Route traffic in App Service
By default, all client requests to the app's production URL (http://<app_name>.azurewebsites.net) are routed to the production slot. You can route a portion of the traffic to another slot. This feature is useful if you need user feedback for a new update, but you're not ready to release it to production.
Route production traffic automatically
To route production traffic automatically:
Go to your app's resource page and select Deployment slots.
In the Traffic % column of the slot you want to route to, specify a percentage (between 0 and 100) to represent the amount of total traffic you want to route. Select Save.
After the setting is saved, the specified percentage of clients is randomly routed to the non-production slot.
After a client is automatically routed to a specific slot, it's "pinned" to that slot for the life of that client session. On the client browser, you can see which slot your session is pinned to by looking at the x-ms-routing-name cookie in your HTTP headers. A request that's routed to the "staging" slot has the cookie x-ms-routing-name=staging. A request that's routed to the production slot has the cookie x-ms-routing-name=self.
Route production traffic manually
In addition to automatic traffic routing, App Service can route requests to a specific slot. This is useful when you want your users to be able to opt in to or opt out of your beta app. To route production traffic manually, you use the x-ms-routing-name query parameter.
To let users opt out of your beta app, for example, you can put this link on your webpage:
<a href="<webappname>.azurewebsites.net/?x-ms-routing-name=self">Go back to production app</a>
The string x-ms-routing-name=self specifies the production slot. After the client browser accesses the link, it's redirected to the production slot. Every subsequent request has the x-ms-routing-name=self cookie that pins the session to the production slot.
To let users opt in to your beta app, set the same query parameter to the name of the non-production slot. Here's an example:
<webappname>.azurewebsites.net/?x-ms-routing-name=staging
By default, new slots are given a routing rule of 0%, a default value is displayed in grey. When you explicitly set the routing rule value to 0% it's displayed in black, your users can access the staging slot manually by using the x-ms-routing-name query parameter. But they won't be routed to the slot automatically because the routing percentage is set to 0. This is an advanced scenario where you can "hide" your staging slot from the public while allowing internal teams to test changes on the slot.