A summary for those who don't follow IRC:
- POE keeps a priority queue of pending events
- The current system time is used as the priority
- If the system time is skewed (sysadmin, ntpd), events could happen at the
"wrong time"
An example of this problem would be calling
$poe_kernel->delay( something => 10 );
Then the sysadmin or ntpd moves the time 5 seconds back. The 'something' would
be posted after 15 seconds, not 10 as expected. A pathelogical case is calling
$poe_kernel->yield( 'something' );
And then the sytem time is moved 1 day back. The 'something' would only be
delivered tomorrow!
The included patch adds POE::Resource::Clock which uses POSIX::RT::Clock's
'monotonic' time source as the queue priority and the 'realtime' time source as
the system time.
However, some cheating has to be done; if converting from system time to
monotonic time is not static, then the order following events are delivered is
non-defined.
$poe_kernel->alarm( one => $time );
$poe_kernel->alarm( two => $time );
This patch is not finale; it still needs to detect clock skew and adjust the
queue priorities of alarms (but not delays or other events) when it happens.
-Philip
POE-Resource-Clock.PG.01.patch
Description: POE-Resource-Clock.PG.01.patch
