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POE::Resource::Statistics(3pm) User Contributed Perl Documentation POE::Resource::Statistics(3pm)
NAME
POE::Resource::Statistics -- experimental runtime statistics for POE
SYNOPSIS
my %stats = $poe_kernel->stat_getdata;
printf "Idle = %3.2f\n", 100*$stats{avg_idle_seconds}/$stats{interval};
DESCRIPTION
POE::Resource::Statistics is a mix-in class for POE::Kernel. It provides features for
gathering runtime statistics about POE::Kernel and the applications that use it.
Statistics gathering is enabled with the TRACE_STATISTICS constant. There is no runtime
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.
Runtime 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 Statistics
stat_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 AT morganstanley.com>.
Please see POE for more information about authors and contributors.
perl v5.10.0 2008-06-26 POE::Resource::Statistics(3pm)
Generated by $Id: phpMan.php,v 4.49 2006/02/26 13:18:18 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2012-05-25 00:25 @38.107.179.238 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)