relationship of backend_start, query_start, state_change
Hello,
I'm looking at my pg_stat_activity and trying to figure out what is causing
some of these processes. I'm using this query:
SELECT pid, wait_event, state_change, backend_start, xact_start,
query_start, state_change - query_start, query from pg_stat_activity where
datname= 'my_database' and state in ('idle', 'idle in transaction', 'idle
in transaction (aborted)', 'disabled');
and what I see is the same PID which have been around for a while in the
same query (COMMIT), but the query_start and state_change are updated and
close to each other:
pid | wait_event | state_change | backend_start
| xact_start | query_start |?column? |
query
---++---+---++---+-+
32506 | ClientRead | 2020-04-23 09:29:05.6793-07 | 2020-04-23
01:00:19.612478-07 || 2020-04-23 09:29:05.679275-07 |
00:00:00.25 | COMMIT
32506 | ClientRead | 2020-04-23 09:30:33.247119-07 | 2020-04-23
01:00:19.612478-07 | | 2020-04-23
09:30:33.247109-07 | 00:00:00.1 | COMMIT
32506 | ClientRead | 2020-04-23 09:31:31.506914-07 | 2020-04-23
01:00:19.612478-07 | | 2020-04-23
09:31:31.506905-07 | 00:00:00.09 | COMMIT
32506 | ClientRead | 2020-04-23 09:32:32.06656-07 | 2020-04-23
01:00:19.612478-07 || 2020-04-23 09:32:32.066552-07 |
00:00:00.08 | COMMIT
32506 | ClientRead | 2020-04-23 09:36:51.579939-07 | 2020-04-23
01:00:19.612478-07 || 2020-04-23 09:36:51.579931-07 |
00:00:00.08 | COMMIT
So can we close this thread because it's been around since 1 AM and the
last query is always "COMMIT"? Or should we keep it open because the
query_start keeps updating, and the state_change is basically keeping up
with query_start?
-
Si Chen
Open Source Strategies, Inc.
Our Mission: https://www.youtube.com/watch?v=Uc7lmvnuJHY
Re: Ned to understand why all the idle connections
Hello David & David, I have a similar problem -- a lot of idle transactions. I'm using the PostgreSQL JDBC driver. The connections look like this: pid | wait_event | state_change | backend_start | xact_start | query_start | ?column? | query ---++---+---++---+-+ 32506 | ClientRead | 2020-04-23 09:29:05.6793-07 | 2020-04-23 01:00:19.612478-07 || 2020-04-23 09:29:05.679275-07 | 00:00:00.25 | COMMIT 32506 | ClientRead | 2020-04-23 09:30:33.247119-07 | 2020-04-23 01:00:19.612478-07 | | 2020-04-23 09:30:33.247109-07 | 00:00:00.1 | COMMIT 32506 | ClientRead | 2020-04-23 09:31:31.506914-07 | 2020-04-23 01:00:19.612478-07 | | 2020-04-23 09:31:31.506905-07 | 00:00:00.09 | COMMIT 32506 | ClientRead | 2020-04-23 09:32:32.06656-07 | 2020-04-23 01:00:19.612478-07 || 2020-04-23 09:32:32.066552-07 | 00:00:00.08 | COMMIT 32506 | ClientRead | 2020-04-23 09:36:51.579939-07 | 2020-04-23 01:00:19.612478-07 || 2020-04-23 09:36:51.579931-07 | 00:00:00.08 | COMMIT It seems like they haven't been doing anything for a long time, but the state_change keeps getting updated. Is it possible that state_change is being updated, maybe by the JDBC driver? Do you recommend using PgBouncer with JDBC? - Si Chen Open Source Strategies, Inc. Our Mission: https://www.youtube.com/watch?v=Uc7lmvnuJHY On Thu, Apr 23, 2020 at 11:41 AM David G. Johnston < david.g.johns...@gmail.com> wrote: > On Thursday, April 23, 2020, David Gauthier > wrote: > >> Hi: >> >> psql (9.6.7, server 11.3) on linux >> >> I have what appear to be a log of idle connections to my DB. Query of >> pg_stat_activity indicates well over half (127/206) are like this... >> >> >> dvdb=# select state_change,wait_event_type,wait_event,state,backend_type >> from pg_stat_activity where query = ''; >> state_change | wait_event_type | wait_event | >> state | backend_type >> >> ---+-+-+---+-- >> 2020-04-23 12:57:58.215854-04 | Client | ClientRead | >> idle | client backend >> >> What does this indicate? >> >> The vast majority of the connections are through perl/dbi. If a >> connection is made, and is currently not doing anything, does it appear in >> pg_stat_activity as "idle" ? If, in DBI, $dbh->disconnect is used whenever >> the DB is no longer needed, will it disconnect from the DB and NOT appear >> as an idle in pg_stat_activity ? >> >> If there are any other column s in pg_stat-activity you'd like to see, or >> any other query in any of the system tables, please advise. >> > > If the server has an active, authenticated, connection/process running it > shows up here. Yes, idle is the state used to denote the the session is > “not doing anything”... > > $dbh->disconnect typically will indeed close the connection. There can be > exceptions if your architecture uses connection pooling. > > David J. > >
Re: Ned to understand why all the idle connections
Thanks for answering my questions. Sorry I didn't mean to "top post" I thought that my other email got lost because I had sent it to lists.postgresql.org - Si Chen Open Source Strategies, Inc. Our Mission: https://www.youtube.com/watch?v=Uc7lmvnuJHY On Thu, Apr 23, 2020 at 2:31 PM David G. Johnston < david.g.johns...@gmail.com> wrote: > Please don't top-post; and this is a fairly rude hijack posting given that > you already have a thread going, from today no less, where you've basically > asked this very same question. > > On Thu, Apr 23, 2020 at 2:18 PM Si Chen > wrote: > >> Hello David & David, >> >> I have a similar problem -- a lot of idle transactions. I'm using the >> PostgreSQL JDBC driver. The connections look like this: >> >> pid | wait_event | state_change | >> backend_start | xact_start | query_start | >> ?column? | query >> >> >> ---++---+---++---+-+ >> >> 32506 | ClientRead | 2020-04-23 09:29:05.6793-07 | 2020-04-23 >> 01:00:19.612478-07 || 2020-04-23 09:29:05.679275-07 | >> 00:00:00.25 | COMMIT >> >> 32506 | ClientRead | 2020-04-23 09:30:33.247119-07 | 2020-04-23 >> 01:00:19.612478-07 | | 2020-04-23 >> 09:30:33.247109-07 | 00:00:00.1 | COMMIT >> >> 32506 | ClientRead | 2020-04-23 09:31:31.506914-07 | 2020-04-23 >> 01:00:19.612478-07 | | 2020-04-23 >> 09:31:31.506905-07 | 00:00:00.09 | COMMIT >> >> 32506 | ClientRead | 2020-04-23 09:32:32.06656-07 | 2020-04-23 >> 01:00:19.612478-07 || 2020-04-23 09:32:32.066552-07 | >> 00:00:00.08 | COMMIT >> >> 32506 | ClientRead | 2020-04-23 09:36:51.579939-07 | 2020-04-23 >> 01:00:19.612478-07 || 2020-04-23 09:36:51.579931-07 | >> 00:00:00.08 | COMMIT >> >> It seems like they haven't been doing anything for a long time, but the >> state_change keeps getting updated. >> > > If the state_change timestamp keeps changing then by definition they are > doing something.. > > >> Is it possible that state_change is being updated, maybe by the JDBC >> driver? >> > > Directly, no, that particular field is read-only by the user and so > nothing is going to directly update it. However, as soon as the session > changes state it will change as well. > > The most likely answer is that your setup for JDBC includes a connection > pool that is periodically checking to see if its session is still active. > You should work on trying to prove or disprove that assumption. > > Do you recommend using PgBouncer with JDBC? >> > > I try to avoid making recommendations without knowing the situation in > which something is operating. Given the level of expertise demonstrated > here I would, however, advise against adding another architectural > component to your setup until your understand completely what you are > already working with. If at that point you can define a problem that you > want to solve, and pgBouncer would constitute a solution, then you could > consider adding it. > > David J. > >
