Perl (om_perl)
The Perl programming language is widely used for log processing and comes with a broad set of modules bundled or available from CPAN. Code can be written more quickly in Perl than in C, and code execution is safer because exceptions (croak/die) are handled properly and will only result in an unfinished attempt at log processing rather than taking down the whole NXLog process.
This module makes it possible to execute Perl code in an output module that can handle the data directly in Perl. See also the im_perl and xm_perl modules.
The module will parse the file specified in the PerlCode directive when NXLog starts the module. The Perl code must implement the write_data subroutine which will be called by the module when there is data to process. This subroutine is called for each event record and the event record is passed as an argument. To access event data, the Log::Nxlog Perl module must be included, which provides the following methods.
- log_debug(msg)
-
Send the message msg to the internal logger on DEBUG log level. This method does the same as the log_debug() procedure in NXLog.
- log_info(msg)
-
Send the message msg to the internal logger on INFO log level. This method does the same as the log_info() procedure in NXLog.
- log_warning(msg)
-
Send the message msg to the internal logger on WARNING log level. This method does the same as the log_warning() procedure in NXLog.
- log_error(msg)
-
Send the message msg to the internal logger on ERROR log level. This method does the same as the log_error() procedure in NXLog.
- get_field(event, key)
-
Retrieve the value associated with the field named key. The method returns a scalar value if the key exists and the value is defined, otherwise it returns undef.
For the full NXLog Perl API, see the POD documentation in
Nxlog.pm. The documentation can be read with perldoc Log::Nxlog.
Perl prerequisites for Windows
You must install a separate Perl environment to use the om_perl module on Windows. We only guarantee compatibility with Strawberry Perl 5.32.0.1. Newer versions will likely work too, but older versions (5.30.3.1 and before) are not supported. See the Strawberry Perl Releases page to manually download and install the required package.
The following PowerShell script automatically downloads and installs Perl from the MSI file.
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
$baseuri="http://strawberryperl.com/download/5.32.0.1"
$msifile="strawberry-perl-5.32.0.1-64bit.msi"
Invoke-WebRequest -uri $baseuri/$msifile -OutFile $msifile
msiexec /passive /i $msifileConfiguration
The om_perl module accepts the following directives in addition to the common module directives.
Required directives
The following directives are required for the module to start.
This mandatory directive expects a file containing valid Perl code. This file is read and parsed by the Perl interpreter.
|
Optional directives
This optional directive specifies the Perl subroutine to invoke. With
this directive, you can call only specific subroutines from your Perl code.
If the directive is not specified, the default subroutine |
|||
This optional directive allows you to pass configuration strings to the script file defined by the PerlCode directive.
This is a block directive and any text enclosed within
|
Examples
This output module sends events to the Perl script, which simply writes the
data from the $raw_event field into a file.
<Output out>
Module om_perl
PerlCode "modules/output/perl/perl-output.pl"
Call write_data1
</Output># Use FindBin to add the NXLog Perl module directory to Perl's search path
use FindBin;
use lib "$FindBin::Bin/../../../../opt/nxlog/Network/Library/Perl/5.30"; (1)
use strict;
use warnings;
use Log::Nxlog;
sub write_data1
{
my ($event) = @_;
my $rawevt = Log::Nxlog::get_field($event, 'raw_event');
open(OUT, '>', 'tmp/output') || die("cannot open tmp/output: $!");
print OUT $rawevt, "(from perl)", "\n";
close(OUT);
}| 1 | Perl may return a Can’t locate Log/Nxlog.pm in @INC (you may need to install the Log::Nxlog module) error if it can’t find the NXLog Perl module.
Use FindBin to add NXLog’s Perl module directory to Perl’s search path.
By default, the NXLog Perl module path is:
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