Self-learning:Overview of Updating a Windows Azure Service

 rolling upgrade

A rolling upgrade is a deployment feature of Windows Azure that allowsservice instances to be stopped and upgradedindividually without bringing all of your instances down at the same time. This allows your sedrvice to remain operational during upgrade periods (albeit in a degraded state).

http://msdn.microsoft.com/en-us/library/hh472157.aspx

Updated: October 17, 2011

You can upgrade your Windows Azure hosted service to a new service version by using the Windows Azure Platform Management Portal or the Windows Azure Service Management API. Windows Azure provides two mechanisms for upgrading your deployed service:

• In-place upgrade. You can upgrade either a single role or all the roles within your service in place. You can perform an in-place upgrade when there are no changes to your service model between versions.Changes to the number of rolesor the size of virtual machine that is used for a role also are supported, but require special handling. To avoid service interruptions during an in-place upgrade, Windows Azure stops some instances of your roles to upgrade them while keeping other instances running. 
  

Note : Service Model (from http://blogsprajeesh.blogspot.com/2010/08/windows-azure-service-model.html)

The Windows Azure service model is determined by the service definition file. The service definition defines what kind of code the role is made of. This is specified when building the service, and can't be changed dynamically when the application is running. The service definition file defines the roles that comprise a service, optional local storage resources, configuration settings, and certificates for SSL endpoints.The service definition details goes into the ServiceDefinition.cscfg file. This file acts as a simplified service model for the Role. If lays out a few critical components of the role like:

• Options for these roles (virtual machine size, whether native code execution is supported)
• Input endpoints for these roles.
• Local disk storage that the role will need.
• Configuration settings that the role will use.

The service configuration file sets values for the service that can be configured while the service is running in the fabric. The values that can be specified in the service configuration file include the number of instances that needed to be deployed for each role. The service configuration contains tweakable settings which can be changed on-the-fly without having to rebuild and redeploy the application. Service configuration file (ServiceConfiguration.cscfg) contains two key elements:

• Number of role instances used by the role.
• Value for the settings defined in the Service definition file.

• Swap VIP upgrade. You can deploy a new version of your service to the staging environment, and then swap that deployment with the deployment currently in production. This type of upgrade is referred to as a VIP swap because the virtual IP address (VIP) of the service in the staging environment is swapped with the friendlier VIP address of the service in the production environment. 
  
  

For more information about how Windows Azure processes both types of upgrade and a list of the types of service changes that each type of upgrade supports, see Overview of Updating a Windows Azure Service.

In this section

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How to Perform In-Place Upgrades on a Hosted Service in Windows Azure

How to Deploy a Service Upgrade to Production by Swapping VIPs in Windows Azure

See Also

Concepts

Overview of Updating a Windows Azure Service 

Other Resources

Windows Azure Service Management REST API Reference