[Zope] - pcgi and multi concurrent access

[Jim Fulton]

Service Informatique CHSR wrote:
> 
> Hello,
> 
> as far as i understand, only one process is created with pcgi.

Actually, one application process is started.  In addition,
a thin pcgi wrapper process is started for each request.
 
> What if 2 clients send 2 queries simultaneously?

Each client gets a separate (thin) PCGI wrapper process that
collects input from the browser, forwards the input to 
the long running application, gets all of the output from the
long-running application, and then sends it back to the browser.

> Does one client wait until the other complete the request?

No.  Requests can be processed simultanteously by the wrappers.
Currently, the long-running application can process only one request 
at a time, so wrappers may have to queue up to get access to 
the application.  Keep in mind, however, that most of the clock
time for most requests is spent doing socket I/O with the client, 
and this I/O is done concurrently.
 
In the future, the application itself will be able to 
handle multiple requests simultaneously.  This will be
especially emportant if there are requests that consume alot
of application time, like indexing large databases.

Jim

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