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

Question

The goal is to guarantee that when a schema‑change script executed through nodemon’s --exec option fails, a user‑defined rollback script runs automatically to revert any partially applied changes, thereby providing a safety net for database migrations.

Currently nodemon only restarts the Node.js process on file changes and does not wrap the --exec command in a transaction or provide a built‑in rollback hook. It also lacks a permission boundary to prevent accidental execution of destructive migrations in production, relying solely on user‑configured ignore patterns. An open decision in the nodemon issue tracker is whether to add a --rollback flag or similar hook that would invoke a rollback script after a failed exec, which remains unresolved.

Should nodemon introduce a --rollback option that triggers a user‑defined script on exec failure? How would nodemon determine the appropriate moment to invoke the rollback without interfering with its normal restart behavior? What configuration would allow users to specify separate rollback scripts for different environments (e.g., development vs. production)?

Tasadduq Burney · Answer

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

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

Make it executable: chmod +x run-migrate.sh.
Configure nodemon in package.json or a nodemon config file:
{
  "scripts": {
    "migrate": "nodemon --watch src --exec ./run-migrate.sh"
  }
}

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.

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

1 answer

Should nodemon add a --rollback flag?

Likely explanation / recommendation

Steps to implement automatic rollback today

Verification

Your perspective belongs here.

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