About one and a half months ago, I introduced Java2Script Simple Pipe, another Comet implementation. At that time, I knew there were lots of performance issues on such Comet technology. Because at that time I were busy and it was not a urgent deal for me, I didn’t write test codes to test out the performances at that moment.
Only recently, I took some tests on performance issues. And the results said Simple Pipe’s Comet implementation performs really bad!
Opening 10 Comet connections using Simple Pipe does not affect the whole server. But when I opened 20 Comet connections, the CPU usage is up to 100% quickly! It’s not a problem of the application logics. It is a matter of Comet connection.
Java2Script Simple Pipe supports switching pipe mode into query mode. It is very easy, just call a static method:
After switching to query mode for the pipe, I can open up to 100+ connections to the server to receive stream data back to browser. The peak of CPU usage is about 60% ~ 70%. The average CPU usage may be about 20%-30%. It is an acceptable technology with such performances under the pressure tests.
( I did not test those server with special Comet optimizations. I just tested Simple Pipe on Apache Tomcat 5.5. Maybe those Comet optimized should have a better results. )