From 235685aa61c594dfad9bd043bcb71b49a898f7b6 Mon Sep 17 00:00:00 2001
From: Eric Mc Sween <5454374+emcsween@users.noreply.github.com>
Date: Tue, 14 Jul 2026 08:42:18 -0400
Subject: [PATCH] Merge pull request #35432 from
 overleaf/em-change-library-mongo-cluster-migration-script

Copy library collections to the auxiliary Mongo cluster

GitOrigin-RevId: 87c0433b4345fdaa3fe3c141af888eaa0106ea45
---
 services/web/app/src/infrastructure/mongodb.mjs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/services/web/app/src/infrastructure/mongodb.mjs b/services/web/app/src/infrastructure/mongodb.mjs
index e467327e82..3f828c669f 100644
--- a/services/web/app/src/infrastructure/mongodb.mjs
+++ b/services/web/app/src/infrastructure/mongodb.mjs
@@ -254,6 +254,18 @@ export async function getCollectionInternal(name) {
   return internalDb.collection(name)
 }
 
+/**
+ * Direct access to a collection on the auxiliary Mongo cluster, bypassing
+ * the dual-write mirror in `db`. For use by data-migration scripts that need
+ * to write to the auxiliary cluster without also writing to the primary one.
+ */
+export async function getAuxCollectionInternal(name) {
+  if (!auxInternalDb) {
+    throw new OError('no auxiliary Mongo cluster configured')
+  }
+  return auxInternalDb.collection(name)
+}
+
 export async function waitForDb() {
   await connectionPromise
   await auxConnectionPromise