Commit a5c1e2e5 authored by Gabriel Mazetto's avatar Gabriel Mazetto

Added Redis Sentinel support documentation

parent 32bb4211
......@@ -22,7 +22,7 @@ production:
# http://redis.io/topics/sentinel
#
# You must specify a list of a few sentinels that will handle client connection
# please read here for more information: https://github.com/redis/redis-rb#sentinel-support
# please read here for more information: https://docs.gitlab.com/ce/administration/high_availability/redis.html
##
# url: redis://master:6379
# sentinels:
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......@@ -3,6 +3,113 @@
You can choose to install and manage Redis yourself, or you can use GitLab
Omnibus packages to help.
## Experimental Redis Sentinel support
Since 8.10 release, 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 process 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
[Redis Sentinel documentation](http://redis.io/topics/sentinel) first, as
faling to configure it correctly can lead to data-loss.
### 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 Sentinels 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 like this:
```conf
slaveof 192.168.1.1 6379
```
You can increase the security by defining a `requirepass` configuration in
the master:
```conf
requirepass "<password>
```
and adding this line to all the slave servers:
```conf
masterauth "<password>"
```
> **Note** This setup is not safe to be used by a machine accessible by the
internet. Use it in combination with tight firewall rules.
### Sentinel setup
The support for Sentinel in ruby have some [caveats](https://github.com/redis/redis-rb/issues/531).
While you can give any name for the `master-group-name` part of the
configuration, as in this example:
```conf
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 otherwhise you will get an error message like this one:
`Redis::CannotConnectError: No sentinels available.`.
Here is an example configuration file (`sentinel.conf`) for a Sentinel node:
```conf
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 locmaster-redis.example.comalhost 0
```
### GitLab setup
You can enable or disable sentinel support at any time in new or existing
installs. From the GitLab application perspective, all it requires is
the correct credentials for the Master redis and for a few Sentinels 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.
For a source based install, you must change `/home/git/gitlab/config/resque.yml`,
following the example in `/home/git/gitlab/config/resque.yml.example` and
uncommenting the sentinels line, changing to the correct server credentials,
and resstart GitLab.
For a Omnibus install you have to add/change this lines from the
`/etc/gitlab/gitlab.rb` configuration file:
```ruby
gitlab['gitlab-rails']['redis_host'] = "master-redis.example.com"
gitlab['gitlab-rails']['redis_port'] = 6379
gitlab['gitlab-rails']['redis_password'] = "redis-secure-password-here"
gitlab['gitlab-rails']['redis_socket'] = nil
gitlab['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}
]
```
After the change run the reconfigure command:
```bash
sudo gitlab-ctl reconfigure
```
## Configure your own Redis server
If you're hosting GitLab on a cloud provider, you can optionally use a
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