I think we only need to add #1 above. For #2, a server may always reject/fail a request. I don't think we need to clarify that point.
On Mon, Oct 12, 2026 at 12:46 AM youngrae kim <[email protected]> wrote: > Thanks everyone. Summarizing where the thread landed: > > 1. Add "none" to X-Iceberg-Access-Delegation, meaning the client does not > need delegated access from the catalog (Dan's suggestion, +1 from Yufei and > Dmitri). > 2. Clarify the header description so that failing the request is > explicitly allowed: "The server may choose to supply access via any or none > of the requested mechanisms, or fail the request." > > Unless someone objects, I am happy to open a spec PR with these two > changes so the discussion can continue on concrete wording. > > Youngrae Kim > > 2026년 10월 8일 (목) 오전 8:03, Dmitri Bourlatchkov <[email protected]>님이 작성: > >> Hi Alex, Dan, >> >> Thanks for proposing this change. "None" sounds like a good idea to >> me. It is certainly clearer than "local" in the >> context of X-Iceberg-Access-Delegation. >> >> Cheers, >> Dmitri. >> >> On Mon, Oct 5, 2026 at 4:18 PM Daniel Weeks <[email protected]> wrote: >> >>> Alex, >>> >>> Rather than 'local', I think I would prefer 'none'. Rather than saying >>> what the client is intending to do, express that the client isn't asking >>> for or doesn't need credentials/access from the catalog. >>> >>> At least then, the catalog could skip the generation. >>> >>> -Dan >>> >>> On Mon, Oct 5, 2026 at 12:51 AM Alex Dutra <[email protected]> wrote: >>> >>>> Hi all, >>>> >>>> How about at least introducing a new enum constant "local" in the >>>> X-Iceberg-Access-Delegation header? If the intent of that header was >>>> to express capabilities, this new constant would convey the notion of >>>> "I can work with my own credentials" more firmly than letting the >>>> server second-guess. E.g.: "local,remote-signing,vended-credentials" >>>> would mean the client can either work with vended credentials, remote >>>> signing, or its own credentials. >>>> >>>> Thanks, >>>> Alex >>>> >>>> On Tue, Sep 29, 2026 at 4:08 AM youngrae kim <[email protected]> >>>> wrote: >>>> > >>>> > Thanks Dan and Alex. >>>> > >>>> > Dan, that background is helpful, and I take the point: with >>>> storage-credentials and remote-signing-config >>>> > the catalog can state what it provides, so the spec does not need to >>>> mandate a failure when the requested >>>> > mechanisms cannot be provided. Polaris will keep its current behavior >>>> as an implementation choice, >>>> > documented as such, and I will report that outcome on the Polaris >>>> list. >>>> > >>>> > The one thing I would still find useful is Alex's narrower point: a >>>> sentence saying whether the >>>> > header is a capability statement or a requirement, and what an absent >>>> header means. >>>> > That does not constrain what the catalog decides to provide; it only >>>> tells servers and clients how to read the header. >>>> > If there is appetite for that I am happy to draft it; otherwise I am >>>> fine leaving the wording as is and >>>> > letting the catalog-driven model evolve with the File type work. >>>> > >>>> > Thanks, >>>> > Youngrae Kim >>>> > >>>> > 2026년 9월 29일 (화) 오전 6:28, Daniel Weeks <[email protected]>님이 작성: >>>> >> >>>> >> I'm not sure I agree with the model of a client bringing its own >>>> credentials if the catalog is also responsible for controlling access >>>> (can't really stop people from using that model, but as I said above, it >>>> feels like an anti-pattern). >>>> >> >>>> >> The current wording in the spec was intentionally loose so that the >>>> catalog can make decisions without being forced into specific >>>> security/access decisions. I still don't think that updating the wording >>>> would be flexible enough. >>>> >> >>>> >> I'm not sure what all catalogs do, but I can say that it's always >>>> safe for the catalog to return credentials/remote config even if the client >>>> was externally configured to use its own. The current reference >>>> implementation bypasses that, I believe, but conceptually a client does not >>>> need to use the mechanism provided by the catalog. This again feels like a >>>> bit of an anti-pattern: if there's a reason to bring sidecar credentials, >>>> it implies a gap in the delegation model that we should be looking into >>>> addressing. >>>> >> >>>> >> Dan >>>> >> >>>> >> On Mon, Sep 28, 2026 at 10:00 AM Alex Dutra <[email protected]> >>>> wrote: >>>> >>> >>>> >>> Hi all, >>>> >>> >>>> >>> > The delegation header intended to allow the client to communicate >>>> its capabilities, but we've aligned more clearly on catalogs controlling >>>> access as opposed to clients defining behavior. >>>> >>> >>>> >>> IMO, this header isn't ideal for communicating client capabilities. >>>> >>> Notably, it fails to represent a key capability: that of using the >>>> >>> client's own storage credentials to bypass access delegation >>>> entirely. >>>> >>> Right now, the only way to imply this capability is by omitting the >>>> >>> header altogether, which introduces ambiguity into the >>>> specification. >>>> >>> Put simply, a client cannot explicitly communicate e.g.: "I can >>>> >>> function either without access delegation or using vended >>>> credentials, >>>> >>> but I do not support remote signing." >>>> >>> >>>> >>> Therefore, Apache Polaris today treats this header as an explicit >>>> >>> requirement rather than just a capability statement. IOW, it treats >>>> >>> the header presence as an indication that the client cannot function >>>> >>> without access delegation, and that at least one specified mode must >>>> >>> be satisfied. >>>> >>> >>>> >>> I would be interested to hear how other catalog implementations are >>>> >>> approaching this. >>>> >>> >>>> >>> In any case, I still think that a minor spec clarification would be >>>> >>> welcome, if for nothing else, at least to lift the ambiguity around >>>> >>> what it means when the header is absent and clarify whether the >>>> header >>>> >>> is a capability statement, or a requirement. >>>> >>> >>>> >>> Thanks, >>>> >>> Alex >>>> >>> >>>> >>> >>>> >>> On Mon, Sep 28, 2026 at 5:03 PM Daniel Weeks <[email protected]> >>>> wrote: >>>> >>> > >>>> >>> > Youngrae, >>>> >>> > >>>> >>> > I think the issue with #2 above is that it's a bit of an >>>> anti-pattern for the client to concurrently own access. Either the catalog >>>> should be the authority on access or it shouldn't. Security around the >>>> physical data shouldn't really be a negotiation between the client and the >>>> server. If the catalog is delegating access to the data, it should be the >>>> sole source of truth. >>>> >>> > >>>> >>> > It feels like we're trying to make this a negotiation between the >>>> catalog and client, but the catalog should be responsible for access >>>> delegation in a secure environment. >>>> >>> > >>>> >>> > The background on this header is important: The original access >>>> control mechanism was remote signing only, which was not originally part of >>>> the REST protocol (it was separate and S3 specific). We later introduced >>>> vended credentials, but only through the config payload. Since then, a lot >>>> has changed: we introduced the Storage Credentials and now the Remote >>>> Signing Config, which means that we're in a much better position for the >>>> catalog to clearly indicate which mechanism the client should use. The >>>> mechanisms are more standardized, and clients should be able to report if >>>> they cannot support what the catalog has provided. >>>> >>> > >>>> >>> > While there may be some residual value in the client signaling >>>> its capabilities, I'm not convinced we need to change the wording in the >>>> spec and we need to improve the other mechanisms as we evolve to support >>>> new functionality like File type, which may mix different modes of access. >>>> >>> > >>>> >>> > The behavior you describe in Polaris is perfectly fine as an >>>> implementation choice, but I don't think catalogs SHOULD fail if they >>>> cannot provide any requested mechanism. The catalog can provide an >>>> alternative (e.g. you requested signing, but I'm only providing >>>> credentials), which the client can error on if it does not understand. >>>> Alternatively, the catalog could reject all requested forms and return only >>>> the metadata, effectively signaling that the client can only see the >>>> metadata, but has no access to the physical data. >>>> >>> > >>>> >>> > -Dan >>>> >>> > >>>> >>> > >>>> >>> > On Fri, Sep 25, 2026 at 8:18 PM youngrae kim < >>>> [email protected]> wrote: >>>> >>> >> >>>> >>> >> Thanks Alex, Yufei and Dan. >>>> >>> >> >>>> >>> >> Dan, I think the catalog-controlled direction and Alex's wording >>>> are compatible, and it may help to separate the two roles the header plays >>>> today: >>>> >>> >> >>>> >>> >> 1. Which mechanism to use. >>>> >>> >> That is already the catalog's decision in Polaris: the server >>>> picks among the mechanisms >>>> >>> >> it supports for that catalog and storage, and the header only >>>> tells it which ones the client can consume. >>>> >>> >> Nothing in the proposed sentence changes that. >>>> >>> >> >>>> >>> >> 2. Whether the client can access the data at all without >>>> delegation. Today the header is the >>>> >>> >> only signal a client has for "I have no storage credentials of >>>> my own". >>>> >>> >> If the catalog cannot provide any mechanism the client can >>>> consume, the request cannot succeed in any >>>> >>> >> useful sense, and the question is only where the failure >>>> surfaces: at load time with a >>>> >>> >> message naming the cause, or at the first data access with a >>>> storage error. >>>> >>> >> >>>> >>> >> The proposed SHOULD covers exactly the empty-intersection case >>>> in (2); a server that knows its >>>> >>> >> clients carry their own credentials can still return the table, >>>> which is why SHOULD rather than MUST seems right. >>>> >>> >> >>>> >>> >> If the longer-term direction is to rely less on the header, I >>>> would be interested in how a >>>> >>> >> catalog-driven model would express (2), for example the client >>>> learning from /v1/config which >>>> >>> >> mechanisms the catalog offers, so it can decide before loading a >>>> table. That seems like a >>>> >>> >> larger change than the clarification this thread started with, >>>> so I would suggest landing the >>>> >>> >> one-sentence clarification for the current header and taking the >>>> catalog-driven model as a >>>> >>> >> separate discussion, unless you see a conflict between the two. >>>> >>> >> >>>> >>> >> Thanks, >>>> >>> >> Youngrae Kim >>>> >>> >> >>>> >>> >> 2026년 9월 26일 (토) 오전 8:52, Daniel Weeks <[email protected]>님이 작성: >>>> >>> >>> >>>> >>> >>> I'm not convinced that we're thinking about this the right way. >>>> >>> >>> >>>> >>> >>> The delegation header intended to allow the client to >>>> communicate its capabilities, but we've aligned more clearly on catalogs >>>> controlling access as opposed to clients defining behavior. >>>> >>> >>> >>>> >>> >>> If we leaned more into that direction, then access would be >>>> determined by the catalog based on the availability of vented credentials >>>> or the new remote signing configuration. >>>> >>> >>> >>>> >>> >>> There may be an opportunity here to rely less on the header and >>>> give responsibility back on th e catalog to determine the access model. >>>> >>> >>> >>>> >>> >>> -Dan >>>> >>> >>> >>>> >>> >>> On Fri, Sep 25, 2026, 4:39 PM Yufei Gu <[email protected]> >>>> wrote: >>>> >>> >>>> >>>> >>> >>>> I tend to agree with Alex and Youngrae. A fail-fast approach >>>> provides a clear behavioral contract between the server and clients, while >>>> the current spec introduces ambiguity. >>>> >>> >>>> >>>> >>> >>>> I am not sure if this ambiguity was intentional. Please chime >>>> in if you can provide more context; otherwise, I suggest we update the spec >>>> to eliminate it. >>>> >>> >>>> >>>> >>> >>>> Yufei >>>> >>> >>>> >>>> >>> >>>> >>>> >>> >>>> On Thu, Sep 24, 2026 at 10:12 AM Alex Dutra <[email protected]> >>>> wrote: >>>> >>> >>>>> >>>> >>> >>>>> Hi Youngrae, >>>> >>> >>>>> >>>> >>> >>>>> Thanks for starting this thread! >>>> >>> >>>>> >>>> >>> >>>>> I believe the phrase "via any or none of the requested >>>> mechanisms" >>>> >>> >>>>> requires clarification. >>>> >>> >>>>> >>>> >>> >>>>> If a client requests modes A and B, a server returning only >>>> mode B is >>>> >>> >>>>> perfectly acceptable. However, returning a 200 OK response >>>> with >>>> >>> >>>>> neither mode A nor B represents an ambiguous outcome. >>>> >>> >>>>> >>>> >>> >>>>> The current wording likely assumes the client could >>>> theoretically >>>> >>> >>>>> proceed using its own fallback storage credentials. In >>>> practice, >>>> >>> >>>>> operators configure clients intentionally; requesting access >>>> >>> >>>>> delegation "just in case" is unrealistic. A fail-fast error >>>> is a >>>> >>> >>>>> better outcome, as opposed to letting the client proceed, >>>> only to see >>>> >>> >>>>> it fail later on. >>>> >>> >>>>> >>>> >>> >>>>> I propose updating the specification to mandate an error >>>> response when >>>> >>> >>>>> no requested mechanism is available, while also clarifying >>>> whether >>>> >>> >>>>> providing multiple delegation modes is supported: >>>> >>> >>>>> >>>> >>> >>>>> "The server MAY supply access via any or all of the requested >>>> >>> >>>>> mechanisms. If none of the requested mechanisms is available, >>>> the >>>> >>> >>>>> server SHOULD return an HTTP 400 (Bad Request) response." >>>> >>> >>>>> >>>> >>> >>>>> Thanks, >>>> >>> >>>>> Alex >>>> >>> >>>>> >>>> >>> >>>>> On Wed, Sep 23, 2026 at 11:14 AM youngrae kim < >>>> [email protected]> wrote: >>>> >>> >>>>> > >>>> >>> >>>>> > Hi all, >>>> >>> >>>>> > The REST catalog spec describes X-Iceberg-Access-Delegation >>>> as an "optional signal to the server that the client supports delegated >>>> access via a comma-separated list of access mechanisms. The server may >>>> choose to supply access via any or none of the requested mechanisms." [1] >>>> >>> >>>>> > >>>> >>> >>>>> > In Apache Polaris we recently discussed what a server >>>> should do when the header is present but it can satisfy none of the >>>> requested mechanisms, for example vended-credentials against an >>>> S3-compatible store without STS, or remote-signing on a server that does >>>> not implement it [2]. >>>> >>> >>>>> > >>>> >>> >>>>> > Polaris fails such requests with HTTP 400 and a message >>>> naming the reason, because in these cases the inability is a static >>>> property of the catalog and a 200 without credentials would only move the >>>> failure to the first data access. >>>> >>> >>>>> > >>>> >>> >>>>> > Two readings of "any or none" came up and the text does not >>>> settle which is intended: >>>> >>> >>>>> > (a) "none" means the server returns 200 with the table >>>> and no delegated access, and the client detects this from the response: an >>>> empty storage-credentials (and, we understand, an empty >>>> remote-signing-config once that field lands in 1.12), falling back to the >>>> config map for older servers [3]. >>>> >>> >>>>> > >>>> >>> >>>>> > (b) "none" also permits the server to reject the request >>>> when it cannot provide any of the requested mechanisms. >>>> >>> >>>>> > >>>> >>> >>>>> > Questions for the community: >>>> >>> >>>>> > 1. Is rejecting the request a permitted server choice >>>> under the current text, or is (a) the only intended behavior? >>>> >>> >>>>> > 2. If rejection is permitted, is there a preferred status >>>> code and error type, so clients can distinguish "delegation unavailable" >>>> from other 400s? >>>> >>> >>>>> > 3. If (a) is the intended behavior, should the spec state >>>> explicitly that the absence of credentials in both storage-credentials and >>>> config (and of remote-signing-config) is the signal that no delegation was >>>> applied? >>>> >>> >>>>> > >>>> >>> >>>>> > I'm happy to draft a clarification to the parameter >>>> description once there is agreement. >>>> >>> >>>>> > >>>> >>> >>>>> > [1] >>>> https://github.com/apache/iceberg/blob/778d103c0fa802be5e85e4cb2e4e4b4bcd8ac891/open-api/rest-catalog-open-api.yaml#L2151-L2161 >>>> >>> >>>>> > [2] >>>> https://lists.apache.org/thread/9oyv4v0vk3t8stv9832npl8t0yyp4j8r >>>> >>> >>>>> > [3] >>>> https://github.com/apache/iceberg/blob/778d103c0fa802be5e85e4cb2e4e4b4bcd8ac891/open-api/rest-catalog-open-api.yaml#L4246-L4249 >>>> >>> >>>>> > >>>> >>> >>>>> > Thanks, >>>> >>> >>>>> > Youngrae Kim >>>> >>>
