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#query#request#body#post#cache#rfc#http#idempotent#method#data

Discussion (72 Comments)Read Original on HackerNews

100msabout 3 hours ago
Including a strong motivating example might have helped sell this, using an example that could trivially be expressed as a GET is extremely distracting.

Even imagining a QUERY with a large JSON filtering structure, or say an image input as request body, it feels extremely odd to include the request body as part of the cache key. It also implies an unbounded and user-controlled cache key, with the only really meaningful general caching strategy being bitwise compare of the request body (or a hash), which in a hostile scenario implies cache busting would be trivial.

This invokes multiple semantic oddities in one go with obvious difficulties for a very niche use case. If I'm writing a service that needs complex filtering or complex input like an image, any form of caching (e.g. individual data columns of a join, or embeddings keyed by perceptual hashes of a decoded image input) is going to be far away from the HTTP layer and certainly unrelated to the exact bit representation of the request on the wire.

Why even bother trying to capture this in a generic way?

I would be far more inclined to try and capture this caching semantic as a new header for POST. Something like "Vary: request-body" or similar. Perfectly backwards compatible and perfectly ignorable for all but the 0.1% of CDN use cases where the behaviour might turn out useful

Joker_vDabout 2 hours ago
> It also implies an unbounded and user-controlled cache key,

The query part of GET's URI is also barely bounded in practice and user-controlled, and is indeed used as part of the cache key (because it's a part of URI), so I am not sure why you raise this objection at all.

PunchyHamsterabout 1 hour ago
Well, because it is more code. Current caching software caches by headers + query string. It now needs to be expaned to cache by body too.

It feels very pointless and there is no drawback of just using POST

OvervCW40 minutes ago
There is: your browser or other type of client does not know it can repeat a POST request if it fails, whereas a QUERY request can be freely repeated in case of errors.
afavour42 minutes ago
Is caching not the primary reason to use this over POST? You should never want to cache POST requests.
giancarlostoroabout 2 hours ago
> and user-controlled

I've found some sites that tack on a session ID and if you try to tamper with the URL in any way, it sends you back to "Page 1" really annoys me lol at that point let me skip to any page with your web UI.

CodesInChaosabout 2 hours ago
The browser can simply store a collision resistant hash (e.g. SHA-256) of the body, if it wants a smaller cache key. I can't really think of any caching related attacks that don't equally apply to a query parameter. Generating a unique 30 character query parameter is just as easy as generating a 30 MB request body, if you want to flood the cache.
ralferoo26 minutes ago
Not necessarily that simple, as you'd have sort all the input parameters to maintain a useable cache key. Not especially difficult, but if the data is large and so re-allocation and sorting is required, then you're starting to open up the attack surface where bugs might have been introduced.
inigyou39 minutes ago
Not all usage scenarios are the public internet, and something doesn't have to be useful on the public internet to be standardized.

Realistically, systems for the public internet will use a secure hash as the cache key so it'll always be the same size. The cache key already includes a URL that can be very long, and an arbitrary set of header values.

ralferoo23 minutes ago
Except that by definition, in a URL the data has no implicit meaning so for a cache hit you need an exact match, including order and case, but for a list of POST parameters, they could legitimately be in any order and so you can't just hash it all as a blob, you need to sort the keys, possibly copy data around (unless using keys plus hash), probably allocating more memory, etc. I'm pretty certain we'll see at least one CVE out of the first few implementations of this!
cryptonymabout 2 hours ago
Sure you can provide an image as request body, but you could already do it with b64 query parameter. If you try hard enough, you can poorly use any proposed standard. GET with query parameters already is opaque and makes cache busting trivial.
layer8about 2 hours ago
Query parameters are length-limited, because HTTP URIs are: https://www.rfc-editor.org/info/rfc9110/#section-4.1-5. There is no expectation for arbitrarily long HTTP URLs to be functioning.
cryptonymabout 2 hours ago
Your link doesn't say URIs are length-limited
friendzisabout 2 hours ago
> It also implies an unbounded and user-controlled cache key.

While the concern is valid, caching is entirely optional at query level, therefore it is totally valid to cache only certain "filters".

epolanskiabout 2 hours ago
> Why even bother trying to capture this in a generic way?

I guess it's about resolving the odd semantics of using POST which is not idempotent and thus allowing easier control flow of caches and retrys.

Your perspective is 100% correct if you think at the application-layer, but with a dedicated method, you can have that behaviour out-of-the-box out of your HTTP infrastructure (whether it's at your hyperscaler's router or your apache/nginx/browser whatever) and stop implementing yourself the post-as-a-query edge case.

davidkwastabout 2 hours ago
I would use a hash of the body content (the query) as a URL parameter

/?hash=123456789

Joker_vDabout 2 hours ago
Why? That's pushing more work to do both on yourself and the cache.
wang_liabout 2 hours ago
If you control the full stack then the functionality described here can be implemented with POST. The only way this comes into play is if some second party client of your service is trying to impose rules on how your backend works. My answer to that is no. I will be defining the contract by which my services operate.
CodesInChaosabout 2 hours ago
I wonder if HTML forms will add support for QUERY:

    <form action="..." method="query">
This would avoid the annoying re-submission warnings you're getting if you refresh a page that was returned by a POST form submission, since QUERY is required to be idempotent.
amluto4 minutes ago
One oddity of forms: the result of a form POST is a page that has a location (the URL) but that cannot loaded via that location. As far as I know, the fact that the page is a POST and not a GET is not stored anywhere visible to the user or to JS. And refresh works oddly.

If method=QUERY were added, there would be a new variety of this weirdness.

bob1029about 2 hours ago
This is better solved with the post redirect get pattern.
tempfileabout 1 hour ago
Depends whether your form submission should expect side effects or not. Most forms submissions have side effects. If the effect is truly idempotent, wouldn't PUT be a better verb? That is also supposed to be idempotent.
echoangle15 minutes ago
You can’t use PUT as a form action though.
100msabout 2 hours ago
Forms, HTTP implementations, public API surfaces, and all for what exactly. Introducing a new verb for this feels profoundly misplaced
jagged-chiselabout 2 hours ago
Idempotency is an important attribute for correctness. Yep, you can document that POSTing to $ENDPOINT is idempotent, but you can't communicate that to caching layers throughout the network. QUERY, by definition, is idempotent and cacheable.
jnewton_devabout 2 hours ago
Does anyone know if this approach works at significantly larger scales? Curious about where it breaks down.
alpinismeabout 2 hours ago
At least support - or lack thereof - for a new verb is unambiguous (compared to changing the semantics of GET)
ctdinjeu7about 2 hours ago
Now HN’s UX can finally be decent.

The team will have to wait for a new header and textarea specs to fix the rest of the jank.

This site is so awful lol. Why don’t they update it?

CodesInChaosabout 2 hours ago
Where does HN use POST for safe operations? I can't think of any.

Comment submission isn't safe, so QUERY can't be used there. And it doesn't suffer from the problem anyways, since HN returns a 3XX on successful submission, so refreshing doesn't show a warning.

ynac38 minutes ago
Just in case anyone wants to pretend it's still that other century:

https://www.rfc-editor.org/rfc/rfc10008.txt

jjice25 minutes ago
I'll forever love a long, totally plain text document like this. So many good times with video game FAQs as a kid. It really is a superior form of information in a lot of ways (not all).
riffic10 minutes ago
I have a thesis brewing that explores how rich text WYSIWYG editors create a "what you see is all there is" cognitive bias, while plain text overcomes it.
riffic15 minutes ago
beautiful formatting. I should crib this style template for internal work memos, it's timeless.
piterrroabout 2 hours ago
> GET request with a body was heavily considered by the IETF working group, but it was ultimately rejected in favor of creating the new QUERY method. The decision to create a distinct method came down to historical interoperability issues and strict compliance with the core architectural definitions of HTTP.

I've been sending request body along GET method for years now

huskyrabout 1 hour ago
Apparently some load balancers drop the body.
inigyou36 minutes ago
I expect all sorts of intermediaries may drop the body, since having a body is forbidden by the standard.

When it's your client talking to your server you can obviously do whatever you want - it doesn't cause problems until you want to involve third-party code, such as a reverse proxy (such as nginx) or a CDN. This includes proxies your customers may be using.

preisschild23 minutes ago
> I've been sending request body along GET method for years now

Generally not a great idea. With some http implementations this is not even possible (for example, fetch)

https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/U...

> You cannot include a body with GET requests

And transparent caching might result in weird issues.

tonymplsabout 1 hour ago
As "just a guy that programs" (ok, now guides agents to program) and tries to follow the rules (with a big dose of pragmatism), this totally makes sense to me. This is also the first time I've seen or heard about this coming.

I like that we now have a way to not being forced to define Resources when we want to query. It always felt like I was missing something that there could be an infinite, defined-on-the-fly number of Resources for a "part" of a given Resource. Do I really want to define "all cats that sleep more than 20 hours a day and like sunbeams and want to eat breakfast at 3 am" as a Resource? (ok, we all know that is actually the full set of cats). I'm ok that you want to define that as a Resource but in my system, it makes more sense that Cats is the Resource and I just need some accepted way to query.

I like the implementation (again, as just a guy that programs). I don't see how it could have done it better or simpler which probably hides the complexity of getting there.

I also especially appreciate how the spec is written. Opening a spec, I wonder how far I'll get before I don't know what the heck they're talking about (and, again, as just a guy that programs). I don't think it's easy to write a spec that is complete and approachable like this. Really appreciate that.

inigyou33 minutes ago
The standards have always been a bit more abstract than you use in practice. Common practice prior to this would be /catsearch?sleep=20&sunbeams=yes&breakfast=0300 where the "resource" is /catsearch and the rest are query parameters, but you could also use /catsearch/sleep/20/sunbeams/yes/breakfast/0300 which looks like a "resource", but nobody is actually enforcing that it is a "resource".
pwdisswordfishqabout 3 hours ago
Wait, it's already past 10 thousand?
rhplusabout 3 hours ago
Someone has an ambiguous bet predicting when RFC 10000 will be published, but the numbers went straight from 9998 to 10008. No-one wins!

https://manifold.markets/CollectedOverSpread/when-will-rfc-1...

echoangle10 minutes ago
> This question resolves to the month of publication of the lowest-numbered RFC with a number greater than or equal to 10000.

So of 10008 is the first one after 10000, that date is the one to bet on.

ekr____about 2 hours ago
RFC 10000 will not be published. They're just going to skip past the number.

https://mailarchive.ietf.org/arch/msg/tools-discuss/EpoQcVt_...

RFC #s are issued sometime before publication, so they can come out out of order. I would expect 9999, 10001, etc. to show up eventually.

Imustaskforhelpabout 3 hours ago
Everytime I think that prediction markets bets can't get worse, they do, all in weird ways. I never expected someone betting over when RFC 10,000 will be published but somehow its fits just about right for prediction markets.

just wow, people seem to be having too much money it seems for them to bet over when RFC's are gonna get released.

This isn't even one of the worst offenders on prediction market or even comparable to it but I am just amazed (in a negative manner, surprised? its just strange) by the depth on what people actually bet on these markets.

networkedabout 2 hours ago
People aren't betting real money on this. Manifold uses "mana" points similar to HN karma, which is why you get more for-fun silly bets. I don't see anything inherently wrong with it. Disclosure: my mana net worth is 75k; I haven't been active on Manifold.
andltsemi3about 3 hours ago
If this is actually going to replace GET requests w/ query strings in the wild, Im very much hoping for browser bookmarks to support keeping request parameters.
inigyouabout 3 hours ago
Probably won't. Probably will replace whenever POST is currently used for a query.
mlhpdxabout 1 hour ago
Wow, it still isn’t a standard? I’ve been building with the QUERY method for years now.

I’ve enjoyed the combination with Range headers for paging, despite this tidbit:

> It is expected that these built-in features will be used instead of HTTP Range Requests

Using the QUERY request as the definition of a set, and Range to retrieve subsets seems very natural.

smashedabout 1 hour ago
Use the QUERY method in your http query to query search results. Do not add query parameters.

I think the name is confusing because the term 'query' is already used to refer to http requests in general.

Just the title of the RFC confused me.

toybeaverabout 3 hours ago
This makes me happy tbh, I was never a fan of creating `POST /search` endpoints when working with robust APIs
brookstabout 3 hours ago
Wouldn’t just putting an etag on POST requests accomplish the same thing? If I’m understanding it the server has to maintain state to ensure idempotency.
CodesInChaosabout 3 hours ago
QUERY is GET with a request body. So it must be safe, not just idempotent. Where safe means it has no significant side-effects. Typically servers will not keep any state for QUERY requests.

There is one interesting variant though, which uses state: The client sends a QUERY containing the full query, and the server returns a url usable with GET with which this query can be triggered in the future. Similar to prepared statements in SQL databases.

Using QUERY for GraphQL queries (not mutations) would be a good match. These only read data, but are sometimes bigger than the url length limit.

brookstabout 2 hours ago
Thanks for the explanation!

I still don’t get how idempotency can typically be ensured without state. It very much depends on data model and application design. Even side effects like using a user’s lookup quota need to be handled at a higher layer than HTTP (I think?).

inigyou30 minutes ago
Yes it varies. Using the QUERY method doesn't automatically mean your app is idempotent - it means the browser, and any intermediaries, can assume it's idempotent. So when you go forward and then back they're free to reissue the request and you won't get the "this may repeat whatever you just did" popup.

If it's not actually idempotent but you're telling the browser it is, of course you may cause bugs. Same as GET.

wongarsuabout 1 hour ago
Imagine a forum where comment ids are client-generated UUIDs, and comments are inserted with "ON CONFLICT IGNORE". Submitting the same comment twice would simply be a noop

But what the Query method really targets are things like a graphql query that can be multiple kb for a single query, but only reads data. Sure, it might count against rate limits, trigger logs, etc. But at a conceptual level resubmitting the same query should give the same result (if the data didn't change). And since you are only reading data, resubmitting is safe

Joker_vDabout 2 hours ago
> I still don’t get how idempotency can typically be ensured without state.

Well, how is "GET /index.html HTTP/1.1" made idempotent in practice without (additional) state?

CodesInChaosabout 2 hours ago
Minor side-effects like quotas or request logging are generally ignored when considering the semantics of http methods. I don't see any complications for QUERY that don't already apply to GET. It just allows you to bypass the url length limit by putting the data in the body instead of the url itself.
n_eabout 2 hours ago
Interestingly, despite the QUERY request being safe, the RFC says it's subject to preflight requests:

> A QUERY request from user agents implementing Cross-Origin Resource Sharing (CORS) will require a "preflight" request, as QUERY does not belong to the set of CORS-safelisted methods (see [FETCH]).

CodesInChaosabout 2 hours ago
That paragraph merely describes how existing browsers behave, it doesn't specify how future browsers must behave. After all, a HTTP RFC isn't really the right place to specify browser specific behavior like CORS, that belongs in a W3C/WHATWG specification.
trollbridgeabout 3 hours ago
Ideally, libraries like FastAPI, etc. could be configured to translate QUERYs to GETs, until you can rewrite your code to automatically support both.
Joker_vDabout 2 hours ago

    Unlike POST, however, the method is explicitly safe and idempotent, allowing
    functions like caching and automatic retries to operate.
Essentially, it's for things that are inherently safe/idempotent already (e.g. search or indeed, anything that you don't mind being retried) but require a lot of data passed in the request.
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nottorpabout 2 hours ago
It's as bookmarkable as a query with its parameters in the POST data...
drzaiusx11about 1 hour ago
I don't hate it. Covers all the bases: 1.1, 2, 3/quic and solves real problems: get query limitations vs body content & post-without-mutation. Yes there are preexisting workarounds, but they're non-obvious.
lanycrostabout 3 hours ago
query strings always had size limit, seems this new type will solve it which will be really good.
haeseongabout 2 hours ago
QUERY has existed in spirit for nearly two decades as WebDAV's SEARCH method https://www.rfc-editor.org/rfc/rfc5323 and the thing that always killed it in practice was intermediaries. Plenty of proxies, WAFs, and load balancers either strip the body from methods they do not recognize or reject the request outright, so the guarantee that sending a body is safe evaporates the moment traffic crosses a middlebox you do not control. Until gateway and CDN support is real rather than just on paper, POST with a header marking the body as part of the cache key stays the pragmatic choice.