I am using the Django ORM to build and manipulate models from outside
of a web context and within a long running daemonized application. I'm
using the django ORM talking to a postgresql db for this processing
since the results of this external processing are then used by a
Django based web reporting application and it was exceptionally
convenient to have a library that acted on these objects in a
consistent way regardless of whether it was called from the daemon vs
from a web request.
I've been seeing more and more database errors occurring within the
external processor. For example, I get a lot of these:
InternalError: current transaction is aborted, commands ignored
until end of transaction block
I get a few of these:
InternalError: SET TRANSACTION ISOLATION LEVEL must be called before
any query
The postgresql logs are not very descriptive as to what the root
problem is:
2009-08-04 14:04:08 EDT STATEMENT: BEGIN; SET TRANSACTION ISOLATION
LEVEL READ COMMITTED
2009-08-04 14:04:14 EDT ERROR: current transaction is aborted,
commands ignored until end of transaction block
The research I've seen so far leads me to think the problem is that
the ORM is building transactions that ordinarily would be closed at
the end of a view, but are being kept open in my case since I really
don't have a 'view' life-cycle. I've tried decorating my db-hitting
routines in the daemon code with django.db.transaction.commit_manually
along with appropriate calls to commit() and rollback() in case of
error, yet the problem persists. I've read the docs (and some of the
code) associated with transactions, yet the focus (naturally) is on
views and functions that have a typical request/response lifecycle.
I'm wondering what suggestions people would have for using the ORM in
a long running daemon (e.g. should I be closing the db connection
periodically? how would you suggest managing the transactions?).
The basic flow of my code is:
daemonize my process
while True:
listen for an external event (e.g. from the net)
process that event into model based objects
save the objects
Any help would be appreciated.
-- William
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