IPlanet 4.0 SP9 & SingleThreadModel

Question

Hi:
We are developping a web server using iPlanet 4.0 SP9
and servlets. The server will server several users at
same time, for this reason, we are using the interface
SingleThreadModel, in order to avoid problems related to
the use of threads and multiple users.
But, this seems not to work properly. When two users are connected to our server, the second one must wait for
the first one. In other words, if the first user executes
an option that take a lot of time to be completed and
meantime the second user tries to use the web server, he
will wait until the first user's task was finished. The
web server looks like to be locked.
We are thinking about the iPlanet is misconfigured.
Any idea, remark, tip, etc.?
Thanks in advance.
Alberto

Answer 1

My advice - don't use SingleThreadModel. They shouldn't have provided this in the first place and here's why
3.2 Number of Instances
In the case of a servlet that implements the SingleThreadModel interface, the servlet container
may instantiate multiple instances of that servlet so that it can handle a heavy request load while
still serializing requests to a single instance.
3.2.1 Note about SingleThreadModel
The use of the SingleThreadModel interface guarantees that one thread at a time will execute
through a given servlet instance�s service method. It is important to note that this guarantee only
applies to servlet instance. Objects that can be accessible to more than one servlet instance at a
time, such as instances of HttpSession, may be available to multiple servlets, including those
that implement SingleThreadModel, at any particular time.
Here's a simple example: if you use a text file for storing/retrieving data and the server decides to instantiate another instance of your single threaded servlet - guess what's gonna happen?
Always use the normal multi-threaded servlets and develop them properly for multiple thread use.