Deployment slots for staging in Azure - Step-by-Step Execution

Process Flow - Deployment slots for staging

Create Web App

↓

Add Deployment Slot: Staging

↓

Deploy Code to Staging Slot

↓

Test Staging Slot

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Swap Slots: Staging <-> Production

↓

Production Runs New Version

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Old Production Becomes Staging

This flow shows how a staging slot is created, code is deployed and tested there, then swapped with production for safe release.

Execution Sample

Azure

az webapp deployment slot create --name MyApp --resource-group MyRG --slot staging
az webapp deployment slot swap --name MyApp --resource-group MyRG --slot staging

Creates a staging slot for the web app and then swaps it with production to release new code safely.

Process Table

Step	Action	Slot State	Result
1	Create Web App 'MyApp'	Production: running, Staging: none	Web app created with only production slot
2	Create staging slot	Production: running, Staging: created (empty)	Staging slot ready for deployment
3	Deploy code to staging	Production: running, Staging: running new code	New version running in staging slot
4	Test staging slot	Production: running, Staging: running new code	Tests passed, ready to swap
5	Swap staging with production	Production: running new code, Staging: running old code	Slots swapped; production runs new code
6	Post-swap state	Production: running new code, Staging: running old code	Old production version now in staging slot

💡 Swap completes, production runs new version safely with rollback option in staging slot

Status Tracker

Slot	Initial	After Creation	After Deploy	After Swap
Production	Running old code	Running old code	Running old code	Running new code
Staging	None	Created empty	Running new code	Running old code

Key Moments - 3 Insights

Why do we create a separate staging slot instead of deploying directly to production?

Creating a staging slot lets us test new code safely without affecting users. Execution table step 3 shows new code running only in staging before swap.

What happens during the swap step?

The swap exchanges the content and traffic between production and staging slots. Step 5 shows production running new code after swap, step 6 confirms the post-swap state.

Can we quickly rollback if the new code has issues?

Yes, because the old production version moves to staging slot after swap (step 6), we can swap again to rollback.

Visual Quiz - 3 Questions

Look at the execution table, what is the state of the staging slot after step 3?

A Staging slot is empty

B Staging slot is running new code

C Staging slot is running old code

D Staging slot does not exist

💡 Hint

Check the 'Slot State' column for step 3 in the execution table

At which step does production start running the new code?

A Step 5

B Step 4

C Step 6

D Step 3

💡 Hint

Look at the 'Slot State' column after swap completes in the execution table

If we skip testing in staging (step 4), what risk increases?

A No risk, swap is safe

B Staging slot will be deleted automatically

C New code might have bugs affecting production

D Production slot will stop running

💡 Hint

Refer to the purpose of step 4 in the concept flow and key moments

Concept Snapshot

Deployment slots let you run a staging version of your app.
Deploy and test new code in staging without affecting users.
Swap staging with production to release safely.
Old production version moves to staging for quick rollback.
Use Azure CLI commands to create slots and swap them.

Full Transcript

Deployment slots for staging in Azure let you create a separate environment for your web app. You first create your main web app with a production slot. Then you add a staging slot where you deploy new code. You test the staging slot to ensure the new version works well. When ready, you swap the staging slot with production. This swap makes the new code live for users while moving the old production version to staging. This way, you can quickly rollback if needed. The process uses Azure CLI commands to create slots and swap them. This method helps release updates safely without downtime or risk to users.

Practice

1. What is the main purpose of using deployment slots in Azure App Service?

easy

A. To create multiple independent apps with separate resources

B. To test new app versions safely before making them live

C. To increase the storage capacity of the app

D. To backup the app data automatically

Solution

1. Step 1: Understand deployment slots purpose

   Deployment slots allow you to deploy a new version of your app in a separate slot to test it without affecting the live app.

2. Step 2: Compare options with deployment slots function

   Options A, B, and D describe unrelated features like independent apps, storage, or backups, which are not the main purpose of deployment slots.

3. Final Answer:

   To test new app versions safely before making them live -> Option B

4. Quick Check:

   Deployment slots = safe testing before live [OK]

Hint: Deployment slots = safe app version testing before live [OK]

Common Mistakes:

• Thinking slots increase storage
• Confusing slots with separate apps
• Assuming slots are for backups

2. Which of the following is the correct way to swap a staging slot with the production slot in Azure CLI?

easy

A. az webapp deployment swap --name MyApp --resource-group MyGroup --slot staging

B. az webapp slot swap --name MyApp --resource-group MyGroup --slot production

C. az webapp deployment slot swap --name MyApp --resource-group MyGroup --slot staging

D. az webapp deployment slot switch --name MyApp --resource-group MyGroup --slot staging

Solution

1. Step 1: Identify correct Azure CLI command syntax

   The correct command to swap deployment slots is az webapp deployment slot swap with parameters for app name, resource group, and slot.

2. Step 2: Check each option's command correctness

   az webapp deployment slot swap --name MyApp --resource-group MyGroup --slot staging matches the correct syntax exactly. Options B, C, and D have incorrect command names or parameters.

3. Final Answer:

   az webapp deployment slot swap --name MyApp --resource-group MyGroup --slot staging -> Option C

4. Quick Check:

   Correct CLI swap command = az webapp deployment slot swap --name MyApp --resource-group MyGroup --slot staging [OK]

Hint: Use 'az webapp deployment slot swap' with --slot staging [OK]

Common Mistakes:

• Using 'slot swap' instead of 'deployment slot swap'
• Swapping with production slot explicitly
• Misspelling 'deployment' or 'swap'

3. Given the following Azure App Service slots setup:

Production slot URL: https://myapp.azurewebsites.net
Staging slot URL: https://myapp-staging.azurewebsites.net

If you deploy a new version to the staging slot and then swap slots, what will be the URL of the new live app?

medium

A. https://myapp-staging.azurewebsites.net

B. https://myapp-live.azurewebsites.net

C. https://myapp-staging-live.azurewebsites.net

D. https://myapp.azurewebsites.net

Solution

1. Step 1: Understand slot URLs and swapping behavior

   Each slot has its own URL. When you swap staging with production, the staging app becomes live at the production URL.

2. Step 2: Identify the live app URL after swap

   After swapping, the new live app runs at the production slot URL https://myapp.azurewebsites.net. The staging URL remains for the old production app now in staging.

3. Final Answer:

   https://myapp.azurewebsites.net -> Option D

4. Quick Check:

   Swap keeps live URL as production slot URL [OK]

Hint: Live app URL stays production slot URL after swap [OK]

Common Mistakes:

• Assuming staging URL becomes live URL
• Thinking swap creates new URLs
• Confusing slot names with URLs

4. You tried to swap your staging slot with production but received an error saying the swap failed due to configuration conflicts. What is the most likely cause?

medium

A. The staging slot has app settings marked as 'slot setting' that differ from production

B. The staging slot is using a different Azure subscription

C. The production slot is stopped and cannot be swapped

D. The staging slot has no deployment

Solution

1. Step 1: Understand slot setting behavior during swap

   App settings marked as 'slot setting' stay with their slot and do not swap. Conflicts arise if these settings differ between slots.

2. Step 2: Analyze error cause possibilities

   The staging slot has app settings marked as 'slot setting' that differ from production explains configuration conflicts due to slot settings. Options B, C, and D do not cause swap configuration conflicts.

3. Final Answer:

   The staging slot has app settings marked as 'slot setting' that differ from production -> Option A

4. Quick Check:

   Slot setting conflicts cause swap errors [OK]

Hint: Check 'slot setting' app settings for conflicts before swap [OK]

Common Mistakes:

• Ignoring slot setting app configuration
• Assuming subscription mismatch causes swap errors
• Trying to swap when production is stopped

5. You want to minimize downtime during a major app update using deployment slots. Which strategy best achieves this?

hard

A. Deploy the new version to a staging slot, test it, then swap with production slot

B. Deploy directly to production slot during off-hours without staging

C. Create a new app service and switch DNS to it after deployment

D. Stop the production slot, deploy update, then start it again

Solution

1. Step 1: Understand deployment slots for zero downtime

   Deployment slots allow deploying and testing new versions without affecting live traffic, then swapping instantly to minimize downtime.

2. Step 2: Evaluate each strategy for downtime impact

   Deploy the new version to a staging slot, test it, then swap with production slot uses deployment slots correctly. Options A, B, and C cause downtime or complex DNS changes.

3. Final Answer:

   Deploy the new version to a staging slot, test it, then swap with production slot -> Option A

4. Quick Check:

   Use staging slot deployment and swap for minimal downtime [OK]

Hint: Deploy to staging slot, test, then swap to production [OK]

Common Mistakes:

• Deploying directly to production causing downtime
• Using DNS switch instead of slot swap
• Stopping production slot during update