The Azure Container App does not accept Incoming request from external

Question

The Azure Container App does not accept Incoming request from external

Santi Cuni 0

I have created two Azure Container apps. I have verified that the internal communications between the frontend and backend worked properly. However, the UI does not go up, even if the Azure container's console shows that Streamlit is up and rûnning. I have also added configuration to properly redirect HTTP to HTTPS. Indeed, Azure containers expect HTTPS, but my frontend and backend talk on HTTP. Here is the Dockerfile for the frontend: What I have to do it? Thanks Regards

FROM python:3.11-slim
COPY . /app/Production
ENV PYTHONPATH=/app
WORKDIR /app/Production/frontend
RUN pip install --no-cache-dir -r requirements.txt
CMD ["streamlit", "run", "frontend.py", "--server.port=8501", "--server.address=0.0.0.0", "--server.enableXsrfProtection=false", "--server.enableCORS=false"]

Pravallika KV 12,730 Reputation points Microsoft External Staff Moderator

2026-03-16T17:57:05.2966667+00:00
Hi @Santi Cuni ,

Thanks for reaching out to Microsoft Q&A.

By default, Azure Container Apps ingress listens on port 80 (or 443 for HTTPS) unless you tell it otherwise, and TLS termination happens at the platform layer. Here’s what you can do:

Expose the correct port in your Docker file.

Add an EXPOSE line so the Container Apps platform knows which port your app is listening on:

FROM python:3.11-slim WORKDIR /app/Production/frontend COPY . . ENV PYTHONPATH=/app RUN pip install --no-cache-dir -r requirements.txt EXPOSE 8501 CMD ["streamlit", "run", "frontend.py", "--server.port=8501", "--server.address=0.0.0.0", "--server.enableXsrfProtection=false", "--server.enableCORS=false"]

Configure ingress on your Container App In the Azure portal (or via CLI), go to your frontend Container App → Settings → Ingress and:

Enable Ingress

Set “Ingress traffic” to Accepting traffic from anywhere

Set Target port to 8501 (that matches your EXPOSE)

Keep Transport as HTTP/1 or HTTP/2 as needed

Remove the in-app HTTP=>HTTPS redirect Azure Container Apps terminates TLS for you. If your Streamlit app is forcing HTTP→HTTPS inside the container, the built-in ingress will never receive a “clean” request and could cause redirect loops or failures. Let the Container App handle TLS and just speak HTTP on port 8501.

Hit the Container App’s FQDN over HTTPS Once ingress is set up, browse to https://<your-container-app-fqdn>. You should be able to see the UI.

Hope this helps!
Praveen Kumar Gudipudi 2,275 Reputation points Microsoft External Staff Moderator

2026-03-24T10:02:23.3133333+00:00
Hi @Santi Cuni ,

This issue usually happens due to incorrect ingress or port configuration rather than a problem with Streamlit itself. Since your logs show that Streamlit is running, the container is healthy — the problem is with how Azure Container Apps exposes it externally.

Please verify the following:

Configure Ingress Correctly

In your Azure Container App → Ingress settings:

Enable Ingress

Set Ingress traffic to Accepting traffic from anywhere

Set Target port to 8501 (must match your Streamlit port)

Set Transport to HTTP

Ensure External ingress is enabled (not internal)

Let Azure Handle HTTPS (No Changes Needed in App)

You do not need to configure HTTPS or redirects inside your Streamlit app.

Azure Container Apps automatically handles TLS (HTTPS). The correct flow is:

Browser (HTTPS) → Azure Ingress → HTTP → Streamlit (port 8501)

Your current Streamlit command does not enforce HTTPS, so nothing needs to be removed.

Update Dockerfile (Important)

Make sure your Dockerfile explicitly exposes the correct port:

EXPOSE 8501

Also, ensure Streamlit binds to all interfaces:

CMD ["streamlit", "run", "frontend.py",

"--server.port=8501",

"--server.address=0.0.0.0",

"--browser.serverAddress=0.0.0.0",

"--server.enableXsrfProtection=false",

"--server.enableCORS=false"]

Use the Correct URL

Do not try to access the app using a port.

Always use the Container App’s FQDN:

https://<your-app-name>.<region>.azurecontainerapps.io

Verify Logs

Check the logs and confirm Streamlit is listening on:

http://0.0.0.0:8501

If it shows 127.0.0.1, the app will not be accessible externally.
Praveen Kumar Gudipudi 2,275 Reputation points Microsoft External Staff Moderator

2026-03-26T11:45:02.4366667+00:00

Hi @Santi Cuni ,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

3 answers

Your answer

Pravallika KV 12,730 Reputation points Microsoft External Staff Moderator

2026-03-16T17:57:05.2966667+00:00

Hi @Santi Cuni ,

Thanks for reaching out to Microsoft Q&A.

By default, Azure Container Apps ingress listens on port 80 (or 443 for HTTPS) unless you tell it otherwise, and TLS termination happens at the platform layer. Here’s what you can do:

Expose the correct port in your Docker file.

Add an EXPOSE line so the Container Apps platform knows which port your app is listening on:

FROM python:3.11-slim WORKDIR /app/Production/frontend COPY . . ENV PYTHONPATH=/app RUN pip install --no-cache-dir -r requirements.txt EXPOSE 8501 CMD ["streamlit", "run", "frontend.py", "--server.port=8501", "--server.address=0.0.0.0", "--server.enableXsrfProtection=false", "--server.enableCORS=false"]

Configure ingress on your Container App In the Azure portal (or via CLI), go to your frontend Container App → Settings → Ingress and:

Enable Ingress

Set “Ingress traffic” to Accepting traffic from anywhere

Set Target port to 8501 (that matches your EXPOSE)

Keep Transport as HTTP/1 or HTTP/2 as needed

Remove the in-app HTTP=>HTTPS redirect Azure Container Apps terminates TLS for you. If your Streamlit app is forcing HTTP→HTTPS inside the container, the built-in ingress will never receive a “clean” request and could cause redirect loops or failures. Let the Container App handle TLS and just speak HTTP on port 8501.

Hit the Container App’s FQDN over HTTPS Once ingress is set up, browse to https://<your-container-app-fqdn>. You should be able to see the UI.

Hope this helps!
Praveen Kumar Gudipudi 2,275 Reputation points Microsoft External Staff Moderator

2026-03-24T10:02:23.3133333+00:00

Hi @Santi Cuni ,

This issue usually happens due to incorrect ingress or port configuration rather than a problem with Streamlit itself. Since your logs show that Streamlit is running, the container is healthy — the problem is with how Azure Container Apps exposes it externally.

Please verify the following:

Configure Ingress Correctly

In your Azure Container App → Ingress settings:

Enable Ingress

Set Ingress traffic to Accepting traffic from anywhere

Set Target port to 8501 (must match your Streamlit port)

Set Transport to HTTP

Ensure External ingress is enabled (not internal)

Let Azure Handle HTTPS (No Changes Needed in App)

You do not need to configure HTTPS or redirects inside your Streamlit app.

Azure Container Apps automatically handles TLS (HTTPS). The correct flow is:

Browser (HTTPS) → Azure Ingress → HTTP → Streamlit (port 8501)

Your current Streamlit command does not enforce HTTPS, so nothing needs to be removed.

Update Dockerfile (Important)

Make sure your Dockerfile explicitly exposes the correct port:

EXPOSE 8501

Also, ensure Streamlit binds to all interfaces:

CMD ["streamlit", "run", "frontend.py",

"--server.port=8501",

"--server.address=0.0.0.0",

"--browser.serverAddress=0.0.0.0",

"--server.enableXsrfProtection=false",

"--server.enableCORS=false"]

Use the Correct URL

Do not try to access the app using a port.

Always use the Container App’s FQDN:

https://<your-app-name>.<region>.azurecontainerapps.io

Verify Logs

Check the logs and confirm Streamlit is listening on:

http://0.0.0.0:8501

If it shows 127.0.0.1, the app will not be accessible externally.
Praveen Kumar Gudipudi 2,275 Reputation points Microsoft External Staff Moderator

2026-03-26T11:45:02.4366667+00:00

Hi @Santi Cuni ,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

Answer 1

Santi Cuni 0

Hi @Pravallika KV I have done as suggested by you, however, the issue is still there. How I can do it?

User's image

Pravallika KV 12,730 Reputation points Microsoft External Staff Moderator

2026-03-16T18:33:05.69+00:00
Your screenshot shows that the Streamlit UI is actually loading, but the application logic is failing (those red error boxes come from Streamlit). So the problem is not Azure ingress anymore, it’s likely the frontend failing to call the backend API.

Check how the frontend calls the backend:

Inside your frontend.py, if you have something like:

requests.post("http://localhost:8000/api")

or

requests.post("http://backend:8000/api")

This will fail in Azure unless the backend service name is correct.

Instead, you should call the backend using the internal Container App DNS name:

http://<backend-container-app-name>:<port>

Example:

http://rag-backend:8000/query

Container Apps automatically provide internal DNS between apps in the same environment.

Your backend should likely be:

Ingress: Disabled

because it is internal only. Frontend calls it internally.

Check frontend logs:

Go to:

Container App → frontend → Logs

Look for errors like:

Connection refused Name not resolved Timeout

This will confirm the backend call is failing.

Open a shell in the frontend container and test:

curl http://backend-name:8000/health

If it fails → DNS or port issue.

Update the frontend backend URL to:

BACKEND_URL = "http://rag-backend:8000"
Santi Cuni 0 Reputation points

2026-03-16T18:51:44.77+00:00

Hello,

Inside the frontend.py I have this: http://backend_sanitas:8000/session/create (local with my .env file). Instead in the environment variable in the Azure Container app I have setup as showed below

Could we make I believe very fast a Teams meeting ? I am available if you can. Thanks

Regards

Answer 2

Santi Cuni 0

Hi @Pravallika KV

Thanks for your answer. I have changed the Dockerfile and rebuild and push the image. Also, I have attached the settings on Ingress.

User's image

However, I did not get the points 3 that you described. Point 3: I do not think that I have added any HTTP=>HTTPS redirect cpuld you tell me how Remove the in-app HTTP=>HTTPS redirect? My Streamlit does not force inside the container any HTTP to HTTPS redirect. What does mean "let the Container App handle TLS and just speak HTTP on port 8501"?. Thanks

Reagrds

Pravallika KV 12,730 Reputation points Microsoft External Staff Moderator

2026-03-16T18:26:45.4566667+00:00
If you did not explicitly add code that redirects HTTP =>HTTPS, then you already satisfy point 3.

CMD ["streamlit", "run", "frontend.py", "--server.port=8501", "--server.address=0.0.0.0", "--server.enableXsrfProtection=false", "--server.enableCORS=false"]

does NOT add any redirect so you don’t need to remove anything.

What does mean "let the Container App handle TLS and just speak HTTP on port 8501"?

Microsoft Azure Container Apps handles HTTPS automatically.

Your container should only serve HTTP on port 8501.

Azure receives HTTPS from the browser, decrypts it, and forwards HTTP to your container.

Flow:

Browser → HTTPS → Azure Container App → HTTP → Streamlit (port 8501)

Just ensure in Container App =>Ingress:

Ingress: Enabled Target Port: 8501 Transport: HTTP

Answer 3

Hi @Pravillika

Thanks for your answer. I have changed the Dockerfile and rebuild and push the image. Also, I have attached the settings on Ingress.

User's image

However, I did not get the points 3 that you described. Point 3: I do not think that I have added any HTTP=>HTTPS redirect cpuld you tell me how Remove the in-app HTTP=>HTTPS redirect? My Streamlit does not force inside the container any HTTP to HTTPS redirect. What does mean "let the Container App handle TLS and just speak HTTP on port 8501"?. Thanks

Reagrds

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The Azure Container App does not accept Incoming request from external

3 answers

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