Rollbacks

Rollbacks are a powerful feature that allows you to easily revert changes to your application. This is particularly useful when you encounter issues or want to revert to a previous version of your application.

Requirements

1. Have a /health endpoint in your application.
2. Have curl available in your container (if you use alpine for example, it won't be installed by default).

Steps to Rollback

Let's suppose we have a NodeJS application that has a health check route /api/health that returns a 200 status code and running in the port 3000.

1. In your application is necessary to have a Path or Health Route to be able to achieve zero downtime deployments eg. in the case of a NodeJS app you can have a route /api/health that returns a 200 status code.
2. Go to Advanced Tab and go to Cluster Settings and enter to Swarm Settings
3. There are a couple options that you can use, in this case we will focus on Health Check and Update Config.
4. Paste this code in the health check field: Make sure the API Route exists in your application

{
  "Test": [
    "CMD",
    "curl",
    "-f",
    "http://localhost:3000/api/health"
  ],
  "Interval": 30000000000,
  "Timeout": 10000000000,
  "StartPeriod": 30000000000,
  "Retries": 3
}

5. Now in the Update Config

Now when the application is getting unhealthy response from the health check, the container will rollback to the previous version.

Paste the following code:

{
  "Parallelism": 1,
  "Delay": 10000000000,
  "FailureAction": "rollback",
  "Order": "start-first"
}