mongorewind

A terminal UI tool that watches a MongoDB cluster for changes and lets you rewind them — undoing inserts, updates, replaces, and deletes in reverse order.

Why?

When preparing to release a new version of an application, developers often restore a copy of the production database into a test cluster to verify that everything works correctly. Depending on the size of the database, this restore process can take a significant amount of time.

If something goes wrong during testing and the data needs to be in its original state to run the test again, the only option — without mongorewind — is to wait through another full restore cycle.

With mongorewind, you can instantly rewind all the changes made during the test run and start over, without touching the backup or waiting for a restore.

How it works

mongorewind opens a cluster-wide change stream and records every data-modifying event to a local log file. When you press R to rewind, it applies the inverse of each recorded operation in reverse chronological order:

Recorded operation	Rewind action
insert	deleteOne
update / replace	replaceOne with pre-image (upsert)
delete	replaceOne with pre-image (upsert)

Pre-images (the document state before each change) are captured automatically using MongoDB's changeStreamPreAndPostImages collection option, which mongorewind enables on every collection it finds — and on any new collection the moment it is created.

Requirements

• Go 1.24+
• MongoDB 6.0+ running as a replica set or sharded cluster (change streams are not available on standalone instances)

Installation

git clone https://github.com/zelmario/mongorewind.git
cd mongorewind
go build -o mongorewind .

Or install directly:

go install github.com/zelmario/mongorewind@latest

Usage

mongorewind [flags]

Flags:
  -uri string   MongoDB connection URI (default "mongodb://localhost:27017")
  -log string   Path to the on-disk change log (default "rewind.log")

Run mongorewind --help to see all flags.

Replica set URI

For replica sets, include all hosts and the replicaSet parameter so the driver can discover the primary automatically:

mongorewind --uri "mongodb://host1:27017,host2:27017,host3:27017/?replicaSet=rs0"

Keyboard controls

Key	Action
R	Rewind — invert all recorded changes, newest first
C	Clear — discard the recorded log without rewinding
Q / Ctrl-C	Quit

CI / non-interactive rewind

Run mongorewind --rewind from any shell or script to trigger a rewind in the already-running instance and wait for it to complete:

# start the watcher (e.g. as a background service or in another terminal)
mongorewind --uri "mongodb://..." &

# run your test suite
run_tests

# rewind all changes and run again
mongorewind --rewind
run_tests

mongorewind --rewind exits with code 0 on success and 1 on error, so it integrates naturally into CI pipelines.

If you use a custom --log path, pass the same value to --rewind so it finds the correct socket:

mongorewind --log /tmp/mytest.log --uri "mongodb://..." &
mongorewind --log /tmp/mytest.log --rewind

Display

  mongorewind
  ────────────────────────────────────────────────────────────────
  ● watching   4 operation(s) pending rewind

  Database                       Inserts    Updates    Deletes
  ────────────────────────────────────────────────────────────────
  myapp                                1          2          1
  ────────────────────────────────────────────────────────────────
  Total                                1          2          1

  R=rewind  C=clear  Q=quit

The status indicator shows ● watching (green) while the change stream is active, or ○ idle (yellow) during a rewind operation.

Development

testdata.sh is a load generator that hammers MongoDB with random inserts, updates, and deletes across multiple databases and collections. Useful for testing mongorewind:

# defaults: mongodb://localhost:27017, 0.1s delay between ops, 5 parallel workers
./testdata.sh

# custom URI, faster
./testdata.sh "mongodb://localhost:27017/?replicaSet=rs0" 0.05 10

Requires mongosh on $PATH.

Notes

• Replica set requirement — MongoDB change streams require a replica set or sharded cluster. A standalone mongod will not work. You can start a single-node replica set for local development with mongod --replSet rs0 followed by rs.initiate() in the mongo shell.
• Pre-images — mongorewind uses fullDocumentBeforeChange to capture the state of a document before every update or delete. It enables this automatically on all collections via collMod, and polls every 2 seconds to catch newly created collections.
• Log file — Changes are persisted as raw BSON to rewind.log (configurable with --log). The file is truncated on startup and after a successful rewind, so each session starts clean.
• Scope — The change stream watches the entire cluster. System databases (admin, local, config) and system.* collections are ignored.

License

MIT