mod_rrd_graph
=============

RRDtool[1] stores and graphs time-series data. ngx_rrd_graph provides an HTTP
interface to RRDtool's graphing facilities. By linking RRDtool code directly
into Nginx, it is faster than scripts and CGIs with similar purposes.

To install, compile nginx with this option:

    --add-module=/path/to/this/directory

ngx_rrd_graph requires RRDtool 1.3 or later. 

After compiling, installing, and restarting Nginx, ngx_rrd_graph can be enabled
at a particular location with the "rrd_graph" directive, like so:

    location /rrdtool {
        rrd_graph;
    }

RRDtool graphing commands can then be appended to that location in request
URLs. The syntax is just the same as the arguments to the "rrdtool graph"
command, omitting the filename. (Refer to rrdgraph(1).) These commands should
be URL-encoded, so that this command-line invocation:

    rrdtool graph --start now-300s \
                  --end now \
                  DEF:ds0=test.rrd:reading:AVERAGE \
                  LINE1:ds0#00FF00

becomes:

    http://mysite.com/rrdtool--start%20now-300s%20--end%20now%20DEF%3Ads0%3Dtest.rrd%3Areading%3AAVERAGE%20LINE1%3Ads0%2300FF00

If you need spaces in arguments, put quotation marks ("") around the string.

The module supports all the features of your copy of RRDtool. It can output
PNG, PDF, SVG, and EPS graphics (see the --imgformat option of rrdgraph(1)).

If you'd prefer not to provide absolute paths to files referenced in DEF commands,
you may supply a root directory with the "rrd_graph_root" directive. Files mentioned
in DEF commands will be automatically prefixed with the value of rrd_graph_root.
As of this writing there are no guards against relative paths (e.g. "..").

Questions/comments to emmiller@gmail.com.

[1] http://oss.oetiker.ch/rrdtool/