Hi all,
I’m just experimenting with WebKit and database connection pooling, and
some questions/suggestions came up which I hope can be answered here:
As far as I understand I have to use either MiscUtils/DBPool.py which
is pretty simple, or (as I noticed just now by searching the archives)
a much more complex and sophisticated DbConnectionPool.py that has been
put into the sandbox by Warren A. Smith.
I haven’t checked out DbConnectionPool yet. Which status has it?
Warren, are you still working on it? Are you/somebody else interested
in improving/testing this module and getting it into Webware, e.g.
MiscUtils? If yes, I’d like to contribute if I can.
For the time being I have only tested DBPool.py. Here are my
questions/suggestions:
* The module docstring talks about “DB API”. I think this should
be specified to “DB API 2”, since DB API version 1 has no
threadsafety attribute and thus will not work with DBPool.
* There is an irritating comment that says:
# These functions are used with DB modules
# that have connection level threadsafety, like PostgreSQL:
def _unthreadsafe_addConnection(self, con):
...
- Shouldn’t it rather say “... that *DO NOT* have connection level
threadsafety...”? (threadsafety 0 = not threadsafe,
1 = module level, 2 = connection level, 3 = cursor level)
- PostgreSQL is not a DB module, but a DBMS, so shouldn’t it say
“like PyGreSQL” or something (another PostGreSQL interface,
psycopg, has threadsafety=2)?
* Wouldn’t it be good to have minConnections and startConnections
in addition to maxConnections? This would be analogous to the
parameters in AppServer.config.
* If a database connection crashes or gets disconnected, it will
never be restarted. Wouldn’t it be good to let the getConnection
method check whether the connection is still usable and reopen
or restart it in case it is not?
* My last important question: Maybe I understand something wrong,
but if I use DBPool for WebKit servlets, i.e. with the
ThreadedAppServer, wouldn’t it be much more reasonable to
automatically bind the connections 1:1 to the servlet threads
created by the AppServer, instead of making an independent
database connection pool? So each thread would have it’s own
private database connection, servlets could never block each
other, there would be no threadsafety issues at all,
and you wouldn’t need to configure any pool size,
but there would be always just as many connections as stated
in the AppServer.config. As far as I see it, this would have
only advantages. Do I overlook anything?
Could this be implemented with Webware/WebKit out of the box?
If not, shouldn’t such a feature be added?
I’d be glad to read some answers/opinions.
-- Christoph
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