mongodb-migrate

mongodb-migrate is a tool to migrate MongoDB data from one server to another without downtime using change streams. It works by executing a mongodump on the source database followed by a mongorestore on the destination database and then synchronizing further document insertions, updates, replacements and deletions. The watcher is set up before the initial execution mongodump so no changes will go missing.

Caveats:

• change streams are only available for replica sets and sharded clusters (note that a standalone mongod instance can be converted to a replica set)
• the tool uses mongodump and mongorestore executables which must be available in the system path
• the tool only synchronizes one database, if you want to migrate multiple databases then run the tool multiple times in parallel or sequentially
• collection indexes are synchronized after the intial mongorestore but indexes created in the source database afterwards are not synchronized

Usage

Install globally

npm i -g @leede/mongodb-migrate

The package provides a mongodb-migrate executable:

usage: mongodb-migrate [-h] -s SRC -d DST [-e EXCLUDE] [-w EXCLUDEWATCH]

MongoDB migration tool

optional arguments:
  -h, --help            show this help message and exit
  -s SRC, --src SRC     Source database uri, must include database name
  -d DST, --dst DST     Destination database uri, must include database name
  -e EXCLUDE, --exclude EXCLUDE
                        Exclude collections, separate collection names with comma to exclude multiple collections
  -w EXCLUDEWATCH, --excludeWatch EXCLUDEWATCH
                        Exclude collections from being watched for changes - only a snapshot for these will be copied and further changes
                        will not be synchronized, separate collection names with comma to exclude multiple collections

Example (note that specifying a database name is mandatory in both the src and dst connection uris):

mongodb-migrate --src mongodb://user:pass@some-mongodb-server/mydb --dst mongodb://user2:pass2@another-mongodb-server/mynewdb

Migration steps:

1. Run mongodb-migrate
2. Wait until the intial mongorestore is completed
3. Change MongoDB connection uri in all your applications
4. Watch the output of the tool until it reports that no more changes are being made in the source database
5. Use Ctrl+C to stop mongodb-migrate when no more changes are anticipated in the source database