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sequelize-migration-hello

Testing of db migrations

Description

This repo is a simple demo of a basic database migration. It demonstrates the usage of Sequelize and Umzug to perform database migrations along with the application code changes that accompany the migration each step of the way. The emphasis is on demonstrating a database migration that can be applied while production code is running in the wild, ensuring backwards compatibility each step of the way.

A simple web server is provided that allows you to interact with the app at each step of the way via simple get/post requests with following endpoints:

  • GET /users: view all users
  • POST /users: create a new user
  • GET /users/dsql: view sequelize description of users table
  • GET /users/dpg: view postgres description of users table

The repo demonstrates 5 steps.

  1. Initial Setup (branch: 01-initial)
  2. DB: Add column with default value (branch: 02-addCol)
  3. App: Support column in data model, enforce validation (branch: 03-app-support-added)
  4. DB: Remove default value, require value (branch: 04-lock-down-db)
  5. App: Remove default value (branch: 05-lock-down-app)

The repo comes with a helper script for executing migration steps: migrate.js. It supports the following commands:

  • status: print current migration status
  • up/migrate: executed all unexecuted migrations
  • down/reset: revert all executed migrations
  • next/migrate-next: execute the next pending migration
  • prev/reset-prev: revert the previous executed migration
  • reset-hard: reset the database using a dropdb/createdb postgres command

Execute a command via:

node ./migrate.js <command>

Full demo flow

HOST="localhost:8080"
GET="curl -H "Content-Type: application/json" -X GET"
POST="curl -H "Content-Type: application/json" -X POST"

npm install

# start webserver
# will automatically restart when code changes
npm start

git checkout 01-initial
node ./migrate.js up

${GET} ${HOST}/users
${POST} ${HOST}/users -d '{"firstName":"Abel","lastName":"Allison"}'
${GET} ${HOST}/users
# Not supported yet
${POST} ${HOST}/users -d '{"firstName":"Abel","lastName":"Allison","eyeColor":"blue"}'

git checkout 02-addCol
node ./migrate.js up

# should see new column with default values
${GET} ${HOST}/users
# old app code still works, new column not yet supported
${POST} ${HOST}/users -d '{"firstName":"Abel","lastName":"Allison"}'
${POST} ${HOST}/users -d '{"firstName":"Abel","lastName":"Allison","eyeColor":"blue"}'

git checkout 03-app-support-added
node ./migrate.js up

# both verisons of add should now work
${POST} ${HOST}/users -d '{"firstName":"Abel","lastName":"Allison"}'
${POST} ${HOST}/users -d '{"firstName":"Abel","lastName":"Allison","eyeColor":"blue"}'

git checkout 04-lock-down-db
node ./migrate.js up

# both verisons of add should now work, db enforces not null and no default value
${POST} ${HOST}/users -d '{"firstName":"Abel","lastName":"Allison"}'
${POST} ${HOST}/users -d '{"firstName":"Abel","lastName":"Allison","eyeColor":"blue"}'

git checkout 05-lock-down-app
node ./migrate.js up

# old version of add now is forbidden
${POST} ${HOST}/users -d '{"firstName":"Abel","lastName":"Allison"}'

Setup

# Create admin-user and db
createuser sequelize_demo_admin --createdb --superuser
createdb sequelize_migration_demo --username sequelize_demo_admin

# Verify works
psql -d sequelize_migration_demo -U sequelize_demo_admin