[pgpool-general: 7226] Re: Idle connection in database

Tatsuo Ishii ishii at sraoss.co.jp
Sun Aug 30 18:09:48 JST 2020


> Hi Tatsuo,
> 
> I was thinking on that line initially that may be because of
> serialize_accept it is not working but I didn't dwell into it much and
> didn't test it.
> 
> Thanks for your input Tatsuo, you have been of immense help to find this
> problem.
> 
> Will this fix, when it is done,  be included in all 4.0 and 4.1 versions?

Not sure if there's actually a fix, but if there were a fix for this,
it will be definitely included in 4.0 and 4.1 branches.

> On Sun, Aug 30, 2020, 14:08 Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> 
>> Ok, I found that if following is set:
>>
>> serialize_accept=on
>>
>> then, connection_life_time does not work. (The alarm is not
>> fired). Don't know why but I am going to fix this.
>>
>> > Hi Tatsuo,
>> >
>> > I am using Pgpool v4.1.1.
>> >
>> > I have seen similiar behaviour in v4.0.9 as well.
>> >
>> > Thanks and Regards,
>> > Nikhil
>> >
>> > On Sun, Aug 30, 2020, 13:11 Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
>> >
>> >> Ok, I have tried with your test data and pgpool settings. Also I added
>> >> log_disconnections to postgresql.conf so that when Pgpool-II
>> >> disconnects backend.  However I was not able to reproduce your
>> >> problem. Pgpool-II worked as expected (10 seconds after the test
>> >> script ends, connection was terminated on all backends).
>> >>
>> >> What version of Pgpool-II are you using?
>> >>
>> >> > Hi Tatsuo,
>> >> >
>> >> >
>> >> > No, because my primary has node ID 0 and standby has node ID 1.
>> >> >
>> >> > Patch will help if my primary node ID is not 0 rite?
>> >> >
>> >> > Thanks and Regards,
>> >> > Nikhil
>> >> >
>> >> >
>> >> > On Sun, Aug 30, 2020, 12:19 Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
>> >> >
>> >> >> Before these tests, have applied the patch?
>> >> >>
>> >> >> > Hi Tatsuo,
>> >> >> >
>> >> >> >
>> >> >> > I have to reopen this issue because after a lot of debugging and
>> >> reading
>> >> >> > documentation on connection_life_time though there is not much of
>> it,
>> >> >> this
>> >> >> > parameter doesn't work as it should.
>> >> >> >
>> >> >> > First I want to be correct in my understanding that this parameter
>> >> >> > terminates cached backend connections in the database.So, I test a
>> >> simple
>> >> >> > scenario as follows:
>> >> >> >
>> >> >> > PGPOOL -  128.199.224.132
>> >> >> >
>> >> >> > *Parameters set for pooling*
>> >> >> > serialize_accept=on
>> >> >> > child_life_time=0
>> >> >> > child_max_connections=0
>> >> >> > client_idle_limit=0
>> >> >> > connection_life_time=10
>> >> >> >
>> >> >> > *I am running a mixed.sql file which contain below statements*
>> >> >> > BEGIN;
>> >> >> > SELECT CURRENT_TIMESTAMP;
>> >> >> > INSERT  into t1 values(3);
>> >> >> > INSERT  into t1 values(4);
>> >> >> > select pg_sleep(5);
>> >> >> > INSERT  into t1 values(5);
>> >> >> > UPDATE t1 set id=4 where id=5;
>> >> >> > END;
>> >> >> >
>> >> >> > After executing some inserts it will sleep for 5 seconds and then
>> >> execute
>> >> >> > one update and an insert before closing the connection.
>> >> >> >
>> >> >> >
>> >> >> > *1) Status of nodes*
>> >> >> > -bash-4.2$ psql -h 128.199.224.132 -p 9999 -U enterprisedb
>> >> >> > psql.bin (11.6.13)
>> >> >> > Type "help" for help.
>> >> >> >
>> >> >> > edb=# show pool_nodes;
>> >> >> >  node_id |    hostname     | port | status | lb_weight |  role   |
>> >> >> > select_cnt | load_balance_node | replication_delay |
>> >> replication_state |
>> >> >> > replication_syn
>> >> >> > c_state | last_status_change
>> >> >> >
>> >> >>
>> >>
>> ---------+-----------------+------+--------+-----------+---------+------------+-------------------+-------------------+-------------------+----------------
>> >> >> > --------+---------------------
>> >> >> >  0       | 128.199.222.92  | 5445 | up     | 0.000000  | primary |
>> 0
>> >> >> >    | false             | 0                 |                   |
>> >> >> >         | 2020-08-30 04:58:24
>> >> >> >  1       | 128.199.222.124 | 5445 | up     | 1.000000  | standby |
>> 0
>> >> >> >    | true              | 0                 |                   |
>> >> >> >         | 2020-08-30 04:58:24
>> >> >> > (2 rows)
>> >> >> >
>> >> >> > *2) Running the mixed.sql file*
>> >> >> > -bash-4.2$ psql -h 128.199.224.132 -p 9999 -U enterprisedb -f
>> >> mixed.sql
>> >> >> > BEGIN
>> >> >> >         current_timestamp
>> >> >> > ----------------------------------
>> >> >> >  30-AUG-20 10:31:47.396527 +05:30
>> >> >> > (1 row)
>> >> >> >
>> >> >> > INSERT 0 1
>> >> >> > INSERT 0 1
>> >> >> >  pg_sleep
>> >> >> > ----------
>> >> >> >
>> >> >> > (1 row)
>> >> >> >
>> >> >> > INSERT 0 1
>> >> >> > UPDATE 1
>> >> >> > COMMIT
>> >> >> > -bash-4.2$
>> >> >> >
>> >> >> > *3) pool_pools output shows pgpool (pid - 31560) created one
>> >> connection
>> >> >> to
>> >> >> > master(pid - 31550) and one to standby (pid - 28954) *
>> >> >> >
>> >> >> > edb=# show pool_pools;
>> >> >> >  pool_pid |     start_time      | pool_id | backend_id | database |
>> >> >> > username   |     create_time     | majorversion | minorversion |
>> >> >> > pool_counter | pool_
>> >> >> > backendpid | pool_connected
>> >> >> >
>> >> >>
>> >>
>> ----------+---------------------+---------+------------+----------+--------------+---------------------+--------------+--------------+--------------+------
>> >> >> > -----------+----------------
>> >> >> >  31560    | 2020-08-30 04:51:54 | 0       | 0          | edb      |
>> >> >> > enterprisedb | 2020-08-30 05:01:47 | 3            | 0            |
>> 1
>> >> >> >      | 31550
>> >> >> >            | 0
>> >> >> >  31560    | 2020-08-30 04:51:54 | 0       | 1          | edb      |
>> >> >> > enterprisedb | 2020-08-30 05:01:47 | 3            | 0            |
>> 1
>> >> >> >      | 28954
>> >> >> >            | 0
>> >> >> >
>> >> >> > *4) Status of process id 31550 on master.After the run, as seen
>> below
>> >> on
>> >> >> > the database is idle*
>> >> >> >
>> >> >> > -bash-4.2$ ps -ef |grep 224.132
>> >> >> > enterpr+ 31550  9148  0 05:01 ?        00:00:00 postgres:
>> enterprisedb
>> >> >> edb
>> >> >> > 128.199.224.132[49656] idle
>> >> >> >
>> >> >> > *5) Status of processid 31560 on pgpool.* *After the run, as seen
>> >> below
>> >> >> > pgpool has released connection as soon as transaction completes*
>> >> >> > [root at pgpool-p pgpool4.1]# ps -ef |grep 31560
>> >> >> > enterpr+ 31560 31557  0 04:51 ?        00:00:00 pgpool: wait for
>> >> accept
>> >> >> lock
>> >> >> >
>> >> >> >
>> >> >> > *6) After 10 seconds, this cached connection on database should
>> have
>> >> been
>> >> >> > terminated as per my understanding of connection_life_time
>> parameter
>> >> but
>> >> >> as
>> >> >> > seen below it has not terminated*
>> >> >> > edb=# select * from pg_stat_activity where client_addr
>> >> >> ='128.199.224.132';
>> >> >> > -[ RECORD 1 ]----+---------------------------------
>> >> >> > datid            | 67127
>> >> >> > datname          | edb
>> >> >> > pid              | 31550
>> >> >> > usesysid         | 10
>> >> >> > usename          | enterprisedb
>> >> >> > application_name | psql.bin
>> >> >> > client_addr      | 128.199.224.132
>> >> >> > client_hostname  |
>> >> >> > client_port      | 49656
>> >> >> > backend_start    | 30-AUG-20 10:31:47.380345 +05:30
>> >> >> > xact_start       |
>> >> >> > query_start      | 30-AUG-20 10:31:52.411607 +05:30
>> >> >> > state_change     | 30-AUG-20 10:31:52.411714 +05:30
>> >> >> > wait_event_type  | Client
>> >> >> > wait_event       | ClientRead
>> >> >> > state            | idle
>> >> >> > backend_xid      |
>> >> >> > backend_xmin     |
>> >> >> > query            |  DISCARD ALL
>> >> >> > backend_type     | client backend
>> >> >> >
>> >> >> > Do not mind the timestamp, it is in IST for the above query.
>> >> >> >
>> >> >> > *7) From the pgpool logs, it sets the alarm after 10 sec but
>> doesn't
>> >> >> really
>> >> >> > close the connection after 10 seconds*
>> >> >> > Aug 30 05:01:52 Pgpool-p pgpool[*31560*]: [252-2] 2020-08-30
>> 05:01:52:
>> >> >> pid
>> >> >> > 31560: DETAIL:  setting alarm after 10 seconds
>> >> >> >
>> >> >> > Attaching pgpool logs as well.
>> >> >> >
>> >> >> >
>> >> >> > On Wed, Aug 12, 2020 at 9:02 PM Nikhil Shetty <
>> nikhil.dba04 at gmail.com
>> >> >
>> >> >> > wrote:
>> >> >> >
>> >> >> >> Hi Tatsuo,
>> >> >> >>
>> >> >> >> Thank you, I will check how this works.
>> >> >> >>
>> >> >> >>
>> >> >> >> On Tue, Aug 11, 2020 at 5:52 PM Tatsuo Ishii <ishii at sraoss.co.jp>
>> >> >> wrote:
>> >> >> >>
>> >> >> >>> Hi Nikhil,
>> >> >> >>>
>> >> >> >>> > Hi Tatsuo,
>> >> >> >>> >
>> >> >> >>> > We are checking the patch internally before we go ahead and
>> >> deploy in
>> >> >> >>> > production.
>> >> >> >>>
>> >> >> >>> Ok.
>> >> >> >>>
>> >> >> >>> > If I want to set only one of either connection_life_time or
>> >> >> >>> > client_idle_limit. What do you recommend? Should I set
>> >> >> >>> > client_idle_limit=120 and  connection_life_time=0, do you
>> foresee
>> >> any
>> >> >> >>> > effects of these settings for connection pooling?
>> >> >> >>>
>> >> >> >>> In general connection_life_time is better because:
>> >> >> >>>
>> >> >> >>> 1. when client_idle_limit expires, pgpool needs to fork a new
>> >> process,
>> >> >> >>>    but connection_life_time does not.
>> >> >> >>>
>> >> >> >>> 2. when client_idle_limit expires, it looses mutiple connection
>> >> pools
>> >> >> >>>    (this only applicatable fro max_pool > 1 case) because the
>> >> >> >>>    connection pools the process hold go away.
>> >> >> >>>
>> >> >> >>> However if you have very short and frequent sessions, more alarm
>> >> >> >>> system calls with connection_life_time are required and maybe
>> >> >> >>> client_idle_limit wins in this case.
>> >> >> >>>
>> >> >> >>> > Thank you for your time and support.
>> >> >> >>> >
>> >> >> >>> > Thanks and Regards,
>> >> >> >>> > Nikhil
>> >> >> >>> >
>> >> >> >>> > On Mon, Aug 10, 2020 at 11:58 AM Tatsuo Ishii <
>> ishii at sraoss.co.jp
>> >> >
>> >> >> >>> wrote:
>> >> >> >>> >
>> >> >> >>> >> Hi Nikhil,
>> >> >> >>> >>
>> >> >> >>> >> I have been investigating if there's any case when
>> >> >> >>> >> connection_life_time is not working. Actually it *is*. If
>> primary
>> >> >> node
>> >> >> >>> >> is not node 0, connection_life_time does not work. Attached is
>> >> the
>> >> >> >>> >> patch to fix that.  Please try, if you like.
>> >> >> >>> >>
>> >> >> >>> >> > According to your previous message, corresponding pgpool
>> >> process
>> >> >> was
>> >> >> >>> >> > not there, but PostgreSQL backend process were still
>> running. I
>> >> >> >>> >> > suspect the backend process was waiting for TCP/IP
>> connection
>> >> was
>> >> >> >>> >> > terminated. But to know what was actually happening, I was
>> >> waiting
>> >> >> >>> for
>> >> >> >>> >> > your response.
>> >> >> >>> >> >
>> >> >> >>> >> >>> "DISCARD ALL" and state idle. I will have to test again to
>> >> check
>> >> >> >>> the
>> >> >> >>> >> socket
>> >> >> >>> >> >>> status of pid.I will get back on this
>> >> >> >>> >> >
>> >> >> >>> >> > What was that?
>> >> >> >>> >> >
>> >> >> >>> >> >> Hi Tatsuo,
>> >> >> >>> >> >>
>> >> >> >>> >> >>
>> >> >> >>> >> >> Ant reason why connection_idle_limit doesn't remove backend
>> >> >> >>> connection
>> >> >> >>> >> >> after time limit is crossed
>> >> >> >>> >> >>
>> >> >> >>> >> >> Thanks and Regards,
>> >> >> >>> >> >> Nikhil
>> >> >> >>> >> >>
>> >> >> >>> >> >> On Sun, Aug 2, 2020, 12:48 Nikhil Shetty <
>> >> nikhil.dba04 at gmail.com
>> >> >> >
>> >> >> >>> >> wrote:
>> >> >> >>> >> >>
>> >> >> >>> >> >>> Hi Tatsuo,
>> >> >> >>> >> >>>
>> >> >> >>> >> >>> I want to correct my statement from previous email:
>> >> >> >>> >> >>>
>> >> >> >>> >> >>> From ps status *I could not see *that the process (18190
>> and
>> >> >> 18193)
>> >> >> >>> >> were
>> >> >> >>> >> >>> still present on pgpool but the backend process was still
>> >> >> present
>> >> >> >>> with
>> >> >> >>> >> >>> "DISCARD ALL" and state idle. I will have to test again to
>> >> check
>> >> >> >>> the
>> >> >> >>> >> socket
>> >> >> >>> >> >>> status of pid.I will get back on this
>> >> >> >>> >> >>>
>> >> >> >>> >> >>> On Sun, Aug 2, 2020 at 12:15 PM Nikhil Shetty <
>> >> >> >>> nikhil.dba04 at gmail.com>
>> >> >> >>> >> >>> wrote:
>> >> >> >>> >> >>>
>> >> >> >>> >> >>>> Hi Tatsuo,
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> >> Assuming you executed "show pool_pools" long after
>> >> >> 2020-08-01
>> >> >> >>> >> >>>> >> 06:21:26, that is very strange because
>> >> connection_life_time
>> >> >> >>> should
>> >> >> >>> >> >>>> >> have been already expired. I wonder if pgpool tried to
>> >> >> >>> disconnect
>> >> >> >>> >> the
>> >> >> >>> >> >>>> >> connection but failed. To check what actually happend,
>> >> can
>> >> >> you
>> >> >> >>> >> check
>> >> >> >>> >> >>>> >> ps status of pgpool process 18190 and 18193?
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> >> Also it would be nice you can examine the socket
>> status
>> >> of
>> >> >> >>> >> PostgreSQL
>> >> >> >>> >> >>>> >> backend 29321 and 29619, and pgpool socket status of
>> >> process
>> >> >> >>> 18190
>> >> >> >>> >> and
>> >> >> >>> >> >>>> >> 18193?
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> From ps status I could see that the process (18190 and
>> >> 18193)
>> >> >> were
>> >> >> >>> >> still
>> >> >> >>> >> >>>> present on pgpool. I will have to test again to check the
>> >> >> socket
>> >> >> >>> >> status of
>> >> >> >>> >> >>>> pid.I will get back on this
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> Meanwhile, I did some testing of my own for these two
>> >> >> parameters(
>> >> >> >>> >> >>>> client_idle_limit and connection_life_time ) and their
>> >> >> behaviour:
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *Test:*
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> Database IP:128.199.222.92(master)
>> >> >> >>> >> >>>> Pgpool IP: 128.199.224.132
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *Scenario1:*
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> max_pool=1
>> >> >> >>> >> >>>> num_init_children=100
>> >> >> >>> >> >>>> serialize_accept=on
>> >> >> >>> >> >>>> child_max_connections=0
>> >> >> >>> >> >>>> child_life_time=0
>> >> >> >>> >> >>>> connection_life_time=60
>> >> >> >>> >> >>>> client_idle_limit=0
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *1. Connected to Pgpool and ran a query with \watch 1:*
>> >> >> >>> >> >>>> select count(*) from pgbench_accounts ;
>> >> >> >>> >> >>>> \watch 1
>> >> >> >>> >> >>>> Sat 01 Aug 2020 07:25:54 AM UTC (every 1s)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>   count
>> >> >> >>> >> >>>> ---------
>> >> >> >>> >> >>>>  6000000
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *2. Checking session in database, one session is active
>> from
>> >> >> >>> pgpool*
>> >> >> >>> >> >>>>                             Sat 01 Aug 2020 07:26:14 AM
>> UTC
>> >> >> >>> (every 1s)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>  pid  |                  query                  |
>>  usename
>> >> >> |
>> >> >> >>> >> >>>> client_addr   | count | state
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >>
>> >> >> >>>
>> >> >>
>> >>
>> ------+-----------------------------------------+--------------+-----------------+-------+--------
>> >> >> >>> >> >>>>  3420 | select count(*) from pgbench_accounts ; |
>> >> enterprisedb
>> >> >> |
>> >> >> >>> >> >>>> 128.199.224.132 |     1 | active
>> >> >> >>> >> >>>> (1 row)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *3. Stopped the query after sometime using Ctrl-C but
>> >> session
>> >> >> is
>> >> >> >>> still
>> >> >> >>> >> >>>> open*
>> >> >> >>> >> >>>> Sat 01 Aug 2020 07:27:35 AM UTC (every 1s)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>   count
>> >> >> >>> >> >>>> ---------
>> >> >> >>> >> >>>>  6000000
>> >> >> >>> >> >>>> (1 row)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> ^Cedb=#
>> >> >> >>> >> >>>> edb=#
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *4. Checking session in database, state is now idle*
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>                            Sat 01 Aug 2020 07:28:14 AM
>> UTC
>> >> >> (every
>> >> >> >>> 1s)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>  pid  |                  query                  |
>>  usename
>> >> >> |
>> >> >> >>> >> >>>> client_addr   | count | state
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >>
>> >> >> >>>
>> >> >>
>> >>
>> ------+-----------------------------------------+--------------+-----------------+-------+-------
>> >> >> >>> >> >>>>  3420 | select count(*) from pgbench_accounts ; |
>> >> enterprisedb
>> >> >> |
>> >> >> >>> >> >>>> 128.199.224.132 |     1 | idle
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *5. Checking session in database after 2 minutes, I can
>> >> still
>> >> >> see
>> >> >> >>> the
>> >> >> >>> >> >>>> database session idle*
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>                            Sat 01 Aug 2020 07:30:02 AM
>> UTC
>> >> >> (every
>> >> >> >>> 1s)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>  pid  |                  query                  |
>>  usename
>> >> >> |
>> >> >> >>> >> >>>> client_addr   | count | state
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >>
>> >> >> >>>
>> >> >>
>> >>
>> ------+-----------------------------------------+--------------+-----------------+-------+-------
>> >> >> >>> >> >>>>  3420 | select count(*) from pgbench_accounts ; |
>> >> enterprisedb
>> >> >> |
>> >> >> >>> >> >>>> 128.199.224.132 |     1 | idle
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *6. Checking connection on pgpool server. connection is
>> >> still
>> >> >> open
>> >> >> >>> >> from
>> >> >> >>> >> >>>> pgpool to database*
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> ps -ef|grep edb
>> >> >> >>> >> >>>> enterpr+ 24170 24162  0 06:51 ?        00:00:00 pgpool:
>> >> >> >>> enterprisedb
>> >> >> >>> >> edb
>> >> >> >>> >> >>>> 128.199.222.92(34402) idle
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *7. After being idle for more than 60 seconds,
>> connections
>> >> are
>> >> >> >>> still
>> >> >> >>> >> open
>> >> >> >>> >> >>>> from pgpool and on database.Connection is removed from
>> >> pgpool
>> >> >> >>> server
>> >> >> >>> >> after
>> >> >> >>> >> >>>> I quit from the psql terminal but still present in the
>> >> >> database as
>> >> >> >>> >> show
>> >> >> >>> >> >>>> below:*
>> >> >> >>> >> >>>>               Sat 01 Aug 2020 07:34:26 AM UTC (every 1s)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>  pid  |    query     |   usename    |   client_addr   |
>> >> count |
>> >> >> >>> state
>> >> >> >>> >> >>>>
>> >> >> >>>
>> >> ------+--------------+--------------+-----------------+-------+-------
>> >> >> >>> >> >>>>  3420 |  DISCARD ALL | enterprisedb | 128.199.224.132 |
>> >>  1 |
>> >> >> >>> idle
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *Scenario2:*
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> max_pool=1
>> >> >> >>> >> >>>> num_init_children=100
>> >> >> >>> >> >>>> serialize_accept=on
>> >> >> >>> >> >>>> child_max_connections=0
>> >> >> >>> >> >>>> child_life_time=0
>> >> >> >>> >> >>>> connection_life_time=0
>> >> >> >>> >> >>>> client_idle_limit=60
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *1. Connected to Pgpool and ran a query with \watch 1:*
>> >> >> >>> >> >>>> edb=# \! date
>> >> >> >>> >> >>>> Sat Aug  1 07:38:45 UTC 2020
>> >> >> >>> >> >>>> select count(*) from pgbench_accounts ;
>> >> >> >>> >> >>>> \watch 1
>> >> >> >>> >> >>>> edb=# select count(*) from pgbench_accounts ;
>> >> >> >>> >> >>>>   count
>> >> >> >>> >> >>>> ---------
>> >> >> >>> >> >>>>  6000000
>> >> >> >>> >> >>>> (1 row)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *2. Checking session in database, one session is active
>> from
>> >> >> >>> pgpool*
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>                             Sat 01 Aug 2020 07:39:55 AM
>> UTC
>> >> >> >>> (every 1s)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>   pid  |                  query                  |
>>  usename
>> >> >>   |
>> >> >> >>> >> >>>> client_addr   | count | state
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >>
>> >> >> >>>
>> >> >>
>> >>
>> -------+-----------------------------------------+--------------+-----------------+-------+--------
>> >> >> >>> >> >>>>  13427 | select count(*) from pgbench_accounts ; |
>> >> >> enterprisedb |
>> >> >> >>> >> >>>> 128.199.224.132 |     1 | active
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *3. Stopped the query after sometime using Ctrl-C but
>> >> session
>> >> >> is
>> >> >> >>> still
>> >> >> >>> >> >>>> open*
>> >> >> >>> >> >>>> Sat 01 Aug 2020 07:41:39 AM UTC (every 1s)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>   count
>> >> >> >>> >> >>>> ---------
>> >> >> >>> >> >>>>  6000000
>> >> >> >>> >> >>>> ^Cedb=#
>> >> >> >>> >> >>>> edb=#
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *4. Checking session in database, state is now idle*
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>                             Sat 01 Aug 2020 07:42:12 AM
>> UTC
>> >> >> >>> (every 1s)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>   pid  |                  query                  |
>>  usename
>> >> >>   |
>> >> >> >>> >> >>>> client_addr   | count | state
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >>
>> >> >> >>>
>> >> >>
>> >>
>> -------+-----------------------------------------+--------------+-----------------+-------+-------
>> >> >> >>> >> >>>>  13427 | select count(*) from pgbench_accounts ; |
>> >> >> enterprisedb |
>> >> >> >>> >> >>>> 128.199.224.132 |     1 | idle
>> >> >> >>> >> >>>> (1 row)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *5. Checking session in database after 2 minutes, there
>> is
>> >> no
>> >> >> >>> session
>> >> >> >>> >> in
>> >> >> >>> >> >>>> the database.*
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>   Sat 01 Aug 2020 07:42:42 AM UTC (every 1s)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>  pid | query | usename | client_addr | count | state
>> >> >> >>> >> >>>> -----+-------+---------+-------------+-------+-------
>> >> >> >>> >> >>>> (0 rows)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *6. Checking connection on pgpool server. No connection
>> >> open in
>> >> >> >>> >> pgpool to
>> >> >> >>> >> >>>> database*
>> >> >> >>> >> >>>> ps -ef|grep edb
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> *Observations:*
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> With client_idle_limit of 60 seconds, all connections are
>> >> >> closed
>> >> >> >>> after
>> >> >> >>> >> >>>> being idle for more than 1 minute. I can see psql
>> session in
>> >> >> >>> database
>> >> >> >>> >> is
>> >> >> >>> >> >>>> still present as shown below, because
>> >> >> >>> >> >>>> I did not quit from psql terminal yet:
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> [root at master ~]# ps -ef |grep 128.199.224.132
>> >> >> >>> >> >>>> enterpr+ 13193 28563  0 07:38 pts/0    00:00:00 /bin/bash
>> >> >> >>> /bin/psql -p
>> >> >> >>> >> >>>> 9999 -h 128.199.224.132
>> >> >> >>> >> >>>> enterpr+ 13198 13193  0 07:38 pts/0    00:00:00
>> >> /bin/psql.bin
>> >> >> -p
>> >> >> >>> 9999
>> >> >> >>> >> -h
>> >> >> >>> >> >>>> 128.199.224.132
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> From scenario 2( client_idle_limit = 60), we can say that
>> >> when
>> >> >> >>> >> >>>> client_idle_limit is triggered client is disconnected, no
>> >> >> database
>> >> >> >>> >> >>>> connection is in use but the session still remains on
>> >> >> server.If i
>> >> >> >>> >> start
>> >> >> >>> >> >>>> running query
>> >> >> >>> >> >>>> on same psql session, it will first reset connection and
>> >> then
>> >> >> run
>> >> >> >>> the
>> >> >> >>> >> >>>> query, this will again create a new connection to the
>> >> database.
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> From scenario 1(connection_life_time = 60), there is no
>> real
>> >> >> >>> benefit I
>> >> >> >>> >> >>>> see. I assumed the connections(DISCARD ALL) present in
>> >> database
>> >> >> >>> will
>> >> >> >>> >> be
>> >> >> >>> >> >>>> reused but each time I connected to the database, it
>> >> created a
>> >> >> new
>> >> >> >>> >> >>>> connection as seen below:
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>   pid  |    query     |   usename    |   client_addr   |
>> >> count
>> >> >> |
>> >> >> >>> state
>> >> >> >>> >> >>>>
>> >> >> >>> >>
>> >> >>
>> -------+--------------+--------------+-----------------+-------+-------
>> >> >> >>> >> >>>>  12895 |              | enterprisedb | 128.199.224.132 |
>> >>  1
>> >> >> |
>> >> >> >>> idle
>> >> >> >>> >> >>>>   3420 |  DISCARD ALL | enterprisedb | 128.199.224.132 |
>> >>  1
>> >> >> |
>> >> >> >>> idle
>> >> >> >>> >> >>>>  12531 |  DISCARD ALL | enterprisedb | 128.199.224.132 |
>> >>  1
>> >> >> |
>> >> >> >>> idle
>> >> >> >>> >> >>>>  12636 |  DISCARD ALL | enterprisedb | 128.199.224.132 |
>> >>  1
>> >> >> |
>> >> >> >>> idle
>> >> >> >>> >> >>>>  12698 |  DISCARD ALL | enterprisedb | 128.199.224.132 |
>> >>  1
>> >> >> |
>> >> >> >>> idle
>> >> >> >>> >> >>>>  12751 |  DISCARD ALL | enterprisedb | 128.199.224.132 |
>> >>  1
>> >> >> |
>> >> >> >>> idle
>> >> >> >>> >> >>>>  12773 |  DISCARD ALL | enterprisedb | 128.199.224.132 |
>> >>  1
>> >> >> |
>> >> >> >>> idle
>> >> >> >>> >> >>>>  12862 |  DISCARD ALL | enterprisedb | 128.199.224.132 |
>> >>  1
>> >> >> |
>> >> >> >>> idle
>> >> >> >>> >> >>>>  12878 |  DISCARD ALL | enterprisedb | 128.199.224.132 |
>> >>  1
>> >> >> |
>> >> >> >>> idle
>> >> >> >>> >> >>>> (9 rows)
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> Thanks and Regards,
>> >> >> >>> >> >>>> Nikhil
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>> On Sat, Aug 1, 2020 at 6:45 PM Tatsuo Ishii <
>> >> >> ishii at sraoss.co.jp>
>> >> >> >>> >> wrote:
>> >> >> >>> >> >>>>
>> >> >> >>> >> >>>>> > Hi,
>> >> >> >>> >> >>>>> >
>> >> >> >>> >> >>>>> > Yes, we can see the pid
>> >> >> >>> >> >>>>> >
>> >> >> >>> >> >>>>> > show pool_pools;
>> >> >> >>> >> >>>>> > pool_pid |     start_time      | pool_id | backend_id
>> |
>> >> >> >>> database |
>> >> >> >>> >> >>>>> > username   |     create_time     | majorversion |
>> >> >> minorversion
>> >> >> >>> |
>> >> >> >>> >> >>>>> > pool_counter | pool_backendpid | pool_connected
>> >> >> >>> >> >>>>> >
>> >> >> >>> >> >>>>> > 18190    | 2020-08-01 06:14:41 | 0       | 1
>> |
>> >> edb
>> >> >> >>>   |
>> >> >> >>> >> >>>>> > enterprisedb | 2020-08-01 06:19:52 | 3            | 0
>> >> >> >>>   |
>> >> >> >>> >> 1
>> >> >> >>> >> >>>>> >      | *29321*          | 0
>> >> >> >>> >> >>>>> > 18193    | 2020-08-01 06:14:41 | 0       | 1
>> |
>> >> edb
>> >> >> >>>   |
>> >> >> >>> >> >>>>> > enterprisedb | 2020-08-01 06:21:26 | 3            | 0
>> >> >> >>>   |
>> >> >> >>> >> 1
>> >> >> >>> >> >>>>> >      | *29619          *| 0
>> >> >> >>> >> >>>>> >
>> >> >> >>> >> >>>>> >
>> >> >> >>> >> >>>>> > select pid,query,usename,state from pg_stat_activity
>> >> where
>> >> >> >>> >> >>>>> > client_addr='128.199.224.132' group by
>> usename,query,pid;
>> >> >> >>> >> >>>>> >  pid  |    query     |   usename    | state
>> >> >> >>> >> >>>>> > -------+--------------+--------------+-------
>> >> >> >>> >> >>>>> >  *29321 *|  DISCARD ALL | enterprisedb | idle
>> >> >> >>> >> >>>>> >  *29619* |  DISCARD ALL | enterprisedb | idle
>> >> >> >>> >> >>>>>
>> >> >> >>> >> >>>>> Assuming you executed "show pool_pools" long after
>> >> 2020-08-01
>> >> >> >>> >> >>>>> 06:21:26, that is very strange because
>> connection_life_time
>> >> >> >>> should
>> >> >> >>> >> >>>>> have been already expired. I wonder if pgpool tried to
>> >> >> >>> disconnect the
>> >> >> >>> >> >>>>> connection but failed. To check what actually happend,
>> can
>> >> you
>> >> >> >>> check
>> >> >> >>> >> >>>>> ps status of pgpool process 18190 and 18193?
>> >> >> >>> >> >>>>>
>> >> >> >>> >> >>>>> Also it would be nice you can examine the socket status
>> of
>> >> >> >>> PostgreSQL
>> >> >> >>> >> >>>>> backend 29321 and 29619, and pgpool socket status of
>> >> process
>> >> >> >>> 18190
>> >> >> >>> >> and
>> >> >> >>> >> >>>>> 18193?
>> >> >> >>> >> >>>>>
>> >> >> >>> >> >>>>> Best regards,
>> >> >> >>> >> >>>>> --
>> >> >> >>> >> >>>>> Tatsuo Ishii
>> >> >> >>> >> >>>>> SRA OSS, Inc. Japan
>> >> >> >>> >> >>>>> English: http://www.sraoss.co.jp/index_en.php
>> >> >> >>> >> >>>>> Japanese:http://www.sraoss.co.jp
>> >> >> >>> >> >>>>>
>> >> >> >>> >> >>>>
>> >> >> >>> >> > _______________________________________________
>> >> >> >>> >> > pgpool-general mailing list
>> >> >> >>> >> > pgpool-general at pgpool.net
>> >> >> >>> >> > http://www.pgpool.net/mailman/listinfo/pgpool-general
>> >> >> >>> >>
>> >> >> >>>
>> >> >> >>
>> >> >>
>> >>
>>


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