Working with the bundled PgBouncer service

As part of its High Availability stack, GitLab Premium includes a bundled version of PgBouncer that can be managed through /etc/gitlab/gitlab.rb. PgBouncer is used to seamlessly migrate database connections between servers in a failover scenario. Additionally, it can be used in a non-HA setup to pool connections, speeding up response time while reducing resource usage.

In a HA setup, it’s recommended to run a PgBouncer node separately for each database node with an internal load balancer (TCP) serving each accordingly.

Operations

Running PgBouncer as part of an HA GitLab installation

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Running PgBouncer as part of a non-HA GitLab installation

  1. Generate PGBOUNCER_USER_PASSWORD_HASH with the command gitlab-ctl pg-password-md5 pgbouncer

  2. Generate SQL_USER_PASSWORD_HASH with the command gitlab-ctl pg-password-md5 gitlab. We’ll also need to enter the plaintext SQL_USER_PASSWORD later

  3. On your database node, ensure the following is set in your /etc/gitlab/gitlab.rb 

    postgresql['pgbouncer_user_password'] = 'PGBOUNCER_USER_PASSWORD_HASH'
postgresql['sql_user_password'] = 'SQL_USER_PASSWORD_HASH'
postgresql['listen_address'] = 'XX.XX.XX.Y' # Where XX.XX.XX.Y is the ip address on the node postgresql should listen on
postgresql['md5_auth_cidr_addresses'] = %w(AA.AA.AA.B/32) # Where AA.AA.AA.B is the IP address of the pgbouncer node

  4. Run gitlab-ctl reconfigure

    Note: If the database was already running, it will need to be restarted after reconfigure by running gitlab-ctl restart postgresql.

  5. On the node you are running PgBouncer on, make sure the following is set in /etc/gitlab/gitlab.rb 

    pgbouncer['enable'] = true
pgbouncer['databases'] = {
  gitlabhq_production: {
    host: 'DATABASE_HOST',
    user: 'pgbouncer',
    password: 'PGBOUNCER_USER_PASSWORD_HASH'
  }
}

  6. Run gitlab-ctl reconfigure

  7. On the node running Puma, make sure the following is set in /etc/gitlab/gitlab.rb 

    gitlab_rails['db_host'] = 'PGBOUNCER_HOST'
gitlab_rails['db_port'] = '6432'
gitlab_rails['db_password'] = 'SQL_USER_PASSWORD'

  8. Run gitlab-ctl reconfigure

  9. At this point, your instance should connect to the database through PgBouncer. If you are having issues, see the Troubleshooting section

Enable Monitoring

Introduced in GitLab 12.0.

If you enable Monitoring, it must be enabled on all PgBouncer servers.

  1. Create/edit /etc/gitlab/gitlab.rb and add the following configuration: 

    # Enable service discovery for Prometheus
consul['enable'] = true
consul['monitoring_service_discovery'] =  true

# Replace placeholders
# Y.Y.Y.Y consul1.gitlab.example.com Z.Z.Z.Z
# with the addresses of the Consul server nodes
consul['configuration'] = {
   retry_join: %w(Y.Y.Y.Y consul1.gitlab.example.com Z.Z.Z.Z),
}

# Set the network addresses that the exporters will listen on
node_exporter['listen_address'] = '0.0.0.0:9100'
pgbouncer_exporter['listen_address'] = '0.0.0.0:9188'

  2. Run sudo gitlab-ctl reconfigure to compile the configuration.

Interacting with PgBouncer

Administrative console

As part of Omnibus GitLab, we provide a command gitlab-ctl pgb-console to automatically connect to the PgBouncer administrative console. Please see the PgBouncer documentation for detailed instructions on how to interact with the console.

To start a session, run 

# gitlab-ctl pgb-console
Password for user pgbouncer:
psql (11.7, server 1.7.2/bouncer)
Type "help" for help.

pgbouncer=#

The password you will be prompted for is the PGBOUNCER_USER_PASSWORD

To get some basic information about the instance, run 

pgbouncer=# show databases; show clients; show servers;
        name         |   host    | port |      database       | force_user | pool_size | reserve_pool | pool_mode | max_connections | current_connections
---------------------+-----------+------+---------------------+------------+-----------+--------------+-----------+-----------------+---------------------
 gitlabhq_production | 127.0.0.1 | 5432 | gitlabhq_production |            |       100 |            5 |           |               0 |                   1
 pgbouncer           |           | 6432 | pgbouncer           | pgbouncer  |         2 |            0 | statement |               0 |                   0
(2 rows)

 type |   user    |      database       | state  |   addr    | port  | local_addr | local_port |    connect_time     |    request_time     |    ptr    | link
| remote_pid | tls
------+-----------+---------------------+--------+-----------+-------+------------+------------+---------------------+---------------------+-----------+------
+------------+-----
 C    | gitlab    | gitlabhq_production | active | 127.0.0.1 | 44590 | 127.0.0.1  |       6432 | 2018-04-24 22:13:10 | 2018-04-24 22:17:10 | 0x12444c0 |
|          0 |
 C    | gitlab    | gitlabhq_production | active | 127.0.0.1 | 44592 | 127.0.0.1  |       6432 | 2018-04-24 22:13:10 | 2018-04-24 22:17:10 | 0x12447c0 |
|          0 |
 C    | gitlab    | gitlabhq_production | active | 127.0.0.1 | 44594 | 127.0.0.1  |       6432 | 2018-04-24 22:13:10 | 2018-04-24 22:17:10 | 0x1244940 |
|          0 |
 C    | gitlab    | gitlabhq_production | active | 127.0.0.1 | 44706 | 127.0.0.1  |       6432 | 2018-04-24 22:14:22 | 2018-04-24 22:16:31 | 0x1244ac0 |
|          0 |
 C    | gitlab    | gitlabhq_production | active | 127.0.0.1 | 44708 | 127.0.0.1  |       6432 | 2018-04-24 22:14:22 | 2018-04-24 22:15:15 | 0x1244c40 |
|          0 |
 C    | gitlab    | gitlabhq_production | active | 127.0.0.1 | 44794 | 127.0.0.1  |       6432 | 2018-04-24 22:15:15 | 2018-04-24 22:15:15 | 0x1244dc0 |
|          0 |
 C    | gitlab    | gitlabhq_production | active | 127.0.0.1 | 44798 | 127.0.0.1  |       6432 | 2018-04-24 22:15:15 | 2018-04-24 22:16:31 | 0x1244f40 |
|          0 |
 C    | pgbouncer | pgbouncer           | active | 127.0.0.1 | 44660 | 127.0.0.1  |       6432 | 2018-04-24 22:13:51 | 2018-04-24 22:17:12 | 0x1244640 |
|          0 |
(8 rows)

 type |  user  |      database       | state |   addr    | port | local_addr | local_port |    connect_time     |    request_time     |    ptr    | link | rem
ote_pid | tls
------+--------+---------------------+-------+-----------+------+------------+------------+---------------------+---------------------+-----------+------+----
--------+-----
 S    | gitlab | gitlabhq_production | idle  | 127.0.0.1 | 5432 | 127.0.0.1  |      35646 | 2018-04-24 22:15:15 | 2018-04-24 22:17:10 | 0x124dca0 |      |
  19980 |
(1 row)

Troubleshooting

In case you are experiencing any issues connecting through PgBouncer, the first place to check is always the logs: 

# gitlab-ctl tail pgbouncer

Additionally, you can check the output from show databases in the Administrative console. In the output, you would expect to see values in the host field for the gitlabhq_production database. Additionally, current_connections should be greater than 1.

Message: LOG: invalid CIDR mask in address

See the suggested fix in Geo documentation.

Message: LOG: invalid IP mask "md5": Name or service not known

See the suggested fix in Geo documentation.