Today we are releasing two new features that will allow customers an easier scaling experience.
First, you are now able to add an app slave with a different size than your app master. If your application instances begin experiencing higher load, you may decide you need a larger size application instance. In the past, you would need to stop your environment and bring up larger size instances - causing some downtime. With this new feature, you can move to larger sizes without having to stop your environment and incur downtime. In addition, you can also use this technique to grow the volume size of your instances. Just create new app slave(s) of the desired size, then phase out the older, smaller instances.
Second, you can now trigger a promotion for your application instances. This will promote an application slave to become the new application master. This is automatically done for you by Engine Yard Cloud if we detect problems with the application master, but now you can trigger this event to occur. This can be extremely useful if you are trying to increase the size of your application instances using the new feature above, or if there is a particular outage in the Amazon Availability Zone in which the Application Master is running.
Choosing different size app instances is now available to all customers. Promoting app slaves is part of our Early Access program - which allows you to enable/disable this feature as needed.
You can learn more in our documentation.