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Configuring Redis for GitLab HA
You can choose to install and manage Redis yourself, or you can use the one that comes bundled with GitLab Omnibus packages.
Note: Redis does not require authentication by default. See Redis Security documentation for more information. We recommend using a combination of a Redis password and tight firewall rules to secure your Redis service.
Configure your own Redis server
If you're hosting GitLab on a cloud provider, you can optionally use a managed service for Redis. For example, AWS offers a managed ElastiCache service that runs Redis.
Configure Redis using Omnibus
If you don't want to bother setting up your own Redis server, you can use the one bundled with Omnibus. In this case, you should disable all services except Redis.
-
Download/install GitLab Omnibus using steps 1 and 2 from GitLab downloads. Do not complete other steps on the download page.
-
Create/edit
/etc/gitlab/gitlab.rb
and use the following configuration. Be sure to change theexternal_url
to match your eventual GitLab front-end URL:external_url 'https://gitlab.example.com' # Disable all services except Redis redis['enable'] = true bootstrap['enable'] = false nginx['enable'] = false unicorn['enable'] = false sidekiq['enable'] = false postgresql['enable'] = false gitlab_workhorse['enable'] = false mailroom['enable'] = false # Redis configuration redis['port'] = 6379 redis['bind'] = '0.0.0.0' # If you wish to use Redis authentication (recommended) redis['password'] = 'Redis Password'
-
Run
sudo gitlab-ctl reconfigure
to install and configure PostgreSQL.Note: This
reconfigure
step will result in some errors. That's OK - don't be alarmed. -
Run
touch /etc/gitlab/skip-auto-migrations
to prevent database migrations from running on upgrade. Only the primary GitLab application server should handle migrations.
Experimental Redis Sentinel support
Introduced in GitLab 8.11.
Since GitLab 8.11, you can configure a list of Redis Sentinel servers that will monitor a group of Redis servers to provide you with a standard failover support.
There is currently one exception to the Sentinel support: mail_room
, the
component that processes incoming emails. It doesn't support Sentinel yet, but
we hope to integrate a future release that does support it.
To get a better understanding on how to correctly setup Sentinel, please read the Redis Sentinel documentation first, as failing to configure it correctly can lead to data loss.
The configuration consists of three parts:
- Redis setup
- Sentinel setup
- GitLab setup
Read carefully how to configure those components below.
Redis setup
You must have at least 2 Redis servers: 1 Master, 1 or more Slaves. They should be configured the same way and with similar server specs, as in a failover situation, any Slave can be elected as the new Master by the Sentinel servers.
In a minimal setup, the only required change for the slaves in redis.conf
is the addition of a slaveof
line pointing to the initial master.
You can increase the security by defining a requirepass
configuration in
the master, and masterauth
in slaves.
Configuring your own Redis server
-
Add to the slaves'
redis.conf
:# IP and port of the master Redis server slaveof 10.10.10.10 6379
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Optionally, set up password authentication for increased security. Add the following to master's
redis.conf
:# Optional password authentication for increased security requirepass "<password>"
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Then add this line to all the slave servers'
redis.conf
:masterauth "<password>"
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Restart the Redis services for the changes to take effect.
Using Redis via Omnibus
-
Edit
/etc/gitlab/gitlab.rb
of a master Redis machine (usualy a single machine):## Redis TCP support (will disable UNIX socket transport) redis['bind'] = '0.0.0.0' # or specify an IP to bind to a single one redis['port'] = 6379 ## Master redis instance redis['password'] = '<huge password string here>'
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Edit
/etc/gitlab/gitlab.rb
of a slave Redis machine (should be one or more machines):## Redis TCP support (will disable UNIX socket transport) redis['bind'] = '0.0.0.0' # or specify an IP to bind to a single one redis['port'] = 6379 ## Slave redis instance redis['master_ip'] = '10.10.10.10' # IP of master Redis server redis['master_port'] = 6379 # Port of master Redis server redis['master_password'] = "<huge password string here>"
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Reconfigure the GitLab for the changes to take effect:
sudo gitlab-ctl reconfigure
Now that the Redis servers are all set up, let's configure the Sentinel servers.
Sentinel setup
We don't provide yet an automated way to setup and run the Sentinel daemon from Omnibus installation method. You must follow the instructions below and run it by yourself.
The support for Sentinel in Ruby has some caveats.
While you can give any name for the master-group-name
part of the
configuration, as in this example:
sentinel monitor <master-group-name> <ip> <port> <quorum>
,for it to work in Ruby, you have to use the "hostname" of the master Redis
server, otherwise you will get an error message like:
Redis::CannotConnectError: No sentinels available.
. Read
Sentinel troubleshooting for more information.
Here is an example configuration file (sentinel.conf
) for a Sentinel node:
port 26379
sentinel monitor master-redis.example.com 10.10.10.10 6379 1
sentinel down-after-milliseconds master-redis.example.com 10000
sentinel config-epoch master-redis.example.com 0
sentinel leader-epoch master-redis.example.com 0
The final part is to inform the main GitLab application server of the Redis master and the new sentinels servers.
GitLab setup
You can enable or disable sentinel support at any time in new or existing installations. From the GitLab application perspective, all it requires is the correct credentials for the master Redis and for a few Sentinel nodes.
It doesn't require a list of all Sentinel nodes, as in case of a failure, the application will need to query only one of them.
Note: The following steps should be performed in the GitLab application server.
For source based installations
- Edit
/home/git/gitlab/config/resque.yml
following the example in/home/git/gitlab/config/resque.yml.example
, and uncomment the sentinels line, changing to the correct server credentials. - Restart GitLab for the changes to take effect.
For Omnibus installations
-
Edit
/etc/gitlab/gitlab.rb
and add/change the following lines:gitlab-rails['redis_host'] = "master-redis.example.com" gitlab-rails['redis_port'] = 6379 gitlab-rails['redis_password'] = '<huge password string here>' gitlab-rails['redis_sentinels'] = [ {'host' => '10.10.10.1', 'port' => 26379}, {'host' => '10.10.10.2', 'port' => 26379}, {'host' => '10.10.10.3', 'port' => 26379} ]
-
Reconfigure the GitLab for the changes to take effect.
Sentinel troubleshooting
If you get an error like: Redis::CannotConnectError: No sentinels available.
,
there may be something wrong with your configuration files or it can be related
to this issue (pull request that should make things better).
It's a bit rigid the way you have to config resque.yml
and sentinel.conf
,
otherwise redis-rb
will not work properly.
The hostname ('my-primary-redis') of the primary Redis server (sentinel.conf
)
must match the one configured in GitLab (resque.yml
for source installations
or gitlab-rails['redis_*']
in Omnibus) and it must be valid ex:
# sentinel.conf:
sentinel monitor my-primary-redis 10.10.10.10 6379 1
sentinel down-after-milliseconds my-primary-redis 10000
sentinel config-epoch my-primary-redis 0
sentinel leader-epoch my-primary-redis 0
# resque.yaml
production:
url: redis://my-primary-redis:6378
sentinels:
-
host: slave1
port: 26380 # point to sentinel, not to redis port
-
host: slave2
port: 26381 # point to sentinel, not to redis port
When in doubt, please read Redis Sentinel documentation
To make sure your configuration is correct:
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SSH into your GitLab application server
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Enter the Rails console:
# For Omnibus installations sudo gitlab-rails console # For source installations sudo -u git rails console RAILS_ENV=production
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Run in the console:
redis = Redis.new(Gitlab::Redis.params) redis.info
Keep this screen open and try to simulate a failover below.
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To simulate a failover on master Redis, SSH into the Redis server and run:
# port must match your master redis port redis-cli -h localhost -p 6379 DEBUG sleep 60
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Then back in the Rails console from the first step, run:
redis.info
You should see a different port after a few seconds delay (the failover/reconnect time).
Read more on high-availability configuration: