Shutting Down a Multi-Tiered Deployment

Overview

Whether or not your RightScale-managed Deployment in the cloud is designed to scale or not, it is very common to configure it with multiple tiers. For example, the following three tiers are typical:

1. Front-end tier that services (and load-balances) requests
2. Middle application tier
3. Back-end database tier

There are two common configurations of the above multi-tiered Deployment model as well. One has the first two tiers completely separate; that is, tier one is strictly for load balancers, and tier two is strictly for the application (usually a scalable Server Array with a minimum instance count of two).  The other combines your application and front-end services for two Servers (and adds a scalable Server Array as well). 

In this example, the application is being served by both the FrontEnd Servers and Servers in the Server Array.

In this example, the application is only being served by Servers in the Server Array.

Depending on your specific configuration, how you shut down or start up your Deployment could differ somewhat. 

The key for determining the order in which to shut down or start up your Deployment components is dependencies--for example, what do the Servers running your application depend on to start up or shut down correctly?

Disclaimer

Because each specific application and Deployment for that application is different, there is not a strict set of rules for shutting down or starting up a multi-tiered Deployment that applies in every scenario.  For that reason, please consider the information in this document as guidelines (and not strict rules). 

Remember to implement reboot-safe RightScripts (and/or Chef Recipes), and test out your Boot- and Decommission-phase scripts thoroughly.

Shutting Down

Important!  Rarely (if ever) will you shut down an entire production Deployment. However, you may want to shut down an entire staging or test Deployment at night or over a weekend to save on usage costs.

Shutting down a multi-tiered Deployment is usually more straightforward than starting it back up.  A common shutdown order by tier is as follows:

• Shut down the front-end load balancer tier first. This will prevent future requests--which may or may not require additional computation at the application (middle) tier and read/write actions on the database tier--from being serviced.
• Shut down the application tier. If you are using a scalable Server Array, remember to disable the array first.  If you forget to do this and terminate all running instances, new instances will automatically be launched (in accordance with the minimum count for Servers in your Array).
• Once the application tier has shut down, shut down the database tier.

See Also

• Starting up a Multi-tiered Deployment
• Typical scalable web architectures