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Stan Hu 7e209d86f4 Add documentation on upgrading GitLab HA nodes 
As mentioned in
https://gitlab.com/gitlab-org/gitlab-ce/issues/58121#note_145299901, it
wasn't obvious that upgrading an GitLab HA cluster required special
care. Link to the Omnibus documentation for upgrade instructions.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/58121
2019-02-26 15:14:38 -08:00
..
database.md Correct grammar (setup to set-up) in Docs 2018-09-21 16:29:14 +02:00
gitlab.md Add documentation on upgrading GitLab HA nodes 2019-02-26 15:14:38 -08:00
load_balancer.md Docs: Realign several CE docs that diverged from EE unnecessarily 2019-02-12 12:34:21 +00:00
nfs.md Resolve Markdown ordered lists not conforming to styleguide 2018-11-13 10:53:38 +10:00
README.md Resolve "CE documentation is not CommonMark compliant" 2018-09-06 16:52:18 +00:00
redis.md Merge branch 'docs-anchors4-ha' into 'master' 2019-02-26 02:28:17 +00:00
redis_source.md Add punctuation. 2019-02-21 06:18:28 +00:00

README.md

High Availability

GitLab supports several different types of clustering and high-availability. The solution you choose will be based on the level of scalability and availability you require. The easiest solutions are scalable, but not necessarily highly available.

GitLab provides a service that is usually essential to most organizations: it enables people to collaborate on code in a timely fashion. Any downtime should therefore be short and planned. Luckily, GitLab provides a solid setup even on a single server without special measures. Due to the distributed nature of Git, developers can still commit code locally even when GitLab is not available. However, some GitLab features such as the issue tracker and Continuous Integration are not available when GitLab is down.

Keep in mind that all Highly Available solutions come with a trade-off between cost/complexity and uptime. The more uptime you want, the more complex the solution. And the more complex the solution, the more work is involved in setting up and maintaining it. High availability is not free and every HA solution should balance the costs against the benefits.

Architecture

There are two kinds of setups:

  • active/active
  • active/passive

Active/Active

This architecture scales easily because all application servers handle 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.

Follow the steps below to configure an active/active setup:

  1. Configure the database
  2. Configure Redis
    1. Configure Redis for GitLab source installations
  3. Configure NFS
  4. Configure the GitLab application servers
  5. Configure the load balancers

Active/Active HA Diagram

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.

Note: GitLab recommends against choosing this HA method because of the complexity of managing DRBD and crafting automatic failover. This is compatible with GitLab, but not officially supported. If you are an EE customer, support will help you with GitLab related problems, but if the root cause is identified as DRBD, we will not troubleshoot further.

Components/Servers Required: 2 servers/virtual machines (one active/one passive)

Active/Passive HA Diagram