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Allow multiple secondary nodes behind a load balancer

Michael Kozono requested to merge mk/decouple-geo-node-identity-from-external-url into master

What does this MR do?

Background

A Geo node has a record in the geo_nodes table. It knows which one it belongs to by comparing its external_url in gitlab.rb with the geo_nodes.url column.

Problem

geo_nodes.url must be unique so it can be used as an identifier. But this forces external_url to be unique as well. This constraint on external_url prevents at least the following use cases:

  • All secondaries can be accessed via a geographically-aware load balancer
  • Active-passive Geo nodes (if we implement secondaries as transparent primaries)

Solution

Decouple GeoNode identity from external_url.

Add a gitlab.rb setting (let's say gitlab_rails['geo_node_name']) paired with a new geo_nodes column (let's say name) and use those as identifiers.

Here is the omnibus MR adding the gitlab.rb setting: omnibus-gitlab!3201 (merged)

In this MR, gitlab_rails['geo_node_name'] ends up in Rails as Gitlab.config.geo.node_name.

Backwards-compatible

  • Gitlab.config.geo.node_name defaults to external_url (plus a terminating /).
  • geo_nodes.name copies geo_nodes.url in a one-time data migration. This is reversible as long as all nodes' name and url remain identical.

Side note: Difference from initial proposal

In the initial proposal https://gitlab.com/gitlab-org/gitlab-ee/issues/9123#note_153433953, I suggested we can rename geo_nodes.url to geo_nodes.name. It turns out there are a number of instances where we secondary nodes need to know a user-facing primary node URL:

etc.

And the primary needs to know the secondary URLs to set the OAuth application redirect URI.

So we should retain geo_nodes.url for these purposes. As a bonus, a URL field is needed later so the primary can specify a unique, user-facing URL when we allow all nodes to be put behind a load balancer #10888 (closed).

Though the primary must have a unique URL in #10888 (closed), we need to remove the uniqueness constraint so secondaries can all use the same URL (to resolve this MR's issue).

Screenshot of new Name field in Geo Node Edit form

image

Does this MR meet the acceptance criteria?

Conformity

Performance and testing

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

  • Label as security and @ mention @gitlab-com/gl-security/appsec
  • The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
  • Security reports checked/validated by a reviewer from the AppSec team

To do

Edited by Michael Kozono

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