Re: Threads vs Processes

> -----Original Message-----
> From: Tom Lane [mailto:tgl@sss.pgh.pa.us]
> Sent: Friday, September 26, 2003 9:27 AM
> To: Bruce Momjian
> Cc: Shridhar Daithankar; pgsql-hackers@postgresql.org;
> pgsql-hackers-win32@postgresql.org
> Subject: Re: [HACKERS] Threads vs Processes
>
>
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > One solution is for me to continue with this in the Win32
> CVS version
> > until I have fork/exec() working on Unix, then test on
> Win32.  I think
> > that could be done in a few weeks, if not less.
>
> > Another solution, already mentioned, is to use threads and
> TLS.  This
> > is what SRA's code uses.  I know SRA wants to contribute that code
> > back to the community, so I can ask them to see if they are
> ready to
> > release it.
>
> If you are willing to expend the effort, I think it would be
> worth the time to pursue both approaches.  We don't yet have
> enough info to decide which one will be cleaner, so we need
> to push forward on both until we can make a realistic comparison.

I think the ideal situation would be a server that both threads and
forks.

Sometimes, we want the server to take on a new personality (with the
rights of the attaching user).  In such a case, threading is not a
sufficient answer.  Also, a forked process is a bit safer (though you
can put a try/catch around threads).

For performance with multiple queries from a single user, threads are
going to be faster than forking.  I think that the best model will be a
server that does both.

I know that there is some aversion to using C++, but the ACE framework
offers a consistent threading model that works for just about every
computer under the sun.
http://www.cs.wustl.edu/~schmidt/ACE.html

The license is basically BSD (it is called ACE, but it works exactly
like a BSD license).  With ACE, you program to a single API, and the
code works the same on every platform with a simple recompile.  It might
even be worthwhile to use the ACE higher level components to create a
server that supports multiple models of connection and threading.