Hi!<br><div class="gmail_quote"><br>I'm new to freeswitch and I like to report my success with it and a few failures. I'll be a little bit vague on some details because I must protect some business details. Sorry for that.<br>
<br>I have no experience with asterisk, so many concepts were new to me.<br>
<br>We run a hosted IVR system with a few hundred lines. We have a few servers running a SIP/VoiceXML application server and connect to the network with SIP/ISDN gateways.<br><br>Recently we started an IVR with very short calls and very high CPS. Our existing software doesn't handle this scenario very well, so I started looking into alternatives.<br>
<br>FreeSwitch caught my eye because of its support for multiple scripting languages. I love python and this feature put FS into the evaluation list. So I started on friday. I installed FS from the debian repositories on my ubuntu 8.04 laptop and tried some examples from the wiki ("Some thing to try out!"). I was very impressed that everything worked right out of the box.<br>
<br>I was a little disappointed that mod_python wasn't included in the distribution so I checked out the source and compiled everything. An hour later I had another installation of FS.<br><br>It took me a few hous to get the dialplan right. Because our service only runs IVRs and uses no switching, I removed everything from the default dialplan (mainly because it conflicted with the ANI numbers we get from the gateways).<br>
<br>Another hour later, I had a simple IVR in python done: use a web service for a database lookup and play an appropriate prompt. I didn't use the database directly because I wanted the best possible comparison to what our current system does, and (our) VoiceXML can't use databases directly, but can use web services.<br>
<br>In less than 1 working day I had everything running. Quite good.<br><br>Time for load testing :-) Our old software handles around 20 CPS on my laptop. I inceased max_sessions to 5000 and sessions-per-second to 100 and started sipp. The result was quite bad - I could not get over 8 CPS! The processor barely noticed that FS was running, so I had no idea what the bottleneck was. I still don't. After fiddling with this for a while, I gave up and decided to try it on one of our production machines. Weekends are not very busy, so I took one offline. It's a HP proliant server with 1 quad-core xeon on 2 GHz, 2G ecc ram and 10krpm disks. The server is also running ubuntu 8.04 (server edition) so I just copied the binaries.<br>
<br>I ran sipp from another machine, with the uac scenario and limiting the call duration to 4secs:<br>sipp <FS server ip> -sn uac -d 4000 -s <ivr_number> <br>Theoretically, as each call lasts 4 seconds, the total calls number should never exceed 4x current CPS.<br>
<br>These are the results:<br><br>With up to 27 CPS everything was stable. The calls count was almost exactly 4 timee the CPS, indicating that new calls were ansewered immediately. This I also verified by calling in.<br>
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Up to 30 CPS everything was stable for a while, but then the total calls number exploded to the limit set by sipp. The processor load was very reasonable, so I again I ran into the bottleneck mentioned above. After sipp hits the total call limit, it will not create new calls until some are released. So CPS oscillated between 0 and 30 as shown by sipp. CDRs show that there was an average of 27 CPS. At this point, when I called in, I got ringback tone for as long as the operator allows (60s) and then I was dropped. With a softphone I could reach the IVR after about 80 sec.<br>
<br>When I set sipp to more than 30 CPS, the number of total calls exploded immediately.<br><br>Experimenting some more, I found I could contain the explosion (and the instability in CPS) by limiting the number of total calls to 4x current cps when cps was up to 30. Thus, by starting sipp like this:<br>
sipp <FS server ip> -sn uac -d 4000 -s <ivr_number> -l 120<br>I could go up to 30CPS and get reasonably stable real 30CPS. When calling in with a real phone, I would reach the IVR after 2-3 seconds of ringback, which is acceptable. This simulation run for several hours without any other problems.<br>
<br>With <br>sipp <FS server ip> -sn uac -d 4000 -s <ivr_number> -l 160<br>and setting cps to 40, the total calls count obviously never passed 160, but the cps shown by sipp became unstable, oscillating between 0 and 40.<br>
<br>These results are only slightly better than our current SIP server.<br><br>Today I put FreeSwitch into production. The unexpected thing here was that when FreeSwitch talked to our gateways instead of sipp, it crashed a few times. I don't associate these crashes with load because it happened equally on low and high load. Here's the log:<br>
<br>2008-06-09 09:34:33 [NOTICE] switch_core_session.c:753 switch_core_session_thread() Session 166 (sofia/internal/---- deleted stuff -----) Ended<br>2008-06-09 09:34:33 [NOTICE] switch_core_session.c:755 switch_core_session_thread() Close Channel sofia/internal/---- deleted stuff ----- [CS_HANGUP]<br>
2008-06-09 09:34:33 [CRIT] switch_core_state_machine.c:218 print_trace() Obtained 10 stack frames.<br>/usr/local/freeswitch/lib/libfreeswitch.so.1 [0xb7e413b1]<br>[0xb7f69420]<br>/usr/local/freeswitch/mod/mod_python.so [0xb011b46a]<br>
/usr/lib/libpython2.5.so.1.0(PyCFunction_Call+0xfa) [0xb002a50a]<br>/usr/lib/libpython2.5.so.1.0(PyObject_Call+0x37) [0xafff38d7]<br>/usr/lib/libpython2.5.so.1.0(PyEval_EvalFrameEx+0x4067) [0xb0076907]<br>/usr/lib/libpython2.5.so.1.0(PyEval_EvalCodeEx+0x748) [0xb007a368]<br>
/usr/lib/libpython2.5.so.1.0(PyEval_EvalFrameEx+0x601c) [0xb00788bc]<br>/usr/lib/libpython2.5.so.1.0(PyEval_EvalCodeEx+0x748) [0xb007a368]<br>/usr/lib/libpython2.5.so.1.0 [0xb001667f]<br>2008-06-09 09:34:33 [CRIT] switch_core_state_machine.c:319 switch_core_session_run() Thread has crashed for channel sofia/internal/---- deleted stuff -----<br>
<br>It seems like mod_python is not quite ready for production yet :-) I have a few core dumps available on demand, cca 2MB each.<br><br>Turning crash protection on didn't help. FreeSwitch would reject new calls, and wouldn't shutdown completely. I had to kill it.<br>
<br>I would still like to replace our existing system with FreeSwitch because I find way more comfortable to work with. It has great potential and I'm sure it is being succesully deployed in many places as I write this.<br>
<br>The python crash is probably a simple bug. The invisible bottleneck is what troubles me more. Any help would be greatly appreciated.<br><br>Finally, this is all with FreeSwitch Version 1.0.pre4 (8760).<br>-- <br>kresho
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