Make sure 204 status responses have no body in accordance with HTTP spec #2094

C-Loftus · 2025-08-26T18:27:39Z

Overview

This PR makes it so http responses with a 204 status have no body in accordance with the http spec.

Background

Currently if you raise a ProviderNoDataError it will return a response with status 204.

class ProviderNoDataError(ProviderGenericError):
    """provider no data error"""
    ogc_exception_code = 'InvalidParameterValue'
    http_status_code = HTTPStatus.NO_CONTENT
    default_msg = 'No data found

However, currently it will include data in the response. This deviates from the spec which states that the response must not include any content

To fix this I make it return early and not add any data into the body.

Issue this solves

Currently in the starlette backend, if you raise a 204 but have data in the body, it will raise an error and fail.

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    raise ProviderNoDataError()
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[2025-08-26 18:18:30 +0000] [24] [ERROR] Exception in ASGI application
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Traceback (most recent call last):   File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/uvicorn/protocols/http/h11_impl.py", line 403, in run_asgi     result = await app(  # type: ignore[func-returns-value]
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             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in __call__
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    return await self.app(scope, receive, send)
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           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/applications.py", line 113, in __call__
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    await self.middleware_stack(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/middleware/errors.py", line 186, in __call__
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    raise exc
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/middleware/errors.py", line 164, in __call__
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    await self.app(scope, receive, _send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/middleware/cors.py", line 93, in __call__
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    await self.simple_response(scope, receive, send, request_headers=headers)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/middleware/cors.py", line 144, in simple_response
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    await self.app(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 63, in __call__
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    await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
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    raise exc
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
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    await app(scope, receive, sender)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/routing.py", line 716, in __call__
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    await self.middleware_stack(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/routing.py", line 736, in app
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    await route.handle(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/routing.py", line 462, in handle
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    await self.app(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/routing.py", line 716, in __call__
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    await self.middleware_stack(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/routing.py", line 736, in app
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    await route.handle(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/routing.py", line 290, in handle
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    await self.app(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/routing.py", line 78, in app
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    await wrap_app_handling_exceptions(app, request)(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
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    raise exc
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
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    await app(scope, receive, sender)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/routing.py", line 76, in app
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    await response(scope, receive, send)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/responses.py", line 165, in __call__
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    await send({"type": prefix + "http.response.body", "body": self.body})
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 39, in sender
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    await send(message)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 39, in sender
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    await send(message)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/middleware/cors.py", line 148, in send
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    await send(message)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/starlette/middleware/errors.py", line 161, in _send
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    await send(message)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/uvicorn/protocols/http/h11_impl.py", line 500, in send
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    output = self.conn.send(event=h11.Data(data=data))
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             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/h11/_connection.py", line 538, in send
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    data_list = self.send_with_data_passthrough(event)
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                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/h11/_connection.py", line 571, in send_with_data_passthrough
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    writer(event, data_list.append)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/h11/_writers.py", line 65, in __call__
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    self.send_data(event.data, write)
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  File "/opt/pygeoapi/.venv/lib/python3.12/site-packages/h11/_writers.py", line 91, in send_data
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    raise LocalProtocolError("Too much data for declared Content-Length")
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pygeoapi.provider.base.ProviderNoDataError: None
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h11._util.LocalProtocolError: Too much data for declared Content-Length

Additional information

Dependency policy (RFC2)

I have ensured that this PR meets RFC2 requirements

Updates to public demo

I have ensured that breaking changes to the pygeoapi master demo server have been addressed
- https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines

tomkralidis · 2025-09-11T10:46:08Z

Thanks @C-Loftus. As a first step, can you provide steps to reproduce the issue that this PR aims to address?

C-Loftus · 2025-09-11T12:58:56Z

As a first step, can you provide steps to reproduce the issue that this PR aims to address?

Thanks for your reply @tomkralidis . To reproduce, make a custom provider that can potentially return no data, run pygeoapi with starlette, create a condition in the provider that throws a ProviderNoDataError within pygeoapi. You will then see the error in the logs.

I quickly made up a repo with a minimal example for you here: https://github.com/cgs-earth/pygeoapi-starlette-issue-reproduction

tomkralidis

Thanks for the test case @C-Loftus. Please see change requests. Thanks!

pygeoapi/api/__init__.py

tests/api/test_no_data_response.py

C-Loftus · 2025-09-15T13:34:19Z

pygeoapi/starlette_app.py

-        # NOTE: that gzip currently doesn't work in starlette
-        #       https://github.com/geopython/pygeoapi/issues/1591
-        content = apply_gzip(headers, content)
+        # 204 responses must have an empty body, but gzip
+        # encoding would add gzip metadata, thus we skip
+        if status != HTTPStatus.NO_CONTENT:
+            content = apply_gzip(headers, content)


I have removed a comment linking to an issue that was resolved and then added a clarifying comment on why we need to skip applying gzip when it is a 204 response. Without this, the apply_gzip function zips empty content, and empty content still will include a gzip header and thus raise an error

tests/api/test_api.py

C-Loftus added 2 commits August 26, 2025 13:23

Fix provider no data error

466f18a

fix flake8

c512713

tomkralidis requested changes Sep 14, 2025

View reviewed changes

pygeoapi/api/__init__.py Outdated Show resolved Hide resolved

tests/api/test_no_data_response.py Outdated Show resolved Hide resolved

C-Loftus added 3 commits September 15, 2025 08:47

Merge branch 'geopython:master' into fixStarletteContentLengthIssue

185da61

address feedback

e4b44cd

fix gzip issue which adds a header and deviates from the spec

8a515d8

C-Loftus commented Sep 15, 2025

View reviewed changes

tests/api/test_api.py Show resolved Hide resolved

C-Loftus requested a review from tomkralidis September 15, 2025 13:36

tomkralidis added this to the 0.22.0 milestone Sep 15, 2025

tomkralidis merged commit 579345d into geopython:master Sep 15, 2025
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Make sure 204 status responses have no body in accordance with HTTP spec #2094

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C-Loftus commented Aug 26, 2025

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C-Loftus Sep 15, 2025 •

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Make sure 204 status responses have no body in accordance with HTTP spec #2094

Make sure 204 status responses have no body in accordance with HTTP spec #2094

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C-Loftus commented Aug 26, 2025

Overview

Background

Issue this solves

Additional information

Dependency policy (RFC2)

Updates to public demo

Contributions and licensing

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tomkralidis commented Sep 11, 2025

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