On Sat, 2 Mar 2002, Hancock, David (DHANCOCK) wrote:
> (Apache benchmarker) and have it make a couple thousand requests, with 10-40
> concurrent. With only a couple concurrent requests, no problems. With 10 or
> more, I get a seg fault pretty quickly.
I have no Oracle experience, but I'm going to go out on a limb and guess
that the driver you're using isn't thread-safe, or isn't being used by the
Python wrappers in a thread-safe manner.
Just off the top of my head, I'd create a per-connection wrapper object
that uses a reentrant lock (see threading.RLock) to lock access to each
connection.
(more comments follow code snippet)
> class dhPage(ExamplePage):
> import DCOracle2
> dbconn = DCOracle2.connect('scott/tiger@oralin')
>
> def writeBody(self):
> self.write('<h3>select * from emp results</h3>')
> res = dhPage.dbconn.execute('select * from emp')
> list = dhPage.dbconn.fetchall()
Yeah, I'm pretty sure you're running into a thread-safety issue here. I'm
willing to bet that the connection object is barfing all over itself when
you end up with multiple threads running queries and trying to fetch their
result sets.
Here's a really cheesy rewrite:
class SafeConnection:
import DCOracle2
import threading.RLock as RLock
def __init__ (self, init):
self._conn = DCOracle2.connect(init)
self._lock = RLock()
def lock (self):
self._lock.acquire()
def unlock (self):
self._lock.release()
def doquery (self, query):
results = []
self.lock()
try:
self._conn.execute(query)
results = self._conn.fetchall()
finally:
## this finally / unlock is very important
## to make sure that other requests don't hang
## if the query or something barfs.
## You might want to harden it a bit more by
## catching the exception and possibly closing /
## reopening the connection.
self.unlock()
return results
class dhPage(ExamplePage):
def __init__ (self):
ExamplePage.__init__(self)
self._conn = SafeConnection('scott/tiger@oralin')
def writeBody (self):
res = self._conn.doquery('select * from emp')
# ... etc.
Of course, you don't -have- to break the connection and lock out into a
separate object, but if you -do-, then you'll have an easier time putting
this into a pool later.
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