Azure Container Apps Scale to Zero Resolution

Implement containerized solutions

Answer Correct answer: A — Enabling ingress and applying an HTTP scale rule allows the Azure Container App to scale up from zero instances.

Note: This question is part of a series of questions that present the same scenario. Each question in the series contains a unique solution that might meet the stated goals. Some question sets might have more than one correct solution, while others might not have a correct solution. After you answer a question in this section, you will NOT be able to return to it. As a result, these questions will not appear in the review screen. You deploy an Azure Container Apps app and disable ingress on the container app. Users report that they are unable to access the container app. You investigate and observe that the app has scaled to 0 instances. You need to resolve the issue with the container app. Solution: Enable ingress, create an HTTP scale rule, and apply the rule to the container app. Does the solution meet the goal?

Yes Correct Answer
No

Community Votes

100%

100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.

Community Insight

Azure Container Apps can scale from zero instances when ingress is enabled, as the ingress proxy queues requests and triggers the scale rule, unlike non-HTTP custom scalers that require minReplicas.

This page determines if enabling ingress and applying an HTTP scale rule resolves an Azure Container App scaling to zero issue. Enabling ingress allows the app to scale from zero instances upon receiving requests.

Choosing 'No' because of the misconception that an HTTP scale rule cannot trigger a scale-up from zero instances since no app instances exist to process the initial request.

Community Discussion (10 comments)

MarcosAn 👍 9 Selected: B

Must be carefull with Default Scale Rule: https://learn.microsoft.com/en-us/azure/container-apps/scale-app?pivots=azure-cli#default-scale-rule Make sure you create a scale rule or set minReplicas to 1 or more if you don't enable ingress. If ingress is disabled and you don't define a minReplicas or a custom scale rule, then your container app will scale to zero and have no way of starting back up.

8ac3742 👍 3 Selected: A

enabled ingress->create an HTTP scale rule to extend instances based on incoming traffic

Chriscrea8 👍 2

No, the solution does not meet the goal. Enabling ingress and creating an HTTP scale rule won't directly address the issue of the container app scaling down to 0 instances. Enabling ingress only allows external traffic to reach the container app, but it doesn't guarantee that the app will scale up or have instances available to handle incoming requests. To resolve the issue of the container app scaling down to 0 instances, you need to adjust the scaling settings to ensure that there are always instances available to handle incoming requests, even when traffic is low. This may involve modifying the minimum instance count or configuring auto-scaling rules based on metrics such as CPU usage or incoming requests. So, the correct answer is B. No.

Mahesh1222 👍 3

Though Enable Ingress, Set Scale rule to Http is correct, it will work based on Http traffic coming in when the Instance is already running. But it doesn't address the problem mentioned in the question - where it already scaled down to 0 instances. So to address this first, we need to ensure that there is at least one instance of the container app running to handle incoming requests. This may involve adjusting the scaling settings, configuring minimum instance limits, or implementing a health check mechanism to keep at least one instance running at all times, even during periods of low traffic.

jobolesonihal 👍 1 Selected: B

The HTTP scale rule in Azure App Service allows you to automatically scale your app based on HTTP traffic. However, if the Azure container app is scaled down to 0 instances, the HTTP scale rule will not work because there are no instances to scale. In other words, the HTTP scale rule only applies when there are active instances of the app to handle incoming HTTP requests. When the app is scaled down to 0 instances, no requests are being processed, and the scale rule does not have any effect. Therefore, if you want the HTTP scale rule to work, you need to ensure that there are at least one or more instances of the app running.

Ushakanth 👍 2 Selected: B

emysa341 👍 1

A is correct since scale rule can be HTTP https://learn.microsoft.com/en-us/azure/container-apps/scale-app?pivots=azure-cli#:~:text=Scale%20rules%20are%20implemented%20as%20HTTP%2C%20TCP%2C%20or%20custom.

FeriAZ 👍 3

Answer is A: Enabling Ingress: This would allow external traffic to reach the container app, which is necessary for users to access the app from outside the Azure network. Creating an HTTP Scale Rule: Azure Container Apps can automatically scale based on various metrics, including HTTP traffic. An HTTP scale rule would allow the app to scale up based on the incoming HTTP traffic. Applying the Rule to the Container App: Implementing the scale rule ensures that the container app scales appropriately in response to traffic, preventing it from scaling down to 0 instances when there is demand.

ryuhei 👍 2 Selected: B

Answer is B

manopeydakon 👍 2

No! Enabling ingress and creating an HTTP scale rule won't directly address the issue of the app having scaled to 0 instances. Ingress relates to the network traffic coming into the app, and scale rules define when and how the app scales based on certain conditions. However, they won't directly bring the app back to running instances if it has scaled down to 0. To address the issue of the app having 0 instances, you might need to investigate why the app scaled down and take appropriate action, such as adjusting the scaling settings, reviewing resource constraints, or identifying any issues in the app itself.

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Expert Analysis

Why the Answer Is Correct

Enabling ingress on an Azure Container App allows the built-in Envoy proxy to intercept incoming HTTP requests. Even when the app is scaled to zero instances, the proxy holds the request and triggers the KEDA HTTP scaler to spin up an instance. Creating and applying an HTTP scale rule explicitly defines the scaling behavior, ensuring the app scales up from zero to handle traffic. Therefore, this solution successfully resolves the issue of the app being stuck at zero instances and inaccessible.

Why the Other Options Are Wrong

Option B is incorrect because it assumes the proposed solution fails to resolve the scaling issue. Many learners mistakenly believe that if an app is at zero instances, it cannot process HTTP requests to trigger a scale rule. However, Azure Container Apps' ingress architecture specifically supports scaling from zero by handling the request at the environment's ingress proxy before routing it to the container.

Community Comment Notes

Several commenters argued that an HTTP scale rule will not work if the app is already at zero instances, as noted by Mahesh1222 who stated "it will work based on Http traffic coming in when the Instance is already running." This reflects a misunderstanding of how Azure Container Apps handles HTTP ingress; the ingress proxy operates independently of the app instances to wake the app up. MarcosAn highlighted the documentation stating that without ingress or minReplicas, the app has "no way of starting back up," which implicitly confirms that enabling ingress does provide a way to start back up.

Official Reference

https://learn.microsoft.com/en-us/azure/container-apps/scale-app?pivots=azure-cli#default-scale-rule

Exam Strategy

Understand how Azure Container Apps scale from zero. Remember that HTTP ingress allows scaling from zero because the environment's proxy handles the initial connection, whereas TCP or custom scalers without minReplicas cannot wake the app.

Related Analysis

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