1RRDs(3) User Contributed Perl Documentation RRDs(3)
2
6 RRDs - Access RRDtool as a shared module
7
9 use RRDs;
10 RRDs::error
11 RRDs::last ...
12 RRDs::info ...
13 RRDs::create ...
14 RRDs::update ...
15 RRDs::updatev ...
16 RRDs::graph ...
17 RRDs::fetch ...
18 RRDs::tune ...
19 RRDs::times(start, end)
20 RRDs::dump ...
21 RRDs::restore ...
22 RRDs::flushcached ...
23 RRDs::register_fetch_cb ...
24 $RRDs::VERSION
25
27 Calling Sequence
28 This module accesses RRDtool functionality directly from within Perl.
29 The arguments to the functions listed in the SYNOPSIS are explained in
30 the regular RRDtool documentation. The command line call
31 rrdtool update mydemo.rrd --template in:out N:12:13
33 gets turned into
35 RRDs::update ("mydemo.rrd", "--template", "in:out", "N:12:13");
37 Note that
39 --template=in:out
41 is also valid.
43 The RRDs::times function takes two parameters: a "start" and "end"
45 time. These should be specified in the AT-STYLE TIME SPECIFICATION
46 format used by RRDtool. See the rrdfetch documentation for a detailed
47 explanation on how to specify time.
48 Error Handling
50 The RRD functions will not abort your program even when they cannot
51 make sense out of the arguments you fed them.
52 The function RRDs::error should be called to get the error status after
54 each function call. If RRDs::error does not return anything then the
55 previous function has completed its task successfully.
56 use RRDs;
58 RRDs::update ("mydemo.rrd","N:12:13");
59 my $ERR=RRDs::error;
60 die "ERROR while updating mydemo.rrd: $ERR\n" if $ERR;
61 Return Values
63 The functions RRDs::last, RRDs::graph, RRDs::info, RRDs::fetch and
64 RRDs::times return their findings.
65 RRDs::last returns a single INTEGER representing the last update time.
67 $lastupdate = RRDs::last ...
69 RRDs::graph returns an ARRAY containing the x-size and y-size of the
71 created image and a pointer to an array with the results of the PRINT
72 arguments.
73 ($result_arr,$xsize,$ysize) = RRDs::graph ...
75 print "Imagesize: ${xsize}x${ysize}\n";
76 print "Averages: ", (join ", ", @$averages);
77 RRDs::info returns a pointer to a hash. The keys of the hash represent
79 the property names of the RRD and the values of the hash are the values
80 of the properties.
81 $hash = RRDs::info "example.rrd";
83 foreach my $key (keys %$hash){
84 print "$key = $$hash{$key}\n";
85 }
86 RRDs::graphv takes the same parameters as RRDs::graph but it returns a
88 pointer to hash. The hash returned contains meta information about the
89 graph. Like its size as well as the position of the graph area on the
90 image. When calling with '-' as the filename then the contents of the
91 graph will be returned in the hash as well (key 'image').
92 RRDs::updatev also returns a pointer to hash. The keys of the hash are
94 concatenated strings of a timestamp, RRA index, and data source name
95 for each consolidated data point (CDP) written to disk as a result of
96 the current update call. The hash values are CDP values.
97 RRDs::fetch is the most complex of the pack regarding return values.
99 There are 4 values. Two normal integers, a pointer to an array and a
100 pointer to an array of pointers.
101 my ($start,$step,$names,$data) = RRDs::fetch ...
103 print "Start: ", scalar localtime($start), " ($start)\n";
104 print "Step size: $step seconds\n";
105 print "DS names: ", join (", ", @$names)."\n";
106 print "Data points: ", $#$data + 1, "\n";
107 print "Data:\n";
108 for my $line (@$data) {
109 print " ", scalar localtime($start), " ($start) ";
110 $start += $step;
111 for my $val (@$line) {
112 printf "%12.1f ", $val;
113 }
114 print "\n";
115 }
116 RRDs::xport exposes the rrdxport functionality and returns data with
118 the following structure:
119 my ($start,$end,$step,$cols,$names,$data) = RRDs::xport ...
121 # $start : timestamp
123 # $end : timestamp
124 # $step : seconds
125 # $cols : number of returned columns
126 # $names : arrayref with the names of the columns
127 # $data : arrayref of arrayrefs with the data (first index is time, second is column)
128 RRDs::times returns two integers which are the number of seconds since
130 epoch (1970-01-01) for the supplied "start" and "end" arguments,
131 respectively.
132 See the examples directory for more ways to use this extension.
134 Fetch Callback Function
136 Normally when using graph, xport or fetch the data you see will come
137 from an actual rrd file. Some people who like the look of rrd charts,
138 therefore export their data from a database and then load it into an
139 rrd file just to be able to call rrdgraph on it. Using a custom
140 callback, you can supply your own code for handling the data requests
141 from graph, xport and fetch.
142 To do this, you have to first write a fetch function in perl, and then
144 register this function using "RRDs::fetch_register_callback".
145 Finally you can use the pseudo path name cb//[filename] to tell rrdtool
147 to use your callback routine instead of the normal rrdtool fetch
148 function to organize the data required.
149 The callback function must look like this:
151 sub fetch_callback {
153 my $args_hash = shift;
154 # {
155 # filename => 'cb//somefilename',
156 # cd => 'AVERAGE',
157 # start => 1401295291,
158 # end => 1401295591,
159 # step => 300 }
160 # do some clever thing to get that data ready
162 return {
164 start => $unix_timestamp,
165 step => $step_width,
166 data => {
167 dsName1 => [ value1, value2, ... ],
168 dsName2 => [ value1, value2, ... ],
169 dsName3 => [ value1, value2, ... ],
170 }
171 };
172 }
173
175 If you are manipulating the TZ variable you should also call the POSIX
176 function tzset(3) to initialize all internal states of the library for
177 properly operating in the timezone of your choice.
178 use POSIX qw(tzset);
180 $ENV{TZ} = 'CET';
181 POSIX::tzset();
182
184 Tobias Oetiker <tobi@oetiker.ch>
185perl v5.30.0 2019-07-26 RRDs(3)