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Geo undergoes significant changes from release to release. Upgrades **are** supported and [documented](#updating-geo), but you should ensure that you're using the right version of the documentation for your installation.
Fetching large repositories can take a long time for teams located far from a single GitLab instance.
To make sure you're using the right version of the documentation, navigate to [the Geo page on GitLab.com](https://gitlab.com/gitlab-org/gitlab/blob/master/doc/administration/geo/index.md) and choose the appropriate release from the **Switch branch/tag** dropdown. For example, [`v13.7.6-ee`](https://gitlab.com/gitlab-org/gitlab/-/blob/v13.7.6-ee/doc/administration/geo/index.md).
Geo uses a set of defined terms that is described in the [Geo Glossary](glossary.md), please familiarize yourself with those terms.
- Can be used for cloning and fetching projects, in addition to reading any data available in the GitLab web interface (see [limitations](#limitations)).
- Read-only **secondary** sites: Maintain one **primary** GitLab site while still enabling read-only **secondary** sites for each of your distributed teams.
- Authentication system hooks: **Secondary** sites receives all authentication data (like user accounts and logins) from the **primary** instance.
- An intuitive UI: **Secondary** sites use the same web interface your team has grown accustomed to. In addition, there are visual notifications that block write operations and make it clear that a user is on a **secondary** sites.
Your Geo instance can be used for cloning and fetching projects, in addition to reading any data. This will make working with large repositories over large distances much faster.
- In GitLab Premium 10.0 and later, the **primary** site no longer talks to **secondary** sites to notify for changes (API).
- Pushing directly to a **secondary** site (for both HTTP and SSH, including Git LFS) was [introduced](https://about.gitlab.com/releases/2018/09/22/gitlab-11-3-released/) in [GitLab Premium](https://about.gitlab.com/pricing/#self-managed) 11.3.
- The **primary** site behaves as a full read-write GitLab instance.
- **Secondary** sites are read-only but proxy Git push operations to the **primary** site. This makes **secondary** sites appear to support push operations themselves.
[Web terminal](../../ci/environments/index.md#web-terminals) support requires your load balancer to correctly handle WebSocket connections.
When using HTTP or HTTPS proxying, your load balancer must be configured to pass through the `Connection` and `Upgrade` hop-by-hop headers. See the [web terminal](../integration/terminal.md) integration guide for more details.
We recommend that if you use LDAP on your **primary** site, you also set up secondary LDAP servers on each **secondary** site. Otherwise, users will not be able to perform Git operations over HTTP(s) on the **secondary** site using HTTP Basic Authentication. However, Git via SSH and personal access tokens will still work.
It is possible for all **secondary** sites to share an LDAP server, but additional latency can be an issue. Also, consider what LDAP server will be available in a [disaster recovery](disaster_recovery/index.md) scenario if a **secondary** site is promoted to be a **primary** site.
Check for instructions on how to set up replication in your LDAP service. Instructions will be different depending on the software or service used. For example, OpenLDAP provides [these instructions](https://www.openldap.org/doc/admin24/replication.html).
### Geo Tracking Database
The tracking database instance is used as metadata to control what needs to be updated on the disk of the local instance. For example:
- Download new assets.
- Fetch new LFS Objects.
- Fetch changes from a repository that has recently been updated.
When something is marked to be updated in the tracking database instance, asynchronous jobs running on the **secondary** site will execute the required operations and update the state.
This new architecture allows GitLab to be resilient to connectivity issues between the sites. It doesn't matter how long the **secondary** site is disconnected from the **primary** site as it will be able to replay all the events in the correct order and become synchronized with the **primary** site again.
## Limitations
WARNING:
This list of limitations only reflects the latest version of GitLab. If you are using an older version, extra limitations may be in place.
- Pushing directly to a **secondary** site redirects (for HTTP) or proxies (for SSH) the request to the **primary** site instead of [handling it directly](https://gitlab.com/gitlab-org/gitlab/-/issues/1381), except when using Git over HTTP with credentials embedded within the URI. For example, `https://user:password@secondary.tld`.
- The **primary** site has to be online for OAuth login to happen. Existing sessions and Git are not affected. Support for the **secondary** site to use an OAuth provider independent from the primary is [being planned](https://gitlab.com/gitlab-org/gitlab/-/issues/208465).
- The installation takes multiple manual steps that together can take about an hour depending on circumstances. We are working on improving this experience. See [Omnibus GitLab issue #2978](https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/2978) for details.
- Real-time updates of issues/merge requests (for example, via long polling) doesn't work on the **secondary** site.
- [Selective synchronization](replication/configuration.md#selective-synchronization) applies only to files and repositories. Other datasets are replicated to the **secondary** site in full, making it inappropriate for use as an access control mechanism.
- Object pools for forked project deduplication work only on the **primary** site, and are duplicated on the **secondary** site.
- GitLab Runners cannot register with a **secondary** site. Support for this is [planned for the future](https://gitlab.com/gitlab-org/gitlab/-/issues/3294).
- Configuring Geo **secondary** sites to [use high-availability configurations of PostgreSQL](https://gitlab.com/groups/gitlab-org/-/epics/2536) is currently in **alpha** support.
- [Selective synchronization](replication/configuration.md#selective-synchronization) only limits what repositories are replicated. The entire PostgreSQL data is still replicated. Selective synchronization is not built to accomodate compliance / export control use cases.
### Limitations on replication/verification
There is a complete list of all GitLab [data types](replication/datatypes.md) and [existing support for replication and verification](replication/datatypes.md#limitations-on-replicationverification).
After installing GitLab on the **secondary** site(s) and performing the initial configuration, see the following documentation for post-installation information.
In some circumstances, like during [upgrades](replication/updating_the_geo_nodes.md) or a [planned failover](disaster_recovery/planned_failover.md), it is desirable to pause replication between the primary and secondary.
If `postgresql` is on a standalone database node, ensure that `gitlab.rb` on that node contains the configuration line `gitlab_rails['geo_node_name'] = 'node_name'`, where `node_name` is the same as the `geo_name_name` on the application node.
For information on configuring Geo for multiple nodes, see [Geo for multiple servers](replication/multiple_servers.md).
### Configuring Geo with Object Storage
For information on configuring Geo with object storage, see [Geo with Object storage](replication/object_storage.md).
### Disaster Recovery
For information on using Geo in disaster recovery situations to mitigate data-loss and restore services, see [Disaster Recovery](disaster_recovery/index.md).
For more information on Geo security, see [Geo security review](replication/security_review.md).
### Tuning Geo
For more information on tuning Geo, see [Tuning Geo](replication/tuning.md).
### Set up a location-aware Git URL
For an example of how to set up a location-aware Git remote URL with AWS Route53, see [Location-aware Git remote URL with AWS Route53](replication/location_aware_git_url.md).
In GitLab 9.5 and later, Geo stores structured log messages in a `geo.log` file. For Omnibus installations, this file is at `/var/log/gitlab/gitlab-rails/geo.log`.
This file contains information about when Geo attempts to sync repositories and files. Each line in the file contains a separate JSON entry that can be ingested into. For example, Elasticsearch or Splunk.
