Re: Connection pool issues with clsql

On Feb 3, 2010, at 7:17 AM, Ralf Mattes wrote:
> But we still have some "issues" with connection pooling. One nagging
> problem we repeatedly run into: the pool never realeases connections, so
> if you have a peek of parallel connections the pool keeps them hanging
> around.

Well, that is the point of the pool -- to keep connections open with the
assumption that they'd all be used at some point in the future. I do see
your point about if there is a significantly higher peak usage than average
usage so non-needed connections are left open.

There are several ways to add flexibility to the logic of removing connections
from the pool that one doesn't think would be needed later on. Some 
possibilities, in increasing order of implementation complexity, are:

1) Use the existing CLEAR-CONN-POOL function in your application to clear 
all connections.

2) Add a variable, such as *MAXIMUM-POOLED-CONNECTIONS* so that if a connection
is released back, but the pool has hit maximum size, then the released connection
will be closed and discarded. A value of NIL means no maximum, which is the current
behavior.

3) Add a variable, such as *MAXIMUM-LIFETIME-UNUSED-POOLED-CONNECTION* which
limits the life of a that a pooled connection will exist unused. Every time a
connection is requested or released, the library will search all pooled 
connections and close/discard any connection which has a unused time greater 
than that variable.

To the degree this issue has been "nagging" for you, the most immediate 
compensation would be to add a periodic call to CLEAR-CONN-POOL from your
application.

Kevin