[pgpool-general: 7178] Re: Idle connection in database
Nikhil Shetty
nikhil.dba04 at gmail.com
Sun Aug 2 16:18:32 JST 2020
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
>>
>
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