phpman > man > RRDs(3pm)

NAME
    RRDs - Access RRDtool as a shared module

SYNOPSIS
      use RRDs;
      RRDs::error
      RRDs::last ...
      RRDs::info ...
      RRDs::create ...
      RRDs::update ...
      RRDs::updatev ...
      RRDs::graph ...
      RRDs::fetch ...
      RRDs::tune ...
      RRDs::times(start, end)
      RRDs::dump ...
      RRDs::restore ...
      RRDs::flushcached ...
      RRDs::register_fetch_cb ...
      $RRDs::VERSION

DESCRIPTION
  Calling Sequence
    This module accesses RRDtool functionality directly from within Perl. The arguments to the
    functions listed in the SYNOPSIS are explained in the regular RRDtool documentation. The command
    line call

     rrdtool update mydemo.rrd --template in:out N:12:13

    gets turned into

     RRDs::update ("mydemo.rrd", "--template", "in:out", "N:12:13");

    Note that

     --template=in:out

    is also valid.

    The RRDs::times function takes two parameters: a "start" and "end" time. These should be
    specified in the AT-STYLE TIME SPECIFICATION format used by RRDtool. See the rrdfetch
    documentation for a detailed explanation on how to specify time.

  Error Handling
    The RRD functions will not abort your program even when they cannot make sense out of the
    arguments you fed them.

    The function RRDs::error should be called to get the error status after each function call. If
    RRDs::error does not return anything then the previous function has completed its task
    successfully.

     use RRDs;
     RRDs::update ("mydemo.rrd","N:12:13");
     my $ERR=RRDs::error;
     die "ERROR while updating mydemo.rrd: $ERR\n" if $ERR;

  Return Values
    The functions RRDs::last, RRDs::graph, RRDs::info, RRDs::fetch and RRDs::times return their
    findings.

    RRDs::last returns a single INTEGER representing the last update time.

     $lastupdate = RRDs::last ...

    RRDs::graph returns an ARRAY containing the x-size and y-size of the created image and a pointer
    to an array with the results of the PRINT arguments.

     ($result_arr,$xsize,$ysize) = RRDs::graph ...
     print "Imagesize: ${xsize}x${ysize}\n";
     print "Averages: ", (join ", ", @$averages);

    RRDs::info returns a pointer to a hash. The keys of the hash represent the property names of the
    RRD and the values of the hash are the values of the properties.

     $hash = RRDs::info "example.rrd";
     foreach my $key (keys %$hash){
       print "$key = $$hash{$key}\n";
     }

    RRDs::graphv takes the same parameters as RRDs::graph but it returns a pointer to hash. The hash
    returned contains meta information about the graph. Like its size as well as the position of the
    graph area on the image. When calling with '-' as the filename then the contents of the graph
    will be returned in the hash as well (key 'image').

    RRDs::updatev also returns a pointer to hash. The keys of the hash are concatenated strings of a
    timestamp, RRA index, and data source name for each consolidated data point (CDP) written to
    disk as a result of the current update call. The hash values are CDP values.

    RRDs::fetch is the most complex of the pack regarding return values. There are 4 values. Two
    normal integers, a pointer to an array and a pointer to an array of pointers.

      my ($start,$step,$names,$data) = RRDs::fetch ...
      print "Start:       ", scalar localtime($start), " ($start)\n";
      print "Step size:   $step seconds\n";
      print "DS names:    ", join (", ", @$names)."\n";
      print "Data points: ", $#$data + 1, "\n";
      print "Data:\n";
      for my $line (@$data) {
        print "  ", scalar localtime($start), " ($start) ";
        $start += $step;
        for my $val (@$line) {
          printf "%12.1f ", $val;
        }
        print "\n";
      }

    RRDs::xport exposes the rrdxport functionality and returns data with the following structure:

      my ($start,$end,$step,$cols,$names,$data) = RRDs::xport ...

      # $start : timestamp
      # $end   : timestamp
      # $step  : seconds
      # $cols  : number of returned columns
      # $names : arrayref with the names of the columns
      # $data  : arrayref of arrayrefs with the data (first index is time, second is column)

    RRDs::times returns two integers which are the number of seconds since epoch (1970-01-01) for
    the supplied "start" and "end" arguments, respectively.

    See the examples directory for more ways to use this extension.

  Fetch Callback Function
    Normally when using graph, xport or fetch the data you see will come from an actual rrd file.
    Some people who like the look of rrd charts, therefore export their data from a database and
    then load it into an rrd file just to be able to call rrdgraph on it. Using a custom callback,
    you can supply your own code for handling the data requests from graph, xport and fetch.

    To do this, you have to first write a fetch function in perl, and then register this function
    using "RRDs::fetch_register_callback".

    Finally you can use the pseudo path name cb//[*filename*] to tell rrdtool to use your callback
    routine instead of the normal rrdtool fetch function to organize the data required.

    The callback function must look like this:

      sub fetch_callback {
          my $args_hash = shift;
          # {
          #  filename => 'cb//somefilename',
          #  cd => 'AVERAGE',
          #  start => 1401295291,
          #  end => 1401295591,
          #  step => 300 }

          # do some clever thing to get that data ready

          return {
              start => $unix_timestamp,
              step => $step_width,
              data => {
                  dsName1 => [ value1, value2, ... ],
                  dsName2 => [ value1, value2, ... ],
                  dsName3 => [ value1, value2, ... ],
              }
         };
      }

NOTE
    If you are manipulating the TZ variable you should also call the POSIX function tzset(3) to
    initialize all internal states of the library for properly operating in the timezone of your
    choice.

     use POSIX qw(tzset);
     $ENV{TZ} = 'CET';
     POSIX::tzset();

AUTHOR
    Tobias Oetiker <tobi AT oetiker.ch>