NAME

Net::Prometheus::PerlCollector - obtain statistics about the perl interpreter

SYNOPSIS

use Net::Prometheus;
use Net::Prometheus::PerlCollector;

my $client = Net::Prometheus->new;
$client->register( Net::Prometheus::PerlCollector->new );

DESCRIPTION

This module provides a class that collects metrics about the perl interpreter itself.

Metrics

The following metrics are collected:

• perl_info

  An info gauge (i.e. whose value is always 1) with a version label giving the perl interpreter version

  # HELP perl_info Information about the Perl interpreter
  # TYPE perl_info gauge
  perl_info{version="5.30.0"} 1

If the optional XS module was compiled at build time, the following extra are also reported:

• perl_heap_arenas

  A gauge giving the number of arenas the heap is split into.

• perl_heap_svs

  A gauge giving the total number of SVs allocated on the heap.

# 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

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.

Extra detail can be obtained about the types of heap objects by setting

$Net::Prometheus::PerlCollector::DETAIL = 1;

This will be slightly more expensive to count, but will yield in addition a detailed breakdown by object type.

# 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

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.

For an even greater level of detail, set the value to 2 to additionally obtain another breakdown of blessed objects by class:

# 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

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.

The value of this variable can be overridden on a per-collection basis by passing the option

Net::Prometheus->render( { perl_collector_detail => 1 } );  # or 2

This may be more convenient for short-term traces from exporters that parse HTTP query parameters into collector options.

GET .../metrics?perl_collector_detail=1

AUTHOR

Paul Evans <leonerd@leonerd.org.uk>