Runt - SVG & Rails
While developing Runt over the past few months it became obvious mid-way through development that the integration of graphing was somewhat of an afterthought. That’s okay though because we’re agile, right?
Graphing SNMP data in Rails applications (or any other application for that matter) is difficult for a number of reasons:
What the hell do I graph?
- SNMP data is so varied in scope that we need to narrow our scope in order to graph something useful. We don’t want to graph sysName against sysDescr because that’s stupid and completely useless.
- Graphs obviously need need be composed of numerical data, so any SNMP data composed of strings is likely going to be useless.
Right, so what kind of data types should we be looking at (assuming we’re working with protocol version 2c)?
- Integer32/Integer (Enumerated)/Unsigned32/Gauge32/Counter32/TimeTicks/Opaque/Bits
With these data types in mind, our scope is still way too vague for us to be able to graph any meaningful data. With a deadline looming, I made the decision to limit the scope of graphing in Runt to just bandwidth, something which most SNMP graphing applications out there focus on (MRTG for example). Having made my decision I was then faced with some interesting decisions regarding graphing. Initially I wanted graphing to be as sexy as that found in the Tomato firmware installed on my WRT54GL router.
Tomato generates its graphs in between AJAX requests and renders them to the user using SVG. Unfortunately, browser SVG support is patchy for Intel Mac users with Safari 2.0.4 (even though SVG support landed in WebKit landed over two years ago). Adobe have offered a plugin for SVG support in Safari (which is going to be unsupported next year), but only for users running Safari on PowerPC Macs. As an Intel user you could of course run Safari under Rosetta to enable the plugin to function but jesus don’t. Thankfully SVG support will finally find its way into Safari 3.0 in Leopard, but that’s several months away. IE6/7 users enjoy SVG support through the same Adobe plugin, while Gecko based browser users see SVG built-in.
With this in mind, and due to the fact I’m a selfish jerk who uses Safari, I decided against using SVG in Runt, at least for the time being. My options for graphing in Rails boiled down to three contenders:
- Gruff - pretty graphs that are rendered as PNGs. Rails plugin.
- Scruffy - - pretty graphs, internally rendered using SVG and it can spit out your graphs in pretty much any format imaginable. Unfortunately it hasn’t been updated in over 9 months.
- ZiYa - pretty Flash graphs. Flash, ugh.
I eventually rolled with Gruff since I found it the easiest to get to grips with and because it somehow felt more Rails like than the others. I was seriously considering ZiYA for several weeks but considering how much I’ve come to hate almost all implementations of Flash “hay guys lets totally offload the rendering of this website to some proprietary plugin! This is a great idea, right guys! Guys?!” I decided it was best to roll with something I could stomach myself using. Unfortunately, this meant that interactivity with the graph was going to be seriously limited as Gruff was just going to throw rendered PNGs at a user with a rather horrible rendering delay between AJAX requests. This is something that has bothered me ever since I chose to use Gruff, but what’s done is done.
The next iteration of Runt will see me revisit the idea of using SVG rendering because it’s sexy as hell and because, for the time being at least, I’ve begun using Firefox 2.0 regularly once more.