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Multiple Staging Deployment of Azure Web Sites using Slots

How are you dealing the website management before going live with a new version? I have in mind different environments like production, testing, integration, development, persist the old version of the web site into a location that give you possibility to swap between the new one and old one if you have issues.

If you are using Azure Websites you will discover a new feature that gives you the possibility to have multiple staging environments live in the same time. Switching between them is done in real time. Before going further, you should know two things. One, we are not referring to staging environment, this is something more that staging and this feature is available only for Standard plan.
From now, you can deploy a new version of your web site into a separate slot, that is isolated 100% from the production one. There you can test how it’s behave, performance issues and so on. You can have as many slots as you want, each slot is accessible using a unique URL. Anytime, you can switch between them, putting another slot in production (swap). When a swap is done, the web site that was in production will replace the slot with is going in production. The mechanism is pretty simple, because in your slots, the websites are already loaded, resources allocated and so on. Only the DNS is changed. In this way the downtime is eliminated and no requests are dropped.
If during a SWAP something bad is happening and an error occurs, Azure will make automatically a rollback and the original version will be restored.
Be aware, you will pay for each slot that you have, like a normal website. For example if you have 2 slots (INT and TESTING) and another slot that is live, that you will pay 3 X Standard Web Sites.
When you create a new slot, you have the possibility to clone the configuration also. This is a pretty nice feature, especially when you have custom configuration in place. When you make s swap between slots the fallowing information will change:

  • Connection strings
  • General, Diagnostic and Monitoring setting
  • Handler Mapping

Also, there are other configuration that are not changed when you make a swap:

  • Publishing endpoints
  • Scale settings
  • Custom Domain Name
  • Bindings and SSL Certificates

I really like that scale settings are not swap between instances. In this way, we can have in slots normal configuration (one instance of our websites) and in production to have 10 or 20, based on our needs. Don’t forget that database connection string is changed when a swap is made. Because of this you need to change the one from slot to the production one before making a swap.
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