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Maintenance Mode allows administrators to reduce write operations to a minimum while maintenance tasks are performed. The main goal is to block all external actions that change the internal state, including the PostgreSQL database, but especially files, Git repositories, Container repositories, etc.
Once Maintenance Mode is enabled, in-progress actions will finish relatively quickly since no new actions are coming in, and internal state changes will be minimal.
In that state, various maintenance tasks are easier, and services can be stopped completely or be
further degraded for a much shorter period of time than might otherwise be needed, for example stopping cron jobs and draining queues should be fairly quick.
Maintenance Mode allows most external actions that do not change internal state. On a high-level, HTTP POST, PUT, PATCH, and DELETE requests are blocked and a detailed overview of [how special cases are handled](#rest-api) is available.
In some cases, the visual feedback from an action could be misleading, for example when starring a project, the **Star** button changes to show the **Unstar** action, however, this is only the frontend update, and it doesn't take into account the failed status of the POST request. These visual bugs are to be fixed [in follow-up iterations](https://gitlab.com/gitlab-org/gitlab/-/issues/295197).
All users can log in and out of the GitLab instance but no new users can be created.
If there are [LDAP syncs](../auth/ldap/index.md) scheduled for that time, they will fail since user creation is disabled. Similarly, [user creations based on SAML](../../integration/saml.md#general-setup) will fail.
### Git actions
All read-only Git operations will continue to work, for example
`git clone` and `git pull`. All write operations will fail, both through the CLI and Web IDE with the error message: `Git push is not allowed because this GitLab instance is currently in (read-only) maintenance mode.`
If Geo is enabled, Git pushes to both primary and secondaries will fail.
### Merge requests, issues, epics
All write actions except those mentioned above will fail. For example, a user cannot update merge requests or issues.
### Incoming email
Creating new issue replies, issues (including new Service Desk issues), merge requests [by email](../incoming_email.md) will fail.
### Outgoing email
Notification emails will continue to arrive, but emails that require database writes, like resetting the password, will not arrive.
### REST API
For most JSON requests, POST, PUT, PATCH, and DELETE are blocked, and the API returns a 403 response with the error message: `You cannot perform write operations on a read-only instance`. Only the following requests are allowed:
| POST | `/admin/application_settings/general` | To allow updating application settings in the admin UI |
| PUT | `/api/v4/application/settings` | To allow updating application settings with the API |
| POST | `/users/sign_in` | To allow users to log in. |
| POST | `/users/sign_out`| To allow users to log out. |
| POST | `/oauth/token` | To allow users to log in to a Geo secondary for the first time. |
| POST | `/admin/session`, `/admin/session/destroy` | To allow [Admin mode for GitLab administrators](https://gitlab.com/groups/gitlab-org/-/epics/2158) |
| POST | Paths ending with `/compare`| Git revision routes. |
| POST | `.git/git-upload-pack` | To allow Git pull/clone. |
| POST | `/api/v4/internal` | [internal API routes](../../development/internal_api.md) |
| POST | `/admin/sidekiq` | To allow management of background jobs in the admin UI |
| POST | `/admin/geo` | To allow updating Geo Nodes in the admin UI |
| POST | `/api/v4/geo_replication`| To allow certain Geo-specific admin UI actions on secondary sites |
`POST /api/graphql` requests are allowed but mutations are blocked with the error message `You cannot perform write operations on a read-only instance`.
[Incident management](../../operations/incident_management/index.md) functions will be limited. The creation of [alerts](../../operations/incident_management/alerts.md) and [incidents](../../operations/incident_management/incidents.md#incident-creation) will be paused entirely. Notifications and paging on alerts and incidents will therefore be disabled.
- [Development feature flags](../../development/feature_flags/index.md) cannot be turned on or off through the API, but can be toggled through the Rails console.
- [The feature flag service](../../operations/feature_flags.md) will respond to feature flag checks but feature flags cannot be toggled
Replication and verification will continue to work but proxied Git pushes to primary will not work.
### Secure features
Features that depend on creating issues or creating or approving Merge Requests, will not work.
Exporting a vulnerability list from a Vulnerability Report page will not work.
Changing the status on a finding or vulnerability object will not work, even though no error is shown in the UI.
SAST and Secret Detection cannot be initiated because they depend on passing CI jobs to create artifacts.
## An example use case: a planned failover
In the use case of [a planned failover](../geo/disaster_recovery/planned_failover.md), a few writes in the primary database are acceptable, since they will be replicated quickly and are not significant in number.
The resulting database writes are acceptable. Here, the trade-off is between more service degradation and the completion of replication.
However, during a planned failover, we [ask users to turn off cron jobs that are not related to Geo, manually](../geo/disaster_recovery/planned_failover.md#prevent-updates-to-the-primary-node). In the absence of new database writes and non-Geo cron jobs, new background jobs would either not be created at all or be minimal.