Provided by: librrdtool-oo-perl_0.36-2_all 
NAME
RRDTool::OO - Object-oriented interface to RRDTool
SYNOPSIS
use RRDTool::OO;
# Constructor
my $rrd = RRDTool::OO->new(
file => "myrrdfile.rrd" );
# 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..5) {
$rrd->update($_);
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(
image => "mygraph.png",
vertical_label => 'My Salary',
start => time() - 10,
draw => {
type => "area",
color => '0000FF',
legend => "Salary over Time",
}
);
# Same using rrdtool's graphv
$rrd->graphv(
image => "mygraph.png",
[...]
};
DESCRIPTION
"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 (if you find a
feature that's not implemented, let me know).
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.
Additionally, the RRD start time can be specified by specifying a "start" parameter.
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) explicitly:
$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".
If you're defining multiple data sources or multiple archives, just provide them in this manner:
# Define the RRD
my $rc = $rrd->create(
step => 60,
data_source => { name => 'load1',
type => 'GAUGE',
},
data_source => { name => 'load2',
type => 'GAUGE',
},
archive => { rows => 5,
cpoints => 10,
cfunc => 'AVERAGE',
},
archive => { rows => 5,
cpoints => 10,
cfunc => 'MAX',
},
);
$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->updatev( ... )
This is identical to "update", but uses rrdtool's updatev function internally. The only difference
is when using the "print_results" method described below, which then contains additional information.
$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.
Note that there might be more than one value coming back from "fetch_next" if the RRA defines more
than one datasource):
I<($time, @values_of_all_ds) = $rrd-E<gt>fetch_next()>
It is not possible to fetch only a specific datasource, as rrdtool doesn't provide this.
($time, $value, ...) = $rrd->fetch_next()
$rrd->graph( ... )
If there's only one data source in the RRD, drawing a nice graph in an image file on disk is as easy
as
$rrd->graph(
image => $image_file_name,
vertical_label => 'My Salary',
draw => { thickness => 2,
color => 'FF0000',
legend => 'Salary over Time',
},
);
This will assume a start time of 24 hours before now and an end time of now. Specify "start" and
"end" explicitly to be clear:
$rrd->graph(
image => $image_file_name,
vertical_label => 'My Salary',
start => time() - 24*3600,
end => time(),
draw => { thickness => 2,
color => 'FF0000',
legend => 'Salary over Time',
},
);
As always, "RRDTool::OO" will pick reasonable defaults for parameters not specified. The values for
data source and consolidation function default to the first values it finds in the RRD. If there are
multiple datasources in the RRD or multiple archives with different values for "cfunc", just specify
explicitly which one to draw:
$rrd->graph(
image => $image_file_name,
vertical_label => 'My Salary',
draw => {
thickness => 2,
color => 'FF0000',
dsname => "load",
cfunc => 'MAX'},
);
If "draw" doesn't define a "type", it defaults to "line". If you don't want to define a type (because
the graph shouldn't be drawn), use "type => "hidden"". Other values are "area" for solid colored
areas. The "stack" type (for graphical values stacked on top of each other) has been deprecated sind
rrdtool-1.2, but RRDTool::OO still supports it by transforming it into an 'area' type with a 'stack'
option.
And you can certainly have more than one graph in the picture:
$rrd->graph(
image => $image_file_name,
vertical_label => 'My Salary',
draw => {
type => 'area',
color => 'FF0000', # red area
dsname => "load",
cfunc => 'MAX'},
draw => {
type => 'area',
stack => 1,
color => '00FF00', # a green area stacked on top of the red one
dsname => "load",
cfunc => 'AVERAGE'},
);
Graphs may assemble data from different RRD files. Just specify which file you want to draw the data
from, using "draw":
$rrd->graph(
image => $image_file_name,
vertical_label => 'Network Traffic',
draw => {
file => "file1.rrd",
legend => "First Source",
},
draw => {
file => "file2.rrd",
type => 'area',
stack => 1,
color => '00FF00', # a green area stacked on top of the red one
dsname => "load",
legend => "Second Source",
cfunc => 'AVERAGE'
},
);
If a "file" parameter is specified per "draw", the defaults for "dsname" and "cfunc" are fetched from
this file, not from the file that's attached to the "RRDTool::OO" object $rrd used.
Graphs may also consist of algebraic calculations of previously defined graphs. In this case, graphs
derived from real data sources need to be named, so that subsequent "cdef" definitions can refer to
them and calculate new graphs, based on the previously defined graph:
$rrd->graph(
image => $image_file_name,
vertical_label => 'Network Traffic',
draw => {
type => 'line',
color => 'FF0000', # red line
dsname => 'load',
name => 'firstgraph',
legend => 'Unmodified Load',
},
draw => {
type => 'line',
color => '00FF00', # green line
cdef => "firstgraph,2,*",
legend => 'Load Doubled Up',
},
);
Note that the second "draw" doesn't refer to a datasource "dsname" (nor does it fall back to the
default data source), but defines a "cdef", performing calculations on a previously defined draw
named "firstgraph". The calculation is specified using RRDTool's reverse polish notation, where
instructions are separated by commas ("firstgraph,2,*" simply multiplies "firstgraph"'s values by 2).
On a global level, in addition to the "vertical_label" parameter shown in the examples above, "graph"
offers a plethora of parameters:
"vertical_label", "title", "start", "end", "x_grid", "y_grid", "alt_y_grid", "no_minor",
"alt_y_mrtg", "alt_autoscale", "alt_autoscale_max", "base", "units_exponent", "units_length",
"width", "height", "interlaced", "imginfo", "imgformat", "overlay", "unit", "lazy", "rigid",
"lower_limit", "upper_limit", "logarithmic", "color", "no_legend", "only_graph",
"force_rules_legend", "title", "step".
Some options (e.g. "alt_y_grid") don't expect values, they need to be specified like
alt_y_grid => undef
in order to be passed properly to RRDTool.
The "color" option expects a reference to a hash with various settings for the different graph areas:
"back" (background), "canvas", "shadea" (left/top border), "shadeb" (right/bottom border), "grid",
"mgrid" major grid, "font", "frame" and "arrow":
$rrd->graph(
...
color => { back => '#0e0e0e',
arrow => '#ff0000',
canvas => '#eebbbb',
},
...
);
Fonts for various graph elements may be specified in "font" blocks, which must either name a TrueType
font file or a PDF/Postscript font name. You may optionally specify a size and element name
(defaults to DEFAULT, which to RRD means "use this font for everything). Example:
font => {
name => "/usr/openwin/lib/X11/fonts/TrueType/GillSans.ttf",
size => 16,
element => "title"
}
Please check the RRDTool documentation for a detailed description on what each option is used for:
http://people.ee.ethz.ch/~oetiker/webtools/rrdtool/manual/rrdgraph.html
Sometimes it's useful to print max, min or average values of a given graph at the bottom of the chart
or to STDOUT. That's what "gprint" and "print" options are for. They are printing variables which are
defined as "vdef"s somewhere else:
$rrd->graph(
image => $image_file_name,
# Real graph
draw => {
name => "first_draw",
dsname => "load",
cfunc => 'MAX'
},
# vdef for calculating average of real graph
draw => {
type => "hidden",
name => "average_of_first_draw",
vdef => "first_draw,AVERAGE"
},
gprint => {
draw => 'average_of_first_draw',
format => 'Average=%lf',
},
);
The "vdef" performs a calculation, specified in RPN notation, on a real graph, which it refers to. It
uses a hidden graph for this.
The "gprint" option then refers to the "vdef" virtual graph and prints "Average=x.xx" at the bottom
of the graph, showing what the average value of graph "first_draw" is.
To write comments to the graph (like gprints, but with no associated RRD data source) use "comment",
like this:
$rrd->graph(
image => $image_file_name,
draw => {
name => "first_draw",
dsname => "load",
cfunc => 'MAX'},
comment => "Remember, 83% of all statistics are made up",
);
Multiple comment lines can be specified in a single comment specification like this:
comment => [ "All the king's horses and all the king's men\\n",
"couldn't put Humpty together again.\\n",
],
Vertical rules (lines) may be placed into the graph by using a "vrule" block like so:
vrule => { time => time()-3600, }
These can be useful for indicating when the most recent day on the graph started, for example.
vrules can have a color specification (they default to black) and also an optional legend string
specified:
vrule => { time => $first_thing_today,
color => "#0000ff",
legend => "When we crossed midnight"
},
hrules can have a color specification (they default to black) and also an optional legend string
specified:
hrule => { value => $numeric_value,
color => "#0000ff",
legend => "a static line at your value"
},
Horizontal rules can be added by using a "line" block like in
line => {
value => "fixed num value or draw name",
color => "#0000ff",
legend => "a blue horizontal line",
width => 120,
stack => 1,
}
If instead of a horizontal line, a rectangular area is supposed to be added to the graph, use an
"area" block:
area => {
value => "fixed num value or draw name",
color => "#0000ff",
legend => "a blue horizontal line",
stack => 1,
}
The "graph" method can also generate tickmarks (vertical lines) for every defined value, using the
"tick" option:
tick => {
draw => "drawname",
color => "#0000ff",
legend => "a blue horizontal line",
stack => 1,
}
The graph may be shifted relative to the time axis:
shift => {
draw => "drawname",
offset => $offset,
}
$rrd->graphv( ... )
This is identical to "graph", but uses rrdtool's graphv function internally. The only difference is
when using the "print_results" method described below, which then contains additional information.
Be aware that rrdtool 1.3 is required for "graphv" to work.
$rrd->dump()
Available as of rrdtool 1.0.49.
Dumps the RRD in XML format to STDOUT. If you want to dump it into a file instead, do this:
my $pid;
unless ($pid = open DUMP, "-|") {
die "Can't fork: $!" unless defined $pid;
$rrd->dump();
exit 0;
}
waitpid($pid, 0);
open OUT, ">out";
print OUT $_ for <DUMP>;
close OUT;
my $hashref = $rrd->xport(...)
Feed a perl structure with RRA data (Cf. rrdxport man page).
my $results = $rrd->xport(
start => $start_time,
end => $end_time ,
step => $step,
def => [{
vname => "load1_vname",
file => "foo",
dsname => "load1",
cfunc => "MAX",
},
{
vname => "load2_vname",
file => "foo",
dsname => "load2",
cfunc => "MIN",
}],
cdef => [{
vname => "load2_vname_multiply",
rpn => "load2_vname,2,*",
}],
xport => [{
vname => "load1_vname",
legend => "it_s_gonna_be_legend_",
},
{
vname => "load2_vname",
legend => "wait_for_it",
},
{
vname => "load2_vname_multiply",
legend => "___dary",
}],
);
my $data = $results->{data};
my $metadata = $results->{meta};
print "### METADATA ###\n";
print "StartTime: $metadata->{start}\n";
print "EndTime: $metadata->{end}\n";
print "Step: $metadata->{step}\n";
print "Number of data columns: $metadata->{columns}\n";
print "Number of data rows: $metadata->{rows}\n";
print "Legend: ", join(", ", @{$metadata->{legend}}), "\n";
print "\n### DATA ###\n";
foreach my $entry (@$data) {
my $entry_timestamp = shift(@$entry);
print "[$entry_timestamp] ", join(" ", @$entry), "\n";
}
my $hashref = $rrd->info()
Grabs the RRD's meta data and returns it as a hashref, holding a map of parameter names and their
values.
my $time = $rrd->first()
Return the RRD's first update time.
my $time = $rrd->last()
Return the RRD's last update time.
$rrd->restore(xml => "file.xml")
Available as of rrdtool 1.0.49.
Restore a RRD from a "dump". The "xml" parameter specifies the name of the XML file containing the
dump. If the optional flag "range_check" is set to a true value, "restore" will make sure the values
in the RRAs do not exceed the limits defined for the different datasources:
$rrd->restore(xml => "file.xml", range_check => 1);
$rrd->tune( ... )
Alter a RRD's data source configuration values:
# Set the heartbeat of the RRD's only datasource to 100
$rrd->tune(heartbeat => 100);
# Set the minimum of DS 'load' to 1
$rrd->tune(dsname => 'load', minimum => 1);
# Set the maximum of DS 'load' to 10
$rrd->tune(dsname => 'load', maximum => 10);
# Set the type of DS 'load' to AVERAGE
$rrd->tune(dsname => 'load', type => 'AVERAGE');
# Set the name of DS 'load' to 'load2'
$rrd->tune(dsname => 'load', name => 'load2');
$rrd->error_message()
Return the message of the last error that occurred while interacting with "RRDTool::OO".
Aberrant behavior detection
RRDTool supports aberrant behavior detection (ABD), which takes a data source, stuffs its values into a
special RRA, smoothes the data stream, tries to predict future values and triggers an alert if actual
values are way off the predicted values.
Using a fairly elaborate algorithm not only allows it to find out if a data source produces a value that
exceeds a certain fixed threshold. The algorithm constantly adapts its parameters to the input data and
acts dynamically on slowly changing values.
The "alpha" parameter specifies the baseline and lies between 0 and 1. Values close to 1 specify that
most recent values have the most weight on the prediction, whereas values close to 0 indicate that past
values carry higher weight.
On top of that, ABD can deal with data input that displays continuously rising values (slope). The "beta"
parameters, again between 0 and 1, specifies whether past values or more recent values carry the most
weight.
And, furthermore, it deals with seasonal cycles, so it won't freak out if there's a daily peak at noon.
The "gamma" parameter indicates this, if you don't specify it, it defaults to the value of "alpha".
In the easiest case, an RRA with aberrant behavior detection can be created like
# Create a round-robin database
$rrd->create(
step => 1, # one-second intervals
data_source => { name => "mydatasource",
type => "GAUGE" },
hwpredict => { rows => 3600,
},
);
where "alpha" and "beta" default to 0.5, and the "seasonal_period" defaults to 1/5 of the rows number.
"rows" is the number of primary data points that are stored in the RRA before a wrap-around happens. Note
that with ABD enabled, RRDTool won't consolidate the data from a data source before stuffing it into the
HWPREDICT RRAs, as the whole point of ABD is to smooth unfiltered data and predict future values.
A violation happens if a new measured value falls outside of the prediction. If "threshold" or more
violations happen within "window_length", an error is reported to the FAILURES RRA. "threshold" defaults
to 7, "window_length" to 9.
A more elaborate RRD could be defined as
# Create a round-robin database
$rrd->create(
step => 1, # one-second intervals
data_source => { name => "mydatasource",
type => "GAUGE" },
hwpredict => { rows => 3600,
alpha => 0.1,
beta => 0.1,
gamma => 0.1,
threshold => 7,
window_length => 9,
},
);
If you want to peek under the hood (not that you need to, just for your entertainment), with the
specification above, RRDTool::OO will create the following five RRAs according to the RRDtool
specification and fill in these values:
* RRA:HWPREDICT:rows:alpha:beta:seasonal_period:rra-num
* RRA:SEASONAL:seasonal period:gamma:rra-num
* RRA:DEVSEASONAL:seasonal period:gamma:rra-num
* RRA:DEVPREDICT:rows:rra-num
* RRA:FAILURES:rows:threshold:window_length:rra-num
The "rra-num" argument is an internal index referencing other RRAs (for example, HWPREDICT references
SEASONAL), but this will be taken care of automatically by RRDTool::OO with no user interaction required
whatsoever.
Development Status
The following methods are not yet implemented:
"rrdresize", "xport", "rrdcgi".
Print Output
The "graph" method can be configured to have RRDTool's "graph" function to print data. Calling rrdtool on
the command line, this data ends up on STDOUT, but calling something like
$rrd->graph(
image => "mygraph.png",
start => $start_time,
# ...
draw => {
type => "hidden",
name => "in95precent",
vdef => "firstdraw,95,PERCENT"
},
print => {
draw => 'in95percent',
format => "95 Percent Result = %3.2lf",
},
# ...
captures the print data internally. To get access to a reference to the array containing the different
pieces of data written in this way, call
my $array_ref = $rrd->print_results();
If no print output is available, the array referenced by $array_ref is empty.
If the "graphv" function is used instead of "graph", the return value of print_results is a hashref
containing the same information in the "print" keys, along with additional keys containing detailed
information on the graph. See "rrdtool" documentation for more detail. Here is an example:
use Data::Dumper;
$rrd -> graphv (
image => "-",
start => $start_time,
# ...
my $hash_ref = $rrd->print_results();
print Dumper $hash_ref;
$VAR1 = {
'print[2]' => '1600.00',
'value_min' => '200',
'image_height' => 64,
'graph_height' => 10,
'print[1]' => '3010.18',
'graph_end' => 1249391462,
'print[3]' => '1600.00',
'graph_left' => 51,
'print[4]' => '2337.29',
'print[0]' => '305.13',
'value_max' => '10000',
'graph_width' => 10,
'image_width' => 91,
'graph_top' => 22,
'image' => '#PNG
[...lots of binary rubbish your terminal won't like...]
',
'graph_start' => 1217855462
};
In this case, the option (image => "-") has been used to create the hash key with the same name, the
value of which actually contains the BLOB of the image itself. This is useful when image needs to be
passed to other modules (e.g. Image::Magick), instead of writing it to disk. Be aware that rrdtool 1.3
is required for "graphv" to work.
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.rrd",
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 particularly 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.rrd --step 1 \
DS:mydatasource:GAUGE:2:U:U RRA:MAX:0.5:1:5
rrdtool update myrrdfile.rrd N:1
rrdtool update myrrdfile.rrd N:2
rrdtool update myrrdfile.rrd N:3
rrdtool fetch myrrdfile.rrd MAX
Often handy for cut-and-paste.
Allow New rrdtool Parameters
"RRDTool::OO" tracks rrdtool's progress loosely, so it might happen that at a given point in time,
rrdtool introduces a new option that "RRDTool::OO" doesn't know about yet.
This might lead to problems, since default, "RRDTool::OO" has its "strict" mode enabled, rejecting all
unknown options. This mode is usually helpful, because it catches typos (like "verical_label"), but if
you want to use a new rrdtool option, it's in the way.
To work around this problem until a new version of "RRDTool::OO" supports the new parameter, you can use
$rrd->option_add("graph", "frobnication_level");
to add it to the optional parameter list of the "graph" (or whatever) rrd function. Note that some
functions in "RRDTool::OO" have sub-methods, which you can specify with the dash notation. The "graph"
method with its various "graph/draw", "graph/color", "graph/font" are notable examples.
And, as a band-aid, you can disable strict mode in these situation by setting the "strict" parameter to 0
in "RRDTool::OO"'s constructor call:
my $rrd = RRDTool::OO->new(
strict => 0,
file => "myrrdfile.rrd",
);
Note that "RRDTool::OO" follows the convention that parameters names do not contain dashes, but
underscores instead. So, you need to say "vertical_label", not "vertical-label". The underlying rrdtool
layer, however, expects dashes, not underscores, which is why "RRDTool::OO" converts them automatically,
e.g. transforming "vertical_label" to "--vertical-label" before the underlying rrdtool call happens.
Dry Run Mode
If you want to use "RRDTool::OO" to create RRD commands without executing them directly, thanks to
Jacquelin Charbonnel, there's the dry run mode. Here's how it works:
my $rrd = RRDTool::OO->new(
file => "myrrdfile.rrd",
dry_run => 1
);
With dry_run set to a true value, you can run commands like
$rrd->create(
step => 60,
data_source => { name => "mydatasource",
type => "GAUGE" },
archive => { rows => 5 });
but since dry_mode is on, they won't be handed through to the rrdtool layer anymore. Instead, RRDTool::OO
allows you to retrieve a reference to the RRDs function it was about to call including its arguments:
my ($subref, $args) = $rrd->get_exec_env();
You can now examine or modify the subroutine reference $subref or the arguments in the array reference
$args. Later, simply call
$subref->(@$args);
to execute the RRDs function with the modified argument list later. In this case, @$args would contain
the following items:
("myrrdfile.rrd", "--step", "60",
"DS:mydatasource:GAUGE:120:U:U", "RRA:MAX:0.5:1:5")
If you're interested in the RRD function name to be executed, retrieve the third parameter of
"get_exec_env":
my ($subref, $args, $funcname) = $rrd->get_exec_env();
INSTALLATION
"RRDTool::OO" requires a rrdtool installation with the "RRDs" Perl module, that comes with the "rrdtool"
distribution.
Download the tarball from
http://oss.oetiker.ch/rrdtool/pub/rrdtool.tar.gz
and then unpack, compile and install:
tar zxfv rrdtool.tar.gz
cd rrdtool-1.2.26
./configure --enable-perl-site-install --prefix=/usr \
--disable-tcl --disable-rrdcgi
make
make install
cd bindings/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
• My articles on rrdtool in "Linux Magazine" (UK) and "Linux Magazin" (Germany):
(English)
http://www.linux-magazine.com/issue/44/Perl_RDDtool.pdf
(German)
http://www.linux-magazin.de/Artikel/ausgabe/2004/06/perl/perl.html
AUTHOR
Mike Schilli, <m@perlmeister.com>
COPYRIGHT AND LICENSE
Copyright (C) 2004-2009 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.