MongoDB → Azure Cosmos DB for MongoDB

📖 Overview & Scope

This SOP covers a full copy (all documents) from a MongoDB 4.4+ source into an Azure Cosmos DB for MongoDB API target using the Endrias Bridge GUI. Because both are document databases, no schema translation occurs — documents are copied verbatim. Containers (collections) and their partition keys must be created in Cosmos DB before migration begins; indexes must be recreated manually after migration.

✅ Prerequisites — Source (MongoDB)

MongoDB must be running in replica set mode. Standalone instances have no oplog and cannot use Change Data Capture (CDC) mode. For full-copy mode, standalone instances are supported but CDC will be unavailable.

// Verify replica set status — must show PRIMARY + at least one SECONDARY
rs.status()

// Set oplog retention to 720 hours (30 days) to protect against migration gaps
db.adminCommand({ setParameter: 1, oplogMinRetentionHours: 720 })

// Source connection URI (generic placeholder)
// mongodb://MigrationUser:password@mongo-source-server:27017/EndriasBridge?authSource=admin

// Grant migration user read access on source DB + clusterMonitor for Change Streams
use admin
db.createUser({
  user: "MigrationUser",
  pwd: "password",
  roles: [
    { role: "read", db: "EndriasBridge" },
    { role: "clusterMonitor", db: "admin" }
  ]
})

✅ Prerequisites — Target (Cosmos DB for MongoDB)

Cosmos DB containers require a partition key that cannot be changed after creation. Plan partition keys carefully before creating containers.

// Target connection URI (generic placeholder)
// mongodb://cosmos-account.mongo.cosmos.azure.com:10255/EndriasBridgeTarget
//   ?ssl=true&replicaSet=globaldb&retrywrites=false

// Recommended: set throughput to 10,000 RU/s (autoscale) during migration
// Scale down to steady-state (400–2,000 RU/s) after migration completes

Open Endrias Bridge and navigate to Migration Projects. Create a new project and fill in both connection blocks as shown:

Switch to the Assessment tab and click Run Assessment. Endrias Bridge will connect to the MongoDB source, enumerate all collections with document counts and index definitions, and report any compatibility notes for the Cosmos DB target.

Return to Migration Projects. Click Load Collections from Source. All 5 collections are selected by default. Deselect any collections you want to skip.

Click Start Migration. The migration log updates live as each collection's documents are bulk-inserted. Monitor for RU throttling (error 16500) and increase RU/s if needed.

1. Click Verify Document Counts — compares source vs. target document counts per collection and logs mismatches.
2. Run manual count validation:

   // On source (mongosh)
   db.users.countDocuments()
   
   // On Cosmos DB target (mongosh)
   db.users.count()

3. Test a sample of queries against the Cosmos DB target to confirm document shape and partition key distribution.
4. Click Export Report (enabled once migration finishes) to save an HTML summary of collections migrated, document counts, and any warnings.

Complete the following tasks after verifying document counts:

⚠️ Known Issues

📊 Collection & Object Mapping (MongoDB → Cosmos DB)