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.\" ========================================================================
.\"
.IX Title "Net::Prometheus::PerlCollector 3pm"
.TH Net::Prometheus::PerlCollector 3pm 2024-03-07 "perl v5.38.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
"Net::Prometheus::PerlCollector" \- obtain statistics about the perl interpreter
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\&   use Net::Prometheus;
\&   use Net::Prometheus::PerlCollector;
\&
\&   my $client = Net::Prometheus\->new;
\&   $client\->register( Net::Prometheus::PerlCollector\->new );
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This module provides a class that collects metrics about the perl interpreter
itself.
.SS Metrics
.IX Subsection "Metrics"
The following metrics are collected:
.IP \(bu 2
\&\f(CW\*(C`perl_info\*(C'\fR
.Sp
An info gauge (i.e. whose value is always 1) with a \f(CW\*(C`version\*(C'\fR label giving
the perl interpreter version
.Sp
.Vb 3
\&   # HELP perl_info Information about the Perl interpreter
\&   # TYPE perl_info gauge
\&   perl_info{version="5.30.0"} 1
.Ve
.PP
If the optional XS module was compiled at build time, the following extra are
also reported:
.IP \(bu 2
\&\f(CW\*(C`perl_heap_arenas\*(C'\fR
.Sp
A gauge giving the number of arenas the heap is split into.
.IP \(bu 2
\&\f(CW\*(C`perl_heap_svs\*(C'\fR
.Sp
A gauge giving the total number of SVs allocated on the heap.
.PP
.Vb 6
\&   # HELP perl_heap_arenas Number of arenas in the Perl heap
\&   # TYPE perl_heap_arenas gauge
\&   perl_heap_arenas 159
\&   # HELP perl_heap_svs Number of SVs in the Perl heap
\&   # TYPE perl_heap_svs gauge
\&   perl_heap_svs 26732
.Ve
.PP
Note that the way these metrics are collected requires counting them all every
time. While this code is relatively efficient, it is still a linear scan, and
may itself cause some slowdown of the process at the time it is collected, if
the heap has grown very large, containing a great number of SVs.
.PP
Extra detail can be obtained about the types of heap objects by setting
.PP
.Vb 1
\&   $Net::Prometheus::PerlCollector::DETAIL = 1;
.Ve
.PP
This will be slightly more expensive to count, but will yield in addition a
detailed breakdown by object type.
.PP
.Vb 11
\&   # HELP perl_heap_svs_by_type Number of SVs classified by type
\&   # TYPE perl_heap_svs_by_type gauge
\&   perl_heap_svs_by_type{type="ARRAY"} 2919
\&   perl_heap_svs_by_type{type="CODE"} 1735
\&   perl_heap_svs_by_type{type="GLOB"} 2647
\&   perl_heap_svs_by_type{type="HASH"} 470
\&   perl_heap_svs_by_type{type="INVLIST"} 68
\&   perl_heap_svs_by_type{type="IO"} 12
\&   perl_heap_svs_by_type{type="NULL"} 8752
\&   perl_heap_svs_by_type{type="REGEXP"} 171
\&   perl_heap_svs_by_type{type="SCALAR"} 9958
.Ve
.PP
This level of detail is unlikely to be useful for most generic production
purposes but may be helpful to set in specific processes when investigating
specific memory-related issues for a limited time.
.PP
For an even greater level of detail, set the value to 2 to additionally obtain
another breakdown of blessed objects by class:
.PP
.Vb 6
\&   # HELP perl_heap_svs_by_class Number of SVs classified by class
\&   # TYPE perl_heap_svs_by_class gauge
\&   ...
\&   perl_heap_svs_by_class{class="Net::Prometheus"} 1
\&   perl_heap_svs_by_class{class="Net::Prometheus::PerlCollector"} 1
\&   perl_heap_svs_by_class{class="Net::Prometheus::ProcessCollector::linux"} 1
.Ve
.PP
Note that this will yield a large amount of output for any non-trivially sized
program, so should only be enabled under carefully-controlled conditions.
.PP
The value of this variable can be overridden on a per-collection basis by
passing the option
.PP
.Vb 1
\&   Net::Prometheus\->render( { perl_collector_detail => 1 } );  # or 2
.Ve
.PP
This may be more convenient for short-term traces from exporters that parse
HTTP query parameters into collector options.
.PP
.Vb 1
\&   GET .../metrics?perl_collector_detail=1
.Ve
.SH AUTHOR
.IX Header "AUTHOR"
Paul Evans <leonerd@leonerd.org.uk>