[pgpool-general: 5473] Re: FW: show pool_nodes status 0

Gabriel Fernández Martínez gfernandez at hotelbeds.com
Tue May 16 18:45:20 JST 2017


Hello,

Thank you so much for all the colleagues who has replay my question.

It has been quite helpfully to improve my understanding of the product.

Regards

From: PVY [mailto:balroga3 at yandex.ru]
Sent: lunes, 15 de mayo de 2017 14:08
To: Gabriel Fernández Martínez <gfernandez at hotelbeds.com>
Subject: Re: [pgpool-general: 5465] Re: FW: show pool_nodes status 0

Hello Gabriel.

You can also start pgpool with "-D" command-line option, it tells pgpool to discard the status file on startup.

Hi Lucas,

Thank you show much for your response, it works ☺

In the status file before follow your sequence we can find the following values:
up
unused

Once I have apply your suggested action plan now shows:
up
up

Please can you let me know where I can get more details about the usage of this file, I can see on some documents that this file is it read during the start-up and I can see that the file it is not removed after the application shutdown (I do not know if it is the expected behavior).

Regards

From: Lucas Luengas [mailto:lucasluengas at gmail.com]
Sent: miércoles, 10 de mayo de 2017 20:09
To: Gabriel Fernández Martínez <gfernandez at hotelbeds.com<mailto:gfernandez at hotelbeds.com>>
Cc: pgpool-general at pgpool.net<mailto:pgpool-general at pgpool.net>
Subject: Re: [pgpool-general: 5445] FW: show pool_nodes status 0

Hello.

I don't use your pgpool-II version. I am using pgpool-II version 3.4.6.

You can check pgpool status file. With pgpool-II version 3.4.6 the file is /tmp/pgpool_status by default. Check configuration "logdir" in your pgpool.conf.

You can try:
- Stop pgpool.
- Remove pgpool status file (/tmp/pgpool_status by default)
- Start pgpool.
- Check node status.

Kind regards.


On Tue, May 9, 2017 at 12:00 PM, Gabriel Fernández Martínez <gfernandez at hotelbeds.com<mailto:gfernandez at hotelbeds.com>> wrote:
Hi,

I am evaluating if PgPool can be useful to support the business activity of one application. For testing purposes, I have deploy a 3.5.2 pgpool release on the same server where I am running the primary PostgresSQL 9.5.

I had deployed a two PosgresSQL nodes using streaming replication and I am trying to configure the pgpool like a load balancer, but I am stuck with the configuration because the standby server it is in status 0 and no selects are run on this server

******-web=> show pool_nodes;
node_id |       hostname       | port | status | lb_weight |  role   | select_cnt
---------+----------------------+------+--------+-----------+---------+------------
0       | *************196.*** | 5*** | 2      | 0.500000  | primary | 0
1       | *************198.*** | 5*** | 0      | 0.500000  | standby | 0
(2 filas)

I had used the template pgpool.conf.sample-stream and I have modify the following parameters to adapt to my environment:
-          listen_addresses = '*'

-          backend_hostname0 = '**********196.***'
-          backend_port0 = 5***
-          backend_weight0 = 1
-          backend_data_directory0 = '/data/******1'
-          backend_flag0 = 'ALLOW_TO_FAILOVER'

-          backend_hostname1 = '**********198.***'
-          backend_port1 = 5***
-          backend_weight1 = 1
-          backend_data_directory1 = '/data/******2'
-          backend_flag1 = 'ALLOW_TO_FAILOVER'

-          enable_pool_hba = on

-          logdir = '/var/log/pgpool-II-95'
-          pid_file_name = '/data/node1/pgpool-II-95/pgpool.pid'

-          sr_check_user = 'pgpool'
-          sr_check_password = '*********'

I have created a user in the PostgreSQL cluster called pgpool and I have check that I can connect with this user to the Postgres database running on 196 & 198 nodes.

From the pgpool startup output log, I can see that the primary it is properly identified, but no explanation about why the standby show a status 0:
2017-05-08 18:05:05: pid 17334: LOG:  pgpool-II successfully started. version 3.5.2 (ekieboshi)
2017-05-08 18:05:05: pid 17334: LOG:  find_primary_node: checking backend no 0
2017-05-08 18:05:05: pid 17368: DEBUG:  I am 17368
2017-05-08 18:05:05: pid 17368: DEBUG:  initializing backend status
2017-05-08 18:05:05: pid 17334: DEBUG:  pool_read: read 13 bytes from backend 0
2017-05-08 18:05:05: pid 17334: DEBUG:  authenticate kind = 5
2017-05-08 18:05:05: pid 17334: DEBUG:  pool_write: to backend: kind:p
2017-05-08 18:05:05: pid 17368: DEBUG:  pool_read: read 13 bytes from backend 0
2017-05-08 18:05:05: pid 17368: DEBUG:  authenticate kind = 5
2017-05-08 18:05:05: pid 17368: DEBUG:  pool_write: to backend: kind:p
2017-05-08 18:05:05: pid 17368: DEBUG:  pool_read: read 327 bytes from backend 0
2017-05-08 18:05:05: pid 17368: DEBUG:  authenticate kind = 0
2017-05-08 18:05:05: pid 17368: DEBUG:  authenticate backend: key data received
2017-05-08 18:05:05: pid 17334: DEBUG:  pool_read: read 327 bytes from backend 0
2017-05-08 18:05:05: pid 17368: DEBUG:  authenticate backend: transaction state: I
2017-05-08 18:05:05: pid 17334: DEBUG:  authenticate kind = 0
2017-05-08 18:05:05: pid 17368: DEBUG:  pool_write: to backend: kind:X
2017-05-08 18:05:05: pid 17334: DEBUG:  authenticate backend: key data received
2017-05-08 18:05:05: pid 17334: DEBUG:  authenticate backend: transaction state: I
2017-05-08 18:05:05: pid 17334: DEBUG:  do_query: extended:0 query:"SELECT pg_is_in_recovery()"
2017-05-08 18:05:05: pid 17334: DEBUG:  pool_write: to backend: kind:Q
2017-05-08 18:05:05: pid 17334: DEBUG:  pool_read: read 75 bytes from backend 0
2017-05-08 18:05:05: pid 17334: DEBUG:  do_query: kind: 'T'
2017-05-08 18:05:05: pid 17334: DEBUG:  do_query: received ROW DESCRIPTION ('T')
2017-05-08 18:05:05: pid 17334: DEBUG:  do_query: row description: num_fileds: 1
2017-05-08 18:05:05: pid 17334: DEBUG:  do_query: kind: 'D'
2017-05-08 18:05:05: pid 17334: DEBUG:  do_query: received DATA ROW ('D')
2017-05-08 18:05:05: pid 17334: DEBUG:  do_query: kind: 'C'
2017-05-08 18:05:05: pid 17334: DEBUG:  do_query: received COMMAND COMPLETE ('C')
2017-05-08 18:05:05: pid 17334: DEBUG:  do_query: kind: 'Z'
2017-05-08 18:05:05: pid 17334: DEBUG:  do_query: received READY FOR QUERY ('Z')
2017-05-08 18:05:05: pid 17334: DEBUG:  pool_write: to backend: kind:X
2017-05-08 18:05:05: pid 17334: LOG:  find_primary_node: primary node id is 0

I have executed the pgbench to verify the load balancing between nodes and I can show that only the master is supporting load:
$ pgbench –h ********196.*** -p 9999 -c 10 -S -T 10 -U ******-web test
Password:
starting vacuum...end.
transaction type: SELECT only
scaling factor: 1
query mode: simple
number of clients: 10
number of threads: 1
duration: 10 s
number of transactions actually processed: 218728
latency average: 0.457 ms
tps = 21871.048129 (including connections establishing)
tps = 21879.150205 (excluding connections establishing)

******-web=> show pool_nodes;
node_id |       hostname       | port | status | lb_weight |  role   | select_cnt
---------+----------------------+------+--------+-----------+---------+------------
0       | *************196.*** | 5*** | 2      | 0.500000  | primary | 218560
1       | *************198.*** | 5*** | 0      | 0.500000  | standby | 0
(2 filas)


I had configured the pcp management in order to be able to use pcp_node_info, and I got the same output (as expected):

[postgres@********196 ~]$ pcp_node_info -U pgpool -h ip-10-222-64-196.ods --node=0 -v
Password:
Hostname: *******196.***
Port    : 5***
Status  : 2
Weight  : 0.500000
[postgres@********196~]$ pcp_node_info -U pgpool -h ip-10-222-64-196.ods --node=1 -v
Password:
Hostname: ********198.***
Port    : 5322
Status  : 0
Weight  : 0.500000


Any suggestion is welcome, I have try to go thought the documentation and I cannot find any clue who help me to resolve the issue.

Best regards

Gabriel Fernández
Technology
Architecture

tel: (+34) 971 189 188<tel:+34%20971%2018%2091%2088>
Ed. Mirall Cami de Son Fangos 100, B-2
E-07007, Palma de Mallorca, Spain
gfernandez at hotelbeds.com<mailto:gfernandez at hotelbeds.com>

[cid:image001.jpg at 01D2CE39.E402C450]<http://group.hotelbeds.com/>


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--
С уважением,
PVY                          mailto:balroga3 at yandex.ru
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