#36081: HttpResponse 204 (No Content) causes client code to hang if data is
present.
-------------------------------------+-------------------------------------
Reporter: Cleophus Robinson | Type:
| Uncategorized
Status: new | Component: HTTP
| handling
Version: 4.2 | Severity: Normal
Keywords: | Triage Stage:
204,HTTP,API,Timeout | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
**What Happened**
I discovered this when returning "{}" as the body for a 204 status
response.
**Explanation**
When returning an HttpResponse to the client with a status of 204 (no
content), their system will hang if data is actually sent back in the
body.
It does this because it's an invalid response and it breaks the HTTP spec.
Clients will hang until a valid response is returned from the server.
https://developer.mozilla.org/en-
US/docs/Web/HTTP/Status/204#compatibility_notes
"Although this status code is intended for responses with no body, servers
may erroneously include data after the headers. This issue is observable
in persistent connections, where the invalid body may include a distinct
response to a subsequent request. The HTTP protocol allows browsers to
handle such responses differently (there is an ongoing discussion
regarding the specification text in the HTTPWG http-core GitHub
repository).
Apple Safari rejects any such data. Google Chrome and Microsoft Edge
discard up to four invalid bytes preceding a valid response. Firefox
tolerates over a kilobyte of invalid data preceding a valid response."
**Examples**
1. This is observed in Postman and other systems, the response is already
returned but it's still "Receiving Response". In this case, it will
timeout after a minute. Browsers may handle it differently.
2. My webhook made the client code timeout and forced the webhook into a
retry sequence.
**Solution**
I think Django should raise an exception in the HttpResponse class if this
happens. Browsers take their own approach on what to do in this scenario
and an opinionated stance may be warranted. It will also save developers
from bizarre behavior.
--
Ticket URL: <https://code.djangoproject.com/ticket/36081>
Django <https://code.djangoproject.com/>
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