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author | Achilleas Pipinellis <axilleas@axilleas.me> | 2016-11-16 15:51:00 +0300 |
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committer | Achilleas Pipinellis <axilleas@axilleas.me> | 2016-11-16 15:51:00 +0300 |
commit | a9f7ce47f9f0752e312340e1e7db7e59c0597652 (patch) | |
tree | caeb290ab255bb91979a25ffaafc47e720cce69c /doc | |
parent | 95f6cf339a8c0f5d63178a92eaef2d02bcfb297f (diff) | |
parent | 850405b42ef408785c6133ab7ba9c7f7303f18b6 (diff) |
Merge branch 'doc/sentinel' of gitlab.com:gitlab-org/gitlab-ce into doc/sentinel
Diffstat (limited to 'doc')
-rw-r--r-- | doc/administration/high_availability/README.md | 33 | ||||
-rw-r--r-- | doc/administration/high_availability/redis.md | 1017 | ||||
-rw-r--r-- | doc/administration/high_availability/redis_source.md | 387 |
3 files changed, 1107 insertions, 330 deletions
diff --git a/doc/administration/high_availability/README.md b/doc/administration/high_availability/README.md index d74a786ac24..d5a5aef7ec0 100644 --- a/doc/administration/high_availability/README.md +++ b/doc/administration/high_availability/README.md @@ -7,19 +7,10 @@ highly available. ## Architecture -### Active/Passive - -For pure high-availability/failover with no scaling you can use an -active/passive configuration. This utilizes DRBD (Distributed Replicated -Block Device) to keep all data in sync. DRBD requires a low latency link to -remain in sync. It is not advisable to attempt to run DRBD between data centers -or in different cloud availability zones. +There are two kinds of setups: -Components/Servers Required: - -- 2 servers/virtual machines (one active/one passive) - -![Active/Passive HA Diagram](../img/high_availability/active-passive-diagram.png) +- active/active +- active/passive ### Active/Active @@ -28,12 +19,24 @@ user requests simultaneously. The database, Redis, and GitLab application are all deployed on separate servers. The configuration is **only** highly-available if the database, Redis and storage are also configured as such. -![Active/Active HA Diagram](../img/high_availability/active-active-diagram.png) - -**Steps to configure active/active:** +Follow the steps below to configure an active/active setup: 1. [Configure the database](database.md) 1. [Configure Redis](redis.md) 1. [Configure NFS](nfs.md) 1. [Configure the GitLab application servers](gitlab.md) 1. [Configure the load balancers](load_balancer.md) + +![Active/Active HA Diagram](../img/high_availability/active-active-diagram.png) + +### Active/Passive + +For pure high-availability/failover with no scaling you can use an +active/passive configuration. This utilizes DRBD (Distributed Replicated +Block Device) to keep all data in sync. DRBD requires a low latency link to +remain in sync. It is not advisable to attempt to run DRBD between data centers +or in different cloud availability zones. + +Components/Servers Required: 2 servers/virtual machines (one active/one passive) + +![Active/Passive HA Diagram](../img/high_availability/active-passive-diagram.png) diff --git a/doc/administration/high_availability/redis.md b/doc/administration/high_availability/redis.md index e416514bedf..a87c1dde55d 100644 --- a/doc/administration/high_availability/redis.md +++ b/doc/administration/high_availability/redis.md @@ -1,417 +1,809 @@ # 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. +High Availability with [Redis] is possible using a **Master** x **Slave** +topology with a [Redis Sentinel][sentinel] service to watch and automatically +start the failover procedure. -> **Note:** Redis does not require authentication by default. See +You can choose to install and manage Redis and Sentinel yourself, use +a hosted cloud solution or you can use the one that comes bundled with +Omnibus GitLab packages. + +> **Notes:** +- Redis requires authentication for High Availability. See [Redis Security](http://redis.io/topics/security) documentation for more information. We recommend using a combination of a Redis password and tight firewall rules to secure your Redis service. +- You are highly encouraged to read the [Redis Sentinel][sentinel] documentation + 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 installation](redis_source.md) guide. +- Redis Sentinel daemon is bundled with Omnibus GitLab Enterprise Edition only. + For configuring Sentinel with the Omnibus GitLab Community Edition and + installations from source, read the + [Available configuration setups](#available-configuration-setups) section + below. <!-- START doctoc generated TOC please keep comment here to allow auto update --> <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE --> **Table of Contents** -- [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 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) - - [GitLab setup](#gitlab-setup) - - [Sentinel troubleshooting](#sentinel-troubleshooting) - - [Omnibus install](#omnibus-install) - - [Source install](#source-install-1) +- [Overview](#overview) + - [High Availability with Sentinel](#high-availability-with-sentinel) + - [Recommended setup](#recommended-setup) + - [Redis setup overview](#redis-setup-overview) + - [Sentinel setup overview](#sentinel-setup-overview) + - [Available configuration setups](#available-configuration-setups) +- [Configuring Redis HA](#configuring-redis-ha) + - [Prerequisites](#prerequisites) + - [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) +- [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) + - [Example configuration for Redis master and Sentinel 1](#example-configuration-for-redis-master-and-sentinel-1) + - [Example configuration for Redis slave 1 and Sentinel 2](#example-configuration-for-redis-slave-1-and-sentinel-2) + - [Example configuration for Redis slave 2 and Sentinel 3](#example-configuration-for-redis-slave-2-and-sentinel-3) + - [Example configuration for the GitLab application](#example-configuration-for-the-gitlab-application) +- [Advanced configuration](#advanced-configuration) + - [Control running services](#control-running-services) +- [Troubleshooting](#troubleshooting) + - [Troubleshooting Redis replication](#troubleshooting-redis-replication) + - [Troubleshooting Sentinel](#troubleshooting-sentinel) +- [Changelog](#changelog) + - [Experimental Redis Sentinel support](#experimental-redis-sentinel-support) +- [Further reading](#further-reading) <!-- END doctoc generated TOC please keep comment here to allow auto update --> -## Configure your own Redis server +## Overview -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. +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. -## Configure Redis using Omnibus +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 +that specific way, any issue with the shared environment can bring your entire +setup down. -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. +It is OK to run a Sentinel along with a master or slave Redis instance. +No more than one Sentinel in the same machine though. -1. Download/install GitLab Omnibus 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. - Be sure to change the `external_url` to match your eventual GitLab front-end - URL: +You also need to take in consideration the underlying network topology, +making sure you have redundant connectivity between Redis / Sentinel and +GitLab instances, otherwise the networks will become a single point of +failure. - ```ruby - 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_rails['enable'] = false - gitlab_workhorse['enable'] = false - mailroom['enable'] = false - - # Redis configuration - redis['port'] = 6379 - redis['bind'] = '0.0.0.0' +Make sure that you read this document once as a whole before configuring the +components below. - # If you wish to use Redis authentication (recommended) - redis['password'] = 'redis-password-goes-here' - ``` +### High Availability with Sentinel -1. Run `sudo touch /etc/gitlab/skip-auto-migrations` to prevent database migrations - from running on upgrade. Only the primary GitLab application server should - handle migrations. +>**Notes:** +- 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 built-in. -1. Run `sudo gitlab-ctl reconfigure` to install and configure Redis. +High Availability with Redis requires a few things: - > **Note**: This `reconfigure` step will result in some errors. - That's OK - don't be alarmed. +- Multiple Redis instances +- Run Redis in a **Master** x **Slave** topology +- Multiple Sentinel instances +- Application support and visibility to all Sentinel and Redis instances -## Experimental Redis Sentinel support +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: -> [Introduced][ce-1877] in GitLab 8.11, improved in 8.13. +- Monitors **Master** and **Slaves** instances to see if they are available +- Promotes a **Slave** to **Master** when the **Master** fails +- Demotes a **Master** to **Slave** when the failed **Master** comes back online + (to prevent data-partitioning) +- Can be queried by clients to always connect to the current **Master** server -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. +When a **Master** fails to respond, it's the client's responsibility to handle +timeout and reconnect (querying a **Sentinel** for a new **Master**). To get a better understanding on how to correctly setup Sentinel, please read the [Redis Sentinel documentation](http://redis.io/topics/sentinel) first, as -failing to configure it correctly can lead to data loss. +failing to configure it correctly can lead to data loss or can bring your +whole cluster down, invalidating the failover effort. + +### Recommended setup + +For a minimal setup, you will install the Omnibus GitLab package in `3` +**independent** machines, both with **Redis** and **Sentinel**: -Redis Sentinel can handle the most important tasks in a HA environment to help -keep servers online with minimal to no downtime: +- Redis Master + Sentinel +- Redis Slave + Sentinel +- Redis Slave + Sentinel -- Monitors master and slave instances to see if they are available -- Promote a slave to master when the master fails. -- Demote a master to slave when failed master comes back online (to prevent - data-partitioning). -- Can be queried by clients to always connect to the correct master server. +If you are not sure or don't understand why and where the amount of nodes come +from, read [Redis setup overview](#redis-setup-overview) and +[Sentinel setup overview](#sentinel-setup-overview). -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. +For a recommended setup that can resist more failures, you will install +the Omnibus GitLab package in `5` **independent** machines, both with +**Redis** and **Sentinel**: -The configuration consists of three parts: +- Redis Master + Sentinel +- Redis Slave + Sentinel +- Redis Slave + Sentinel +- Redis Slave + Sentinel +- Redis Slave + Sentinel -- Setup Redis Master and Slave nodes -- Setup Sentinel nodes -- Setup GitLab +### Redis setup overview -> **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. +You must have at least `3` Redis servers: `1` Master, `2` Slaves, and they +need to be each in a independent machine (see explanation above). -Read carefully how to configure those components below. +You can have additional Redis nodes, that will help survive a situation +where more nodes goes down. Whenever there is only `2` nodes online, a failover +will not be initiated. -### Redis setup +As an example, if you have `6` Redis nodes, a maximum of `3` can be +simultaneously down. -You must have at least `3` Redis servers: `1` Master, `2` Slaves, and they need to -be each in a independent machine (see explanation above). +Please note that there are different requirements for Sentinel nodes. +If you host them in the same Redis machines, you may need to take +that restrictions into consideration when calculating the amount of +nodes to be provisioned. See [Sentinel setup overview](#sentinel-setup-overview) +documentation for more information. -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 +All Redis nodes should be configured the same way and with similar server specs, as +in a failover situation, any **Slave** can be promoted as the new **Master** by the Sentinel servers. -With Sentinel, you must define a password to protect the access as both -Sentinel instances and other redis instances should be able to talk to +The replication requires authentication, so you need to define a password to +protect all Redis nodes and the Sentinels. They will all share the same +password, and all instances must 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`. +### Sentinel setup overview -Initial `Slave` nodes will have in `redis.conf` an additional `slaveof` line -pointing to the initial `Master`. +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**, that is the minimum amount +of Sentinels that agrees a node is down, in order to be able to start a failover. -#### Source install +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: -**Master Redis instance** +- Promoting a new **Master** +- Reconfiguring the other **Slaves** and make them point to the new **Master** +- Announce the new **Master** to every other Sentinel peer +- Reconfigure the old **Master** and demote to **Slave** when it comes back online -You need to make the following changes in `redis.conf`: +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), +ideally in different geographical areas. -1. Define a `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: +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 +a Sentinel and a Redis instance. - ```conf - # By default, if no "bind" configuration directive is specified, Redis listens - # for connections from all the network interfaces available on the server. - # It is possible to listen to just one or multiple selected interfaces using - # the "bind" configuration directive, followed by one or more IP addresses. - # - # Examples: - # - # bind 192.168.1.100 10.0.0.1 - # bind 127.0.0.1 ::1 - bind 0.0.0.0 # This will bind to all interfaces - ``` +The number of sentinels should ideally always be an **odd** number, for the +consensus algorithm to be effective in the case of a failure. -1. Define a `port` to force redis to listin on TCP so other machines can - connect to it: +In a `3` nodes topology, you can only afford `1` Sentinel node going down. +Whenever the **majority** of the Sentinels goes down, the network partition +protection prevents destructive actions and a failover **will not be started**. - ```conf - # Accept connections on the specified port, default is 6379 (IANA #815344). - # If port 0 is specified Redis will not listen on a TCP socket. - port 6379 - ``` +Here are some examples: -1. Set up password authentication (use the same password in all nodes) +- 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. - ```conf - requirepass "redis-password-goes-here" - masterauth "redis-password-goes-here" - ``` +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). -1. Restart the Redis services for the changes to take effect. +>**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 official documentation: + +- 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. + +### Available configuration setups + +Based on your infrastructure setup and how you have installed GitLab, there are +multiple ways to configure Redis HA. Omnibus GitLab packages have Redis and/or +Redis Sentinel bundled with them so you only need to focus on configuration. +Pick the one that suits your needs. + +- [Installations from source][source]: You need to install Redis and Sentinel + yourself. Use the [Redis HA installation from source](redis_source.md) + documentation. +- [Omnibus GitLab **Community Edition** (CE) package][ce]: Redis is bundled, so you + can use the package with only the Redis service enabled as described in steps + 1 and 2 of this document (works for both master and slave setups). To install + and configure Sentinel, jump directly to the Sentinel section in the + [Redis HA installation from source](redis_source.md#step-3-configuring-the-redis-sentinel-instances) documentation. +- [Omnibus GitLab **Enterprise Edition** (EE) package][ee]: Both Redis and Sentinel + are bundled in the package, so you can use the EE package to setup the whole + Redis HA infrastructure (master, slave and Sentinel) which is described in + this document. +- If you have installed GitLab using the Omnibus GitLab packages (CE or EE), + but you want to use your own external Redis server, follow steps 1-3 in the + [Redis HA installation from source](redis_source.md) documentation, then go + straight to step 4 in this guide to + [set up the GitLab application](#step-4-configuring-the-gitlab-application). + +## Configuring Redis HA + +This is the section where we install and setup the new Redis instances. + +>**Notes:** +- We assume that you install GitLab and all HA components from scratch. If you + already have it installed and running, read how to + [switch from a single-machine installation to Redis HA](#switching-from-an-existing-single-machine-installation-to-redis-ha). +- Redis nodes (both master and slaves) will need the same password defined in + `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. + +### Prerequisites + +The prerequisites for a HA Redis setup are the following: + +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 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][it]), using + firewall. + +### Step 1. Configuring the master Redis instance + +1. SSH into the **master** Redis server and login as root: -**Slave Redis instance** + ``` + sudo -i + ``` -1. Follow same instructions from master with the extra change in `redis.conf`: +1. [Download/install](https://about.gitlab.com/installation) the Omnibus GitLab + package you want 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. - ```conf - # IP and port of the master Redis server - slaveof 10.10.10.10 6379 - ``` +1. Edit `/etc/gitlab/gitlab.rb` and add the contents: -1. Restart the Redis services for the changes to take effect. + ```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 -#### Omnibus Install + # Set up password authentication for Redis (use the same password in all nodes). + redis['password'] = 'redis-password-goes-here' + ``` -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`. +1. To prevent database migrations from running on upgrade, run: -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. + ``` + sudo touch /etc/gitlab/skip-auto-migrations + ``` -To disable redis in the single install, edit `/etc/gitlab/gitlab.rb`: + Only the primary GitLab application server should handle migrations. -```ruby -redis['enable'] = false -``` +1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. -**Master Redis instances** +### Step 2. Configuring the slave Redis instances -You need to make the following changes in `/etc/gitlab/gitlab.rb`: +1. SSH into the **slave** Redis server and login as root: -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 - password in all nodes). + ``` + sudo -i + ``` -```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' -redis['master_password'] = 'redis-password-goes-here' -``` +1. [Download/install](https://about.gitlab.com/installation) the Omnibus GitLab + package you want 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. -Reconfigure GitLab Omnibus for the changes to take effect: `sudo gitlab-ctl reconfigure` +1. Edit `/etc/gitlab/gitlab.rb` and add the contents: -**Slave Redis instances** + ```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' + + # Define a port so Redis can listen for TCP requests which will allow other + # machines to connect to it. + redis['port'] = 6379 -You need to make the same changes listed for the `Master` instance, -with an additional `Slave` section as in the example below: + # The same password for Redeis authentication you set up for the master node. + redis['password'] = 'redis-password-goes-here' -```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' -redis['master_password'] = 'redis-password-goes-here' + # The IP of the master Redis node. + redis['master_ip'] = '10.0.0.1' -## Slave redis instance -redis['master'] = false -redis['master_ip'] = '10.10.10.10' # IP of master Redis server -redis['master_port'] = 6379 # Port of master Redis server -``` + # Port of master Redis server, uncomment to change to non default. Defaults + # to `6379`. + #redis['master_port'] = 6379 + ``` -Reconfigure GitLab Omnibus for the changes to take effect: `sudo gitlab-ctl reconfigure` +1. To prevent database migrations from running on upgrade, run: -#### Troubleshooting Replication + ``` + sudo touch /etc/gitlab/skip-auto-migrations + ``` -You can check if everything is correct by connecting to each server using -`redis-cli` application, and sending the `INFO` command. + Only the primary GitLab application server should handle migrations. -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. +1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. +1. Go through the steps again for all the other slave nodes. -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. +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. -When it's a `slave`, you will see details of the master connection and if -its `up` or `down`. +### Step 3. Configuring the Redis Sentinel instances ---- +>**Note:** +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. If you are not sure if your Redis servers are working and replicating -correctly, please read the [Troubleshooting Replication](#troubleshooting-replication) +correctly, please read the [Troubleshooting Replication](#troubleshooting-replication) and fix it before proceeding with Sentinel setup. -### 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 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. + +--- + +1. SSH into the server that will host Redis Sentinel and login as root: + + ``` + sudo -i + ``` + +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: + + ``` + sudo touch /etc/gitlab/skip-auto-migrations + ``` -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. + Only the primary GitLab application server should handle migrations. -Here is a simple explanation on how Sentinel handles a failover: +1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. +1. Go through the steps again for all the other Sentinel nodes. -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. +### Step 4. Configuring the GitLab application -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. +The final part is to inform the main GitLab application server of the Redis +Sentinels servers and authentication credentials. -The `quorum` is only used to detect failure, not to elect the `leader`. +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 Sentinel nodes. -Official [Sentinel documentation](http://redis.io/topics/sentinel#example-sentinel-deployments) -also lists different network topologies and warns againts situations like -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. +While it doesn't require a list of all Sentinel nodes, in case of a failure, +it needs to access at least one of the listed. -To make Sentinel setup easier, ee provide an [automated way to setup and run](#sentinel-setup-ee-only) -the Sentinel daemon with GitLab EE. +>**Note:** +The following steps should be performed in the [GitLab application server](gitlab.md) +which ideally should not have Redis or Sentinels on it for a HA setup. -#### Sentinel setup (Community Edition) +1. Edit `/etc/gitlab/gitlab.rb` and add/change the following lines: -For GitLab CE, you need to install, configure, execute and monitor Sentinel -by yourself. + ``` + ## 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} + ] + ``` -Here is an example configuration file (`sentinel.conf`) for a minimal Sentinel -node: +1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. -```conf -bind 0.0.0.0 # bind to all interfaces or change to a specific IP -port 26379 # default sentinel port -sentinel auth-pass gitlab-redis redis-password-goes-here -sentinel monitor gitlab-redis 10.0.0.1 6379 2 -sentinel down-after-milliseconds gitlab-redis 10000 -sentinel config-epoch gitlab-redis 0 -sentinel leader-epoch gitlab-redis 0 +## Switching from an existing single-machine installation to Redis HA + +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 catches 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`: + +```ruby +redis['enable'] = false ``` -#### Sentinel setup (EE Only) +If you fail to replicate first, you may loose data (unprocessed background jobs). + +## Example of a minimal configuration with 1 master, 2 slaves and 3 Sentinels + +>**Note:** +Redis Sentinel is bundled with Omnibus GitLab Enterprise Edition only. For +different setups, read the +[available configuration setups](#available-configuration-setups) section. + +In this example we consider that all servers have an internal network +interface with IPs in the `10.0.0.x` range, and that they can connect +to each other using these IPs. + +In a real world usage, you would also setup firewall rules to prevent +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 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 +* `10.0.0.3`: 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** +will change permanently (including in `redis.conf`) from one node to the other, +until a new failover is initiated again. + +The same thing will happen with `sentinel.conf` that will be overridden after the +initial execution, after any new sentinel node starts watching the **Master**, +or a failover promotes a different **Master** node. -To setup sentinel, you must edit `/etc/gitlab/gitlab.rb` file. -This is a minimal configuration required to run the daemon: +### Example configuration for Redis master and Sentinel 1 + +In `/etc/gitlab/gitlab.rb`: ```ruby +redis_master_role['enable'] = true +redis_sentinel_role['enable'] = true +redis['bind'] = '10.0.0.1' +redis['port'] = 6379 +redis['password'] = 'redis-password-goes-here' redis['master_name'] = 'gitlab-redis' # must be the same in every sentinel node +redis['master_password'] = 'redis-password-goes-here' # the same value defined in redis['password'] in the master instance 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 +#redis['master_port'] = 6379 # port of the initial master redis instance, uncomment to change to non default +sentinel['bind'] = '10.0.0.1' +# sentinel['port'] = 26379 # uncomment to change default port +sentinel['quorum'] = 2 +# sentinel['down_after_milliseconds'] = 10000 +# sentinel['failover_timeout'] = 60000 +``` -sentinel['enable'] = true -# sentinel['port'] = 26379 +[Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. -## Quorum must reflect the amount of voting sentinels it take to start a failover. -sentinel['quorum'] = 2 +### Example configuration for Redis slave 1 and Sentinel 2 -## Consider unresponsive server down after x amount of ms. +In `/etc/gitlab/gitlab.rb`: + +```ruby +redis_slave_role['enable'] = true +redis_sentinel_role['enable'] = true +redis['bind'] = '10.0.0.2' +redis['port'] = 6379 +redis['password'] = 'redis-password-goes-here' +redis['master_password'] = 'redis-password-goes-here' +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 +redis['master_name'] = 'gitlab-redis' # must be the same in every sentinel node +sentinel['bind'] = '10.0.0.2' +# sentinel['port'] = 26379 # uncomment to change default port +sentinel['quorum'] = 2 # sentinel['down_after_milliseconds'] = 10000 +# sentinel['failover_timeout'] = 60000 +``` + +[Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. + +### Example configuration for Redis slave 2 and Sentinel 3 + +In `/etc/gitlab/gitlab.rb`: +```ruby +redis_slave_role['enable'] = true +redis_sentinel_role['enable'] = true +redis['bind'] = '10.0.0.3' +redis['port'] = 6379 +redis['password'] = 'redis-password-goes-here' +redis['master_password'] = 'redis-password-goes-here' +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 +redis['master_name'] = 'gitlab-redis' # must be the same in every sentinel node +sentinel['bind'] = '10.0.0.3' +# sentinel['port'] = 26379 # uncomment to change default port +sentinel['quorum'] = 2 +# 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: +[Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. + +### Example configuration for the GitLab application + +In `/etc/gitlab/gitlab.rb`: ```ruby -# Enabled Redis and Sentinel services -redis['enable'] = true +redis['master_name'] = 'gitlab-redis' +redis['password'] = 'redis-password-goes-here' +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' +lives easier. If you want to know what happens underneath keep reading. + +### Control running services + +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: + +```ruby +## Redis Sentinel Role +redis_sentinel_role['enable'] = true + +# When Sentinel Role is enabled, the following services are also enabled sentinel['enable'] = true -# Disabled all other services +# The following services are disabled redis['enable'] = false bootstrap['enable'] = false nginx['enable'] = false -unicorn['enable'] = false -sidekiq['enable'] = false 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). +------- ---- +## Redis master/slave Role +redis_master_role['enable'] = true # enable only one of them +redis_slave_role['enable'] = true # enable only one of them -The final part is to inform the main GitLab application server of the Redis -master and the new sentinels servers. +# 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. -### GitLab setup +# The following services are disabled +sentinel['enable'] = false +bootstrap['enable'] = false +nginx['enable'] = false +postgresql['enable'] = false +gitlab_rails['enable'] = false +mailroom['enable'] = false -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. +# For Redis Slave role, also change this setting from default 'true' to 'false': +redis['master'] = false +``` -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. +You can find the relevant attributes defined in [gitlab_rails.rb][omnifile]. ->**Note:** -The following steps should be performed in the [GitLab application server](gitlab.md). +## Troubleshooting -**For source based installations** +There are a lot of moving parts that needs to be taken care carefully +in order for the HA setup to work as expected. -1. 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. -1. Restart GitLab for the changes to take effect. +Before proceeding with the troubleshooting below, check your firewall rules: -**For Omnibus installations** +- 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` -1. Edit `/etc/gitlab/gitlab.rb` and add/change the following lines: +### Troubleshooting Redis replication - ```ruby - redis['master_name'] = "gitlab-redis" - redis['master_password'] = 'redis-password-goes-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} - ] - ``` +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 +``` -1. [Reconfigure] the GitLab for the changes to take effect. +When it's a `slave`, you will see details of the master connection and if +its `up` or `down`: -### Sentinel troubleshooting +``` +# 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 +``` -#### Omnibus install +### Troubleshooting Sentinel 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 @@ -424,42 +816,6 @@ 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 - -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][gh-531]. - -It's a bit non-intuitive the way you have to config `resque.yml` and -`sentinel.conf`, otherwise `redis-rb` will not work properly. - -The `master-group-name` ('gitlab-redis') defined in (`sentinel.conf`) -**must** be used as the hostname in GitLab (`resque.yml` for source installations -or `gitlab-rails['redis_*']` in Omnibus): - -```conf -# sentinel.conf: -sentinel monitor gitlab-redis 10.10.10.10 6379 2 -sentinel down-after-milliseconds gitlab-redis 10000 -sentinel config-epoch gitlab-redis 0 -sentinel leader-epoch gitlab-redis 0 -``` - -```yaml -# resque.yaml -production: - url: redis://:myredispassword@gitlab-redis/ - sentinels: - - - host: slave1.example.com # or use ip - port: 26380 # point to sentinel, not to redis port - - - host: slave2.exampl.com # or use ip - port: 26381 # point to sentinel, not to redis port -``` - -When in doubt, please read [Redis Sentinel documentation](http://redis.io/topics/sentinel) - --- To make sure your configuration is correct: @@ -487,8 +843,8 @@ To make sure your configuration is correct: 1. To simulate a failover on master Redis, SSH into the Redis server and run: ```bash - # port must match your master redis port - redis-cli -h localhost -p 6379 DEBUG sleep 60 + # port must match your master redis port, and the sleep time must be a few seconds bigger than defined one + redis-cli -h localhost -p 6379 DEBUG sleep 20 ``` 1. Then back in the Rails console from the first step, run: @@ -500,10 +856,34 @@ To make sure your configuration is correct: You should see a different port after a few seconds delay (the failover/reconnect time). ---- -Read more on high-availability configuration: +## Changelog + +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 + +> +Experimental Redis Sentinel support was [Introduced][ce-1877] in GitLab 8.11. +Starting with 8.14, Redis Sentinel is no longer experimental. +If you used with versions `< 8.14` before, please check the updated +documentation here. + +## Further reading + +Read more on High Availability: +1. [High Availability Overview](README.md) 1. [Configure the database](database.md) 1. [Configure NFS](nfs.md) 1. [Configure the GitLab application servers](gitlab.md) @@ -514,3 +894,10 @@ Read more on high-availability configuration: [reconfigure]: ../restart_gitlab.md#omnibus-gitlab-reconfigure [gh-531]: https://github.com/redis/redis-rb/issues/531 [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/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 +[it]: https://gitlab.com/gitlab-org/gitlab-ce/uploads/c4cc8cd353604bd80315f9384035ff9e/The_Internet_IT_Crowd.png diff --git a/doc/administration/high_availability/redis_source.md b/doc/administration/high_availability/redis_source.md new file mode 100644 index 00000000000..e7a8f47355d --- /dev/null +++ b/doc/administration/high_availability/redis_source.md @@ -0,0 +1,387 @@ +# Configuring non-Omnibus Redis for GitLab HA + +This is the documentation for configuring a Highly Available Redis setup when +you have installed Redis all by yourself and not using the bundled one that +comes with the Omnibus packages. + +We cannot stress enough the importance of reading the +[Overview section](redis.md#overview) of the Omnibus Redis HA as it provides +some invaluable information to the configuration of Redis. Please proceed to +read it before going forward with this guide. + +We also highly recommend that you use the Omnibus GitLab packages, as we +optimize them specifically for GitLab, and we will take care of upgrading Redis +to the latest supported version. + +If you're not sure whether this guide is for you, please refer to +[Available configuration setups](redis.md#available-configuration-setups) in +the Omnibus Redis HA documentation. + +--- + +<!-- START doctoc generated TOC please keep comment here to allow auto update --> +<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE --> +**Table of Contents** + +- [Configuring your own Redis server](#configuring-your-own-redis-server) + - [Prerequisites](#prerequisites) + - [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) +- [Example of minimal configuration with 1 master, 2 slaves and 3 Sentinels](#example-of-minimal-configuration-with-1-master-2-slaves-and-3-sentinels) + - [Example configuration for Redis master and Sentinel 1](#example-configuration-for-redis-master-and-sentinel-1) + - [Example configuration for Redis slave 1 and Sentinel 2](#example-configuration-for-redis-slave-1-and-sentinel-2) + - [Example configuration for Redis slave 2 and Sentinel 3](#example-configuration-for-redis-slave-2-and-sentinel-3) + - [Example configuration of the GitLab application](#example-configuration-of-the-gitlab-application) +- [Troubleshooting](#troubleshooting) + +<!-- END doctoc generated TOC please keep comment here to allow auto update --> + +## Configuring your own Redis server + +This is the section where we install and setup the new Redis instances. + +### Prerequisites + +- All Redis servers in this guide must be configured to use a TCP connection + instead of a socket. To configure Redis to use TCP connections you need to + define both `bind` and `port` in the Redis config file. You can bind to all + interfaces (`0.0.0.0`) or specify the IP of the desired interface + (e.g., one from an internal network). +- Since Redis 3.2, you must define a password to receive external connections + (`requirepass`). +- If you are using Redis with Sentinel, you will also need to define the same + password for the slave password definition (`masterauth`) in the same instance. + +In addition, read the prerequisites as described in the +[Omnibus Redis HA document](redis.md#prerequisites) since they provide some +valuable information for the general setup. + +### Step 1. Configuring the master Redis instance + +Assuming that the Redis master instance IP is `10.0.0.1`: + +1. [Install Redis](../../install/installation.md#6-redis) +1. Edit `/etc/redis/redis.conf`: + + ```conf + ## Define a `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: + bind 10.0.0.1 + + ## Define a `port` to force redis to listen on TCP so other machines can + ## connect to it (default port is `6379`). + port 6379 + + ## Set up password authentication (use the same password in all nodes). + ## The password should be defined equal for both `requirepass` and `masterauth` + ## when setting up Redis to use with Sentinel. + requirepass redis-password-goes-here + masterauth redis-password-goes-here + ``` + +1. Restart the Redis service for the changes to take effect. + +### Step 2. Configuring the slave Redis instances + +Assuming that the Redis slave instance IP is `10.0.0.2`: + +1. [Install Redis](../../install/installation.md#6-redis) +1. Edit `/etc/redis/redis.conf`: + + ```conf + ## Define a `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: + bind 10.0.0.2 + + ## Define a `port` to force redis to listen on TCP so other machines can + ## connect to it (default port is `6379`). + port 6379 + + ## Set up password authentication (use the same password in all nodes). + ## The password should be defined equal for both `requirepass` and `masterauth` + ## when setting up Redis to use with Sentinel. + requirepass redis-password-goes-here + masterauth redis-password-goes-here + + ## Define `slaveof` pointing to the Redis master instance with IP and port. + slaveof 10.0.0.1 6379 + ``` + +1. Restart the Redis service for the changes to take effect. +1. Go through the steps again for all the other slave nodes. + +### Step 3. Configuring the Redis Sentinel instances + +Sentinel is a special type of Redis server. It inherits most of the basic +configuration options you can define in `redis.conf`, with specific ones +starting with `sentinel` prefix. + +Assuming that the Redis Sentinel is installed on the same instance as Redis +master with IP `10.0.0.1` (some settings might overlap with the master): + +1. [Install Redis Sentinel](http://redis.io/topics/sentinel) +1. Edit `/etc/redis/sentinel.conf`: + + ```conf + ## Define a `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: + bind 10.0.0.1 + + ## Define a `port` to force Sentinel to listen on TCP so other machines can + ## connect to it (default port is `6379`). + port 26379 + + ## Set up password authentication (use the same password in all nodes). + ## The password should be defined equal for both `requirepass` and `masterauth` + ## when setting up Redis to use with Sentinel. + requirepass redis-password-goes-here + masterauth redis-password-goes-here + + ## Define with `sentinel auth-pass` the same shared password you have + ## defined for both Redis master and slaves instances. + sentinel auth-pass gitlab-redis redis-password-goes-here + + ## Define with `sentinel monitor` the IP and port of the Redis + ## master node, and the quorum required to start a failover. + sentinel monitor gitlab-redis 10.0.0.1 6379 2 + + ## Define with `sentinel down-after-milliseconds` the time in `ms` + ## that an unresponsive server will be considered down. + sentinel down-after-milliseconds gitlab-redis 10000 + + ## Define a value for `sentinel failover_timeout` in `ms`. This has multiple + ## meanings: + ## + ## * 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 30000 + ``` +1. Restart the Redis service for the changes to take effect. +1. Go through the steps again for all the other Sentinel nodes. + +### Step 4. Configuring the GitLab application + +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 Sentinel nodes. + +While it doesn't require a list of all Sentinel nodes, in case of a failure, +it needs to access at least one of listed ones. + +The following steps should be performed in the [GitLab application server](gitlab.md) +which ideally should not have Redis or Sentinels in the same machine for a HA +setup: + +1. Edit `/home/git/gitlab/config/resque.yml` following the example in + [resque.yml.example][resque], and uncomment the Sentinel lines, pointing to + the correct server credentials: + + ```yaml + # resque.yaml + production: + url: redis://:redi-password-goes-here@gitlab-redis/ + sentinels: + - + host: 10.0.0.1 + port: 26379 # point to sentinel, not to redis port + - + host: 10.0.0.2 + port: 26379 # point to sentinel, not to redis port + - + host: 10.0.0.3 + port: 26379 # point to sentinel, not to redis port + ``` + +1. [Restart GitLab][restart] for the changes to take effect. + +## Example of minimal configuration with 1 master, 2 slaves and 3 Sentinels + +In this example we consider that all servers have an internal network +interface with IPs in the `10.0.0.x` range, and that they can connect +to each other using these IPs. + +In a real world usage, you would also setup firewall rules to prevent +unauthorized access from other machines, and block traffic from the +outside ([Internet][it]). + +For this example, **Sentinel 1** will be configured in the same machine as the +**Redis Master**, **Sentinel 2** and **Sentinel 3** in the same machines as the +**Slave 1** and **Slave 2** respectively. + +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 +* `10.0.0.3`: 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** +will change permanently (including in `redis.conf`) from one node to the other, +until a new failover is initiated again. + +The same thing will happen with `sentinel.conf` that will be overridden after the +initial execution, after any new sentinel node starts watching the **Master**, +or a failover promotes a different **Master** node. + +### Example configuration for Redis master and Sentinel 1 + +1. In `/etc/redis/redis.conf`: + + ```conf + bind 10.0.0.1 + port 6379 + requirepass redis-password-goes-here + masterauth redis-password-goes-here + ``` + +1. In `/etc/redis/sentinel.conf`: + + ```conf + bind 10.0.0.1 + port 26379 + sentinel auth-pass gitlab-redis redis-password-goes-here + sentinel monitor gitlab-redis 10.0.0.1 6379 2 + sentinel down-after-milliseconds gitlab-redis 10000 + sentinel failover_timeout 30000 + ``` + +1. Restart the Redis service for the changes to take effect. + +### Example configuration for Redis slave 1 and Sentinel 2 + +1. In `/etc/redis/redis.conf`: + + ```conf + bind 10.0.0.2 + port 6379 + requirepass redis-password-goes-here + masterauth redis-password-goes-here + slaveof 10.0.0.1 6379 + ``` + +1. In `/etc/redis/sentinel.conf`: + + ```conf + bind 10.0.0.2 + port 26379 + sentinel auth-pass gitlab-redis redis-password-goes-here + sentinel monitor gitlab-redis 10.0.0.1 6379 2 + sentinel down-after-milliseconds gitlab-redis 10000 + sentinel failover_timeout 30000 + ``` + +1. Restart the Redis service for the changes to take effect. + +### Example configuration for Redis slave 2 and Sentinel 3 + +1. In `/etc/redis/redis.conf`: + + ```conf + bind 10.0.0.3 + port 6379 + requirepass redis-password-goes-here + masterauth redis-password-goes-here + slaveof 10.0.0.1 6379 + ``` + +1. In `/etc/redis/sentinel.conf`: + + ```conf + bind 10.0.0.3 + port 26379 + sentinel auth-pass gitlab-redis redis-password-goes-here + sentinel monitor gitlab-redis 10.0.0.1 6379 2 + sentinel down-after-milliseconds gitlab-redis 10000 + sentinel failover_timeout 30000 + ``` + +1. Restart the Redis service for the changes to take effect. + +### Example configuration of the GitLab application + +1. Edit `/home/git/gitlab/config/resque.yml`: + + ```yaml + production: + url: redis://:redi-password-goes-here@gitlab-redis/ + sentinels: + - + host: 10.0.0.1 + port: 26379 # point to sentinel, not to redis port + - + host: 10.0.0.2 + port: 26379 # point to sentinel, not to redis port + - + host: 10.0.0.3 + port: 26379 # point to sentinel, not to redis port + ``` + +1. [Restart GitLab][restart] for the changes to take effect. + +## Troubleshooting + +We have a more detailed [Troubleshooting](redis.md#troubleshooting) explained +in the documentation for Omnibus GitLab installations. Here we will list only +the things that are specific to a source installation. + +If you get an error in GitLab like: `Redis::CannotConnectError: No sentinels available.`, +there may be something wrong with your configuration files or it can be related +to [this upstream issue][gh-531]. + +It's a bit non-intuitive the way you have to config `resque.yml` and +`sentinel.conf`, otherwise `redis-rb` will not work properly. + +The `master-group-name` ('gitlab-redis') defined in (`sentinel.conf`) +**must** be used as the hostname in GitLab (`resque.yml`): + +```conf +# sentinel.conf: +sentinel monitor gitlab-redis 10.0.0.1 6379 2 +sentinel down-after-milliseconds gitlab-redis 10000 +sentinel config-epoch gitlab-redis 0 +sentinel leader-epoch gitlab-redis 0 +``` + +```yaml +# resque.yaml +production: + url: redis://:myredispassword@gitlab-redis/ + sentinels: + - + host: 10.0.0.1 + port: 26379 # point to sentinel, not to redis port + - + host: 10.0.0.2 + port: 26379 # point to sentinel, not to redis port + - + host: 10.0.0.3 + port: 26379 # point to sentinel, not to redis port +``` + +When in doubt, please read [Redis Sentinel documentation](http://redis.io/topics/sentinel) + +[gh-531]: https://github.com/redis/redis-rb/issues/531 +[downloads]: https://about.gitlab.com/downloads +[restart]: ../restart_gitlab.md#installations-from-source +[it]: https://gitlab.com/gitlab-org/gitlab-ce/uploads/c4cc8cd353604bd80315f9384035ff9e/The_Internet_IT_Crowd.png |