POE::Resource::StatistUser3Contributed Perl DocumePOE::Resource::Statistics(3)NAMEPOE::Resource::Statistics-- experimental run-time statistics for POE
SYNOPSIS
my %stats = $poe_kernel->stat_getdata;
printf "Idle = %3.2f\n", 100*$stats{avg_idle_seconds}/$stats{interval};
DESCRIPTIONPOE::Resource::Statistics is a mix-in class for POE::Kernel. It
provides features for gathering run-time statistics about POE::Kernel
and the applications that use it.
Statistics gathering is enabled with the TRACE_STATISTICS constant.
There is no run-time performance penalty when tracing is disabled.
Statistics are totaled every 30 seconds, and a rolling average is
maintained for the last two minutes. The data may be retrieved at any
time with the stat_getdata() method. Statistics will also be displayed
on the console shortly before POE::Kernel's run() returns.
The time() function is used to gather statistics over time. If
Time::HiRes is available, it will be used automatically. Otherwise
time is measured in whole seconds, and the resulting rounding errors
will make the statistics much less useful.
Run-time statistics gathering was added to POE 0.28. It is considered
highly experimental. Please be advised that the statistics it gathers
are quite likely wrong. They may in fact be useless. The reader is
invited to investigate and improve the module's methodologies.
Gathered Statisticsstat_getdata() returns a hashref with a small number of accumulated
values. For each accumulator, there will be a corresponding field
prefixed "avg_" which is the rolling average for that accumulator.
blocked
"blocked" contains the number of events (both user and kernel) which
were delayed due to a user event running for too long. On conclusion
of the program, POE will display the blocked count.
In theory, one can compare "blocked" with "user_events" to determine
how much lag is produced by user code. "blocked" should be as low as
possible to ensure minimum user-generated event lag.
In practice, "blocked" is often near or above "user_events". Events
that are even the slightest bit late count as being "blocked". See
"blocked_seconds" for a potentially more useful metric.
blocked_seconds
"blocked_seconds" contains the total number of seconds that events
waited in the queue beyond their nominal dispatch times. The average
("avg_blocked_seconds") is generally more useful.
idle_seconds
"idle_seconds" is the amount of time that POE spent doing nothing at
all. Typically this time is spent waiting for I/O or timers rather
than dispatching events.
interval
"interval" is the average interval over which the statistics counters
are recorded. This will typically be 30 seconds, but it can be more if
long-running user events prevent statistics from being gathered on
time. "interval" may also be less for programs that finish in under
half a minute.
"avg_interval" may often be lower, as the very last measurement taken
before POE::Kernel's run() returns will almost always have an
"interval" less than 30 seconds.
total_duration
"total_duration" contains the total time over which the average was
calculated. The "avg_" accumulators are averaged over a 2-minute
interval. "total_duration" may vary from 120 seconds due to the same
reasons as described in "interval".
user_events
"user_events" contains the number of events that have been dispatched
to user code. "User" events do not include POE's internal events,
although it will include events dispatched on behalf of wheels.
Shortly before POE::Kernel's run() returns, a "user_load" value will be
computed showing the average number of user events that have been
dispatched per second. A very active web server should have a high
"user_load" value. The higher the user load, the more important it is
to have small "blocked" and "blocked_seconds" values.
user_seconds
"user_seconds" is the time that was spent handling user events,
including those handled by wheels. "user_seconds" + "idle_seconds"
should typically add up to "total_duration". Any difference is
unaccounted time in POE, and indicates a flaw in the statistics
gathering methodology.
SEE ALSO
See "TRACE_STATISTICS" in POE::Kernel for instructions to enable
statistics gathering.
BUGS
Statistics may be highly inaccurate. This feature is highly
experimental and may change significantly over time.
AUTHORS & COPYRIGHTS
Contributed by Nick Williams <Nick.Williams@morganstanley.com>.
Please see POE for more information about authors and contributors.
perl v5.14.2 2010-04-03 POE::Resource::Statistics(3)
