The network graphing solution Cacti was designed to provide more ease of use than RRDtool and more flexibility than MRTG.

by Jeff Goldman [January 17, 2007]

Ian Berry first developed the open source network graphing solution Cacti when he was in high school—way back in 2001. While working at a small ISP, Berry says, he began exploring the functionality of tools like MRTG and RRDtool, and saw a need for a new solution. "I really wanted to use RRDtool the same way as MRTG," he says. "That is, I wanted to be able to plug in some devices and have it give me a list of interfaces—and I wanted to just click a few buttons and have it generate some cool RRDtool graphs."

At the time, Berry says, he was in the process of learning PHP and MySQL—so that's what he used to create Cacti. "I came up with some really basic features, and it got to the point where I thought, 'Hey, maybe some other people would be interested in this,' so I posted it on the Internet," he says. "And it caught on pretty quickly. Once people started using it, I just kept developing it, and it became a lot more generalized. At this point in time, it's almost completely independent of myself: I still work on it, I'm involved in it quite a bit, but the community has grown to a point where it's just out there thriving."

A maturing solution
Cacti has grown significantly since the initial 0.5 release back in 2001. "When it was first released, to be honest, it was pretty amateurish," Berry says. "It did a very small subset of things. You could create a data source, you could create a basic graph, you could add some items to it—and it had the ability to poll an SNMP-enabled device for interfaces to graph. That's all it could do. It really didn't have anything in terms of scalability."

During the 0.6 releases that followed, Berry says, he added basic functionality and flexibility, and with the first 0.8 release, he added templates to the solution. "Templating's really important, because you can make one graph template and apply it to a whole bunch of different graphs—and then be able to make changes to the template and have them automatically be applied," he says. "That was a really important step in making Cacti scalable."

The 0.8 release also added a new generic polling interface. "I got to a point where a lot of users were adding more and more data sources," Berry says. "They wanted to poll 1,000, 5,000, or 10,000 RRDtool files every five minutes, and there's only so much you can do with the PHP poller that Cacti was originally shipped with. So a couple of years ago I started working on a C-based poller which uses threads, and it was a lot quicker."

With the 0.8.6 release, Berry started bringing on additional developers—and the result, he says, is that the solution's speed and scalability have taken off, with users now polling 50,000 items every five minutes. "I could list off lots of features that Cacti now has—the ability to export graphs to static images, being able to detect when hosts go up and down and mark different status levels, and different ways to view graphs, like the graph tree, so you just don't have a bunch of standalone graph images any more," he says. "It's really just built upon itself with every subsequent release."

Accessibility and community
Berry's central aim in first developing Cacti, he says, was to offer more ease of use than RRDtool and more flexibility than MRTG. "To actually interface with RRDtool, you have to provide it with all the data, you have to write this nasty command line script to generate the graphs—and that's fine if you're doing some custom work, but Cacti was really designed to put an elegant front end on top of that," he says. "MRTG, on the other hand, is more focused—it's really just designed to graph traffic statistics on routers, or any device for that matter. So it's very specific in its purpose, and it's not very configurable."

In terms of ease of use, Berry says, Cacti benefits greatly from being Web-based. "MRTG and RRDtool are both command line based, and both have text-based configuration, so there's quite a bit of learning curve there—you have to read all the docs and figure out the syntax," he says. "Cacti is mostly point-and-click, and once you get it installed, everything's done through your Web browser. I think for a lot of people that makes it a lot easier."

And for an ISP, Berry says, the kind of functionality that Cacti provides can be crucial. "It really, really pays off," he says. "If you have a server where the disk space starts filling up over a year, you're not going to be able to track that down if it's not for some graph that you can go back to and say, 'You know, last September, this was filling up.' So it's really important to be on top of that stuff."

Looking ahead, Berry says his key aim is to increase the community aspect of the project by adding a plug-in architecture and by making it easier for people to share and publish their graph templates. "Then users could go to a website and they could get all these pre-defined graphs that other users have created, to save them a whole bunch of time," he says. "They won't have to find out how to get the data and what the graph looks like and all that—they can just grab it from this website."

What's next for Berry? Having graduated from college last May, he's now a partner in BitLeap, a new offsite data backup provider. "Most of my development time outside of Cacti is with that," he says. "And we do use Cacti, in case you wanted to know!"

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