[rrd-users] RRD Wishlist: Adding comments to RRD created graphs

[Rob Newman]

Hi RRD folks,

I know this is probably going to garner a 'nope, can't do that  
response', but I was wondering if the RRD developers (Tobi et al) had  
considered the capability of users adding comments to RRD files along  
the lines of timestamp:comment string that could be added in the  
header of an RRD archive. These comments could then be plotted on the  
graphical output when RRDtool graph is called.

An example:
No comments (typical rrdtool graph output): http://eqinfo.ucsd.edu/ 
~rnewman/images/rrd_wishlist/nocomments.gif
With comments: http://eqinfo.ucsd.edu/~rnewman/images/rrd_wishlist/ 
comments.gif

I could see this capability being useful for viewers so they can read  
the attribution of any anomalous changes in data values.

If I do an XML dump of an RRD archive, I see the following in the  
(although not explicitly defined) 'header area':

<!-- Round Robin Database Dump --><rrd> <version> 0003 </version>
         <step> 20 </step> <!-- Seconds -->
         <lastupdate> 1181171131 </lastupdate> <!-- 2007-06-06  
16:05:31 PDT -->

         <ds>
                 <name> m0 </name>
                 <type> GAUGE </type>
                 <minimal_heartbeat> 21600 </minimal_heartbeat>
                 <min> NaN </min>
                 <max> NaN </max>

                 <!-- PDP Status -->
                 <last_ds> -2 </last_ds>
                 <value> -6.6000000000e+01 </value>
                 <unknown_sec> 0 </unknown_sec>
         </ds>

<!-- Round Robin Archives -->

I could see altering this structure to be like (in the XML format of  
rrdtool dump) :

<!-- Round Robin Database Dump --><rrd> <version> 0003 </version>
         <step> 20 </step> <!-- Seconds -->
         <lastupdate> 1181171131 </lastupdate> <!-- 2007-06-06  
16:05:31 PDT -->

         <ds>
                 <name> m0 </name>
                 <type> GAUGE </type>
                 <minimal_heartbeat> 21600 </minimal_heartbeat>
                 <min> NaN </min>
                 <max> NaN </max>

                 <!-- PDP Status -->
                 <last_ds> -2 </last_ds>
                 <value> -6.6000000000e+01 </value>
                 <unknown_sec> 0 </unknown_sec>
         </ds>

	<comments>
		<!-- 2007-06-01 02:46:40 PDT / epochtime --> <row><v>New  
instrument</v></row>
		<!-- 2007-05-01 02:46:40 PDT / epochtime --> <row><v>Mass recenter</ 
v></row>
	</comments>

<!-- Round Robin Archives -->

This could be added using a new command called 'rrdtool comment  
archive_name.rrd timestamp comment_string'.

Comments? Thoughts? I would love to say that I will volunteer to make  
these changes in the RRDTool source code, but it is way above my  
capabilities, so I can meekly retreat back into my corner if someone  
takes umbrage at my request. I wouldn't be asking for this capability  
if RRD wasn't such as awesome tool - Tobi has already done an  
exceptional job.

Thanks!
- Rob
________________________________________________________

Rob Newman Ph.D.
Institute of Geophysics and Planetary Physics
Scripps Institution of Oceanography
University of California, San Diego
9500 Gilman Drive, La Jolla, CA 92093-0225, USA

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