Refactor Redis HA docs

[ci skip]

doc/administration/high_availability/redis.md

@@ -17,10 +17,11 @@ Omnibus GitLab packages.
   before configuring Redis HA with GitLab to fully understand the topology and
   architecture.
 - This is the documentation for the Omnibus GitLab packages. For installations
-  from source, follow the [Redis HA source install](redis_source.md) guide.
+  from source, follow the [Redis HA source installation](redis_source.md) guide.
 - Redis Sentinel daemon is bundled with Omnibus GitLab Enterprise Edition only.
-  For the Omnibus Community Edition and installations from source, follow the
-  [Redis HA source install](redis_source.md) guide.
+  For configuring Sentinel with the Omnibus GitLab Community Edition and
+  installations from source, follow the
+  [Redis HA source installation](redis_source.md) guide.
 
 <!-- START doctoc generated TOC please keep comment here to allow auto update -->
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
@@ -31,16 +32,15 @@ Omnibus GitLab packages.
   - [High Availability with Sentinel](#high-availability-with-sentinel)
   - [Recommended setup](#recommended-setup)
   - [Available configuration setups](#available-configuration-setups)
-  - [Using a non-Omnibus external Redis server](#using-a-non-omnibus-external-redis-server)
   - [Redis setup overview](#redis-setup-overview)
   - [Sentinel setup overview](#sentinel-setup-overview)
-- [Redis HA configuration](#redis-ha-configuration)
-  - [Configuring the Master Redis instance](#configuring-the-master-redis-instance)
-  - [Configuring the Slave Redis instances](#configuring-the-slave-redis-instances)
-  - [Configuring the Sentinel instances](#configuring-the-sentinel-instances)
-  - [Configuring the GitLab application](#configuring-the-gitlab-application)
+- [Configuring Redis HA](#configuring-redis-ha)
+  - [Step 1. Configuring the Master Redis instance](#step-1-configuring-the-master-redis-instance)
+  - [Step 2. Configuring the Slave Redis instances](#step-2-configuring-the-slave-redis-instances)
+  - [Step 3. Configuring the Redis Sentinel instances](#step-3-configuring-the-redis-sentinel-instances)
+  - [Step 4. Configuring the GitLab application](#step-4-configuring-the-gitlab-application)
 - [Switching from an existing single-machine installation to Redis HA](#switching-from-an-existing-single-machine-installation-to-redis-ha)
-- [Minimal example configuration with 1 master, 2 slaves and 3 sentinels](#minimal-example-configuration-with-1-master-2-slaves-and-3-sentinels)
+- [Example of a minimal configuration with 1 master, 2 slaves and 3 sentinels](#example-of-a-minimal-configuration-with-1-master-2-slaves-and-3-sentinels)
   - [Configuration for Redis master](#configuration-for-redis-master)
   - [Configuration for Redis slaves](#configuration-for-redis-slaves)
   - [Configuration for Sentinels](#configuration-for-sentinels)
@@ -50,6 +50,7 @@ Omnibus GitLab packages.
   - [Troubleshooting Redis replication](#troubleshooting-redis-replication)
   - [Troubleshooting Sentinel](#troubleshooting-sentinel)
 - [Changelog](#changelog)
+  - [Experimental Redis Sentinel support](#experimental-redis-sentinel-support)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 
@@ -59,8 +60,6 @@ Before diving into the details of setting up Redis and Redis Sentinel for HA,
 make sure you read this Overview section to better understand how the components
 are tied together.
 
-### Prerequisites
-
 You need at least `3` independent machines: physical, or VMs running into
 distinct physical machines. It is essential that all master and slaves Redis
 instances run in different machines. If you fail to provision the machines in
@@ -84,16 +83,16 @@ components below.
 - Starting with GitLab `8.11`, you can configure a list of Redis Sentinel
   servers that will monitor a group of Redis servers to provide failover support.
 - Starting with GitLab `8.14`, the Omnibus GitLab Enterprise Edition package
-  comes with Redis sentinel daemon support.
+  comes with Redis Sentinel daemon support.
 
 High Availability with Redis requires a few things:
 
 - Multiple Redis instances
-- Run Redis in a **Master** x **Slave** topology
-- Multiple Sentinel instances
+  - Run Redis in a **Master** x **Slave** topology
+  - Multiple Sentinel instances
 - Application support and visibility to all Sentinel and Redis instances
 
-Redis Sentinel can handle the most important tasks in a HA environment and that's
+Redis Sentinel can handle the most important tasks in an HA environment and that's
 to help keep servers online with minimal to no downtime. Redis Sentinel:
 
 - Monitors **Master** and **Slaves** instances to see if they are available
@@ -120,7 +119,8 @@ For a minimal setup, you will install the Omnibus GitLab package in `3`
 - Redis Slave + Sentinel
 
 If you are not sure or don't understand why and where the amount of nodes come
-from, read [Redis Setup](#redis-setup) and [Sentinel Setup](#sentinel-setup).
+from, read [Redis setup overview](#redis-setup-overview) and
+[Sentinel setup overview](#sentinel-setup-overview).
 
 For a recommended setup that can resist more failures, you will install
 the Omnibus GitLab package in `5` **independent** machines, both with
@@ -149,24 +149,9 @@ Pick the one that suits your needs.
   are bundled, so you can use the EE package to setup the whole Redis HA
   infrastructure (master, slave and Sentinel).
 
-Note that if you have installed GitLab using the Omnibus GitLab packages (both
-CE and EE), you can also use an [external Redis server](#using-a-non-omnibus-external-redis-server).
-
-### Using a non-Omnibus external 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.
-
-Managed services can provide High Availability using their own proprietary
-technology and provide a transparent proxy (which means that GitLab doesn't
-need any additional change) or they will use Sentinel and manage it for you.
-
-If your provider uses Sentinel, see [GitLab Setup](#gitlab-setup)
-to understand where you need to provide the list of servers and credentials.
-
-If you want to setup Redis by yourself, without using Omnibus, you can
-read the documentation on [configuring Redis HA for source installs](redis_source.md).
+Note that even if you have installed GitLab using the Omnibus GitLab packages
+(both CE and EE), you can still use an
+[external Redis server](#using-a-non-omnibus-external-redis-server).
 
 ### Redis setup overview
 
@@ -197,13 +182,13 @@ each other over the network.
 
 ### Sentinel setup overview
 
-Sentinels watch both other sentinels and Redis nodes. Whenever a Sentinel
+Sentinels watch both other Sentinels and Redis nodes. Whenever a Sentinel
 detects that a Redis node is not responding, it will announce that to the
-other sentinels. They have to reach the **quorum**, the minimum amount of
-sentinels that agrees that a node is down, to be able to start a failover.
+other Sentinels. They have to reach the **quorum**, that is the minimum amount
+of Sentinels that agrees a node is down, in order to be able to start a failover.
 
-Whenever the **quorum** is met, you need the **majority** of all known
-Sentinel nodes to be available and reachable, to elect the Sentinel **leader**
+Whenever the **quorum** is met, the **majority** of all known Sentinel nodes
+need to be available and reachable, so that they can elect the Sentinel **leader**
 who will take all the decisions to restore the service availability by:
 
 - Promoting a new **Master**
@@ -212,7 +197,8 @@ who will take all the decisions to restore the service availability by:
 - Reconfigure the old **Master** and demote to **Slave** when it comes back online
 
 You must have at least `3` Redis Sentinel servers, and they need to
-be each in a independent machine (that are believed to fail independently).
+be each in a independent machine (that are believed to fail independently),
+ideally in different geographical areas.
 
 You can configure them in the same machines where you've configured the other
 Redis servers, but understand that if a whole node goes down, you loose both
@@ -230,7 +216,7 @@ Here are some examples:
 - With `5` or `6` sentinels, a maximum of `2` can go down for a failover begin.
 - With `7` sentinels, a maximum of `3` nodes can go down.
 
-The **Leader** election can sometimes fail the voting round when **consensus**,
+The **Leader** election can sometimes fail the voting round when **consensus**
 is not achieved (see the odd number of nodes requirement above). In that case,
 a new attempt will be made after the amount of time defined in
 `sentinel['failover_timeout']` (in milliseconds).
@@ -238,7 +224,7 @@ a new attempt will be made after the amount of time defined in
 >**Note:**
 We will see where `sentinel['failover_timeout']` is defined later.
 
-The `failover_timeout` variable has a lot of different use cases, according to
+The `failover_timeout` variable has a lot of different use cases. According to
 the official documentation:
 
 - The time needed to re-start a failover after a previous failover was
@@ -259,7 +245,7 @@ the official documentation:
   the slaves will be reconfigured by the Sentinels anyway, but not with
   the exact parallel-syncs progression as specified.
 
-## Redis HA configuration
+## Configuring Redis HA
 
 This is the section where we install and setup the new Redis instances.
 
@@ -271,95 +257,138 @@ This is the section where we install and setup the new Redis instances.
   `redis['password']`. At any time during a failover the Sentinels can
   reconfigure a node and change its status from master to slave and vice versa.
 
-A summary of what are we going to do:
+### Prerequisites
+
+The prerequisites for a HA Redis setup are the following:
 
-1. Provision the required number of instances specified previously:
-   - You can opt to install Redis and Sentinel in the same machine or each in
-     independent ones.
-   - Don't install Redis and Sentinel in the same machines your GitLab application
-     is running on.
-   - All machines must be able to talk to each other and accept incoming
+1. Provision the minimum required number of instances as specified in the
+   [recommended setup](#recommended-setup) section.
+1. **Do NOT** install Redis or Redis Sentinel in the same machines your
+   GitLab application is running on. You can however opt in to install Redis
+   and Sentinel in the same machine (each in independent ones is recommended
+   though).
+1. All Redis nodes must be able to talk to each other and accept incoming
    connections over Redis (`6379`) and Sentinel (`26379`) ports (unless you
-     change the default ports).
-   - GitLab machines must be able to access these machines and with the same
-     permissions.
-   - Protect them from access from external networks (Internet),
-     to harden the security.
-
-1. Download/install Omnibus GitLab using **steps 1 and 2** from
-   [GitLab downloads](https://about.gitlab.com/downloads) in each node.
-   - Do not complete other steps on the download page.
+   change the default ones).
+1. The server that hosts the GitLab application must be able to access the
+   Redis nodes.
+1. Protect the nodes from access from external networks (Internet), using
+   firewall.
+
+### Step 1. Configuring the master Redis instance
+
+1. SSH into the **master** Redis server and login as root:
+
+    ```
+    sudo -i
+    ```
+
+1. [Download/install](https://about.gitlab.com/installation) the Omnibus GitLab
+   package using **steps 1 and 2** from the GitLab downloads page.
      - Make sure you select the correct Omnibus package, with the same version
        and type (Community, Enterprise editions) of your current install.
+     - Do not complete any other steps on the download page.
 
-1. Run `touch /etc/gitlab/skip-auto-migrations` to prevent database migrations
-   from running on upgrade. Only the primary GitLab application server should
-   handle migrations.
+1. Edit `/etc/gitlab/gitlab.rb` and add the contents:
 
-1. Edit `/etc/gitlab/gitlab.rb` and make the changes based on the
-   [Example Configurations](#example-configurations).
+    ```ruby
+    # Enable the master role and disable all other services in the machine
+    # (you can still enable Sentinel).
+    redis_master_role['enable'] = true
+
+    # IP address pointing to a local IP that the other machines can reach to.
+    # You can also set bind to '0.0.0.0' which listen in all interfaces.
+    # If you really need to bind to an external accessible IP, make
+    # sure you add extra firewall rules to prevent unauthorized access.
+    redis['bind'] = '10.0.0.1'
+
+    # Define a port so Redis can listen for TCP requests which will allow other
+    # machines to connect to it.
+    redis['port'] = 6379
+
+    # Set up password authentication for Redis (use the same password in all nodes).
+    redis['password'] = 'redis-password-goes-here'
+    ```
 
-### Configuring the Master Redis instance
+1. To prevent database migrations from running on upgrade, run:
 
-You will need to configure the following in `/etc/gitlab/gitlab.rb`:
+    ```
+    touch /etc/gitlab/skip-auto-migrations
+    ```
 
-1. Define `redis_master_role['enable']` to `true`, to disable other services
-   in the machine (you can still enable Sentinel)
+    Only the primary GitLab application server should handle migrations.
 
-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 accessible IP, make
-   sure you add extra firewall rules to prevent unauthorized access.
-   - You can also set bind to `0.0.0.0` which listen in all interfaces.
+1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
 
-1. Define a `redis['port']` so redis can listen for TCP requests which will
-   allow other machines to connect to it.
+### Step 2. Configuring the slave Redis instances
 
-1. Set up a password authentication with `redis['password']` and
-   `redis['master_password']` (use the same password in all nodes).
+1. SSH into the **slave** Redis server and login as root:
 
-1. [Reconfigure Omnibus GitLab][reocnfigure] for the changes to take effect.
+    ```
+    sudo -i
+    ```
 
-### Configuring the Slave Redis instances
+1. [Download/install](https://about.gitlab.com/installation) the Omnibus GitLab
+   package using **steps 1 and 2** from the GitLab downloads page.
+     - Make sure you select the correct Omnibus package, with the same version
+       and type (Community, Enterprise editions) of your current install.
+     - Do not complete any other steps on the download page.
+
+1. Edit `/etc/gitlab/gitlab.rb` and add the contents:
 
-You will need to configure the following in `/etc/gitlab/gitlab.rb`:
+    ```ruby
+    # Enable the slave role and disable all other services in the machine
+    # (you can still enable Sentinel). This will also set automatically
+    # `redis['master'] = false`.
+    redis_slave_role['enable'] = true
+
+    # IP address pointing to a local IP that the other machines can reach to.
+    # You can also set bind to '0.0.0.0' which listen in all interfaces.
+    # If you really need to bind to an external accessible IP, make
+    # sure you add extra firewall rules to prevent unauthorized access.
+    redis['bind'] = '10.0.0.2'
 
-1. Define `redis_slaves_role['enable']` to `true`, to disable other services
-   in the machine (you can still enable Sentinel)
-   - This will also set automatically `redis['master'] = false`.
 
-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 accessible IP, make
-   sure you add extra firewall rules to prevent unauthorized access.
-   - You can also set bind to `0.0.0.0` which listen in all interfaces.
+    # Define a port so Redis can listen for TCP requests which will allow other
+    # machines to connect to it.
+    redis['port'] = 6379
 
-1. Define a `redis['port']` so redis can listen for TCP requests which will
-   allow other machines to connect to it.
+    # The same password for Redeis authentication you set up for the master node.
+    redis['password'] = 'redis-password-goes-here'
 
-1. Set up a password authentication with `redis['password']` and
-   `redis['master_password']` (use the same password in all nodes).
+    # The IP of the master Redis node.
+    redis['master_ip'] = '10.0.0.1'
 
-1. Define `redis['master_ip']` with the IP of the **Master** Redis.
+    # Port of master Redis server, uncomment to change to non default. Defaults
+    # to `6379`.
+    #redis['master_port'] = 6379
+    ```
 
-1. Define `redis['master_port']` with the port of the **Master** Redis (default to `6379`).
+1. To prevent database migrations from running on upgrade, run:
 
-Initial **Slave** nodes require `redis['master']` defined to `false` and
-`redis['master_ip']` pointing to the initial **Master**. If you use the
-simplified configuration by enabling `redis_slave_role['enable']`, you
-just need to fill in the `redis['master_ip']`.
+    ```
+    touch /etc/gitlab/skip-auto-migrations
+    ```
+
+    Only the primary GitLab application server should handle migrations.
+
+1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
+1. Go through the steps again for all the other slave nodes.
 
-This values don't have to be changed again in `/etc/gitlab/gitlab.rb` after
+---
+
+These values don't have to be changed again in `/etc/gitlab/gitlab.rb` after
 a failover, as the nodes will be managed by the Sentinels, and even after a
 `gitlab-ctl reconfigure`, they will get their configuration restored by
 the same Sentinels.
 
-### Configuring the Redis Sentinel instances
+### Step 3. Configuring the Redis Sentinel instances
 
 >**Note:**
-- Redis Sentinel is bundled with Omnibus GitLab Enterprise Edition only. For the
-  Omnibus Community Edition and installations from source, follow the
-  [Redis HA source install](redis_source.md) guide.
+Redis Sentinel is bundled with Omnibus GitLab Enterprise Edition only. The
+following section assumes you are using Omnibus GitLab Enterprise Edition.
+For the Omnibus Community Edition and installations from source, follow the
+[Redis HA source install](redis_source.md) guide.
 
 Now that the Redis servers are all set up, let's configure the Sentinel
 servers.
@@ -369,15 +398,112 @@ correctly, please read the [Troubleshooting Replication](#troubleshooting-replic
 and fix it before proceeding with Sentinel setup.
 
 You must have at least `3` Redis Sentinel servers, and they need to
-be each in a independent machine. You can configure them in the same
+be each in an independent machine. You can configure them in the same
 machines where you've configured the other Redis servers.
 
-With GitLab Enterprise Edition, you can use the Omnibus package to setup multiple
-machines with the Sentinel daemon.
+With GitLab Enterprise Edition, you can use the Omnibus package to setup
+multiple machines with the Sentinel daemon.
+
+---
+
+1. SSH into the server that will host Redis Sentinel and login as root:
 
-See [example configuration](#configuration-for-sentinel-ee-only) below.
+    ```
+    sudo -i
+    ```
 
-### Configuring the GitLab application
+1. **You can omit this step if the Sentinels will be hosted in the same node as
+   the other Redis instances.**
+
+     [Download/install](https://about.gitlab.com/downloads-ee) the
+     Omnibus GitLab Enterprise Edition package using **steps 1 and 2** from the
+     GitLab downloads page.
+       - Make sure you select the correct Omnibus package, with the same version
+         the GitLab application is running.
+       - Do not complete any other steps on the download page.
+
+1. Edit `/etc/gitlab/gitlab.rb` and add the contents (if you are installing the
+   Sentinels in the same node as the other Redis instances, some values might
+   be duplicate below):
+
+
+    ```ruby
+    redis_sentinel_role['enable'] = true
+
+    # Must be the same in every sentinel node
+    redis['master_name'] = 'gitlab-redis'
+
+    # The same password for Redis authentication you set up for the master node.
+    redis['password'] = 'redis-password-goes-here'
+
+    # The IP of the master Redis node.
+    redis['master_ip'] = '10.0.0.1'
+
+    # Define a port so Redis can listen for TCP requests which will allow other
+    # machines to connect to it.
+    redis['port'] = 6379
+
+    # Port of master Redis server, uncomment to change to non default. Defaults
+    # to `6379`.
+    #redis['master_port'] = 6379
+
+    ## Configure Sentinel
+    sentinel['bind'] = '10.0.0.1'
+
+    # Port that Sentinel listens on, uncomment to change to non default. Defaults
+    # to `26379`.
+    # sentinel['port'] = 26379
+
+    ## Quorum must reflect the amount of voting sentinels it take to start a failover.
+    ## Value must NOT be greater then the amount 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
+    ```
+
+1. To prevent database migrations from running on upgrade, run:
+
+    ```
+    touch /etc/gitlab/skip-auto-migrations
+    ```
+
+    Only the primary GitLab application server should handle migrations.
+
+1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
+1. Go through the steps again for all the other Sentinel nodes.
+
+### Step 4. Configuring the GitLab application
 
 The final part is to inform the main GitLab application server of the Redis
 Sentinels servers and authentication credentials.
@@ -395,14 +521,23 @@ which ideally should not have Redis or Sentinels on it for a HA setup.
 
 1. Edit `/etc/gitlab/gitlab.rb` and add/change the following lines:
 
-  - `redis['master_name']` - this is the `master-group-name` from sentinel (default: `gitlab-redis`)
-  - `redis['master_password']` - the same password you've defined before for Redis and Sentinels
-  - `gitlab_rails['redis_sentinels']` - a list of sentinels with `host` and `port`
+    ```
+    # Must be the same in every sentinel node
+    redis['master_name'] = 'gitlab-redis'
+
+    # The same password for Redis authentication you set up for the master node.
+    redis['password'] = 'redis-password-goes-here'
+
+    # A list of sentinels with `host` and `port`
+    gitlab_rails['redis_sentinels'] = [
+      {'host' => '10.0.0.1', 'port' => 26379},
+      {'host' => '10.0.0.2', 'port' => 26379},
+      {'host' => '10.0.0.3', 'port' => 26379}
+    ]
+    ```
 
 1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
 
-See [example configuration](#configuration-for-gitlab) below.
-
 ## Switching from an existing single-machine installation to Redis HA
 
 If you already have a single-machine GitLab install running, you will need to
@@ -436,14 +571,15 @@ unauthorized access from other machines and block traffic from the
 outside (Internet).
 
 We will use the same `3` nodes with **Redis** + **Sentinel** topology
-discussed in [Redis Setup](#redis-setup) and [Sentinel Setup](#sentinel-setup)
-documentation.
+discussed in [Redis setup overview](#redis-setup-overview) and
+[Sentinel setup overview](#sentinel-setup-overview) documentation.
 
 Here is a list and description of each **machine** and the assigned **IP**:
 
 * `10.0.0.1`: Redis Master + Sentinel 1
 * `10.0.0.2`: Redis Slave 1 + Sentinel 2
-* `10.0.0.2`: Redis Slave 2 + Sentinel 3
+* `10.0.0.3`: Redis Slave 2 + Sentinel 3
+* `10.0.0.4`: GitLab application
 
 Please note that after the initial configuration, if a failover is initiated
 by the Sentinel nodes, the Redis nodes will be reconfigured and the **Master**
@@ -454,7 +590,7 @@ The same thing will happen with `sentinel.conf` that will be overridden after th
 initial execution, after any new sentinel node starts watching the **Master**,
 or a failover promotes a different **Master** node.
 
-### Configuration for Redis master
+### Example configuration for Redis master
 
 **Example configation for Redis Master:**
 
@@ -466,14 +602,13 @@ redis_master_role['enable'] = true
 redis['bind'] = '10.0.0.1'
 redis['port'] = 6379
 redis['password'] = 'redis-password-goes-here'
-redis['master_password'] = 'redis-password-goes-here'
 ```
 
 [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
 
-### Configuration for Redis slaves
+### Example configuration for Redis slaves
 
-**Example configation for Slave 1:**
+**Example configuration for Slave 1:**
 
 In `/etc/gitlab/gitlab.rb`:
 
@@ -489,9 +624,9 @@ redis['master_ip'] = '10.0.0.1' # IP of master Redis server
 #redis['master_port'] = 6379 # Port of master Redis server, uncomment to change to non default
 ```
 
-Reconfigure Omnibus GitLab for the changes to take effect: `sudo gitlab-ctl reconfigure`
+[Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
 
-**Example configation for Slave 2:**
+**Example configuration for Slave 2:**
 
 In `/etc/gitlab/gitlab.rb`:
 
@@ -509,7 +644,7 @@ redis['master_ip'] = '10.0.0.1' # IP of master Redis server
 
 [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
 
-### Configuration for Sentinels
+### Example configuration for Sentinels
 
 >**Note:**
 Redis Sentinel is bundled with Omnibus GitLab Enterprise Edition only. For the
@@ -519,7 +654,7 @@ Omnibus Community Edition and installations from source, follow the
 Please note that some of the variables are already configured previously
 as they are required for Redis replication.
 
-**Example configation for Sentinel 1:**
+**Example configuration for Sentinel 1:**
 
 In `/etc/gitlab/gitlab.rb`:
 
@@ -534,46 +669,17 @@ redis['master_ip'] = '10.0.0.1' # ip of the initial master redis instance
 ## Configure Sentinel
 sentinel['bind'] = '10.0.0.1'
 # 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
 ```
 
-**Example configation for Sentinel 2:**
+[Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
+
+**Example configuration for Sentinel 2:**
 
 In `/etc/gitlab/gitlab.rb`:
 
@@ -589,45 +695,17 @@ redis['master_ip'] = '10.0.0.1' # ip of the initial master redis instance
 sentinel['bind'] = '10.0.0.2'
 # 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
 ```
 
-**Example configation for Sentinel 3:**
+[Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
+
+**Example configuration for Sentinel 3:**
 
 In `/etc/gitlab/gitlab.rb`:
 
@@ -643,44 +721,37 @@ redis['master_ip'] = '10.0.0.1' # ip of the initial master redis instance
 sentinel['bind'] = '10.0.0.3'
 # 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
 ```
 
+[Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
+
+### Example configuration for the GitLab application
+
+In `/etc/gitlab/gitlab.rb`:
+
+```
+# Must be the same in every sentinel node
+redis['master_name'] = 'gitlab-redis'
+
+# The same password for Redis authentication you set up for the master node.
+redis['password'] = 'redis-password-goes-here'
+
+# A list of sentinels with `host` and `port`
+gitlab_rails['redis_sentinels'] = [
+  {'host' => '10.0.0.1', 'port' => 26379},
+  {'host' => '10.0.0.2', 'port' => 26379},
+  {'host' => '10.0.0.3', 'port' => 26379}
+]
+```
+
+[Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.
+
 ## Advanced configuration
 
 Omnibus GitLab configures some things behind the curtains to make the sysadmins'
@@ -688,8 +759,8 @@ lives easier. If you want to know what happens underneath keep reading.
 
 ### Control running services
 
-In the previous example above we've used `redis_sentinel_role` and
-`redis_master_role` which simplify the amount of configuration changes.
+In the previous example, we've used `redis_sentinel_role` and
+`redis_master_role` which simplifies the amount of configuration changes.
 
 If you want more control, here is what each one sets for you automatically
 when enabled:
@@ -698,10 +769,10 @@ when enabled:
 ## Redis Sentinel Role
 redis_sentinel_role['enable'] = true
 
-# When Sentinel Role is enabled, the following services are enabled/disabled:
+# When Sentinel Role is enabled, the following services are also enabled
 sentinel['enable'] = true
 
-# This others are disabled:
+# The following services are disabled
 redis['enable'] = false
 bootstrap['enable'] = false
 nginx['enable'] = false
@@ -709,17 +780,17 @@ postgresql['enable'] = false
 gitlab_rails['enable'] = false
 mailroom['enable'] = false
 
-## Redis master/slave Role:
+-------
+
+## Redis master/slave Role
 redis_master_role['enable'] = true # enable only one of them
 redis_slave_role['enable'] = true # enable only one of them
 
-# When Redis Master or Slave role are enabled, the following services are enabled/disabled:
-# (Note that if redis and sentinel roles are combined both services will be enabled)
+# When Redis Master or Slave role are enabled, the following services are
+# enabled/disabled. Note that if Redis and Sentinel roles are combined, both
+# services will be enabled.
 
-# When Sentinel Role is enabled, the following services are enabled/disabled:
-redis['enable'] = true
-
-# This others are disabled:
+# The following services are disabled
 sentinel['enable'] = false
 bootstrap['enable'] = false
 nginx['enable'] = false
@@ -727,7 +798,7 @@ postgresql['enable'] = false
 gitlab_rails['enable'] = false
 mailroom['enable'] = false
 
-# Redis Slave role also change this setting from default 'true' to 'false':
+# For Redis Slave role, also change this setting from default 'true' to 'false':
 redis['master'] = false
 ```
 
@@ -856,6 +927,16 @@ To make sure your configuration is correct:
 
 Changes to Redis HA over time.
 
+**8.14**
+
+- Redis Sentinel support is production-ready and bundled in the Omnibus GitLab
+  Enterprise Edition package
+- Documentation restructure for better readability
+
+**8.11**
+
+- Experimental Redis Sentinel support was added
+
 ### Experimental Redis Sentinel support
 
 >
@@ -880,7 +961,7 @@ Read more on high-availability configuration:
 [gh-534]: https://github.com/redis/redis-rb/issues/534
 [redis]: http://redis.io/
 [sentinel]: http://redis.io/topics/sentinel
-[omnifile]: https://gitlab.com/gitlab-org/omnibus-gitlab/blob/82b7345b150f072c8673c79738ce893f92d0d652/files/gitlab-cookbooks/gitlab/libraries/gitlab_rails.rb#L134-159
+[omnifile]: https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/files/gitlab-cookbooks/gitlab/libraries/gitlab_rails.rb
 [source]: ../../install/installation.md
 [ce]: https://about.gitlab.com/downloads
 [ee]: https://about.gitlab.com/downloads-ee