On Aug 24, 10:36 am, pierreth <[email protected]> wrote: > On 24 août, 01:20, mdipierro <[email protected]> wrote: > > > In Java a serverlet, as far as I understand, is a class which conforms > > to some API that allows it to serve one http request. Each instance is > > executed in its own thread. > > Yes, but one instance can be executed by multiple threads at the same > time. It is one thread per request. EJB, Enterprise Java Beans, are > running on their own threads.
it is the same in web2py > >The Python equivalent of the serverlet API > > is a WSGI application and web2py is based on WSGI, therefore the > > parallelization mechanism is equivalent to Java serverlets. > > Is web2py running as a WSGI application when we do "python web2py.py" > or is it only when used in a specific deployment with WSGI? when you do "python web2py.py" you do not start the wsgi app. You start the rocket web server which makes a number of threads. When a new http request arrives it is assigned to a free thread (or a new thread is created) and the wsgi is run in that thread to server that request and only that request. > > In web2py (the same in Django, Pylons, any any WSGI app) each http > > request is executed in its own thread. Threads are recycled to server > > non-concurrent requests and reuse database connections (pooling) > > without need to close and reopen them. The web server can be > > configured for a min number and a max number of threads. > > So, as a web2py developer, what do I have to do to avoid > synchronization problems in my application. Where is the danger of > having multiple threads for the web2py developers? What are the > instances shared my multiple threads? What are the instances living in > their own threads? You do have to do anything because every concurrency issue is taken care automatically. There are some DO NOTs: - do not ever call os.chdir - do not import third party modules that are not thread safe - do not use thread.start_new_thread and threading.Thread.start() - if you open a file that is not uniquely associate to this http/ request/client/session lock the file. > > I think the GIL in this context is a false problem. In fact in > > production you can use Apache and run as many processes as the number > > of cores that you have. Each process will create as many threads as it > > needs to server multiple requests. The GIL is a problems only if one > > process runs multiple threads on multiple cores. It is possible there > > are some caveats with many cores but I have not really played with > > apache configurations and benchmarks. > > Yes but a web2py server is running with only one process and using > more web2py processes for serving the same web2py app will lead to > synchronization problems. With processors having more and more cores, > having a web server that cannot use them is not very fun. In production you should not use the rocket web server. Use Apache and preform more than one process. > It is an > issue to be solved with Python 3.2 I think. We are not moving to 3.2. Not at least until Google App Engine moves to 3.x and all database drivers are supported. Than we'll open this discussion. > > Massimo > > Thank you for this precious information.
