Is it possible to bypass Application Gateway default response buffering setting at code level

Question

Is it possible to bypass Application Gateway default response buffering setting at code level

Kenny Wong (HK) 115

I have an application hosted in AKS (Azure Kubernetes Services) which is behind an NGINX Ingress and then connect to an Application Gateway

The route should be like this

The client I send my request <-> Application Gateway <-> NGINX Ingress <-> Backend

I am not sure why my application is unable to stream.

My streaming endpoint is as follow:


async def simple_generator():
    for i in range(10):
        yield f"data: {i}\n\n"
        await asyncio.sleep(1)


@router.post(
    "/simple_generator"
)
async def test_simple_generator():
    return StreamingResponse(
            simple_generator(),
            media_type="text/event-stream",
            headers={
                "Cache-Control": "no-cache",
                "X-Accel-Buffering": "no"
                # "Connection": "keep-alive",
                # "Transfer-Encoding": "chunked",
            }
        )

Startup command for FastAPI

CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "80", "--workers", "1", "--limit-concurrency", "10", "--limit-max-requests", "1000", "--timeout-keep-alive", "10", "--proxy-headers"]

My NGINX Ingress setup include these configuration:

    additional_annotations:
      kubernetes.io/ingress.class: nginx
      nginx.ingress.kubernetes.io/proxy-body-size: 120m
      nginx.ingress.kubernetes.io/client-body-buffer-size: 120m
      nginx.ingress.kubernetes.io/proxy-connect-timeout: '1200'
      nginx.ingress.kubernetes.io/proxy-send-timeout: '1200'
      nginx.ingress.kubernetes.io/proxy-read-timeout: '1200'
      nginx.ingress.kubernetes.io/keepalive-timeout: '600'
      nginx.ingress.kubernetes.io/proxy-buffering: 'off'
      nginx.ingress.kubernetes.io/proxy-cache: 'off'
      nginx.ingress.kubernetes.io/configuration-snippet: |-
        proxy_set_header Connection "keep-alive";
        proxy_ignore_headers Cache-Control Expires;

My Azure Application Gateway is default settings (Response buffering enabled) and I don't have rights to change that as it is shared by a numbers of applications

Is it possible to bypass this default settings to enable streaming by modifying my endpoint or/and NGINX Ingress settings? If yes, how can I modify it?

Jilakara Hemalatha 3,115 Reputation points Microsoft External Staff Moderator

2025-10-01T07:20:01.22+00:00
Hi Kenny Wong (HK),

To better understand the streaming issue, could you please confirm the following details:

Are other applications sharing this Azure Application Gateway also experiencing streaming issues?

Can you confirm if response buffering is enabled or disabled in the Application Gateway’s "Backend HTTP settings"?

Is the Application Gateway running with any Web Application Firewall (WAF) or custom policies that could affect streaming?

What version of the NGINX Ingress Controller is currently in use, and are there any known response size or timeout configurations applied at the ingress or application level?

Are there any specific error messages or warnings in your application logs or Application Gateway logs when attempting to stream the response?

Kenny Wong (HK) 115

I don't have access to the Azure Application Gateway and also the other applications which share the Application Gateway.

But I think response buffering is enabled as a global settings by default

The configuration of my NGINX Ingress Controller is like this:

additional_annotations:
      kubernetes.io/ingress.class: nginx
      nginx.ingress.kubernetes.io/proxy-body-size: 120m
      nginx.ingress.kubernetes.io/client-body-buffer-size: 120m
      nginx.ingress.kubernetes.io/proxy-connect-timeout: '1200'
      nginx.ingress.kubernetes.io/proxy-send-timeout: '1200'
      nginx.ingress.kubernetes.io/proxy-read-timeout: '1200'
      nginx.ingress.kubernetes.io/keepalive-timeout: '600'
      nginx.ingress.kubernetes.io/proxy-buffering: 'off'
      nginx.ingress.kubernetes.io/proxy-cache: 'off'
      nginx.ingress.kubernetes.io/configuration-snippet: |-
        proxy_set_header Connection "keep-alive";
        proxy_ignore_headers Cache-Control Expires;

No error messages I can see from my application, the response just return in one go after certain time.

Any configuration or code change I can test out to see if streaming can be enabled without changing the Azure Application Gateway settings?

Jilakara Hemalatha 3,115 Reputation points Microsoft External Staff Moderator

2025-10-03T04:38:40.3833333+00:00

Hi Kenny Wong (HK),

Just checking, if the provided response was resolved your query. Please let me know if you have any queries.
Jilakara Hemalatha 3,115 Reputation points Microsoft External Staff Moderator

2025-10-08T13:10:35.82+00:00

Hi Kenny Wong (HK),

If the query has been resolved, please take a moment to accept answers and upvote it 👍 to make it helpful to the community.

Thank you for helping to improve Microsoft Q&A!

1 answer

Your answer

Jilakara Hemalatha 3,115 Reputation points Microsoft External Staff Moderator

2025-10-01T07:20:01.22+00:00

Hi Kenny Wong (HK),

To better understand the streaming issue, could you please confirm the following details:

Are other applications sharing this Azure Application Gateway also experiencing streaming issues?

Can you confirm if response buffering is enabled or disabled in the Application Gateway’s "Backend HTTP settings"?

Is the Application Gateway running with any Web Application Firewall (WAF) or custom policies that could affect streaming?

What version of the NGINX Ingress Controller is currently in use, and are there any known response size or timeout configurations applied at the ingress or application level?

Are there any specific error messages or warnings in your application logs or Application Gateway logs when attempting to stream the response?
Kenny Wong (HK) 115 Reputation points

2025-10-01T07:48:27.3566667+00:00

I don't have access to the Azure Application Gateway and also the other applications which share the Application Gateway.

But I think response buffering is enabled as a global settings by default

The configuration of my NGINX Ingress Controller is like this:

additional_annotations: kubernetes.io/ingress.class: nginx nginx.ingress.kubernetes.io/proxy-body-size: 120m nginx.ingress.kubernetes.io/client-body-buffer-size: 120m nginx.ingress.kubernetes.io/proxy-connect-timeout: '1200' nginx.ingress.kubernetes.io/proxy-send-timeout: '1200' nginx.ingress.kubernetes.io/proxy-read-timeout: '1200' nginx.ingress.kubernetes.io/keepalive-timeout: '600' nginx.ingress.kubernetes.io/proxy-buffering: 'off' nginx.ingress.kubernetes.io/proxy-cache: 'off' nginx.ingress.kubernetes.io/configuration-snippet: |- proxy_set_header Connection "keep-alive"; proxy_ignore_headers Cache-Control Expires;

No error messages I can see from my application, the response just return in one go after certain time.

Any configuration or code change I can test out to see if streaming can be enabled without changing the Azure Application Gateway settings?
Jilakara Hemalatha 3,115 Reputation points Microsoft External Staff Moderator

2025-10-03T04:38:40.3833333+00:00

Hi Kenny Wong (HK),

Just checking, if the provided response was resolved your query. Please let me know if you have any queries.
Jilakara Hemalatha 3,115 Reputation points Microsoft External Staff Moderator

2025-10-08T13:10:35.82+00:00

Hi Kenny Wong (HK),

If the query has been resolved, please take a moment to accept answers and upvote it 👍 to make it helpful to the community.

Thank you for helping to improve Microsoft Q&A!

Answer 1

Hi Kenny Wong (HK),

Unfortunately, it’s not possible to bypass Azure Application Gateway’s default response buffering behavior by modifying your application endpoint or NGINX Ingress settings. This is because response buffering is a resource-level configuration on the Application Gateway itself, and it controls how responses are handled before being sent to the client. If buffering is enabled, the gateway will wait to receive the complete response from the backend before forwarding it, even if the backend is streaming data in chunks.

To achieve real-time streaming behavior response buffering must be disabled directly on the Application Gateway resource. This change can only be performed by someone with sufficient permissions on the gateway resource.

Your FastAPI endpoint and NGINX Ingress are correctly configured to disable buffering upstream. However, these settings only ensure that NGINX does not buffer the response from FastAPI; they cannot override or bypass the buffering enforced by Application Gateway.

Please refer below documentation: https://free.blessedness.top/en-us/azure/application-gateway/use-server-sent-events

https://free.blessedness.top/en-us/azure/application-gateway/proxy-buffers

If the provided response was resolved your query. Could you please accept the answer and upvote it so it will be helpful to community,

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Is it possible to bypass Application Gateway default response buffering setting at code level

1 answer

Your answer