On Mon, Mar 4, 2019 at 10:18 AM Khushboo Vashi < khushboo.va...@enterprisedb.com> wrote:
> > > On Mon, Mar 4, 2019 at 3:43 PM Dave Page <dp...@pgadmin.org> wrote: > >> Hi >> >> On Mon, Mar 4, 2019 at 5:43 AM Khushboo Vashi < >> khushboo.va...@enterprisedb.com> wrote: >> >>> >>> >>> On Fri, Mar 1, 2019 at 10:01 PM Dave Page <dp...@pgadmin.org> wrote: >>> >>>> In investigating #3656 I found the initial problem to be that when >>>> running in a container, Gunicorn will kill the worker process if a thread >>>> doesn't respond for 30 seconds by default. I fixed that by making the >>>> timeout match the application session timeout, but it revealed another >>>> issue. >>>> >>>> Given the function below (from the ticket), if you open the query tool >>>> and run: >>>> >>>> SELECT 1; SELECT fails_after(30); >>>> >>>> the async query actually blocks for 30 seconds in the cur.execute() >>>> call in execute_async() in connection.py (line 968). This causes the entire >>>> app to hang (watch the dashboard requests pile up in pending state in the >>>> network tab of the browser dev tools). >>>> >>>> If you run just the second SELECT, it works as expected, as does >>>> running something like: >>>> >>>> SELECT 1; SELECT pg_sleep(30); >>>> >>>> Anyone have any idea what's going on? >>>> >>> >>> Connection.poll() blocking the call here. ( connection.py - _wait_timeout >>> function line #1378 state = conn.poll() ) >>> In the asynchronous connection, after executing the query, the >>> conn.poll() is being called to fetch the connection status. >>> It gives the status accordingly but in this case, it is blocking and not >>> giving the status. >>> >> >> If I put a breakpoint on the _wait_timeout call (line 969 in >> execute_async), it hits it *after* the 30 seconds has passed (during which >> time all other queries for cancel or dashboards and status etc don't get >> processed). >> >> Put the breakpoint in the _wait_timeout function itself. The line no > 1378 (state = conn.poll()) is blocking the execution 30 seconds. > >> If I walk down the call stack, it returns from the _cursor.execute call >> in cursor.py and then hangs right before it goes into _wait_timeout. >> > Hmm, yeah - my debugger is doing some weird off-by-one thing. If I put the break point on the while 1, it blocks there! If I put it on the poll() call, then it does do as you describe. So, any idea why it's blocking, before I spend more time digging in? Thanks! -- Dave Page Blog: http://pgsnake.blogspot.com Twitter: @pgsnake EnterpriseDB UK: http://www.enterprisedb.com The Enterprise PostgreSQL Company
