nodemon --exec flag: request automatic rollback on migration failure

Should nodemon add a --rollback flag?

Confirmed facts:

• Nodemon restarts the Node.js process on file changes and runs the command given with --exec on each restart.
• It does not inspect the exit status of that command or provide hooks for success/failure.
• Users can wrap the migration command in a shell script that checks $? and runs a rollback script on non‑zero exit.
• If the migration tool itself supports native undo (Flyway undo, Liquibase rollback), the wrapper can invoke that instead of a custom script.

Likely explanation / recommendation

Adding a built‑in --rollback option would be a convenience feature, but it is not required to achieve the safety goal. Nodemon could determine the moment to invoke rollback by checking the exit code of the child process it launches with --exec; a non‑zero status would trigger the rollback script before the next restart. This approach would not interfere with nodemon’s normal restart behavior because the rollback runs as part of the same exec cycle.

Steps to implement automatic rollback today

1. Create a migration wrapper script, e.g. run-migrate.sh:

#!/usr/bin/env bash
set -e
./migrate.sh   # your actual migration command
MIGRATE_STATUS=$?
if [ $MIGRATE_STATUS -ne 0 ]; then
  echo "Migration failed, running rollback..."
  ./rollback.sh   # user‑defined rollback or tool‑specific undo
  exit $MIGRATE_STATUS
fi

2. Make it executable: chmod +x run-migrate.sh.
3. Configure nodemon in package.json or a nodemon config file:

{
  "scripts": {
    "migrate": "nodemon --watch src --exec ./run-migrate.sh"
  }
}

4. To separate environments, export an environment variable before running nodemon, e.g. NODE_ENV=production npm run migrate, and let the wrapper script read $NODE_ENV to choose different rollback scripts:

#!/usr/bin/env bash
set -e
./migrate.sh
if [ $? -ne 0 ]; then
  if [ "$NODE_ENV" = "production" ]; then
    ./rollback-prod.sh
  else
    ./rollback-dev.sh
  fi
  exit 1
fi

Verification

• Create a dummy migrate.sh that exits with exit 1 and a rollback.sh that prints a message.
• Run npm run migrate; nodemon will execute the wrapper, see the non‑zero exit, run the rollback script, and then wait for the next file change.
• Check the console output for the rollback message to confirm it ran exactly once per failure.