40 lines
1.7 KiB
Markdown
40 lines
1.7 KiB
Markdown
---
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stage: none
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group: unassigned
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info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
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---
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# Rails initializers
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By default, Rails loads Zeitwerk after the initializers in `config/initializers` are loaded.
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Autoloading before Zeitwerk is loaded is now deprecated but because we use a lot of autoloaded
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constants in our initializers, we had to move the loading of Zeitwerk earlier than these
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initializers.
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A side-effect of this is that in the initializers, `config.autoload_paths` is already frozen.
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To run an initializer before Zeitwerk is loaded, you need put them in `config/initializers_before_autoloader`.
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Ruby files in this folder are loaded in alphabetical order just like the default Rails initializers.
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Some examples where you would need to do this are:
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1. Modifying Rails' `config.autoload_paths`
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1. Changing configuration that Zeitwerk uses, for example, inflections
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## Database connections in initializers
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Ideally, database connections are not opened from Rails initializers. Opening a
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database connection (e.g. checking the database exists, or making a database
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query) from an initializer means that tasks like `db:drop`, and
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`db:test:prepare` will fail because an active session prevents the database from
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being dropped.
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To help detect when database connections are opened from initializers, we now
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warn in stderr. For example:
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```shell
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DEPRECATION WARNING: Database connection should not be called during initializers (called from block in <module:HasVariable> at app/models/concerns/ci/has_variable.rb:22)
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```
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If you wish to print out the full backtrace, set the
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`DEBUG_INITIALIZER_CONNECTIONS` environment variable.
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