[erlang-questions] UDP sockets and gen_server are hypocritical and it makes me mad

Fred Hebert <>
Wed Jul 18 14:47:50 CEST 2012


Alright, I've got a quick update.

Luckily, the node got stuck again while I was connected on it. I tried 
inspecting the process (node name omitted):

9> io:format("~p~n",[sys:get_status(vmstats_server)]).
** exception exit: {timeout,{sys,get_status,[vmstats_server]}}
      in function  sys:send_system_msg/2 (sys.erl, line 231)
10> whereis(vmstats_server).
<0.919.0>
11> io:format("~p~n",[process_info(pid(0,919,0))]).
[{registered_name,vmstats_server},
  {current_function,{erlang,sched_wall_time,3}},
  {initial_call,{proc_lib,init_p,5}},
  {status,waiting},
  {message_queue_len,2},
  {messages,[{system,{<5998.7341.243>,#Ref<5998.0.3810.221818>},get_status},
{system,{<5998.28757.800>,#Ref<5998.0.3811.260443>},get_status}]},
{links,[<5998.918.0>]},
  {dictionary,[{random_seed,{17770,13214,15044}},
               {'$ancestors',[vmstats_sup,<5998.917.0>]},
               {'$initial_call',{vmstats_server,init,1}}]},
  {trap_exit,false},
  {error_handler,error_handler},
  {priority,normal},
  {group_leader,<5998.916.0>},
  {total_heap_size,122003},
  {heap_size,121393},
  {stack_size,21},
  {reductions,314325681},
  {garbage_collection,[{min_bin_vheap_size,46368},
                       {min_heap_size,233},
                       {fullsweep_after,65535},
                       {minor_gcs,23774}]},
  {suspending,[]}]
ok

The interesting parts:
{current_function,{erlang,sched_wall_time,3}},
{status,waiting},

This tells me the process is stuck waiting for statistics to come back, 
and they don't. Somehow, connecting to the node solves it, but being 
connected already leaves it stuck. I have no idea how to fix it now that 
I'm trapped in the VM.

Your move, OTP team at Ericsson.



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