286 lines
16 KiB
Markdown
286 lines
16 KiB
Markdown
# Replication (Geo) **(PREMIUM ONLY)**
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> - Introduced in GitLab Enterprise Edition 8.9.
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> - Using Geo in combination with
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> [multi-server architectures](../../reference_architectures/index.md)
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> is considered **Generally Available** (GA) in
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> [GitLab Premium](https://about.gitlab.com/pricing/) 10.4.
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Replication with Geo is the solution for widely distributed development teams.
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## Overview
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Fetching large repositories can take a long time for teams located far from a single GitLab instance.
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Geo provides local, read-only instances of your GitLab instances. This can reduce the time it takes
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to clone and fetch large repositories, speeding up development.
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NOTE: **Note:**
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Check the [requirements](#requirements-for-running-geo) carefully before setting up Geo.
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For a video introduction to Geo, see [Introduction to GitLab Geo - GitLab Features](https://www.youtube.com/watch?v=-HDLxSjEh6w).
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CAUTION: **Caution:**
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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.
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To make sure you're using the right version of the documentation, navigate to [the source version of this page on GitLab.com](https://gitlab.com/gitlab-org/gitlab/blob/master/doc/administration/geo/replication/index.md) and choose the appropriate release from the **Switch branch/tag** dropdown. For example, [`v11.2.3-ee`](https://gitlab.com/gitlab-org/gitlab/blob/v11.2.3-ee/doc/administration/geo/replication/index.md).
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## Use cases
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Implementing Geo provides the following benefits:
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- Reduce from minutes to seconds the time taken for your distributed developers to clone and fetch large repositories and projects.
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- Enable all of your developers to contribute ideas and work in parallel, no matter where they are.
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- Balance the read-only load between your **primary** and **secondary** nodes.
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In addition, it:
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- Can be used for cloning and fetching projects, in addition to reading any data available in the GitLab web interface (see [current limitations](#current-limitations)).
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- Overcomes slow connections between distant offices, saving time by improving speed for distributed teams.
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- Helps reducing the loading time for automated tasks, custom integrations, and internal workflows.
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- Can quickly fail over to a **secondary** node in a [disaster recovery](../disaster_recovery/index.md) scenario.
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- Allows [planned failover](../disaster_recovery/planned_failover.md) to a **secondary** node.
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Geo provides:
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- Read-only **secondary** nodes: Maintain one **primary** GitLab node while still enabling read-only **secondary** nodes for each of your distributed teams.
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- Authentication system hooks: **Secondary** nodes receives all authentication data (like user accounts and logins) from the **primary** instance.
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- An intuitive UI: **Secondary** nodes utilize 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** node.
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## How it works
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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.
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When Geo is enabled, the:
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- Original instance is known as the **primary** node.
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- Replicated read-only nodes are known as **secondary** nodes.
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Keep in mind that:
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- **Secondary** nodes talk to the **primary** node to:
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- Get user data for logins (API).
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- Replicate repositories, LFS Objects, and Attachments (HTTPS + JWT).
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- Since GitLab Premium 10.0, the **primary** node no longer talks to **secondary** nodes to notify for changes (API).
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- Pushing directly to a **secondary** node (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.
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- There are [limitations](#current-limitations) in the current implementation.
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### Architecture
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The following diagram illustrates the underlying architecture of Geo.
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In this diagram:
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- There is the **primary** node and the details of one **secondary** node.
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- Writes to the database can only be performed on the **primary** node. A **secondary** node receives database
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updates via PostgreSQL streaming replication.
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- If present, the [LDAP server](#ldap) should be configured to replicate for [Disaster Recovery](../disaster_recovery/index.md) scenarios.
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- A **secondary** node performs different type of synchronizations against the **primary** node, using a special
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authorization protected by JWT:
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- Repositories are cloned/updated via Git over HTTPS.
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- Attachments, LFS objects, and other files are downloaded via HTTPS using a private API endpoint.
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From the perspective of a user performing Git operations:
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- The **primary** node behaves as a full read-write GitLab instance.
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- **Secondary** nodes are read-only but proxy Git push operations to the **primary** node. This makes **secondary** nodes appear to support push operations themselves.
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To simplify the diagram, some necessary components are omitted. Note that:
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- Git over SSH requires [`gitlab-shell`](https://gitlab.com/gitlab-org/gitlab-shell) and OpenSSH.
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- Git over HTTPS required [`gitlab-workhorse`](https://gitlab.com/gitlab-org/gitlab-workhorse).
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Note that a **secondary** node needs two different PostgreSQL databases:
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- A read-only database instance that streams data from the main GitLab database.
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- [Another database instance](#geo-tracking-database) used internally by the **secondary** node to record what data has been replicated.
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In **secondary** nodes, there is an additional daemon: [Geo Log Cursor](#geo-log-cursor).
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## Requirements for running Geo
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The following are required to run Geo:
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- An operating system that supports OpenSSH 6.9+ (needed for
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[fast lookup of authorized SSH keys in the database](../../operations/fast_ssh_key_lookup.md))
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The following operating systems are known to ship with a current version of OpenSSH:
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- [CentOS](https://www.centos.org) 7.4+
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- [Ubuntu](https://ubuntu.com) 16.04+
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- PostgreSQL 11+ with [FDW](https://www.postgresql.org/docs/11/postgres-fdw.html) support and [Streaming Replication](https://wiki.postgresql.org/wiki/Streaming_Replication)
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- Git 2.9+
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- All nodes must run the same GitLab version.
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Additionally, check GitLab's [minimum requirements](../../../install/requirements.md),
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and we recommend you use:
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- At least GitLab Enterprise Edition 10.0 for basic Geo features.
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- The latest version for a better experience.
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### Firewall rules
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The following table lists basic ports that must be open between the **primary** and **secondary** nodes for Geo.
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| **Primary** node | **Secondary** node | Protocol |
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|:-----------------|:-------------------|:-------------|
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| 80 | 80 | HTTP |
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| 443 | 443 | TCP or HTTPS |
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| 22 | 22 | TCP |
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| 5432 | | PostgreSQL |
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See the full list of ports used by GitLab in [Package defaults](https://docs.gitlab.com/omnibus/package-information/defaults.html)
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NOTE: **Note:**
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[Web terminal](../../../ci/environments/index.md#web-terminals) support requires your load balancer to correctly handle WebSocket connections.
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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.
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NOTE: **Note:**
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When using HTTPS protocol for port 443, you will need to add an SSL certificate to the load balancers.
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If you wish to terminate SSL at the GitLab application server instead, use TCP protocol.
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### LDAP
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We recommend that if you use LDAP on your **primary** node, you also set up secondary LDAP servers on each **secondary** node. Otherwise, users will not be able to perform Git operations over HTTP(s) on the **secondary** node using HTTP Basic Authentication. However, Git via SSH and personal access tokens will still work.
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NOTE: **Note:**
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It is possible for all **secondary** nodes 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** node is promoted to be a **primary** node.
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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).
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### Geo Tracking Database
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The tracking database instance is used as metadata to control what needs to be updated on the disk of the local instance. For example:
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- Download new assets.
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- Fetch new LFS Objects.
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- Fetch changes from a repository that has recently been updated.
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Because the replicated database instance is read-only, we need this additional database instance for each **secondary** node.
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The tracking database requires the `postgres_fdw` extension.
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### Geo Log Cursor
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This daemon:
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- Reads a log of events replicated by the **primary** node to the **secondary** database instance.
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- Updates the Geo Tracking Database instance with changes that need to be executed.
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When something is marked to be updated in the tracking database instance, asynchronous jobs running on the **secondary** node will execute the required operations and update the state.
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This new architecture allows GitLab to be resilient to connectivity issues between the nodes. It doesn't matter how long the **secondary** node is disconnected from the **primary** node as it will be able to replay all the events in the correct order and become synchronized with the **primary** node again.
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## Setup instructions
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These instructions assume you have a working instance of GitLab. They guide you through:
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1. Making your existing instance the **primary** node.
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1. Adding **secondary** nodes.
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CAUTION: **Caution:**
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The steps below should be followed in the order they appear. **Make sure the GitLab version is the same on all nodes.**
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### Using Omnibus GitLab
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If you installed GitLab using the Omnibus packages (highly recommended):
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1. [Install GitLab Enterprise Edition](https://about.gitlab.com/install/) on the server that will serve as the **secondary** node. Do not create an account or log in to the new **secondary** node.
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1. [Upload the GitLab License](../../../user/admin_area/license.md) on the **primary** node to unlock Geo. The license must be for [GitLab Premium](https://about.gitlab.com/pricing/) or higher.
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1. [Set up the database replication](database.md) (`primary (read-write) <-> secondary (read-only)` topology).
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1. [Configure fast lookup of authorized SSH keys in the database](../../operations/fast_ssh_key_lookup.md). This step is required and needs to be done on **both** the **primary** and **secondary** nodes.
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1. [Configure GitLab](configuration.md) to set the **primary** and **secondary** nodes.
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1. Optional: [Configure a secondary LDAP server](../../auth/ldap.md) for the **secondary** node. See [notes on LDAP](#ldap).
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1. [Follow the "Using a Geo Server" guide](using_a_geo_server.md).
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## Post-installation documentation
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After installing GitLab on the **secondary** nodes and performing the initial configuration, see the following documentation for post-installation information.
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### Configuring Geo
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For information on configuring Geo, see [Geo configuration](configuration.md).
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### Updating Geo
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For information on how to update your Geo nodes to the latest GitLab version, see [Updating the Geo nodes](updating_the_geo_nodes.md).
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### Configuring Geo for multiple servers
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For information on configuring Geo for multiple servers, see [Geo for multiple servers](multiple_servers.md).
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### Configuring Geo with Object Storage
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For information on configuring Geo with object storage, see [Geo with Object storage](object_storage.md).
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### Disaster Recovery
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For information on using Geo in disaster recovery situations to mitigate data-loss and restore services, see [Disaster Recovery](../disaster_recovery/index.md).
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### Replicating the Container Registry
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For more information on how to replicate the Container Registry, see [Docker Registry for a **secondary** node](docker_registry.md).
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### Security Review
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For more information on Geo security, see [Geo security review](security_review.md).
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### Tuning Geo
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For more information on tuning Geo, see [Tuning Geo](tuning.md).
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### Set up a location-aware Git URL
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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](location_aware_git_url.md).
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## Remove Geo node
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For more information on removing a Geo node, see [Removing **secondary** Geo nodes](remove_geo_node.md).
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## Current limitations
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CAUTION: **Caution:**
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This list of limitations only reflects the latest version of GitLab. If you are using an older version, extra limitations may be in place.
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- Pushing directly to a **secondary** node redirects (for HTTP) or proxies (for SSH) the request to the **primary** node 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`.
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- Cloning, pulling, or pushing repositories that exist on the **primary** node but not on the **secondary** nodes where [selective synchronization](configuration.md#selective-synchronization) does not include the project is not supported over SSH [but support is planned](https://gitlab.com/groups/gitlab-org/-/epics/2562). HTTP(S) is supported.
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- The **primary** node has to be online for OAuth login to happen. Existing sessions and Git are not affected. Support for the **secondary** node to use an OAuth provider independent from the primary is [being planned](https://gitlab.com/gitlab-org/gitlab/issues/208465).
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- 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.
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- Real-time updates of issues/merge requests (for example, via long polling) doesn't work on the **secondary** node.
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- [Selective synchronization](configuration.md#selective-synchronization) applies only to files and repositories. Other datasets are replicated to the **secondary** node in full, making it inappropriate for use as an access control mechanism.
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- Object pools for forked project deduplication work only on the **primary** node, and are duplicated on the **secondary** node.
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- [External merge request diffs](../../merge_request_diffs.md) will not be replicated if they are on-disk, and viewing merge requests will fail. However, external MR diffs in object storage **are** supported. The default configuration (in-database) does work.
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- GitLab Runners cannot register with a **secondary** node. Support for this is [planned for the future](https://gitlab.com/gitlab-org/gitlab/issues/3294).
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### Limitations on replication/verification
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You can keep track of the progress to implement the missing items in
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these epics/issues:
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- [Unreplicated Data Types](https://gitlab.com/groups/gitlab-org/-/epics/893)
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- [Verify all replicated data](https://gitlab.com/groups/gitlab-org/-/epics/1430)
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There is a complete list of all GitLab [data types](datatypes.md) and [existing support for replication and verification](datatypes.md#limitations-on-replicationverification).
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## Frequently Asked Questions
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For answers to common questions, see the [Geo FAQ](faq.md).
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## Log files
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Since GitLab 9.5, Geo stores structured log messages in a `geo.log` file. For Omnibus installations, this file is at `/var/log/gitlab/gitlab-rails/geo.log`.
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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.
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For example:
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```json
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{"severity":"INFO","time":"2017-08-06T05:40:16.104Z","message":"Repository update","project_id":1,"source":"repository","resync_repository":true,"resync_wiki":true,"class":"Gitlab::Geo::LogCursor::Daemon","cursor_delay_s":0.038}
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```
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This message shows that Geo detected that a repository update was needed for project `1`.
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## Troubleshooting
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For troubleshooting steps, see [Geo Troubleshooting](troubleshooting.md).
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