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diff --git a/doc/administration/high_availability/redis.md b/doc/administration/high_availability/redis.md index bc424330656..b4e7bf21e35 100644 --- a/doc/administration/high_availability/redis.md +++ b/doc/administration/high_availability/redis.md @@ -1,265 +1,780 @@ # Configuring Redis for GitLab HA -You can choose to install and manage Redis yourself, or you can use the one -that comes bundled with GitLab Omnibus packages. - -> **Note:** Redis does not require authentication by default. See +> +Experimental Redis Sentinel support was [Introduced][ce-1877] in GitLab 8.11. +Starting with 8.14, Redis Sentinel is no longer experimental. +If you've used it with versions `< 8.14` before, please check the updated +documentation here. + +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. + +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. + +## Overview + +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. + +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. + +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. + +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. + +Make sure that you read this document once as a whole before configuring the +components below. + +### High Availability with Sentinel + +>**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. + +High Availability with Redis requires a few things: + +- Multiple Redis 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 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 +- 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 the application to always connect to the current **Master** + server + +When a **Master** fails to respond, it's the application's responsibility +(in our case GitLab) to handle timeout and reconnect (querying a **Sentinel** +for a new **Master**). -## Configure your own Redis server +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 or can bring your +whole cluster down, invalidating the failover effort. -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. +### Recommended setup -## Configure Redis using Omnibus +For a minimal setup, you will install the Omnibus GitLab package in `3` +**independent** machines, both with **Redis** and **Sentinel**: -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. +- Redis Master + Sentinel +- Redis Slave + Sentinel +- Redis Slave + Sentinel -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: +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). - ```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_workhorse['enable'] = false - mailroom['enable'] = false - - # Redis configuration - redis['port'] = 6379 - redis['bind'] = '0.0.0.0' +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**: - # If you wish to use Redis authentication (recommended) - redis['password'] = 'Redis Password' - ``` +- Redis Master + Sentinel +- Redis Slave + Sentinel +- Redis Slave + Sentinel +- Redis Slave + Sentinel +- Redis Slave + Sentinel -1. Run `sudo gitlab-ctl reconfigure` to install and configure PostgreSQL. +### Redis setup overview - > **Note**: This `reconfigure` step will result in some errors. - That's OK - don't be alarmed. +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). -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. +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. -## Experimental Redis Sentinel support +As an example, if you have `6` Redis nodes, a maximum of `3` can be +simultaneously down. -> [Introduced][ce-1877] in GitLab 8.11. +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. -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. +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. -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. +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. -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. +### Sentinel setup overview -The configuration consists of three parts: +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. -- Redis setup -- Sentinel setup -- GitLab setup +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: -Read carefully how to configure those components below. +- 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 -### Redis setup +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. -You must have at least 2 Redis servers: 1 Master, 1 or more Slaves. -They should be configured the same way and with similar server specs, as -in a failover situation, any Slave can be elected as the new Master by -the Sentinel servers. +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. -In a minimal setup, the only required change for the slaves in `redis.conf` -is the addition of a `slaveof` line pointing to the initial master. -You can increase the security by defining a `requirepass` configuration in -the master, and `masterauth` in slaves. +The number of sentinels should ideally always be an **odd** number, for the +consensus algorithm to be effective in the case of a failure. ---- +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**. -**Configuring your own Redis server** +Here are some examples: -1. Add to the slaves' `redis.conf`: +- 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 - # IP and port of the master Redis server - slaveof 10.10.10.10 6379 - ``` +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. Optionally, set up password authentication for increased security. - Add the following to master's `redis.conf`: +>**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. +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. + +1. Edit `/etc/gitlab/gitlab.rb` and add the contents: - ```conf - # Optional password authentication for increased security - requirepass "<password>" + ```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' ``` -1. Then add this line to all the slave servers' `redis.conf`: +1. Only the primary GitLab application server should handle migrations. To + prevent database migrations from running on upgrade, add the following + configuration to your `/etc/gitlab/gitlab.rb` file: - ```conf - masterauth "<password>" + ``` + gitlab_rails['auto_migrate'] = false ``` -1. Restart the Redis services for the changes to take effect. +1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. ---- +### Step 2. Configuring the slave Redis instances -**Using Redis via Omnibus** +1. SSH into the **slave** Redis server. +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. -1. Edit `/etc/gitlab/gitlab.rb` of a master Redis machine (usualy a single machine): +1. Edit `/etc/gitlab/gitlab.rb` and add the contents: ```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 + # 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 - ## Master redis instance - redis['password'] = '<huge password string here>' - ``` + # The same password for Redeis authentication you set up for the master node. + redis['password'] = 'redis-password-goes-here' -1. Edit `/etc/gitlab/gitlab.rb` of a slave Redis machine (should be one or more machines): + # The IP of the master Redis node. + redis['master_ip'] = '10.0.0.1' - ```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 + # Port of master Redis server, uncomment to change to non default. Defaults + # to `6379`. + #redis['master_port'] = 6379 + ``` - ## Slave redis instance - redis['master_ip'] = '10.10.10.10' # IP of master Redis server - redis['master_port'] = 6379 # Port of master Redis server - redis['master_password'] = "<huge password string here>" +1. To prevent database migrations from running on upgrade, run: + + ``` + sudo touch /etc/gitlab/skip-auto-migrations ``` -1. Reconfigure the GitLab for the changes to take effect: `sudo gitlab-ctl reconfigure` + 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. --- +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. + +### 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. -### Sentinel setup +If you are not sure if your Redis servers are working and replicating +correctly, please read the [Troubleshooting Replication](#troubleshooting-replication) +and fix it before proceeding with Sentinel setup. -We don't provide yet an automated way to setup and run the Sentinel daemon -from Omnibus installation method. You must follow the instructions below and -run it by yourself. +You must have at least `3` Redis Sentinel servers, and they need to +be each in an independent machine. You can configure them in the same +machines where you've configured the other Redis servers. -The support for Sentinel in Ruby has some [caveats](https://github.com/redis/redis-rb/issues/531). -While you can give any name for the `master-group-name` part of the -configuration, as in this example: +With GitLab Enterprise Edition, you can use the Omnibus package to setup +multiple machines with the Sentinel daemon. -```conf -sentinel monitor <master-group-name> <ip> <port> <quorum> -``` +--- -,for it to work in Ruby, you have to use the "hostname" of the master Redis -server, otherwise you will get an error message like: -`Redis::CannotConnectError: No sentinels available.`. Read -[Sentinel troubleshooting](#sentinel-troubleshooting) for more information. +1. SSH into the server that will host Redis Sentinel. +1. **You can omit this step if the Sentinels will be hosted in the same node as + the other Redis instances.** -Here is an example configuration file (`sentinel.conf`) for a Sentinel node: + [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. -```conf -port 26379 -sentinel monitor master-redis.example.com 10.10.10.10 6379 1 -sentinel down-after-milliseconds master-redis.example.com 10000 -sentinel config-epoch master-redis.example.com 0 -sentinel leader-epoch master-redis.example.com 0 -``` +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 -The final part is to inform the main GitLab application server of the Redis -master and the new sentinels servers. + # Must be the same in every sentinel node + redis['master_name'] = 'gitlab-redis' -### GitLab setup + # The same password for Redis authentication you set up for the master node. + redis['password'] = 'redis-password-goes-here' -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. + # The IP of the master Redis node. + redis['master_ip'] = '10.0.0.1' -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. + # Define a port so Redis can listen for TCP requests which will allow other + # machines to connect to it. + redis['port'] = 6379 ->**Note:** -The following steps should be performed in the [GitLab application server](gitlab.md). + # 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 + ``` -**For source based installations** +1. To prevent database migrations from running on upgrade, run: -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. + ``` + sudo touch /etc/gitlab/skip-auto-migrations + ``` -**For Omnibus installations** + 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. + +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 the listed. + +>**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. + +1. SSH into the server where the GitLab application is installed. 1. Edit `/etc/gitlab/gitlab.rb` and add/change the following lines: - ```ruby - gitlab-rails['redis_host'] = "master-redis.example.com" - gitlab-rails['redis_port'] = 6379 - gitlab-rails['redis_password'] = '<huge password string here>' - gitlab-rails['redis_sentinels'] = [ - {'host' => '10.10.10.1', 'port' => 26379}, - {'host' => '10.10.10.2', 'port' => 26379}, - {'host' => '10.10.10.3', 'port' => 26379} + ``` + ## 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] the GitLab for the changes to take effect. +1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. -### Sentinel troubleshooting +## Switching from an existing single-machine installation to Redis HA -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] ([pull request][gh-534] that should make things better). +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. -It's a bit rigid the way you have to config `resque.yml` and `sentinel.conf`, -otherwise `redis-rb` will not work properly. +Make the required changes in configuration and restart the new nodes again. -The hostname ('my-primary-redis') of the primary Redis server (`sentinel.conf`) -**must** match the one configured in GitLab (`resque.yml` for source installations -or `gitlab-rails['redis_*']` in Omnibus) and it must be valid ex: +To disable redis in the single install, edit `/etc/gitlab/gitlab.rb`: -```conf -# sentinel.conf: -sentinel monitor my-primary-redis 10.10.10.10 6379 1 -sentinel down-after-milliseconds my-primary-redis 10000 -sentinel config-epoch my-primary-redis 0 -sentinel leader-epoch my-primary-redis 0 +```ruby +redis['enable'] = false ``` -```yaml -# resque.yaml -production: - url: redis://my-primary-redis:6378 - sentinels: - - - host: slave1 - port: 26380 # point to sentinel, not to redis port - - - host: slave2 - port: 26381 # point to sentinel, not to redis port +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. + +### 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, 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 +``` + +[Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. + +### Example configuration for Redis slave 1 and Sentinel 2 + +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 in doubt, please read [Redis Sentinel documentation](http://redis.io/topics/sentinel) +[Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect. + +### Example configuration for the GitLab application + +In `/etc/gitlab/gitlab.rb`: + +```ruby +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 + +# The following services are disabled +redis['enable'] = false +bootstrap['enable'] = false +nginx['enable'] = false +postgresql['enable'] = false +gitlab_rails['enable'] = false +mailroom['enable'] = false + +------- + +## 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. + +# The following services are disabled +sentinel['enable'] = false +bootstrap['enable'] = false +nginx['enable'] = false +postgresql['enable'] = false +gitlab_rails['enable'] = false +mailroom['enable'] = false + +# For Redis Slave role, also change this setting from default 'true' to 'false': +redis['master'] = false +``` + +You can find the relevant attributes defined in [gitlab_rails.rb][omnifile]. + +## Troubleshooting + +There are a lot of moving parts that needs to be taken care carefully +in order for the HA setup to work as expected. + +Before proceeding with the troubleshooting below, check your firewall rules: + +- Redis machines + - Accept TCP connection in `6379` + - Connect to the other Redis machines via TCP in `6379` +- Sentinel machines + - Accept TCP connection in `26379` + - Connect to other Sentinel machines via TCP in `26379` + - Connect to the Redis machines via TCP in `6379` + +### Troubleshooting Redis replication + +You can check if everything is correct by connecting to each server using +`redis-cli` application, and sending the `INFO` command. + +If authentication was correctly defined, it should fail with: +`NOAUTH Authentication required` error. Try to authenticate with the +previous defined password with `AUTH redis-password-goes-here` and +try the `INFO` command again. + +Look for the `# Replication` section where you should see some important +information like the `role` of the server. + +When connected to a `master` redis, you will see the number of connected +`slaves`, and a list of each with connection details: + +``` +# Replication +role:master +connected_slaves:1 +slave0:ip=10.133.5.21,port=6379,state=online,offset=208037514,lag=1 +master_repl_offset:208037658 +repl_backlog_active:1 +repl_backlog_size:1048576 +repl_backlog_first_byte_offset:206989083 +repl_backlog_histlen:1048576 +``` + +When it's a `slave`, you will see details of the master connection and if +its `up` or `down`: + +``` +# Replication +role:slave +master_host:10.133.1.58 +master_port:6379 +master_link_status:up +master_last_io_seconds_ago:1 +master_sync_in_progress:0 +slave_repl_offset:208096498 +slave_priority:100 +slave_read_only:1 +connected_slaves:0 +master_repl_offset:0 +repl_backlog_active:0 +repl_backlog_size:1048576 +repl_backlog_first_byte_offset:0 +repl_backlog_histlen:0 +``` + +### 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 +to [this issue][gh-531]. + +You must make sure you are defining the same value in `redis['master_name']` +and `redis['master_pasword']` as you defined for your sentinel node. + +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. --- @@ -273,7 +788,7 @@ To make sure your configuration is correct: sudo gitlab-rails console # For source installations - sudo -u git rails console RAILS_ENV=production + sudo -u git rails console production ``` 1. Run in the console: @@ -288,8 +803,8 @@ 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: @@ -301,10 +816,26 @@ 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 + +## 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) @@ -315,3 +846,10 @@ 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 |