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Commit 3242ea6d authored by Gabriel Mazetto's avatar Gabriel Mazetto
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Improved Redis HA and Sentinel documentation.

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doc/administration/high_availability/redis.md
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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.
that comes bundled with Omnibus GitLab packages.
> **Note:** Redis does not require authentication by default. See
[Redis Security](http://redis.io/topics/security) documentation for more
......@@ -15,17 +15,22 @@ that comes bundled with GitLab Omnibus packages.
- [Configure your own Redis server](#configure-your-own-redis-server)
- [Configure Redis using Omnibus](#configure-redis-using-omnibus)
- [Experimental Redis Sentinel support](#experimental-redis-sentinel-support)
- [Redis Sentinel support](#redis-sentinel-support)
- [Redis setup](#redis-setup)
- [Source install](#source-install)
- [Omnibus Install](#omnibus-install)
- [Troubleshooting Replication](#troubleshooting-replication)
- [Sentinel](#sentinel)
- [Sentinel setup (Community Edition)](#sentinel-setup-community-edition)
- [Sentinel setup (EE Only)](#sentinel-setup-ee-only)
- [Existing single-machine installation](#existing-single-machine-installation)
- [Installation from source](#installation-from-source)
- [Omnibus packages](#omnibus-packages)
- [Configuring Sentinel](#configuring-sentinel)
- [How sentinel handles a failover](#how-sentinel-handles-a-failover)
- [Sentinel setup](#sentinel-setup)
- [Community Edition](#community-edition)
- [Enterprise Edition](#enterprise-edition)
- [GitLab setup](#gitlab-setup)
- [Sentinel troubleshooting](#sentinel-troubleshooting)
- [Troubleshooting](#troubleshooting)
- [Redis replication](#redis-replication)
- [Sentinel](#sentinel)
- [Omnibus install](#omnibus-install)
- [Source install](#source-install-1)
- [Source install](#source-install)
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
......@@ -41,7 +46,7 @@ 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.
1. Download/install GitLab Omnibus using **steps 1 and 2** from
1. Download/install Omnibus GitLab using **steps 1 and 2** from
[GitLab downloads](https://about.gitlab.com/downloads). Do not complete other
steps on the download page.
1. Create/edit `/etc/gitlab/gitlab.rb` and use the following configuration.
......@@ -70,7 +75,7 @@ Redis.
redis['password'] = 'redis-password-goes-here'
```
1. Run `sudo gitlab-ctl reconfigure` to install and configure PostgreSQL.
1. Run `sudo gitlab-ctl reconfigure` to install and configure Redis.
> **Note**: This `reconfigure` step will result in some errors.
That's OK - don't be alarmed.
......@@ -81,7 +86,12 @@ Redis.
## Experimental Redis Sentinel support
> [Introduced][ce-1877] in GitLab 8.11, improved in 8.13.
> Experimental Redis Sentinel support was [Introduced][ce-1877] in GitLab 8.11.
Starting with 8.13, Redis Sentinel is no longer experimental.
If you used with versions `< 8.13` before, please check the updated
documentation below.
## Redis Sentinel support
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
......@@ -100,20 +110,19 @@ keep servers online with minimal to no downtime:
data-partitioning).
- Can be queried by clients to always connect to the correct master server.
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 soon.
The configuration consists of three parts:
- Setup Redis Master and Slave nodes
- Setup Sentinel nodes
- Setup GitLab
> **IMPORTANT**: You need at least 3 independent machines: physical, or VMs
running into distinct physical machines. If you fail to provision the
machines in that specific way, any issue with the shared environment can
bring your entire setup down.
### Prerequisites
You need at least `3` independent machines: physical, or VMs running into
distinct physical machines.
If you fail to provision the machines in that specific way, any issue with
the shared environment can bring your entire setup down.
Read carefully how to configure those components below.
......@@ -131,15 +140,35 @@ Sentinel instances and other redis instances should be able to talk to
each other over the network.
You'll need to define both `requirepass` and `masterauth` in all
nodes because they can be re-configured at any time by the Sentinels
during a failover, and change it's status as `Master` or `Slave`.
nodes. At any time during a failover the Sentinels can reconfigure a node
and change it's status from `Master` to `Slave` and vice versa.
Initial `Slave` nodes will have in `redis.conf` an additional `slaveof` line
Initial `Slave` nodes require an additional `slaveof` setting in `redis.conf`
pointing to the initial `Master`.
#### Source install
#### Existing single-machine installation
If you already have a single-machine GitLab install running, you will need to
replicate from this machine first, before de-activating the Redis instance
inside it.
Your single-machine install will be the initial `Master`, and the `3` others
should be configured as `Slave` pointing to this machine.
After replication catchs-up, you will need to stop services in the
single-machine install, to rotate the `Master` to one of the new nodes.
Make the required changes in configuration and restart the new nodes again.
To disable redis in the single install, edit `/etc/gitlab/gitlab.rb`:
**Master Redis instance**
```ruby
redis['enable'] = false
```
#### Installation from source
**Configuring Master Redis instance**
You need to make the following changes in `redis.conf`:
......@@ -178,9 +207,9 @@ You need to make the following changes in `redis.conf`:
1. Restart the Redis services for the changes to take effect.
**Slave Redis instance**
**Configuring Slave Redis instance**
1. Follow same instructions from master with the extra change in `redis.conf`:
1. Follow same instructions from master, with the extra change in `redis.conf`:
```conf
# IP and port of the master Redis server
......@@ -189,33 +218,24 @@ You need to make the following changes in `redis.conf`:
1. Restart the Redis services for the changes to take effect.
#### Omnibus Install
You need to install the omnibus package in 3 different and independent machines.
We will elect one as the initial `Master` and the other 2 as `Slaves`.
#### Omnibus packages
If you are migrating from a single machine install, you may want to setup the
machines as Slaves, pointing to the original machine as `Master`, to migrate
the data first, and than switch to this setup.
To disable redis in the single install, edit `/etc/gitlab/gitlab.rb`:
```ruby
redis['enable'] = false
```
You need to install the Omnibus GitLab package in `3` independent machines.
**Master Redis instances**
**Configuring Master Redis instance**
You need to make the following changes in `/etc/gitlab/gitlab.rb`:
You will need to configure the following:
1. Define a `redis['bind']` address pointing to a local IP that your other machines
can reach you. If you really need to bind to an external acessible IP, make
sure you add extra firewall rules to prevent unauthorized access.
1. Define a `redis['port']` to force redis to listin on TCP so other machines can
connect to it.
1. Set up password authentication with `redis['master_password']` (use the same
1. Define a `redis['port']` so redis can listen for TCP requests which will
allow other machines to connect to it.
1. Set up a password authentication with `redis['master_password']` (use the same
password in all nodes).
In `/etc/gitlab/gitlab.rb`:
```ruby
## Redis TCP support (will disable UNIX socket transport)
redis['bind'] = '0.0.0.0' # or specify an IP to bind to a single one
......@@ -224,15 +244,14 @@ redis['requirepass'] = 'redis-password-goes-here'
redis['master_password'] = 'redis-password-goes-here'
```
Reconfigure GitLab Omnibus for the changes to take effect: `sudo gitlab-ctl reconfigure`
Reconfigure Omnibus GitLab for the changes to take effect: `sudo gitlab-ctl reconfigure`
**Slave Redis instances**
**Configuring Slave Redis instances**
You need to make the same changes listed for the `Master` instance,
with an additional `Slave` section as in the example below:
```ruby
## 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
redis['requirepass'] = 'redis-password-goes-here'
......@@ -244,26 +263,7 @@ redis['master_ip'] = '10.10.10.10' # IP of master Redis server
redis['master_port'] = 6379 # Port of master Redis server
```
Reconfigure GitLab Omnibus for the changes to take effect: `sudo gitlab-ctl reconfigure`
#### Troubleshooting Replication
You can check if everything is correct by connecting to each server using
`redis-cli` application, and sending the `INFO` command.
If authentication was correctly defined, it should fail with:
`NOAUTH Authentication required` error. Try to authenticate with the
previous defined password with `AUTH redis-password-goes-here` and
try the `INFO` command again.
Look for the `# Replication` section where you should see some important
information like the `role` of the server.
When connected to a `master` redis, you will see the number of connected
`slaves`, and a list of each with connection details.
When it's a `slave`, you will see details of the master connection and if
its `up` or `down`.
Reconfigure Omnibus GitLab for the changes to take effect: `sudo gitlab-ctl reconfigure`
---
......@@ -274,26 +274,29 @@ If you are not sure if your Redis servers are working and replicating
correctly, please read the [Troubleshooting Replication](#troubleshooting-replication)
and fix it before proceeding with Sentinel setup.
### Sentinel
### Configuring Sentinel
You must have at least `3` Redis Sentinel servers, and they need to
be each in a independent machine. You can install them in the same
machines you installed the other `3` Redis servers.
be each in a independent machine. You can configure them in the same
machines where you've configured the other Redis servers.
This number is required for the consensus algorithm to be effective
in the case of a failure. You should always have and `odd` number
of Sentinel nodes provisioned.
in the case of a failure. **You should always have and `odd` number
of Sentinel nodes provisioned**.
#### How sentinel handles a failover
Here is a simple explanation on how Sentinel handles a failover:
If (`quorum` value of) Sentinels agree the fact the `master` is not reachable,
Sentinels will try to elect a temporary `Leader`. The **Majority** of the
Sentinels must agree to start a failover.
When a number of Sentinels (`quorum` value) agree the fact the `master` is
not reachable, the **majority** of the sentinels must elect a temporary
Sentinel `leader`, that will be responsible to start the failover proceedings.
If you don't have the **Majority** of the Sentinels online (for example if you
are under a network partitioning), a failover **will not be started**.
As an example, for a cluster of `3` Sentinels, at least `2` must agree on a
`leader`. If you have total of `5` at least `3` must agree on the leader.
For example, for a cluster of `3` Sentinels, at least `2` must agree on a
`Leader`. If you have total of `5` at least `3` must agree on a `Leader`.
The `quorum` is only used to detect failure, not to elect the `leader`.
The `quorum` is only used to detect failure, not to elect the `Leader`.
Official [Sentinel documentation](http://redis.io/topics/sentinel#example-sentinel-deployments)
also lists different network topologies and warns againts situations like
......@@ -301,16 +304,16 @@ network partition and how it can affect the state of the HA solution. Make
sure you read it carefully and understand the implications in your current
setup.
To make Sentinel setup easier, ee provide an [automated way to setup and run](#sentinel-setup-ee-only)
the Sentinel daemon with GitLab EE.
GitLab Enterprise Edition provides [automated way to setup and run](#sentinel-setup-ee-only) the Sentinel daemon.
#### Sentinel setup (Community Edition)
#### Sentinel setup
For GitLab CE, you need to install, configure, execute and monitor Sentinel
by yourself.
##### Community Edition
With GitLab Community Edition, you need to install, configure, execute and
monitor Sentinel from source. Omnibus GitLab Community Edition package does
not support Sentinel configuration.
Here is an example configuration file (`sentinel.conf`) for a minimal Sentinel
node:
A minimal configuration file (`sentinel.conf`) should contain the following:
```conf
bind 0.0.0.0 # bind to all interfaces or change to a specific IP
......@@ -322,35 +325,17 @@ sentinel config-epoch gitlab-redis 0
sentinel leader-epoch gitlab-redis 0
```
#### Sentinel setup (EE Only)
##### Enterprise Edition
To setup sentinel, you must edit `/etc/gitlab/gitlab.rb` file.
This is a minimal configuration required to run the daemon:
To setup sentinel, you edit `/etc/gitlab/gitlab.rb` file:
```ruby
redis['master_name'] = 'gitlab-redis' # must be the same in every sentinel node
redis['master_ip'] = '10.0.0.1' # ip of the initial master redis instance
redis['master_port'] = 6379 # port of the initial master redis instance
redis['master_password'] = 'your-secure-password-here' # the same value defined in redis['password'] in the master instance
sentinel['enable'] = true
# sentinel['port'] = 26379
## When you install Sentinel in a separate machine, you need to control which
## other services will be running in it. Take a look at the following variables
## and enable or disable whenever it fits your strategy:
## Quorum must reflect the amount of voting sentinels it take to start a failover.
sentinel['quorum'] = 2
## Consider unresponsive server down after x amount of ms.
# sentinel['down_after_milliseconds'] = 10000
# sentinel['failover_timeout'] = 60000
```
When you install Sentinel in a separate machine, you need to control which
other services will be running in it. Take a look at the following variables
and enable or disable whenever it fits your strategy:
```ruby
# Enabled Redis and Sentinel services
## Enabled Redis and Sentinel services
redis['enable'] = true
sentinel['enable'] = true
......@@ -364,10 +349,53 @@ postgresql['enable'] = false
gitlab_workhorse['enable'] = false
gitlab_rails['enable'] = false
mailroom['enable'] = false
```
Remember that enabling a new service may also require additional configuration
params (like `redis` for example).
## Configure Redis
redis['master_name'] = 'gitlab-redis' # must be the same in every sentinel node
redis['master_ip'] = '10.0.0.1' # ip of the initial master redis instance
redis['master_port'] = 6379 # port of the initial master redis instance
redis['master_password'] = 'your-secure-password-here' # the same value defined in redis['password'] in the master instance
## Configure Sentinel
# sentinel['port'] = 26379 # uncomment to change default port
## Quorum must reflect the amount of voting sentinels it take to start a failover.
## Value must NOT be greater then the ammount of sentinels.
##
## The quorum can be used to tune Sentinel in two ways:
## 1. If a the quorum is set to a value smaller than the majority of Sentinels
## we deploy, we are basically making Sentinel more sensible to master failures,
## triggering a failover as soon as even just a minority of Sentinels is no longer
## able to talk with the master.
## 1. If a quorum is set to a value greater than the majority of Sentinels, we are
## making Sentinel able to failover only when there are a very large number (larger
## than majority) of well connected Sentinels which agree about the master being down.s
sentinel['quorum'] = 2
## Consider unresponsive server down after x amount of ms.
# sentinel['down_after_milliseconds'] = 10000
## Specifies the failover timeout in milliseconds. It is used in many ways:
##
## - The time needed to re-start a failover after a previous failover was
## already tried against the same master by a given Sentinel, is two
## times the failover timeout.
##
## - The time needed for a slave replicating to a wrong master according
## to a Sentinel current configuration, to be forced to replicate
## with the right master, is exactly the failover timeout (counting since
## the moment a Sentinel detected the misconfiguration).
##
## - The time needed to cancel a failover that is already in progress but
## did not produced any configuration change (SLAVEOF NO ONE yet not
## acknowledged by the promoted slave).
##
## - The maximum time a failover in progress waits for all the slaves to be
## reconfigured as slaves of the new master. However even after this time
## the slaves will be reconfigured by the Sentinels anyway, but not with
## the exact parallel-syncs progression as specified.
# sentinel['failover_timeout'] = 60000
```
---
......@@ -409,9 +437,74 @@ The following steps should be performed in the [GitLab application server](gitla
1. [Reconfigure] the GitLab for the changes to take effect.
### Sentinel troubleshooting
## Troubleshooting
There are a lot of moving parts that needs to be taken care carefully
in order for the HA setup to work as expected.
Before proceeding with the troubleshooting below, check your firewall
rules:
- Redis machines
- Accept TCP connection in `6379`
- Connect to the other Redis machines via TCP in `6379`
- Sentinel machines
- Accept TCP connection in `26379`
- Connect to other Sentinel machines via TCP in `26379`
- Connect to the Redis machines via TCP in `6379`
### Redis replication
You can check if everything is correct by connecting to each server using
`redis-cli` application, and sending the `INFO` command.
If authentication was correctly defined, it should fail with:
`NOAUTH Authentication required` error. Try to authenticate with the
previous defined password with `AUTH redis-password-goes-here` and
try the `INFO` command again.
Look for the `# Replication` section where you should see some important
information like the `role` of the server.
When connected to a `master` redis, you will see the number of connected
`slaves`, and a list of each with connection details:
```
# Replication
role:master
connected_slaves:1
slave0:ip=10.133.5.21,port=6379,state=online,offset=208037514,lag=1
master_repl_offset:208037658
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:206989083
repl_backlog_histlen:1048576
```
When it's a `slave`, you will see details of the master connection and if
its `up` or `down`:
```
# Replication
role:slave
master_host:10.133.1.58
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:208096498
slave_priority:100
slave_read_only:1
connected_slaves:0
master_repl_offset:0
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0
```
### Sentinel
#### Omnibus install
#### Omnibus GitLab
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
......@@ -424,7 +517,7 @@ The way the redis connector `redis-rb` works with sentinel is a bit
non-intuitive. We try to hide the complexity in omnibus, but it still requires
a few extra configs.
#### Source install
#### Install from Source
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
......
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