On 6/25/07, Christian Simms <christian.simms@gmail.com> wrote:
I think your biggest hurdle is that you need to get used to using Deferred's in adbapi and any functions/methods that call adbapi indirectly. Unless you use a fast embedded database like Sqlite, you have to use Deferred's because there's network traffic under the covers to the database server. I'll try to include a little advice below for each item:
Yep this is precisely what I am attempting to do - get used to using deferreds (properly).
I think you have a race condition because (I assume) self.p.lineReceived indirectly did a database insert, and then the self.check did a database select. If that's true, you should make your test use Deferred's like this:
No - I'm just doing a series of runQuerys() when the server starts, the callbacks of which populate dictionaries with objects. The test sends a string identifier to the server which checks whether or not it exists in one of these dictionaries. When the test runs, the dict is empty. However, the load method IS running, just (seemingly) after the test is run. I guess I'm not sure how to code a test for this, as in, "after the database connection has been made and the data loaded, THEN start running tests."
d = defer.succeed(None) d.addCallback(lambda out: self.p.lineReceived('{%s:"PG"}\0' % sserverson.base10toN(104)) d.addCallback(lambda out: self.check("test\0")) return d
You could also write this code using the new defer.inlineCallbacks (needs python 2.5) or the older defer.deferredGenerator, but you might as well get used to using callbacks/errbacks and Deferred's.
Hrm yes, I'm using Debian stock 2.4, but wouldn't be opposed to hand installing a few things (like twisted). I've done it many times. A quick check of deferredGenerator and inlineCallbacks...these look _exactly_ like what I'm asking for. I might just stick with 2.4 and deferredGenerator.
You're right that you need a new paradigm, like this:
def cb(data): # use the data here, in the callback function return getSomethingFromDB().addCallback(cb)
This assumes getSomethingFromDB() returns a Deferred which fires with the result you wanted.
Yep, that's basically exactly what I'm doing now.
You really need to run your twisted app with twistd. That's the abstraction for launching twisted programs -- i.e., you define a variable named "application" in your .tac file and then use twistd to start your app. Of course, there's nothing stopping you from using daemontools on top of it.
Yep, that's exactly what I had considered doing. It doesn't appear to difficult to convert to using twistd run out of daemontools. Thanks! Brendon