There is clearly some facility built into SQLObject for threads - there
is the connection pool, which is designed (per the code) to ensure only
(at most?) one connection is opened per thread, and a sqlhub member
called threadConnection in addition to processConnection. There is also
the _connection parameter to each SQLObject call. Perhaps someone who is
using SQLObject in a threaded context could share their connection
management wisdom.
In fact, I find that ensuring that I "create a connection and only use
it in that thread" is not sufficient to eliminate the issues I'm having
with SQLObject, MySQLdb, and MySQL. It is not clear to me which of
SQLObject or MySQLdb is to blame, but it appears that one of them
(probably MySQLdb) is doing something in a non-thread-safe manner.
For reference, here is the offending code snippet:
sqlhub.processConnection = connectionForURI(connuri)
class AAA(SQLObject):
class sqlmeta:
createSQL = {'mysql': 'ALTER TABLE aa_a ENGINE InnoDB'}
cacheValues = False
value = IntCol(alternateID=True)
def thr1():
localData = threading.local()
localData.conn = connectionForURI(connuri)
for i in range(1000):
try:
a = AAA(value=1,connection=localData.conn)
except dberrors.DuplicateEntryError:
a = AAA.byValue(1,connection=localData.conn)
AAA.dropTable(ifExists=True)
AAA.createTable()
for i in range(20):
t = threading.Thread(target=thr1,args=())
t.start()
Here, each thread has its own connection, I ensure the connection object
is a local variable (do I really need to do this?) but still the
connection gets into a bad state.
- nathan
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