
    trap_exit: true
    status: running
    heap_size: 610
    stack_size: 28
    reductions: 221
  neighbours:

2022-04-28 04:41:06.998647+00:00 [notice] <0.44.0>@application_controller:info_exited/3:1943     application: eimp
    exited: {{function_clause,
                 [{lists,seq,[1,unknown],[{file,"lists.erl"},{line,243}]},
                  {eimp_sup,init,1,[{file,"eimp_sup.erl"},{line,45}]},
                  {supervisor,init,1,[{file,"supervisor.erl"},{line,301}]},
                  {gen_server,init_it,2,[{file,"gen_server.erl"},{line,417}]},
                  {gen_server,init_it,6,[{file,"gen_server.erl"},{line,385}]},
                  {proc_lib,init_p_do_apply,3,
                      [{file,"proc_lib.erl"},{line,226}]}]},
             {eimp_app,start,[normal,[]]}}
    type: temporary

2022-04-28 04:41:06.998896+00:00 [info] <0.120.0>@ejabberd_config:load/1:82 Loading configuration from /etc/ejabberd/ejabberd.yml
2022-04-28 04:41:07.005464+00:00 [notice] <0.120.0>@ejabberd_logger:set/1:367 Changing loglevel from 'info' to 'warning'
2022-04-28 04:41:07.568889+00:00 [critical] <0.339.0>@gen_mod:start_module/4:169 Failed to start module mod_muc:
{error,
    {{function_clause,
         [{lists,seq,[1,unknown],[{file,"lists.erl"},{line,243}]},
          {mod_muc_sup,init,1,[{file,"mod_muc_sup.erl"},{line,63}]},
          {supervisor,init,1,[{file,"supervisor.erl"},{line,301}]},
          {gen_server,init_it,2,[{file,"gen_server.erl"},{line,417}]},
          {gen_server,init_it,6,[{file,"gen_server.erl"},{line,385}]},
          {proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,226}]}]},
     {child,undefined,'mod_muc_sup_nixnet.services',
         {mod_muc_sup,start_link,[<<"nixnet.services">>]},
         permanent,infinity,supervisor,
         [mod_muc_sup]}}}
2022-04-28 04:41:07.569247+00:00 [critical] <0.339.0>@gen_mod:maybe_halt_ejabberd/0:256 ejabberd initialization was aborted because a module start failed.
2022-04-28 04:41:07.568623+00:00 [error] <0.428.0>@proc_lib:crash_report/4:525 CRASH REPORT:
  crasher:
    initial call: supervisor:mod_muc_sup/1
    pid: <0.428.0>
    registered_name: []
    exception error: no function clause matching lists:seq(1,unknown) (lists.erl, line 243)
      in function  mod_muc_sup:init/1 (mod_muc_sup.erl, line 63)
      in call from supervisor:init/1 (supervisor.erl, line 301)
      in call from gen_server:init_it/2 (gen_server.erl, line 417)
      in call from gen_server:init_it/6 (gen_server.erl, line 385)
    ancestors: [ejabberd_gen_mod_sup,ejabberd_sup,<0.120.0>]
    message_queue_len: 0
    messages: []
    links: [<0.411.0>]
    dictionary: []
    trap_exit: true
    status: running
    heap_size: 610
    stack_size: 28
    reductions: 234
  neighbours:

[prefiks]

So this indeed happens because erlang is not able to determine number of processors on that system (and i guess this is something with lxc, maybe erlang process can't access /proc or /sys here, or whatever it uses to determine that?). But this is also something that we can catch in ejabberd, there is couple places where we have similar code, i will try to patch it, for example i commited processone/eimp@48b289e with fix in eimp.

[Amolith]

So it looks like my options are

1. Running ejabberd straight from git
2. Correcting whatever issue with LXC is causing erlang:system_info(logical_processors) to return unknown

with 2 being the better option, right?