Migrations Collection

migrations records which database migrations have run. One document is one migration from tools/migrations/. It is written by the adapter of the east migration tool, tools/migrations/lib/adapter.mjs, not by a running service.

Fields

Field	Type	Meaning	Source
_id	ObjectId	Document id.	adapter.mjs:103
name	String	File name of the migration without the extension, for example 20190912145029_create_tags_indexes.	adapter.mjs:104
migratedAt	Date	When the migration finished.	adapter.mjs:105

Who Writes It

Code	What it does
adapter.mjs:101-107 (markExecuted)	Inserts a document after a migration ran.
adapter.mjs:109-114 (unmarkExecuted)	Deletes it again when a migration is rolled back.

CE runs yarn run migrations migrate -t server-ce at every container start (server-ce/init_scripts/900_run_web_migrations.sh:4-12; -t server-pro when OVERLEAF_IS_SERVER_PRO=true). Only migrations whose tags include that environment run, so only those get a document here.

Who Reads It

Code	What it does
adapter.mjs:72-99 (getExecutedMigrationNames)	east skips every migration whose name is already here.
tools/migrations/lib/helpers.mjs:67-75 (assertDependency)	A migration that needs another one to have run first throws when that name is missing.

Indexes

Name	Keys	Options	Migration
name_1	{ name: 1 }	unique	tools/migrations/20190720165251_create_migrations.mjs

Notes

• Deleting a document makes that migration run again at the next container start, if its tags match.
• With an auxiliary Mongo cluster (mongo.auxUrl), migrations tagged auxiliary are recorded in the migrations collection of that cluster instead (adapter.mjs:8-15, :64-70). mongo.auxUrl comes from MONGO_AUX_CONNECTION_STRING (tools/migrations/config/settings.defaults.js:19), which is unset by default.