Threads to Serve HTTP Request
Java web container use HTTPServlet to serve HTTP request. There are 3 ways tohandle requests:
- Create 1 thread which is used to serve all the HTTP requests. It obvious that
this approach does not scale. It can leverage OS concurrency capability and
multiple CPUs.
- Create 1 thread for every request. If there are too many concurrent requests,
too many threads will be created. With too many threads, a lot of resources
will be spent on context switches.
- Create a pool with a fixed number of threads. This approach can show a
graceful degradation under very heavy loads.
Almost non-trivial web containers use the 3rd approach. I want to make sure that
this assumption is right. So I made some experiments with Tomcat 6. The
experiments results validate the assumption. The toString method of thread to
execute HTTPServlet in Tomcat is like Thread. 8080 is port
number of Tomcat. 2 means HTTP thread ID. It is possible that 5 mains the size
of thread pool.
And it does not hold that a thread is always to serve the requests for the
session. A thread is often used to serve requests from multiple sessions.
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