[erlang-questions] monitor long_schedule and strange timeouts

[Max Lapshin]

Once per hour we get strange situation on customer server.

Log is getting full with messages like:


2016-05-20 02:06:52.204 <0.300.0> flu_sys_monitor:46 Monitor:
{monitor,<0.27485.22>,long_schedule,[{timeout,2591},{in,{gen_server,loop,6}},{out,{gen_server,loop,6}}]}

2016-05-20 02:06:52.210 <0.300.0> flu_sys_monitor:46 Monitor:
{monitor,<0.342.0>,long_schedule,[{timeout,2595},{in,{live_info_storage,loop_setter,1}},{out,{live_info_storage,loop_setter,1}}]}

(loop_setter is a very small function that just reads message and set field
in ets table)

and many processes in system are getting stuck in different places like:


{current_stacktrace,[{erts_internal,await_result,1,[]}


Amount of erlang:statistics(total_active_tasks) is getting down from
average 800 to 200 when such situation happens.


I have two questions:


1) is erlang:statistics(total_active_tasks)  about 800 a normal value or it
is a very huge overload? System is working ok with such metric

2) are there any hints how to debug situation? Is it an external of
something internal? If customer is running some task on this server, then
why long schedules may appear?
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