stdlib Timer bug

Rudolph van Graan <>
Wed Oct 5 13:46:04 CEST 2005


Hi there,

   {ok,TRef} = timer:apply_interval(2000,null,go,[]);

go() ->
   TS = calendar:now_to_local_time(now()),
   io:format("Tick ~p\n",[TS]).

This works as expected:

Tick {{2005,10,5},{13,39,8}}
Tick {{2005,10,5},{13,39,10}}
Tick {{2005,10,5},{13,39,12}}
Tick {{2005,10,5},{13,39,14}}
Tick {{2005,10,5},{13,39,16}}
Tick {{2005,10,5},{13,39,18}}
Tick {{2005,10,5},{13,39,20}}

Now I put the machine to sleep
and wait 20s

Now the timer tries to catch up with the system and posts events for  
the time the machine was sleeping:

Tick {{2005,10,5},{13,39,39}}
Tick {{2005,10,5},{13,39,39}}
Tick {{2005,10,5},{13,39,39}}
Tick {{2005,10,5},{13,39,39}}
Tick {{2005,10,5},{13,39,39}}
Tick {{2005,10,5},{13,39,39}}
Tick {{2005,10,5},{13,39,39}}
Tick {{2005,10,5},{13,39,39}}
Tick {{2005,10,5},{13,39,39}}

And now it continues as per usual

Tick {{2005,10,5},{13,39,40}}
Tick {{2005,10,5},{13,39,42}}
Tick {{2005,10,5},{13,39,44}}
Tick {{2005,10,5},{13,39,46}}
Tick {{2005,10,5},{13,39,48}}
Tick {{2005,10,5},{13,39,50}}

My issue is that if a machine sleeps for 5 hours or more, we can get  
millions of these events in the queue. Obviously, it is not an issue  
on "always on" type systems and is only  visible on my laptop.  
However, I still think there should be a patch for timer to skip  
ahead if it is too far behind and not to try and make things worse.  
On my test system, this effect basically destroys my VM as each timer  
message launches a new process which essentially kills the OS.

Suggestions?

Rudolph van Graan




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