1.4: Create Azure App Service web apps - Explore Azure App Service deployment slots

Question 1

In what App Service tiers can you use deployment slots

Answer 1

• Standard
• Premium
• Isolated

Question 2

Describe the benefits of deploying to a no-production deployment slot

Answer 2

1. You can validate app changes in a staging deployment slot before swapping it with the production slot.
2. Deploying an app to a slot first and swapping it into production makes sure that all instances of the slot are warmed up before being swapped into production. This eliminates downtime when you deploy your app.
3. You can quickly revert to your previous last known good site as it’s swapped into the non-production slot.

Question 3

Describe app scaling and deployment slot considerations

Answer 3

You can’t scale to a tier offering less deployment slots that you’re currentyl using.
(The number of slots you can use varies from tier to tier)

Question 4

Describe how to make settings swappable

Answer 4

To make settings swappable, add the app setting WEBSITE_OVERRIDE_PRESERVE_DEFAULT_STICKY_SLOT_SETTINGS in every slot of the app and set its value to 0 or false.

Question 5

List the settings which are swapped

Answer 5

• General settings, such as framework version, 32/64-bit, web sockets
• App settings (can be configured to stick to a slot)
• Connection strings (can be configured to stick to a slot)
• Handler mappings
• Public certificates
• Public certificates
• Hybrid connections *
• Virtual network integration *
• Service endpoints *
• Azure Content Delivery Network *

‘*’ items are planned to be unswappable

Question 6

List the settings which are unswapped

Answer 6

• Publishing endpoints
• Custom domain names
• Non-public certificates and TLS/SSL settings
• Scale settings
• WebJobs schedulers
• IP restrictions
• Always On
• Diagnostic log settings
• Cross-origin resource sharing (CORS)

Question 7

Describe how to make a settings not swappable

Answer 7

To configure an app setting or connection string to stick to a specific slot (not swapped), go to the Configuration page for that slot. Add or edit a setting, and then select Deployment slot setting. Selecting this check box tells App Service that the setting is not swappable.

Question 8

Describe how to manually swap a deployment slot

Answer 8

1. Go to apps Deployment slots page and select Swap. A dialog box is shown
2. Set the desired Source and Target slots (target is production)
3. Select Swap

Question 9

Describe how to manually swap a deployment slot with preview

Answer 9

A multi-phase swap:

1. Follow the same step as a standard swap, but select Perform swap with preview instead of Swap in step 3
2. When you’re ready to start the swap, select Start Swap.
3. When you’re ready to complete the pending swap, select Complete Swap in Swap action and select Complete Swap.

Question 10

Describe auto swap

Answer 10

Auto swap streamlines Azure DevOps scenarios where you want to deploy your app continuously with zero cold starts and zero downtime for customers of the app.

When auto swap is enabled from a slot into production, every time you push your code changes to that slot, App Service automatically swaps the app into production after it’s warmed up in the source slot.

Question 11

Describe how to configure auto swap

Answer 11

1. Go to your app’s resource page and select the deployment slot you want to configure to auto swap.
   The setting is on the Configuration > General settings page.
2. Set Auto swap enabled to On.
   Then select the desired target slot for Auto swap deployment slot, and select Save on the command bar.
3. Execute a code push to the source slot.
   Auto swap happens after a short time, and the update is reflected at your target slot’s URL.

Question 12

Describe how you can customise the warmup process

Answer 12

You can customise any warm up process by either:
1. Adding a initializationPage section to the web.config
2. Add one of the following app settings:
WEBSITE_SWAP_WARMUP_PING_PATH - endpoint to check
WEBSITE_SWAP_WARMUP_PING_STATUSES - list of valid statuses

Question 13

Describe deployment slot routing

Answer 13

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.</app_name>

Question 14

How do you route production traffic automatically

Answer 14

To route production traffic automatically:

1. Go to your app’s resource page and select Deployment slots.
2. 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.

Question 15

Describe route pinning

Answer 15

Once traffic has been routed it’s pinned to the slot it’s been routed to (a bit like ARR affinity).
You can find out what slot it’s pinned to by checking the x-ms-routing-name cookie in the headers

You can toggle this value via links - so you could offer access to a ‘beta’ site via a link, and once there, access to the current production site if the user wants to go back to it.
e.g.: <webappname>.azurewebsites.net/?x-ms-routing-name=staging