/ 
RRDTool-OO-0.03
River stage one • 3 direct dependents • 3 total dependents
/ RRDTool::OO

NAME

RRDTool::OO - Object-oriented interface to RRDTool

SYNOPSIS

    # Constructor     
my $rrd = RRDTool::OO->new(
             file => "myrrdfile.rdd" );

    # Create a round-robin database
$rrd->create(
     step        => 1,  # one-second intervals
     data_source => { name      => "mydatasource",
                      type      => "GAUGE" },
     archive     => { rows      => 5 });

    # Update RRD with sample values, use current time.
for(1..3) {
    $rrd->update($_);
    sleep(1);
}

    # Start fetching values from one day back, 
    # but skip undefined ones first
$rrd->fetch_start();
$rrd->fetch_skip_undef();

    # Fetch stored values
while(my($time, $value) = $rrd->fetch_next()) {
     print "$time: ", 
           defined $value ? $value : "[undef]", "\n";
}

    # Draw a graph in a PNG image
$rrd->graph(
  file           => "mygraph.png",
  vertical_label => 'My Salary',
  start          => time() - 10,
);

DESCRIPTION

Note: This module is under development.

RRDTool::OO is an object-oriented interface to Tobi Oetiker's round robin database tool rrdtool. It uses rrdtool's RRDs module to get access to rrdtool's shared library.

RRDTool::OO tries to marry rrdtool's database engine with the dwimminess and whipuptitude Perl programmers take for granted. Using RRDTool::OO abstracts away implementation details of the RRD engine, uses easy to memorize named parameters and sets meaningful defaults for parameters not needed in simple cases. For the experienced user, however, it provides full access to rrdtool's API. (Please check "Development Status" to verify how much of it has been implemented yet, though, since this module is under development :).

FUNCTIONS

my $rrd = RRDTool::OO->new( file => $file )

The constructor hooks up with an existing RRD database file $file, but doesn't create a new one if none exists. That's what the create() methode is for. Returns a RRDTool::OO object, which can be used to get access to the following methods.

$rrd->create( ... )

Creates a new round robin database (RRD). A RRD consists of one or more data sources and one or more archives:

$rrd->create(
     step        => 60,
     data_source => { name      => "mydatasource",
                      type      => "GAUGE" },
     archive     => { rows      => 5 });

This defines a RRD database with a step rate of 60 seconds in between primary data points.

It also sets up one data source named my_data_source of type GAUGE, telling rrdtool to use values of data samples as-is, without additional trickery.

And it creates a single archive with a 1:1 mapping between primary data points and archive points, with a capacity to hold five data points.

The RRD's step parameter is optional, and will be set to 300 seconds by rrdtool by default.

In addition to the mandatory settings for name and type, data_source parameter takes the following optional parameters: min (minimum input, defaults to U), max (maximum input, defaults to U), heartbeat (defaults to twice the RRD's step rate).

Archives expect at least one parameter, rows indicating the number of data points the archive is configured to hold. If nothing else is set, rrdtool will store primary data points 1:1 in the archive.

If you want to combine several primary data points into one archive point, specify values for cpoints (the number of points to combine) and cfunc (the consolidation function) explicitely:

$rrd->create(
     step        => 60,
     data_source => { name      => "mydatasource",
                      type      => "GAUGE" },
     archive     => { rows      => 5,
                      cpoints   => 10,
                      cfunc     => 'AVERAGE',
                    });

This will collect 10 data points to form one archive point, using the calculated average, as indicated by the parameter cfunc (Consolidation Function, CF). Other options for cfunc are MIN, MAX, and LAST.

$rrd->update( ... )

Update the round robin database with a new data sample, consisting of a value and an optional time stamp. If called with a single parameter, like in

$rrd->update($value);

then the current timestamp and the defined $value will be used. If update is called with a named parameter list like in

$rrd->update(time => $time, value => $value);

then the given timestamp $time is used along with the given value $value.

When updating multiple data sources, use the values parameter (instead of value) and pass an arrayref:

$rrd->update(time => $time, values => [$val1, $val2, ...]);

This way, rrdtool expects you to pass in the data values in exactly the same order as the data sources were defined in the create method. If that's not the case, then the values parameter also accepts a hashref, mapping data source names to values:

$rrd->update(time => $time, 
             values => { $dsname1 => $val1, 
                         $dsname2 => $val2, ...});

RRDTool::OO will transform this automagically into RRDTool's template syntax.

$rrd->fetch_start( ... )

Initializes the iterator to fetch data from the RRD. This works nicely without any parameters if your archives are using a single consolidation function (e.g. MAX). If there's several archives in the RRD using different consolidation functions, you have to specify which one you want:

$rrd->fetch_start(cfunc => "MAX");

Other options for cfunc are MIN, AVERAGE, and LAST.

fetch_start features a number of optional parameters: start, end and resolution.

If the start time parameter is omitted, the fetch starts 24 hours before the end of the archive. Also, an end time can be specified:

$rrd->fetch_start(start => time()-10*60,
                  end   => time());

The third optional parameter, resolution defaults to the highest resolution available and can be set to a value in seconds, specifying the time interval between the data samples extracted from the RRD. See the rrdtool fetch manual page for details.

Development note: The current implementation fetches all values from the RRA in one swoop and caches them in memory. This might change in the future, to cache only the last timestamp and keep fetching from the RRD with every fetch_next() call.

$rrd->fetch_skip_undef()

rrdtool doesn't remember the time the first data sample went into the archive. So if you run a rrdtool fetch with a start time of 24 hours ago and you've only submitted a couple of samples to the archive, you'll see many undef values.

Starting from the current iterator position (or at the specified start time immediately after a fetch_start()), fetch_skip_undef() will skip all undef values in the RRA and positions the iterator right before the first defined value. If all values in the RRA are undefined, the a following $rrd->fetch_next() will return undef.

($time, $value, ...) = $rrd->fetch_next()

Gets the next row from the RRD iterator, initialized by a previous call to $rrd->fetch_start(). Returns the time of the archive point along with all values as a list.

$rrd->graph( ... )

If there's only one data source in the RRD, drawing nice graph in an image file on disk is as easy as

$rrd->graph(
  file           => $image_file_name,
  vertical_label => 'My Salary',
  draw           => { thickness => 2,
                      color     => 'FF0000'},
);

This will assume a start time of 24 hours before now and an end time of now. Specify start and end explicitely to be clear:

$rrd->graph(
  file           => $image_file_name,
  vertical_label => 'My Salary',
  color          => 'FF0000', # (red)
  start          => time() - 24*3600,
  end            => time(),
  draw           => { thickness => 2,
                      color     => 'FF0000'},
);

If there are multiple datasources in the RRD or multiple archives with different values for cfunc, just specify explicitely which one to draw:

$rrd->graph(
  file           => $image_file_name,
  vertical_label => 'My Salary',
  draw           => {
    thickness => 2,
    color     => 'FF0000',
    dsname    => "load",
    cfunc     => 'MAX'},
);

And you can certainly have more than one graph in the picture:

$rrd->graph(
  file           => $image_file_name,
  vertical_label => 'My Salary',
  draw           => {
    thickness => 2,
    color     => 'FF0000', # red
    dsname    => "load",
    cfunc     => 'MAX'},
  draw        => {
    thickness => 2,
    color     => '00FF00', # green
    dsname    => "load",
    cfunc     => 'AVERAGE'},
);

NOTE: graph() is still under development, the interface displayed above might change.

$rrd->error_message()

Return the message of the last error that occurred while interacting with RRDTool::OO.

Development Status

The following methods are not yet implemented:

graph (partially), dump, restore, tune, last, info, rrdresize, xport, rrdcgi.

Error Handling

By default, RRDTool::OO's methods will throw fatal errors (as in: they're calling die) if the underlying RRDs::* commands indicate failure.

This behaviour can be overridden by calling the constructor with the raise_error flag set to false:

my $rrd = RRDTool::OO->new(
    file        => "myrrdfile.rdd",
    raise_error => 0,
);

In this mode, RRDTool's methods will just pass back values returned from the underlying RRDs functions if an error happens (usually 1 if successful and undef if an error occurs).

Debugging

RRDTool::OO is Log::Log4perl enabled, so if you want to know what's going on under the hood, just turn it on:

use Log::Log4perl qw(:easy);

Log::Log4perl->easy_init({
    level    => $DEBUG
});

If you're interested particularily in rrdtool commands issued by RRDTool::OO while you're operating it, just enable the category "rrdtool":

Log::Log4perl->easy_init({
    level    => $INFO, 
    category => 'rrdtool',
    layout   => '%m%n',
});

This will display all rrdtool commands that RRDTool::OO submits to the shared library. Let's turn it on for the code snippet in the SYNOPSIS section of this manual page and watch the output:

rrdtool create myrrdfile.rdd --step 1 \
        DS:mydatasource:GAUGE:2:U:U RRA:MAX:0.5:1:5
rrdtool update myrrdfile.rdd N:1
rrdtool update myrrdfile.rdd N:2
rrdtool update myrrdfile.rdd N:3
rrdtool fetch myrrdfile.rdd MAX

Often handy for cut-and-paste.

INSTALLATION

RRDTool::OO requires a rrdtool installation with the RRDs Perl module, that comes with the rrdtool distribution.

Download the tarball from

http://people.ee.ethz.ch/~oetiker/webtools/rrdtool/pub/rrdtool.tar.gz

and then unpack, compile and install:

tar zxfv rrdtool.tar.gz
cd rrdtool-1.0.46
make
cd perl-shared
perl Makefile.PL
./configure
make
make test
make install

SEE ALSO

Tobi Oetiker's RRDTool homepage at

http://rrdtool.org

especially the manual page at

http://people.ee.ethz.ch/~oetiker/webtools/rrdtool/manual/index.html

AUTHOR

Mike Schilli, <m@perlmeister.com>

COPYRIGHT AND LICENSE

Copyright (C) 2004 by Mike Schilli

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.3 or, at your option, any later version of Perl 5 you may have available.