Hi Dmitri, > Do you think this is worth discussing with the Iceberg community?
I did already, see this part of my reply [1] where I was advocating for your "local" capability suggestion: > [The header] 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. That being said, I just sent another message to the same Iceberg topic, relaying your suggestion. Thanks, Alex [1]: https://lists.apache.org/thread.html/3r6wrblr0l7xs7cb2f7qs07ovh792vyo On Fri, Oct 2, 2026 at 9:30 PM Dmitri Bourlatchkov <[email protected]> wrote: > > Hi Alex, > > I've been thinking about the perspective using the header as a client > capability. > > I think it has merit; however, I'd expect the client to declare its full > set of capabilities in that case. > > For example, if a client has local storage credentials, I'd expect a header > value like this: > "local,remote-signing,vended-credentials". > > If the client lacks local credentials and does not support remote signing, > it would send: > "vended-credentials". > > With this approach the server (Polaris) would be able to make precise > access decisions and fail requests only when no viable access option > remains. > > Do you think this is worth discussing with the Iceberg community? > > However, since "local" is not something that existing clients provide, I > think Polaris has to resort to heuristic assumptions that a client flagging > _some_ access delegation mechanisms cannot work without them. > > Cheers, > Dmitri. > > On Fri, Oct 2, 2026 at 5:01 AM Alex Dutra <[email protected]> wrote: > > > Hi all, > > > > The recent discussion on the Iceberg mailing list highlighted an > > interesting perspective: some view the delegation header primarily as > > a capability statement rather than a strict requirement. > > > > Under that approach, delegation decisions rely mainly on internal > > catalog configurations (such as warehouse-level allowed modes). The > > header merely serves as an optional hint, making error responses > > unnecessary. > > > > By contrast, Polaris has treated the header as a mandatory requirement > > from the start. The server attempts to fulfill it by finding the > > intersection between supported capabilities and client preferences, > > returning an error if no common mode is available. > > > > Daniel Weeks confirmed that the Polaris model is perfectly valid. > > Consequently, no changes are required on our end, though we should > > keep in mind that Polaris may be taking a distinct path with its > > interpretation of the spec, relative to what other catalogs may be > > doing. > > > > Thanks, > > Alex > > > > > > On Tue, Sep 29, 2026 at 4:11 AM youngrae kim <[email protected]> > > wrote: > > > > > > Thanks Prithvi. > > > > > > Closing the loop on the Iceberg side [1]: Dan Weeks (spec author) prefers > > > to keep the header > > > wording intentionally loose so that the catalog stays the sole authority > > on > > > access delegation. > > > He considers the Polaris fail-fast behavior fine as an implementation > > > choice but does not want the spec > > > to say catalogs SHOULD fail; a catalog may also provide an alternative > > > mechanism or return metadata only. > > > Alex asked for a narrower clarification (capability statement vs > > > requirement, meaning of an absent header), > > > which is still open there. > > > > > > For Polaris nothing changes: we keep the 400 with the two messages, > > > documented in #5591 as our behavior. > > > If the Iceberg thread later lands a clarification I will follow up here. > > > > > > [1] https://lists.apache.org/thread/6zspb6cpb6j2po5lm57mq1sgcp2hppkf > > > > > > Thanks, > > > Youngrae Kim > > > > > > 2026년 9월 25일 (금) 오전 6:25, Prithvi S <[email protected]>님이 작성: > > > > > > > Hi all, > > > > > > > > I agree with failing the request when the server can supply none of the > > > > requested mechanisms, and with Alex's SHOULD. > > > > > > > > In Polaris the two cases we discussed are static properties of the > > catalog. > > > > stsUnavailable will not start working on a later load, and remote > > signing > > > > is not implemented. A 200 with no delegated access only moves the > > failure > > > > to the first data access, where it is much harder to diagnose. We kept > > the > > > > 400 and wrote down both messages, and what the client should change, in > > > > https://github.com/apache/polaris/pull/5591. > > > > > > > > SHOULD is the right strength for the spec. It records the behavior > > > > operators can diagnose, and a server that knows its clients carry > > storage > > > > credentials can still return the table. Polaris does not take that > > path. > > > > The header is often a shared client setting: PyIceberg documents > > > > vended-credentials as the default ( > > > > https://py.iceberg.apache.org/configuration/), so a client can send it > > > > without anyone having decided that this catalog should vend. > > > > > > > > The 400 sentence is the clarification this thread needs. Whether one > > > > response may carry more than one mechanism is a separate change. > > Polaris > > > > selects a single mechanism, and that can stay as it is until a server > > > > returns both. > > > > > > > > HTTP 400 with the existing Bad Request error is enough. Clients already > > > > fail the load on it. The message is what tells the operator which > > mechanism > > > > was missing, and to drop the header or configure storage credentials > > on the > > > > client. A distinct error type can wait until a client needs to branch > > on > > > > this case in code. > > > > > > > > Thanks, > > > > Prithvi S > > > > > > > > On Wed, Sep 23, 2026 at 2:11 PM youngrae kim <[email protected]> > > > > wrote: > > > > > > > > > Thanks Alex, that's helpful context. The backwards-compatibility > > reading > > > > of > > > > > "must first check" > > > > > makes sense, and the upcoming remote-signing-config field in Iceberg > > 1.12 > > > > > following the > > > > > same dual-location pattern is a good reason to get the "delegation > > not > > > > > provided" semantics > > > > > written down before more mechanisms are added. > > > > > > > > > > Since Ayush, Yufei and you all favor asking upstream, I'll open the > > > > > dev@iceberg thread now > > > > > and link it here. I'll frame it as a clarification request: whether > > "any > > > > or > > > > > none" permits > > > > > rejecting the request, and whether an empty storage-credentials > > (and, in > > > > > 1.12, > > > > > remote-signing-config) is the intended signal when the server > > returns 200 > > > > > without delegation. > > > > > > > > > > The Polaris documentation side is done: > > > > > - issue: https://github.com/apache/polaris/issues/5579 > > > > > - PR: https://github.com/apache/polaris/pull/5591 > > > > > > > > > > Thanks, > > > > > Youngrae Kim > > > > > > > > > > 2026년 9월 23일 (수) 오전 1:53, Alex Dutra <[email protected]>님이 작성: > > > > > > > > > > > And to complicate things further, there is a new field coming in > > > > > > Iceberg 1.12: LoadTableResponse.remoteSigningConfig(). > > > > > > > > > > > > The idea is roughly the same as for the storage-credentials field: > > > > > > clients should search for remote signing properties either in the > > new > > > > > > remote-signing-config field, or in the config field for backwards > > > > > > compatibility with older servers. If the client explicitly > > requested > > > > > > remote signing, the absence of remote signing properties in both > > > > > > places would in theory mean that the server didn't allow the > > client to > > > > > > perform remote signing. > > > > > > > > > > > > But that doesn't change the overall feeling that a fail-fast > > solution > > > > > > would be more appropriate, I think. > > > > > > > > > > > > Thanks, > > > > > > Alex > > > > > > > > > > > > > > > > > > On Tue, Sep 22, 2026 at 6:27 PM Alex Dutra <[email protected]> > > wrote: > > > > > > > > > > > > > > Hi all, > > > > > > > > > > > > > > I'm also supportive of Option 1 (fail-fast), and also supportive > > of > > > > > > > asking the Iceberg community to provide a spec clarification. > > > > > > > > > > > > > > @Ayush: > > > > > > > > > > > > > > > The spec does have a signal for "delegation not applied": [...] > > > > > > "Clients must first check whether the respective credentials exist > > in > > > > the > > > > > > storage-credentials field before checking the config for > > credentials". > > > > > > > > > > > > > > I think this sentence is there for backwards compatibility with > > older > > > > > > > clients that do not know about the (relatively recent) > > > > > > > storage-credentials field. That's why Polaris vends credentials > > in > > > > > > > *both* places [1]; the "must first check" imperative is there > > only to > > > > > > > force clients to prefer the ones in the storage-credentials > > field. > > > > > > > > > > > > > > In any case, the absence of credentials in *both* places *could* > > be > > > > > > > interpreted as a signal that the server wasn't able to perform > > access > > > > > > > delegation – but again, failing fast appears to me as a much > > cleaner > > > > > > > behavior. > > > > > > > > > > > > > > Thanks, > > > > > > > Alex > > > > > > > > > > > > > > [1]: > > > > > > > > > > > > > > > > > https://github.com/apache/polaris/blob/e6aacf350fb7464f001f9778b9b678ed80709dcb/runtime/service/src/main/java/org/apache/polaris/service/catalog/iceberg/IcebergCatalogHandler.java#L1246-L1250 > > > > > > > > > > > > > > > > > > > > > On Tue, Sep 22, 2026 at 8:00 AM youngrae kim < > > [email protected] > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > Thanks Yufei. > > > > > > > > > > > > > > > > Agreed that the spec text is ambiguous and worth clarifying > > > > upstream. > > > > > > I'll > > > > > > > > focus on the Polaris documentation first; if nobody else picks > > up > > > > the > > > > > > > > Iceberg-side question, I can raise it on dev@iceberg > > afterwards > > > > and > > > > > > link > > > > > > > > back to this thread. > > > > > > > > > > > > > > > > For the documentation, I'll open the Polaris issue as planned: > > the > > > > > > > > vended-credentials page and the S3 stsUnavailable section will > > > > > describe > > > > > > > > what a client sees when delegation cannot be satisfied (HTTP > > 400 > > > > and > > > > > > the > > > > > > > > two messages), and recommend omitting the header, or > > configuring > > > > > > storage > > > > > > > > credentials on the client, for catalogs that cannot vend. > > > > > > > > > > > > > > > > I'll post the link to the issue here once it is up. > > > > > > > > > > > > > > > > Thanks, > > > > > > > > Youngrae Kim > > > > > > > > > > > > > > > > 2026년 9월 22일 (화) 오전 2:59, Yufei Gu <[email protected]>님이 > > 작성: > > > > > > > > > > > > > > > > > I support keeping fail-fast in Polaris and documenting it. > > > > > > > > > > > > > > > > > > I’d still suggest a discussion in the Iceberg community. The > > spec > > > > > > > > > < > > > > > > > > > > > > > > > > > > > > > > > > > > https://github.com/apache/iceberg/blob/778d103c0fa802be5e85e4cb2e4e4b4bcd8ac891/open-api/rest-catalog-open-api.yaml#L2151-L2161 > > > > > > > > > > > > > > > > > > > says the server may provide “any or none” of the requested > > access > > > > > > > > > mechanisms, but it’s unclear whether that includes rejecting > > the > > > > > > request. > > > > > > > > > Clarifying this would help clients work consistently across > > > > > catalogs. > > > > > > > > > > > > > > > > > > This can happen alongside the Polaris documentation update. > > > > > > > > > Yufei > > > > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Sep 18, 2026 at 5:01 PM youngrae kim < > > > > > [email protected] > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > Thanks Ayush and Dmitri. > > > > > > > > > > > > > > > > > > > > Ayush, you're right about storage-credentials: the signal > > is > > > > > there, > > > > > > > > > > and the real objection to option 2 is that clients aren't > > > > > reliably > > > > > > > > > checking > > > > > > > > > > it. > > > > > > > > > > And the point that both failure cases are static > > properties of > > > > > the > > > > > > > > > catalog > > > > > > > > > > is what settles it for me as well: > > > > > > > > > > there is nothing a later request could do differently, so a > > > > clear > > > > > > error > > > > > > > > > at > > > > > > > > > > load time loses nothing. > > > > > > > > > > > > > > > > > > > > So the direction is option 1: keep fail-fast, and document > > it. > > > > > > > > > > Unless there are objections in the next couple of days, > > I'll > > > > open > > > > > > an > > > > > > > > > issue > > > > > > > > > > to update the docs, > > > > > > > > > > covering the vended-credentials-only and remote-signing > > cases, > > > > > > what the > > > > > > > > > > client sees, > > > > > > > > > > and the recommendation to omit the header (or configure > > storage > > > > > > > > > > credentials) for catalogs that cannot vend. > > > > > > > > > > > > > > > > > > > > On the Iceberg spec: I'll leave it aside for now, > > > > > > > > > > given Dmitri's point that the current text already permits > > > > > > refusing, > > > > > > > > > > and revisit only if someone hits the ambiguity in practice. > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > Youngrae Kim > > > > > > > > > > > > > > > > > > > > 2026년 9월 19일 (토) 오전 12:05, Dmitri Bourlatchkov < > > > > [email protected] > > > > > >님이 > > > > > > 작성: > > > > > > > > > > > > > > > > > > > > > Hi All, > > > > > > > > > > > > > > > > > > > > > > I agree with option 1. > > > > > > > > > > > > > > > > > > > > > > The basic question is whether the client should use local > > > > > > credentials > > > > > > > > > or > > > > > > > > > > > get vended credentials from Polaris. I do not think it > > is a > > > > > > runtime > > > > > > > > > > choice. > > > > > > > > > > > I believe it is a fundamental design decision that > > > > > administrators > > > > > > > > > should > > > > > > > > > > > resolve at deployment time. > > > > > > > > > > > > > > > > > > > > > > Consequently, the client should either delegate access > > > > controls > > > > > > to > > > > > > > > > > Polaris > > > > > > > > > > > via X-Iceberg-Access-Delegation or not use that header at > > > > all. > > > > > > > > > > > > > > > > > > > > > > From another angle, if the client already has access > > > > > > credentials, what > > > > > > > > > > > could be the rationale for also requesting different > > access > > > > > > channels > > > > > > > > > > > via X-Iceberg-Access-Delegation? I do not see any :) > > > > > > > > > > > > > > > > > > > > > > With that in mind, I think Polaris can interpret the > > presence > > > > > > > > > > > of X-Iceberg-Access-Delegation as a strong request for > > > > > > > > > server-controlled > > > > > > > > > > > access methods (request signing or cred. vending). If the > > > > > server > > > > > > cannot > > > > > > > > > > > provide any, it is effectively a deployment / > > configuration > > > > > > mistake, > > > > > > > > > so a > > > > > > > > > > > clear error response is quite appropriate from my POV. > > > > > > > > > > > > > > > > > > > > > > General non-vending Polaris configuration is considered > > > > > > deprecated per > > > > > > > > > > > earlier discussion [1]. The only case when Polaris cannot > > > > vend > > > > > > > > > > credentials > > > > > > > > > > > is when the Storage System does not support it. > > > > > > > > > > > > > > > > > > > > > > Re: Iceberg spec discussion, I'm not sure it is worth the > > > > > > trouble. The > > > > > > > > > > IRC > > > > > > > > > > > spec clearly opted for the most lenient interpretation > > > > > > > > > > > of X-Iceberg-Access-Delegation that does not impose any > > > > strong > > > > > > > > > > > protocol-level requirements on either the client or the > > > > server. > > > > > > I do > > > > > > > > > not > > > > > > > > > > > think it would be wise for the IRC spec to venture into > > > > > > > > > deployment-level > > > > > > > > > > > recommendations because it defines a protocol, not an > > > > > end-to-end > > > > > > > > > system. > > > > > > > > > > I > > > > > > > > > > > think the current IRC spec allows the behaviour proposed > > by > > > > > > option 1 in > > > > > > > > > > > Polaris. This is just my personal opinion, feel free to > > open > > > > an > > > > > > Iceberg > > > > > > > > > > > discussion on this if you prefer. > > > > > > > > > > > > > > > > > > > > > > [1] > > > > > > https://lists.apache.org/thread/1trcnbm04zzqztpxkzrzs1pvrlyd49bg > > > > > > > > > > > > > > > > > > > > > > Cheers, > > > > > > > > > > > Dmitri. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Sep 18, 2026 at 7:40 AM Ayush Saxena < > > > > > > [email protected]> > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > Hi Youngrae, > > > > > > > > > > > > > > > > > > > > > > > > +1 to option 1, with one correction to the premise. > > > > > > > > > > > > > > > > > > > > > > > > The spec does have a signal for "delegation not > > applied": > > > > > > > > > > LoadTableResult > > > > > > > > > > > > carries storage-credentials, and clients are obliged to > > > > look > > > > > > at it — > > > > > > > > > > > > "Clients must first check whether the respective > > > > credentials > > > > > > exist in > > > > > > > > > > the > > > > > > > > > > > > storage-credentials field before checking the config > > for > > > > > > credentials" > > > > > > > > > > > [1]. > > > > > > > > > > > > An empty storage-credentials on a 200 is observable. > > The > > > > > > practical > > > > > > > > > > > > objection to option 2 is that "must check" isn't "does > > > > > check", > > > > > > not > > > > > > > > > that > > > > > > > > > > > the > > > > > > > > > > > > information is missing. > > > > > > > > > > > > > > > > > > > > > > > > What decides it for me is that in Polaris both failure > > > > cases > > > > > > are > > > > > > > > > static > > > > > > > > > > > > properties of the catalog: stsUnavailable is > > configuration > > > > > and > > > > > > remote > > > > > > > > > > > > signing is unimplemented, so neither will start > > working on > > > > a > > > > > > later > > > > > > > > > > > request > > > > > > > > > > > > or for a different table. The usual case for returning > > 200 > > > > > > without > > > > > > > > > > > > delegation is that the server might satisfy it some > > other > > > > > time > > > > > > — that > > > > > > > > > > > > doesn't apply here, so failing at load with a message > > > > naming > > > > > > the > > > > > > > > > reason > > > > > > > > > > > is > > > > > > > > > > > > strictly more diagnosable and nothing is lost. > > > > > > > > > > > > > > > > > > > > > > > > Raising the ambiguity upstream sounds worthwhile either > > > > way — > > > > > > "any or > > > > > > > > > > > > none" doesn't say whether refusing the request is a > > > > permitted > > > > > > choice, > > > > > > > > > > and > > > > > > > > > > > > that's the real gap. > > > > > > > > > > > > > > > > > > > > > > > > -Ayush > > > > > > > > > > > > > > > > > > > > > > > > [1] > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://github.com/apache/iceberg/blob/778d103c0fa802be5e85e4cb2e4e4b4bcd8ac891/open-api/rest-catalog-open-api.yaml#L4246-L4249 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On 2026/09/18 08:44:49 김영래 wrote: > > > > > > > > > > > > > Hi all, > > > > > > > > > > > > > > > > > > > > > > > > > > This came out of the review of PR #5473 (merged), > > where > > > > > > Dmitri > > > > > > > > > > > > > suggested moving the spec-alignment question to the > > list. > > > > > > Short > > > > > > > > > > > version: > > > > > > > > > > > > > today Polaris fails a request whose > > > > > > X-Iceberg-Access-Delegation > > > > > > > > > > header > > > > > > > > > > > > > cannot be satisfied, while the Iceberg REST spec > > reads as > > > > > if > > > > > > the > > > > > > > > > > server > > > > > > > > > > > > may > > > > > > > > > > > > > instead return the table without delegated access. > > I'd > > > > like > > > > > > to > > > > > > > > > agree > > > > > > > > > > on > > > > > > > > > > > > the > > > > > > > > > > > > > intended behavior and document it. > > > > > > > > > > > > > > > > > > > > > > > > > > Current behavior (main, after #5473): > > > > > > > > > > > > > > > > > > > > > > > > > > - "vended-credentials" against a catalog that cannot > > vend > > > > > > > > > credentials > > > > > > > > > > > > (e.g. > > > > > > > > > > > > > S3 with stsUnavailable=true) fails with 400 > > "Credential > > > > > > vending was > > > > > > > > > > > > > requested ... but no credentials are available". > > > > > > > > > > > > > - Anything that resolves to remote signing (not > > > > > implemented) > > > > > > fails > > > > > > > > > > with > > > > > > > > > > > > 400 > > > > > > > > > > > > > "This catalog cannot vend credentials or sign > > requests; > > > > > > request > > > > > > > > > > without > > > > > > > > > > > > > X-Iceberg-Access-Delegation and configure storage > > > > > > credentials on > > > > > > > > > the > > > > > > > > > > > > > client". This covers "remote-signing" alone > > > > > > > > > > > > > and "vended-credentials,remote-signing" when vending > > is > > > > not > > > > > > > > > possible. > > > > > > > > > > > > > > > > > > > > > > > > > > What the spec says > > (iceberg-rest-catalog-open-api.yaml, > > > > > > parameter > > > > > > > > > > > > > X-Iceberg-Access-Delegation): > > > > > > > > > > > > > "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." > > > > > > > > > > > > > > > > > > > > > > > > > > Arguments raised in the PR review: > > > > > > > > > > > > > - For fail-fast (current): a client that asks for > > > > > delegation > > > > > > > > > usually > > > > > > > > > > > has > > > > > > > > > > > > no > > > > > > > > > > > > > storage credentials of its own, so a 200 without > > > > > credentials > > > > > > only > > > > > > > > > > moves > > > > > > > > > > > > the > > > > > > > > > > > > > failure to the first data access, where it is much > > harder > > > > > to > > > > > > > > > > diagnose. > > > > > > > > > > > It > > > > > > > > > > > > > is also consistent with how "vended-credentials" > > alone > > > > has > > > > > > always > > > > > > > > > > > > behaved. > > > > > > > > > > > > > - For following the spec literally: the header is a > > hint, > > > > > and > > > > > > > > > clients > > > > > > > > > > > > that > > > > > > > > > > > > > do have their own storage credentials (instance > > profile, > > > > > > > > > environment > > > > > > > > > > > > > variables) but send the header as a shared setting > > would > > > > > > simply > > > > > > > > > work. > > > > > > > > > > > > > > > > > > > > > > > > > > Options: > > > > > > > > > > > > > 1. Keep fail-fast and document it explicitly. The > > docs > > > > > > currently > > > > > > > > > only > > > > > > > > > > > say > > > > > > > > > > > > > to omit the header for stsUnavailable catalogs. > > > > > > > > > > > > > 2. Follow the spec literally and return the table > > without > > > > > > delegated > > > > > > > > > > > > access. > > > > > > > > > > > > > The spec has no field to signal "delegation not > > applied", > > > > > so > > > > > > > > > clients > > > > > > > > > > > > would > > > > > > > > > > > > > only find out at data access time. > > > > > > > > > > > > > 3. Make it configurable per realm or catalog (feature > > > > flag, > > > > > > default > > > > > > > > > > > > > fail-fast) for deployments that know their clients > > carry > > > > > > storage > > > > > > > > > > > > > credentials. > > > > > > > > > > > > > > > > > > > > > > > > > > I lean towards option 1 unless someone has a concrete > > > > > client > > > > > > that > > > > > > > > > > > depends > > > > > > > > > > > > > on option 2. If there is interest, I can also raise > > the > > > > > > ambiguity > > > > > > > > > on > > > > > > > > > > > the > > > > > > > > > > > > > Iceberg side, since the spec text leaves the choice > > to > > > > the > > > > > > server. > > > > > > > > > > > > > > > > > > > > > > > > > > Context: issue #5472, PR #5473 (see the CHANGELOG > > review > > > > > > thread), > > > > > > > > > and > > > > > > > > > > > the > > > > > > > > > > > > > earlier threads "[DISCUSS] S3 Credential vending > > without > > > > > > STS" (July > > > > > > > > > > > 2025) > > > > > > > > > > > > > and "[DISCUSS] S3 Remote Signing" (August 2025). > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > Youngrae Kim > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
