Vladimir Dudchenko speaks about his recent Load test of IP PBX Asterisk powered by WombatDialer


Vladimir Dudchenko After finishing MIPT - leading Russian technical university in 1973 Vladimir for the next 20 years has been working for Russian space industry, participating in various IT projects for orbit stations and vehicles.

The next 10 years he has been working for private IT companies in different positions, until in 2003 he has founded SoftBCom - company for IT services and consulting.

SoftBCom has expertise in various areas - mainly on IT infrastructure, applications performance management, security and communications. Among its customers industrial and financial leaders, as well as mid-size and small companies.

Last few years the main activity of SoftBCom was devoted to integrated projects combining infrastructural and communication components, including Asterisk and Asterisk-based solutions.

SoftBCom devotes its efforts to searching the most efficient solutions for customers giving them real benefits with highest ROI and smallest expenditures, the most actual in current economical situation.

Q: Why did you decide to perform the load test?
In general - I believe in each project we need to know the performance limit of engines we rely on. Particularly concerning Asterisk: it is an extremely underestimated solution. It's stability, functional power, flexibility is well known, but the main reason used by competitors or opponents is low scalability. The common conviction is that it fits only to small projects, up to 300 extensions or so.
Watching the real load Asterisk creates in production systems we could see that the real limit should be much higher. But to get firm background for our sizing estimations we have been looking for opportunity to perform a direct load test. Load generation for stress tests is not an easy task in each and every area, and finding an instrument which just 100% fits and resolves this problem was a real fortune.

Q: Can you describe the process and the tools used for the analysis and the testing?
The tool gave us such a "happy chance" is Loway WombatDialer. Designed for another purpose it looks just like specially intended for Asterisk load generation. Being integrated with Asterisk, creating as many talk channels as you need, playing sound - it's functionality leaves us very small additional efforts necessary for organizing load testing.
About technical details I would refer to Evgeny Anvaer - our technical expert who designed and conducted this experiment. In our specific case each WombatDialer copy created 100 concurrent talks. After the testing Asterisk server establishes connections to the tested one the WombatDialer has been restarted to initialize new calls, and so on. The previous connections have been kept active, so we could realize any connection number we need.
To include media load we used pause music playback and talks record on tested Asterisk.
The measured CPU load values were captured by "top" commands, number of Asterisk concurrent calls were checked by Asterisk console.
Definitely the talks frame used for measurement is a somewhat specific sample, and you could say it worthwhile using another one, so no problem, we can. But it is already clear that any new result will not dramatically differ, it would be just some fine variation from the result we received.

Q: Can you tell us about your experience of using WombatDialer to run the load test?
It was easy to install, to configure and to connect Loway WombatDialer to Asterisk.
The first load test with WombatDialer we conducted for Asterisk on VM at Hetzner cloud service has shown a limit about 100 concurrent calls. The second one we are discussing now - 1600 concurrent calls on 4-core CPU, much more powerful installation.
WombatDialer is a very handy instrument, and we plan to use it for a number of new tests to get a kind of production capability profile applicable for sizing of different scale projects.
Definitely this will not cover all the needs of sizing estimation one may get, but the methodology we use based on WombatDialer permits to accomplish test for any load emulation scenario.

Q: Did you have any load issue with WombatDialer during the testing phase?
Actually not. Maybe our task is not so complicated as real marketing activities, but for us WombatDialer turned out to be convenient and functional product totally covering our needs. It is just WombatDialer have made possible our load tests and I'm sure will be used in new tests making Asterisk implementation much wider and corresponding projects more efficient.

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