ACA App Shows Running State but Endpoint URL Returns 404 Error

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ACA App Shows Running State but Endpoint URL Returns 404 Error

ramprasad.r 40

I have a container image previously deployed to AKS using Azure Container Registry (ACR). I am now deploying the same image to Azure Container Apps (ACA).

The image successfully pulls from ACR.

The Container App deployment shows Running state.

Ingress is enabled with a valid FQDN.

But when I click the Endpoint URL, it throws a 404 - Not Found error.

I have followed the documentation: https://learn.microsoft.com/en-us/azure/container-apps/rule-based-routing-custom-domain. Please suggest a solution. The same image that was pulled and worked fine in AKS is now deployed in ACA, but it is not accessible at all. The URL under the Ingress section also returns a 404 error.
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Answer 1

Jose Benjamin Solis Nolasco 4,986

@ramprasad.r Hello I hope you are doing well,

Please check the following items most of the time could be a missed configuration

Container Port Configuration

Ensure the container listens on the same target port configured in ACA (default is 80).

Ingress & Routing Rules

Verify that routing rules include a path to / or match your app’s endpoints.
Add a catch-all rule like /* if needed.

Test Image Locally

Run the container locally (docker run -p) and test if / or intended routes respond properly.

Readiness & Startup

App might not be ready when traffic arrives. Add readiness probes to delay traffic until it's ready.

Check Logs

Use Live Logs in the ACA portal or az containerapp logs show to see if the app is throwing errors or serving 404s internally.

Missing Root Route
- If your app doesn’t define a route for /, hitting the root URL will result in a 404. Add a default route if needed.

😊 If my answer helped you resolve your issue, please consider marking it as the correct answer. This helps others in the community find solutions more easily. Thanks!

Jose Benjamin Solis Nolasco 4,986 Reputation points

2025-08-05T13:41:57.1466667+00:00
Just in case double check this:

Custom DNS Suffix Validation

Ensure the TXT record for the root of your DNS suffix (e.g., _apps.dev1.yourdomain.com) was added exactly as required by ACA.

The TXT value should match what Azure generated for domain validation.

After adding it, you must wait for DNS propagation and validate it in the ACA portal.

Validation Status: Go to Azure Portal > Container Apps Environment > Custom Domains, and check if the domain shows as "Validated".

App-Specific Subdomain Mapping

Once the custom domain suffix is validated:

Each Container App must be individually mapped to a subdomain (e.g., dev1.yourdomain.com) under the “Custom Domains” tab of that app.

Ensure you've added:

The custom domain entry (e.g., dev1.yourdomain.com)

Proper ingress path-based routing rules (e.g., /api, /webapp) inside each container app or environment.

ramprasad.r 40

@Jose Benjamin Solis Nolasco ,In the offdev-aca | Custom DNS suffix section of the Container Apps Environment, I have correctly mapped the custom DNS as shown in the attached snapshot. Screenshot 2025-08-05 191755

Screenshot 2025-08-05 192013

I created the following YAML file to configure custom domains and routing:

customDomains:
  - name: dev1.f**************.com
    certificateId: /subscriptions/*************/resourceGroups/ffdev-env/providers/Microsoft.App/managedEnvironments/lldev-aca/certificates/dev1
    bindingType: SniEnabled
rules:
  - description: "Routing to API Service"
    routes:
      - match:
          prefix: "/api"
        action:
          prefixRewrite: "/"
    targets:
      - containerApp: dev-apiservice
  - description: "Routing to Translate Service"
    routes:
      - match:
          prefix: "/translate"
        action:
          prefixRewrite: "/"
    targets:
      - containerApp: dev-translate-apiservice

az containerapp env http-route-config create   --resource-group kkdev-env   --name kkdev-aca   --http-route-config-name my-route-config   --yaml "C:\Users\Mysystem\web-proxy\routing.yml"

I have published this YAML file using one of the route-config, and it has been applied successfully. Please confirm if any other configuration steps are required or if anything has been missed.

Answer 2

@Jose Benjamin Solis Nolasco , Yes, the APIs are now exposed and accessible through the Ingress endpoint URLs. User's image

However, we have configured a custom DNS suffix for our Azure Container Apps environment, which hosts around 20 container apps. We’ve also added a subdomain configuration under the Custom DNS suffix setting for the environment.

We have correctly created the required DNS records, including both A and TXT records, in our DNS provider’s record set. User's image

Despite this setup, the custom subdomain (e.g., dev1.******.com) is not resolving or exposing the API endpoints as expected.

Our goal is to expose the container apps using URLs like:

https://dev1.******.com/api

https://dev1.******.com/reports

https://dev1.******.com/webapp

However, even after the proper configuration, accessing the subdomain results in a 404 error or the endpoints fail to resolve.
User's image

Could you please help us identify what might be missing or misconfigured?

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ACA App Shows Running State but Endpoint URL Returns 404 Error

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