46 lines
2.1 KiB
Markdown
46 lines
2.1 KiB
Markdown
---
|
|
stage: none
|
|
group: unassigned
|
|
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/product/ux/technical-writing/#assignments
|
|
---
|
|
|
|
# Rails initializers
|
|
|
|
By default, Rails loads Zeitwerk after the initializers in `config/initializers` are loaded.
|
|
Autoloading before Zeitwerk is loaded is now deprecated but because we use a lot of autoloaded
|
|
constants in our initializers, we had to move the loading of Zeitwerk earlier than these
|
|
initializers.
|
|
|
|
A side-effect of this is that in the initializers, `config.autoload_paths` is already frozen.
|
|
|
|
To run an initializer before Zeitwerk is loaded, you need put them in `config/initializers_before_autoloader`.
|
|
Ruby files in this folder are loaded in alphabetical order just like the default Rails initializers.
|
|
|
|
Some examples where you would need to do this are:
|
|
|
|
1. Modifying Rails' `config.autoload_paths`
|
|
1. Changing configuration that Zeitwerk uses, for example, inflections
|
|
|
|
## Database connections in initializers
|
|
|
|
Ideally, database connections are not opened from Rails initializers. Opening a
|
|
database connection (for example, checking the database exists, or making a database
|
|
query) from an initializer means that tasks like `db:drop`, and
|
|
`db:test:prepare` will fail because an active session prevents the database from
|
|
being dropped.
|
|
|
|
To prevent this, we stop database connections from being opened during
|
|
routes loading. Doing will result in an error:
|
|
|
|
```shell
|
|
RuntimeError:
|
|
Database connection should not be called during initializers.
|
|
# ./config/initializers/00_connection_logger.rb:15:in `new_client'
|
|
# ./lib/gitlab/database/load_balancing/load_balancer.rb:112:in `block in read_write'
|
|
# ./lib/gitlab/database/load_balancing/load_balancer.rb:184:in `retry_with_backoff'
|
|
# ./lib/gitlab/database/load_balancing/load_balancer.rb:111:in `read_write'
|
|
# ./lib/gitlab/database/load_balancing/connection_proxy.rb:119:in `write_using_load_balancer'
|
|
# ./lib/gitlab/database/load_balancing/connection_proxy.rb:89:in `method_missing'
|
|
# ./config/routes.rb:10:in `block in <main>'
|
|
# ./config/routes.rb:9:in `<main>'
|
|
```
|