debian-mirror-gitlab/doc/administration/geo/replication/multiple_servers.md

stage	group	info	type
Enablement	Geo	To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments	howto

Geo for multiple nodes (PREMIUM SELF)

This document describes a minimal reference architecture for running Geo in a multi-node configuration. If your multi-node setup differs from the one described, it is possible to adapt these instructions to your needs.

Architecture overview

diagram source - GitLab employees only

The topology above assumes the primary and secondary Geo clusters are located in two separate locations, on their own virtual network with private IP addresses. The network is configured such that all machines in one geographic location can communicate with each other using their private IP addresses. The IP addresses given are examples and may be different depending on the network topology of your deployment.

The only external way to access the two Geo deployments is by HTTPS at gitlab.us.example.com and gitlab.eu.example.com in the example above.

NOTE: The primary and secondary Geo deployments must be able to communicate to each other over HTTPS.

Redis and PostgreSQL for multiple nodes

Geo supports:

• Redis and PostgreSQL on the primary node configured for multiple nodes.
• Redis on secondary nodes configured for multiple nodes.

NOTE: Support for PostgreSQL on secondary nodes in multi-node configuration is planned.

Because of the additional complexity involved in setting up this configuration for PostgreSQL and Redis, it is not covered by this Geo multi-node documentation.

For more information on setting up a multi-node PostgreSQL cluster and Redis cluster using the Omnibus GitLab package, see:

• PostgreSQL multi-node documentation
• Redis multi-node documentation

NOTE: It is possible to use cloud hosted services for PostgreSQL and Redis, but this is beyond the scope of this document.

Prerequisites: Two working GitLab multi-node clusters

One cluster serves as the primary node. Use the GitLab multi-node documentation to set this up. If you already have a working GitLab instance that is in-use, it can be used as a primary.

The second cluster serves as the secondary node. Again, use the GitLab multi-node documentation to set this up. It's a good idea to log in and test it. However, be aware that its data is wiped out as part of the process of replicating from the primary node.

Configure the GitLab cluster to be the primary node

The following steps enable a GitLab cluster to serve as the primary node.

Step 1: Configure the primary frontend servers

1. Edit /etc/gitlab/gitlab.rb and add the following:

   ##
   ## Enable the Geo primary role
   ##
   roles ['geo_primary_role']
   
   ##
   ## The unique identifier for the Geo node.
   ##
   gitlab_rails['geo_node_name'] = '<node_name_here>'
   
   ##
   ## Disable automatic migrations
   ##
   gitlab_rails['auto_migrate'] = false
   

After making these changes, reconfigure GitLab so the changes take effect.

NOTE: PostgreSQL and Redis should have already been disabled on the application servers during normal GitLab multi-node setup. Connections from the application servers to services on the backend servers should have also been configured. See multi-node configuration documentation for PostgreSQL and Redis.

Step 2: Configure the primary database

1. Edit /etc/gitlab/gitlab.rb and add the following:

   ##
   ## Configure the Geo primary role and the PostgreSQL role
   ##
   roles ['geo_primary_role', 'postgres_role']
   

Configure a secondary node

A secondary cluster is similar to any other GitLab multi-node cluster, with two major differences:

• The main PostgreSQL database is a read-only replica of the primary node's PostgreSQL database.
• There is also a single PostgreSQL database for the secondary cluster, called the "tracking database", which tracks the synchronization state of various resources.

Therefore, we set up the multi-node components one by one and include deviations from the normal multi-node setup. However, we highly recommend configuring a brand-new cluster first, as if it were not part of a Geo setup. This allows verifying that it is a working cluster. And only then should it be modified for use as a Geo secondary. This helps to separate Geo setup problems from unrelated problems.

Step 1: Configure the Redis and Gitaly services on the secondary node

Configure the following services, again using the non-Geo multi-node documentation:

• Configuring Redis for GitLab for multiple nodes.
• Gitaly, which stores data that is synchronized from the primary node.

NOTE: NFS can be used in place of Gitaly but is not recommended.

Step 2: Configure the main read-only replica PostgreSQL database on the secondary node

NOTE: The following documentation assumes the database runs on a single node only. Multi-node PostgreSQL on secondary nodes is not currently supported.

Configure the secondary database as a read-only replica of the primary database. Use the following as a guide.

1. Generate an MD5 hash of the desired password for the database user that the GitLab application uses to access the read-replica database:

   Note that the username (gitlab by default) is incorporated into the hash.

   gitlab-ctl pg-password-md5 gitlab
   # Enter password: <your_password_here>
   # Confirm password: <your_password_here>
   # fca0b89a972d69f00eb3ec98a5838484
   

   Use this hash to fill in <md5_hash_of_your_password> in the next step.

2. Edit /etc/gitlab/gitlab.rb in the replica database machine, and add the following:

   ##
   ## Configure the Geo secondary role and the PostgreSQL role
   ##
   roles ['geo_secondary_role', 'postgres_role']
   
   ##
   ## The unique identifier for the Geo node.
   ## This should match the secondary's application node.
   ##
   gitlab_rails['geo_node_name'] = '<node_name_here>'
   
   ##
   ## Secondary address
   ## - replace '<secondary_node_ip>' with the public or VPC address of your Geo secondary node
   ## - replace '<tracking_database_ip>' with the public or VPC address of your Geo tracking database node
   ##
   postgresql['listen_address'] = '<secondary_node_ip>'
   postgresql['md5_auth_cidr_addresses'] = ['<secondary_node_ip>/32', '<tracking_database_ip>/32']
   
   ##
   ## Database credentials password (defined previously in primary node)
   ## - replicate same values here as defined in primary node
   ##
   postgresql['sql_user_password'] = '<md5_hash_of_your_password>'
   gitlab_rails['db_password'] = '<your_password_here>'
   
   ##
   ## When running the Geo tracking database on a separate machine, disable it
   ## here and allow connections from the tracking database host. And ensure
   ## the tracking database IP is in postgresql['md5_auth_cidr_addresses'] above.
   ##
   geo_postgresql['enable'] = false
   
   ##
   ## Disable all other services that aren't needed. Note that we had to enable
   ## geo_secondary_role to cause some configuration changes to postgresql, but
   ## the role enables single-node services by default.
   ##
   alertmanager['enable'] = false
   consul['enable'] = false
   geo_logcursor['enable'] = false
   gitaly['enable'] = false
   gitlab_exporter['enable'] = false
   gitlab_workhorse['enable'] = false
   nginx['enable'] = false
   node_exporter['enable'] = false
   pgbouncer_exporter['enable'] = false
   prometheus['enable'] = false
   redis['enable'] = false
   redis_exporter['enable'] = false
   patroni['enable'] = false
   sidekiq['enable'] = false
   sidekiq_cluster['enable'] = false
   puma['enable'] = false
   

After making these changes, reconfigure GitLab so the changes take effect.

If using an external PostgreSQL instance, refer also to Geo with external PostgreSQL instances.

Step 3: Configure the tracking database on the secondary node

NOTE: This documentation assumes the tracking database runs on only a single machine, rather than as a PostgreSQL cluster.

Configure the tracking database.

1. Generate an MD5 hash of the desired password for the database user that the GitLab application uses to access the tracking database:

   Note that the username (gitlab_geo by default) is incorporated into the hash.

   gitlab-ctl pg-password-md5 gitlab_geo
   # Enter password: <your_password_here>
   # Confirm password: <your_password_here>
   # fca0b89a972d69f00eb3ec98a5838484
   

   Use this hash to fill in <tracking_database_password_md5_hash> in the next step.

2. Edit /etc/gitlab/gitlab.rb in the tracking database machine, and add the following:

   ##
   ## Enable the Geo secondary tracking database
   ##
   geo_postgresql['enable'] = true
   geo_postgresql['listen_address'] = '<ip_address_of_this_host>'
   geo_postgresql['sql_user_password'] = '<tracking_database_password_md5_hash>'
   
   ##
   ## Configure PostgreSQL connection to the replica database
   ##
   geo_postgresql['md5_auth_cidr_addresses'] = ['<replica_database_ip>/32']
   gitlab_rails['db_host'] = '<replica_database_ip>'
   
   # Prevent reconfigure from attempting to run migrations on the replica DB
   gitlab_rails['auto_migrate'] = false
   
   ##
   ## Ensure unnecessary services are disabled
   ##
   alertmanager['enable'] = false
   consul['enable'] = false
   geo_logcursor['enable'] = false
   gitaly['enable'] = false
   gitlab_exporter['enable'] = false
   gitlab_workhorse['enable'] = false
   nginx['enable'] = false
   node_exporter['enable'] = false
   pgbouncer_exporter['enable'] = false
   postgresql['enable'] = false
   prometheus['enable'] = false
   redis['enable'] = false
   redis_exporter['enable'] = false
   patroni['enable'] = false
   sidekiq['enable'] = false
   sidekiq_cluster['enable'] = false
   puma['enable'] = false
   

After making these changes, reconfigure GitLab so the changes take effect.

If using an external PostgreSQL instance, refer also to Geo with external PostgreSQL instances.

Step 4: Configure the frontend application servers on the secondary node

In the architecture overview, there are two machines running the GitLab application services. These services are enabled selectively in the configuration.

Configure the GitLab Rails application servers following the relevant steps outlined in the reference architectures, then make the following modifications:

1. Edit /etc/gitlab/gitlab.rb on each application server in the secondary cluster, and add the following:

   ##
   ## Enable the Geo secondary role
   ##
   roles ['geo_secondary_role', 'application_role']
   
   ##
   ## The unique identifier for the Geo node.
   ##
   gitlab_rails['geo_node_name'] = '<node_name_here>'
   
   ##
   ## Disable automatic migrations
   ##
   gitlab_rails['auto_migrate'] = false
   
   ##
   ## Configure the connection to the tracking DB. And disable application
   ## servers from running tracking databases.
   ##
   geo_secondary['db_host'] = '<geo_tracking_db_host>'
   geo_secondary['db_password'] = '<geo_tracking_db_password>'
   geo_postgresql['enable'] = false
   
   ##
   ## Configure connection to the streaming replica database, if you haven't
   ## already
   ##
   gitlab_rails['db_host'] = '<replica_database_host>'
   gitlab_rails['db_password'] = '<replica_database_password>'
   
   ##
   ## Configure connection to Redis, if you haven't already
   ##
   gitlab_rails['redis_host'] = '<redis_host>'
   gitlab_rails['redis_password'] = '<redis_password>'
   
   ##
   ## If you are using custom users not managed by Omnibus, you need to specify
   ## UIDs and GIDs like below, and ensure they match between servers in a
   ## cluster to avoid permissions issues
   ##
   user['uid'] = 9000
   user['gid'] = 9000
   web_server['uid'] = 9001
   web_server['gid'] = 9001
   registry['uid'] = 9002
   registry['gid'] = 9002
   

NOTE: If you had set up PostgreSQL cluster using the omnibus package and had set postgresql['sql_user_password'] = 'md5 digest of secret', keep in mind that gitlab_rails['db_password'] and geo_secondary['db_password'] contains the plaintext passwords. This is used to let the Rails servers connect to the databases.

NOTE: Make sure that current node IP is listed in postgresql['md5_auth_cidr_addresses'] setting of your remote database.

After making these changes Reconfigure GitLab so the changes take effect.

On the secondary the following GitLab frontend services are enabled:

• geo-logcursor
• gitlab-pages
• gitlab-workhorse
• logrotate
• nginx
• registry
• remote-syslog
• sidekiq
• puma

Verify these services by running sudo gitlab-ctl status on the frontend application servers.

Step 5: Set up the LoadBalancer for the secondary node

In this topology, a load balancer is required at each geographic location to route traffic to the application servers.

See Load Balancer for GitLab with multiple nodes for more information.

Step 6: Configure the backend application servers on the secondary node

The minimal reference architecture diagram above shows all application services running together on the same machines. However, for multiple nodes we strongly recommend running all services separately.

For example, a Sidekiq server could be configured similarly to the frontend application servers above, with some changes to run only the sidekiq service:

1. Edit /etc/gitlab/gitlab.rb on each Sidekiq server in the secondary cluster, and add the following:

   ##
   ## Enable the Geo secondary role
   ##
   roles ['geo_secondary_role']
   
   ##
   ## Enable the Sidekiq service
   ##
   sidekiq['enable'] = true
   
   ##
   ## Ensure unnecessary services are disabled
   ##
   alertmanager['enable'] = false
   consul['enable'] = false
   gitaly['enable'] = false
   gitlab_exporter['enable'] = false
   gitlab_workhorse['enable'] = false
   nginx['enable'] = false
   node_exporter['enable'] = false
   pgbouncer_exporter['enable'] = false
   postgresql['enable'] = false
   prometheus['enable'] = false
   redis['enable'] = false
   redis_exporter['enable'] = false
   patroni['enable'] = false
   puma['enable'] = false
   
   ##
   ## The unique identifier for the Geo node.
   ##
   gitlab_rails['geo_node_name'] = '<node_name_here>'
   
   ##
   ## Disable automatic migrations
   ##
   gitlab_rails['auto_migrate'] = false
   
   ##
   ## Configure the connection to the tracking DB. And disable application
   ## servers from running tracking databases.
   ##
   geo_secondary['db_host'] = '<geo_tracking_db_host>'
   geo_secondary['db_password'] = '<geo_tracking_db_password>'
   geo_postgresql['enable'] = false
   
   ##
   ## Configure connection to the streaming replica database, if you haven't
   ## already
   ##
   gitlab_rails['db_host'] = '<replica_database_host>'
   gitlab_rails['db_password'] = '<replica_database_password>'
   
   ##
   ## Configure connection to Redis, if you haven't already
   ##
   gitlab_rails['redis_host'] = '<redis_host>'
   gitlab_rails['redis_password'] = '<redis_password>'
   
   ##
   ## If you are using custom users not managed by Omnibus, you need to specify
   ## UIDs and GIDs like below, and ensure they match between servers in a
   ## cluster to avoid permissions issues
   ##
   user['uid'] = 9000
   user['gid'] = 9000
   web_server['uid'] = 9001
   web_server['gid'] = 9001
   registry['uid'] = 9002
   registry['gid'] = 9002
   

   You can similarly configure a server to run only the geo-logcursor service with geo_logcursor['enable'] = true and disabling Sidekiq with sidekiq['enable'] = false.

   These servers do not need to be attached to the load balancer.