fix: add cache headers for images #9560

arjansingh · 2025-08-26T17:53:49Z

Overview

Fixes Comfy-Org/ComfyUI_frontend#4438

Majority of discussion was in:

[Bug]: Model sidebar makes unnecessary 404 requests for non-existent preview images Comfy-Org/ComfyUI_frontend#4438
[fix] fix #4438 do not repeatedly try to load 404'ed images Comfy-Org/ComfyUI_frontend#5174 and

TL;DR: Add cache controls to store images for 1 day and only try to resolve missing images every 1 hour.

Problem

model_manager.py has an experimental preview endpoint to serve preview images from the filesystem.
frontend code tries to fetch images these images, but there is no cache control on them so we repeatedly fetch and download them.
This causes unnecessary traffic to the server and a lot of network traffic noise in development.
We fix this by adding caching logic for images in our middleware.

Review Points

Are we okay with the default max-age values? One day for images and permanent redirects. One hour for image 404's.

DrJKL · 2025-08-26T17:56:10Z

server.py

+        elif 200 <= response.status < 300:
+            response.headers.setdefault('Cache-Control', f"public, max-age={ONE_DAY}")
+        elif response.status == 301 or response.status == 308:
+            # Permanent redirects - cache for 1 day
+            response.headers.setdefault('Cache-Control', f"public, max-age={ONE_DAY}")


Suggested change

elif 200 <= response.status < 300:

response.headers.setdefault('Cache-Control', f"public, max-age={ONE_DAY}")

elif response.status == 301 or response.status == 308:

# Permanent redirects - cache for 1 day

response.headers.setdefault('Cache-Control', f"public, max-age={ONE_DAY}")

elif 200 <= response.status < 300 or response.status == 301 or response.status == 308:

# Permanent redirects - cache for 1 day

response.headers.setdefault('Cache-Control', f"public, max-age={ONE_DAY}")

DrJKL · 2025-08-26T17:57:44Z

server.py

+        if response.status == 304:
+            # 304 Not Modified - don't set cache headers, inherit from original
+            pass


Could this be an and response.status != 304 on line 70?

DrJKL · 2025-08-26T17:58:17Z

server.py

+            response.headers.setdefault('Cache-Control', f"public, max-age={ONE_DAY}")
+        elif 300 <= response.status < 400:
+            # Temporary redirects (302, 303, 307) and other 3xx - no cache
+            response.headers.setdefault('Cache-Control', 'no-cache')


I just know there's a way to unify this with line 58...

Good instincts, as usual. I'm missing the pattern with line 58. Could you show me what you're seeing there?

@web.middleware async def cache_control(request: web.Request, handler: Callable[[web.Request], Awaitable[web.Response]]) -> web.Response: response: web.Response = await handler(request) if request.path.endswith('.js') or request.path.endswith('.css') or request.path.endswith('index.json'): response.headers.setdefault('Cache-Control', 'no-cache') elif request.path.lower().endswith(IMG_EXTENSIONS): if response.status == 404: response.headers.setdefault('Cache-Control', f"public, max-age={ONE_HOUR}") elif response.status in (200, 201, 202, 203, 204, 205, 206, 301, 308): # Success responses and permanent redirects - cache for 1 day response.headers.setdefault('Cache-Control', f"public, max-age={ONE_DAY}") elif response.status in (302, 303, 307): # Temporary redirects - no cache response.headers.setdefault('Cache-Control', 'no-cache') # Note: 304 Not Modified falls through - no cache headers set return response

Something like this?

response.headers.setdefault('Cache-Control', 'no-cache')

and

response.headers.setdefault('Cache-Control', 'no-cache')

I'd love for each version to occur exactly once.

I'm gonna push back on that last one.

We have clearly defined rules for js and css and images.

I don't think it makes sense to commingle rules for assets. just so that we only set no-cache once.

Better to optimize by asset type than by cache level here. Makes it easier to tweak just images as well.

DrJKL · 2025-08-26T18:00:35Z

tests-unit/server_test/test_cache_control.py

+with patch('app.frontend_management.FrontendManager'):
+    with patch('utils.install_util.get_missing_requirements_message'):
+        with patch('utils.install_util.requirements_path'):


not sure if this is better, but it's an option

Suggested change

with patch('app.frontend_management.FrontendManager'):

with patch('utils.install_util.get_missing_requirements_message'):

with patch('utils.install_util.requirements_path'):

with patch('app.frontend_management.FrontendManager'), patch('utils.install_util.get_missing_requirements_message'), patch('utils.install_util.requirements_path'):

DrJKL · 2025-08-27T01:33:25Z

server.py

+            response.headers.setdefault('Cache-Control', f"public, max-age={ONE_DAY}")
+        elif 300 <= response.status < 400:
+            # Temporary redirects (302, 303, 307) and other 3xx - no cache
+            response.headers.setdefault('Cache-Control', 'no-cache')


response.headers.setdefault('Cache-Control', 'no-cache')

and

response.headers.setdefault('Cache-Control', 'no-cache')

I'd love for each version to occur exactly once.

arjansingh · 2025-08-27T20:05:54Z

tests-unit/server_test/test_cache_control.py

+pytestmark = pytest.mark.asyncio  # Apply asyncio mark to all tests
+
+# Mock the problematic imports before importing server
+with patch('app.frontend_management.FrontendManager'), patch('utils.install_util.get_missing_requirements_message'), patch('utils.install_util.requirements_path'):


@DrJKL this was a good call by you. much easier to read.

arjansingh · 2025-08-29T18:16:53Z

Hold up. Need to refactor the middleware so we don't get stuck in mock hell with pytorch.

Prevents unnecessary repeated requests, especially for 404s

We can test the code without excessively mocking server dependencies

DrJKL · 2025-08-29T19:51:41Z

middleware/cache_middleware.py

+    if (
+        request.path.endswith(".js")
+        or request.path.endswith(".css")
+        or request.path.endswith("index.json")
+    ):
+        response.headers.setdefault("Cache-Control", "no-cache")
+    elif request.path.lower().endswith(IMG_EXTENSIONS):
+        if response.status == 404:
+            response.headers.setdefault("Cache-Control", f"public, max-age={ONE_HOUR}")
+        elif response.status in (200, 201, 202, 203, 204, 205, 206, 301, 308):
+            # Success responses and permanent redirects - cache for 1 day
+            response.headers.setdefault("Cache-Control", f"public, max-age={ONE_DAY}")
+        elif response.status in (302, 303, 307):
+            # Temporary redirects - no cache
+            response.headers.setdefault("Cache-Control", "no-cache")
+        # Note: 304 Not Modified falls through - no cache headers set
+
+    return response


Talked about elsewhere: This is probably more flattenable.

comfyanonymous · 2025-08-31T04:05:28Z

server.py

    except (aiohttp.ClientError, aiohttp.ClientPayloadError, ConnectionResetError, BrokenPipeError, ConnectionError) as err:
        logging.warning("send error: {}".format(err))

 @web.middleware


This line should be removed.

Good catch. My bad.

arjansingh requested review from Kosinkadink, christian-byrne, comfyanonymous, guill, ltdrdata, pythongosssss, robinjhuang, webfiltered and yoland68 as code owners August 26, 2025 17:53

arjansingh mentioned this pull request Aug 26, 2025

[fix] fix #4438 do not repeatedly try to load 404'ed images Comfy-Org/ComfyUI_frontend#5174

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DrJKL reviewed Aug 26, 2025

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DrJKL reviewed Aug 27, 2025

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arjansingh commented Aug 27, 2025

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DrJKL approved these changes Aug 28, 2025

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arjansingh added 9 commits August 29, 2025 12:14

fix: add cache headers for images

3f948e3

Prevents unnecessary repeated requests, especially for 404s

test: test cache handler and fix found issues

4284138

refactor: add 3xx cache-control rules to middleware

4cb20f7

refactor: adjust fall-through order of caching scenarios

0e524c8

refactor: based on code review feedback

a7592de

style: ruff format cache control tests

6c26a50

test: mock torch in cache middleware tests

180e19e

refactor: move cache-controls to /middleware

a0e0840

We can test the code without excessively mocking server dependencies

refactor: parameterize cache middleware tests for readability

7cd6891

arjansingh force-pushed the fix/add-image-cache-headers branch from 7f0e91e to 7cd6891 Compare August 29, 2025 19:35

DrJKL reviewed Aug 29, 2025

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DrJKL approved these changes Aug 29, 2025

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arjansingh added 2 commits August 29, 2025 12:57

refactor: guard clause before image caching logic

8544db8

fix: ruff errors

9bf37b4

DrJKL approved these changes Aug 29, 2025

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comfyanonymous reviewed Aug 31, 2025

View reviewed changes

fix: remove stray middleware decorator

efd299d

comfyanonymous merged commit 3493b9c into comfyanonymous:master Sep 5, 2025
6 checks passed

fix: add cache headers for images #9560

fix: add cache headers for images #9560

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arjansingh commented Aug 26, 2025

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arjansingh Aug 26, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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arjansingh commented Aug 29, 2025

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arjansingh Aug 26, 2025 •

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