A request with a path that reaches a server, is looked up in the routing table or filesystem, resulting in no resources found, is expected to return "404 Not Found".
You can say the path "exists", but only as a label. All labels can exist. Only a subset of these are semantically valid resource locator paths, and only a further subset reference objects that exist.
Colloquially, https://news.ycombinator.com/this/path/does/not/exist (path "/this/path/does/not/exist") "does not exist" because we're talking about the requested resource.
Of course the path exists, I just wrote it and it's semantically valid.
That's not an interesting question though, and if API responses were this shallow -- just a "semantic correctness checker" -- then response codes would be useless.
Why? We all know what it means.
>Colloquially, https://news.ycombinator.com/this/path/does/not/exist (path "/this/path/does/not/exist") "does not exist" because we're talking about the requested resource.
That path is 404 - Not found and returns "Unknown"
https://news.ycombinator.com/item?id=52081900
Returns 200 - No such item.
In 10 years when we have that many threads it will return content.
As I've said in several other places it depends what you want to tell the client. 404 if you want to tell them you didn't find the resource. 200 if you want to tell them the resource doesn't exist.
> 404 if you want to tell them you didn't find the resource. 200 if you want to tell them the resource doesn't exist.
404 is a client error, like all 4xx codes. The requester can correct their request. It does not indicate that the server ~"tried to find but may have overlooked" a resource, it means that the server can authoritatively state that the resource is not findable.
This is essentially, "does not exist at this time". Resources that do not exist today, might exist in the future, or they might not. This is true for both /users/1000 and /some/other/path.
I interpret the RFC to support my belief:
6.5.4. 404 Not Found
The 404 (Not Found) status code indicates that the origin server did
not find a current representation for the target resource or is not
willing to disclose that one exists. A 404 status code does not
indicate whether this lack of representation is temporary or
permanent; the 410 (Gone) status code is preferred over 404 if the
origin server knows, presumably through some configurable means, that
the condition is likely to be permanent.Impressive given that it explicitly contradicts your point:
>the server can authoritatively state that the resource is not findable
>origin server did not find a current representation
Those two are not the same thing.
Those two phrases do not lexically parse in identical ways, but we should not interpret the RFC to be saying the alternative of "I really tried, but boy filesystems are hard and maybe the NFS mount disappeared, and well shucks, couldn't find it! 404!".
There is no defined equivalency between host1/one/path and host2/other/path, even if the resources returned could potentially be the same.
There is no retry formula for a 404 at one URL that might return 200 at another URL.
There is no defined meaning for the same resource at another location. HTTP 404 makes no attempt to comment on the uniqueness or commonness of a resource. No comment on whether that resource existed in the past, is expected to exist later, or in whose imagination it could conceivably exist in the future.
The HTTP response simply states whether the resource was found to exist at the specified location at the time of request. Any further conclusions drawn from a 404 are speculative.