Chris Andrews

NAME

Devel::DTrace::Provider - Create DTrace providers for Perl programs.

SYNOPSIS

  # Listen for the probe we'll fire:

  sudo dtrace -qZn 'provider1*::: { printf("%s:%s:%s:%s\n", probeprov, probemod, probefunc, probename) }'

  # Create a provider and fire a probe:

  use Devel::DTrace::Provider;

  my $provider = Devel::DTrace::Provider->new('provider1', 'perl');
  my $probe = $provider->add_probe('probe1', 'function', ['string']);
  $provider->enable;

  $probe->fire('foo');

  # DTrace output:

  provider15949:perl:function:probe1

  (5949 is the pid of the Perl process)

DESCRIPTION

This module lets you create DTrace providers for your Perl programs, from Perl - no further native code is required.

When you create a provider and call its enable method, the following happens:

Native functions are created for each probe, containing the DTrace tracepoints to be enabled later by the kernel. DOF (DTrace Object Format) is then generated representing the provider and the tracepoints generated, and is inserted into the kernel via the DTrace helper device. Perl functions are created for each probe, so they can be fired from Perl code.

Your program does not need to run as root to create providers.

Providers created by this module should survive fork(), and become visible from both parent and child processes separately.

Using Perl providers

Listing probes available

To list the probes created by your providers, invoke dtrace(1):

  $ sudo /usr/sbin/dtrace -l -n 'myprovider*:::'

where "myprovider" is the name of your provider. To restrict this to a specific process by PID, replace the * by the pid:

  $ sudo /usr/sbin/dtrace -l -n 'myprovider1234:::'
Observing probe activity

To just see the probes firing, use a command like:

  $ sudo /usr/sbin/dtrace -n 'myprovider*:::'

If your script is not already running when you run dtrace(1), use the -Z flag, which indicates that dtrace(1) should wait for the probes to be created, rather than exiting with an error:

  $ sudo /usr/sbin/dtrace -Z -n 'myprovider*:::'
Collecting probe arguments

To collect arguments from a specific probe, you can use the trace() action:

  $ sudo /usr/sbin/dtrace -n 'myprovider*:::myprobe{ trace(arg0); }'

for an integer argument, and:

  $ sudo /usr/sbin/dtrace -n 'myprovider*:::myprobe{ trace(copyinstr(arg0)); }'

for a string argument.

There are numerous other actions and predicates - see the DTrace guide for full details:

  http://docs.sun.com/app/docs/doc/817-6223

CAVEATS

Platform support

This module is supported only on platforms where libusdt is available.

See: https://github.com/chrisa/libusdt

METHODS

new($provider_name, $module_name)

Create a provider. Takes the name of the provider, and the name of the module it should appear to be in to DTrace (in native code this would be the library, kernel module, executable etc).

Returns an empty provider object.

probe($probe_name, @argument_types...)

Adds a probe to the provider, named $probe_name. Arguments are set up with the types specified. Supported types are 'string' (char *) and 'integer' (int). A maximum of 32 arguments is supported.

Returns a probe object.

enable()

Actually adds the provider to the running system. Croaks if there was an error inserting the provider into the kernel, or if memory could not be allocated for the tracepoint functions.

DEVELOPMENT

The source to Devel::DTrace::Provider is in github:

  https://github.com/chrisa/perl-Devel-DTrace-Provider

AUTHOR

Chris Andrews <chris@nodnol.org>

LICENCE AND COPYRIGHT

Copyright (C) 2008-2012, Chris Andrews <chris@nodnol.org>. All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.




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