It seems like there are 2 sub-topics here:
1. should we group operations with tags, or should we do this
per-operation/endpoint?
2. how should we do the capability/versioning for each unit (either per tag
or per operation)
Shall we first conclude on 1?
For 1, my take is that we will need to do it per operation, for 2 reasons:
(1) There are many REST services that would only implement a very small set
of APIs, such as just loadTable and loadView. Some will choose to not
implement very specific endpoints, such as renameTable. Tags seems
convenient but it is mandating people to implement a specific group of APIs
together, which is a lot of burdens for especially small organizations, if
they just want to support very specific goals like reading through IRC.
(2) Suppose a new tag is added in the future, the server returns that tag,
but an older client does not understand it, it might cause mistakes in the
client's understanding of what is supported and what is not, when a tag
contains both features in existing APIs and also new APIs. If we define
that tags do not overlap with each other, this is probably not a concern.
However, (1) still is a problem from a usability perspective.
Best,
Jack Ye
On Wed, Jun 26, 2024 at 9:02 AM Daniel Weeks <dwe...@apache.org> wrote:
> I think Robert's approach is a reasonable compromise here.
>
> If we wanted a "per operation/endpoint" versioning, I think I'd prefer
> Micah's OpenAPI spec based approach because it's more standardized, but I
> feel adds a lot of client complexity.
>
> -Dan
>
>
>
> On Wed, Jun 26, 2024 at 6:59 AM Robert Stupp <sn...@snazy.de> wrote:
>
>> (I think, compatibility deserves a separate thread - it's a "huge" topic)
>>
>> Based on experience, we decided on the following with Nessie:
>>
>> - Unknown fields/attributes in a structure _DO_ cause
>> (de)serialization failures.
>> - "Stable API versions" - endpoint additions and/or added query
>> parameters and/or enhanced structures do _NOT_ require a new API version
>> (as in the endpoint's route/path).
>> - "Flexible spec versions" - new and updated "capabilities" however
>> might cause a bump in the "spec version" that the server announces in its
>> `getConfig` result.
>>
>> Adding new routes/paths may require new endpoint implementations on the
>> server side, which can easily lead to a lot of (unnecessarily boilerplate)
>> code. Using different routes/paths is justified if the API is changed
>> "fundamentally". We call the "path component" (api/v1/..., api/v2/...) API
>> version - the server indicates the minimum and maximum supported API
>> version, in case a client wants to "upgrade". I recommend to _not_ bump the
>> API version in the route/path if it's not really necessary.
>>
>> Regarding the requirement to fail on unknown attributes: Unknown
>> attributes may contain important information. A client may send a newer
>> version of a request object with an important new field, but the (older)
>> server discards the new attribute. Think of an attribute that for example
>> defines a "commit condition" that the client expects to be respected. "New"
>> attributes must be omittable (e.g. don't serialize if null/default) -
>> clients indicate the "usage" of an added attribute using some request
>> attribute (for example: "boolean returnExtendedInformation").
>>
>> The list of capabilities can be indicated with included "spec versions",
>> to tell clients which features/functionalities a server
>> supports."Production" spec versions could start with 1, and "reserve" 0 for
>> experimental/unsupported/poc kind of implementation. It could look like
>> this:
>> capabilities: [
>> "table-spec/2,3", // but not table-spec v1 here
>> "view-spec/1",
>> "table-api/1",
>> "view-api/1",
>> "udf-api/1",
>> "super-feature/2,4,6", // but not spec versions 0,1,3,5,7+
>> ...
>> ]
>> Incrementing a spec version in the list of capabilities doesn't break any
>> client. We could also define a structure to describe each capability:
>> components:
>> schemas:
>> Capability:
>> name:
>> type: string
>> description: Name of the capability
>> versions:
>> type: array:
>> description: List of supported spec versions of this
>> capability. 0 means experimental (non-production) without any guarantees
>> about the stability of schema for request and response parameters.
>> items:
>> type: integer
>> format: int32
>>
>> In Nessie, we ensure backwards and forwards compatibility using a
>> specialized test suite that runs the "in tree" client against older server
>> versions and older client versions against the "in tree" server version. It
>> works fine for us for a few years now - and it did help preventing
>> compatibility issues.
>>
>>
>> On 26.06.24 07:44, Péter Váry wrote:
>>
>> Hi everyone,
>>
>> A few considerations:
>> - I think we should explicitly state which client/service
>> interoperability we are aiming for. I expect that we want to support both
>> old client -> new server, and new client -> old server communications.
>> - I agree with Jack, that we should think about versions in advance - HMS
>> tried to be backwards compatible for everything, and that made it hard to
>> move forward / deprecate things.
>> - Still we should try to keep the backwards incompatible changes minimal.
>> (All clients should be able to ignore unknown incoming fields / New
>> optional input parameter should drive new features / Try to avoid enums in
>> responses where we expect changes (?))
>> - OTOH, it could be important for clients to know which of the backwards
>> compatible changes are implemented for the given server - so I would
>> decouple the URI from the versioning. Maybe major version change should
>> (could) change the URI, but backwards compatible changes should be served
>> on the same URI, but could be identified by different minor versions.
>>
>> This is exciting stuff!
>> Thanks for pushing this forward!
>>
>> Peter
>>
>>
>> On Wed, Jun 26, 2024, 00:15 Jack Ye <yezhao...@gmail.com> wrote:
>>
>>> Hi everyone,
>>>
>>> I feel I do not see a good answer to why not just simply version each
>>> API? When using tag, it means I have to offer capabilities per-tagged
>>> group. However, I could for example just offer loadTable and nothing else
>>> in a catalog, and that should still be Iceberg REST compliant. And I think
>>> we need a versioning story anyway, there is no way around it.
>>>
>>> Here is the workflow in my mind with versioning:
>>>
>>> 1. Going forward, every time the REST catalog spec introduces any new
>>> API endpoints or backwards incompatible changes to the existing APIs, the
>>> version of the specific API is incremented. So suppose the PlanTable API is
>>> added, this API will be at version v1. Suppose UpdateTable is updated with
>>> a new update type, that API will be at version v2, but PlanTable will
>>> remain at v1.
>>>
>>> 2. a catalog must implement getConfig. This API is the only one that is
>>> required.
>>>
>>> 3. in getConfig, in the defaults map (it could be in some new metadata
>>> structure, but since we want strong backwards compatibility guarantee,
>>> reusing string maps seems to be the best way), server returns key-value
>>> pairs of:
>>> - key: operation:<operationName>
>>> - value: version number
>>>
>>> 4. the client assumes that the map is ordered, and resolves API versions
>>> sequentially. For example, suppose I have the following map:
>>>
>>> { "operation:planTable": "1", "operation:loadTable": "2" }
>>>
>>> Note that by "supporting", it means to return a response in a
>>> predictable way that is compliant with the spec. It can also return 406
>>> UnsupportedOperation as a way to support it.
>>>
>>> There is also a special version *, that means any version can work.
>>>
>>> 5. Backwards compatibility: suppose the client is at a higher version
>>> than the server, then the client should always be able to understand the
>>> server's full list of capabilities.
>>>
>>> 6. Forward compatibility: suppose the client is at a lower version than
>>> the server, then the client should parse whatever operation it understands,
>>> and use the highest version it could support to execute the operation.
>>> Suppose the client only supports loadTable v1, then it will continue to hit
>>> the GET v1/namespaces/{ns}/tables/{table} route, instead of GET
>>> v2/namespaces/{ns}/tables/{table}. The v1 route could continue to support
>>> the client, or it could throw 406 to indicate that this route is deprecated
>>> and the client needs to upgrade.
>>>
>>> For initial backwards compatibility, I think not returning anything
>>> should mean that all API that the client understands are having version *.
>>>
>>> What do people think of it, compared to the tag approach?
>>>
>>> Best,
>>> Jack Ye
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Mon, Jun 24, 2024 at 1:42 PM Micah Kornfield <emkornfi...@gmail.com>
>>> wrote:
>>>
>>>> I don't have strong opinions either way here, just thought it was worth
>>>> raising some concerns over possible evolution here. Some responses inline,
>>>> but if capabilities seem to meet the requirement at hand, then it does
>>>> potentially seem the simplest mechanism.
>>>>
>>>>
>>>> I think we also want to avoid relyance on server specific published
>>>>> OpenAPI as they may leak other options/parameters/etc. This may lead to
>>>>> confusion around what the canonical spec is and make clients incompatible
>>>>> if they're generated off of a non-standard spec document.
>>>>
>>>>
>>>> Yeah, I wasn't proposing necessarily using built in functionality but a
>>>> pre-scrubbed document. Since there is no reference service implementation
>>>> for REST it seems like each implementor would need to describe the best way
>>>> of scrubbing there description.
>>>>
>>>>
>>>>
>>>>> @Micah this sounds to me as if the client would then have to parse a
>>>>> bunch of endpoints to figure out whether it's safe to e.g. call loading a
>>>>> view or dropping a table on the given REST server. Rather than having a
>>>>> dedicated endpoint we're just using the */config* endpoint to provide
>>>>> information about what a server supports.
>>>>
>>>>
>>>> I was not suggesting multiple endpoints here, simply different
>>>> contents for */config *I agree in the short term this does add
>>>> complexity on the clients. But given that the canonical REST API clients
>>>> are being developed into the standard library, I'm not sure how much toil
>>>> this would cause in general. This also does not necessarily need to called
>>>> up-front but could be called to verify existence vs a permission issue
>>>> after an error was received.
>>>>
>>>> What round-trips did you have in mind here?
>>>>
>>>>
>>>> All good points though, but I'm not aware of a standard way to handle
>>>>> this.
>>>>
>>>>
>>>> IIUC, this sounds like a standard service description problem to me,
>>>> the solution with capabilities appears to be one level abstraction on top
>>>> of this. Service discovery seems like it has been reimplemented a few
>>>> different times depending on the technology [1][2][3]
>>>>
>>>>
>>>> I think versioning adds another level of complexity, but might be
>>>>> necessary since I expect these will evolve to some extent and may even
>>>>> require hitting versioned urls.
>>>>
>>>>
>>>> If there is no concrete proposal on versioning, I agree it probably
>>>> pays to side step this. The endpoint transitioning from list of strings to
>>>> list of objects, would be an obvious sign to clients that they are out of
>>>> date. I think serving a service description(s), despite its complexity, is
>>>> likely the most principled way of versioning items appropriately, but this
>>>> definitely requires more in depth thought/design.
>>>>
>>>>
>>>> Thanks,
>>>> Micah
>>>>
>>>> [1] https://en.wikipedia.org/wiki/Web_Services_Description_Language
>>>> [2] https://en.wikipedia.org/wiki/Web_Application_Description_Language
>>>> [3] https://developers.google.com/discovery/v1/reference/apis
>>>>
>>>>
>>>>
>>>>
>>>> On Mon, Jun 24, 2024 at 12:42 PM Daniel Weeks <dwe...@apache.org>
>>>> wrote:
>>>>
>>>>> Hey Micah,
>>>>>
>>>>> I think what we're trying to achieve is strike a balance between
>>>>> client complexity and ability to support multiple server-side
>>>>> capabilities. One challenge we've run into is if a client performs an
>>>>> operation (e.g. listViews), but receives a 403 code, it's not clear
>>>>> whether
>>>>> the client doesn't have access or the server doesn't support an endpoint
>>>>> but isn't sending a 404 for security reasons. This is a simple way for
>>>>> the
>>>>> client to understand what it should expect from the server.
>>>>>
>>>>> > Another option would be just list all endpoints . . . and let
>>>>> clients take appropriate actions
>>>>> > This could be done by vending the OpenAPI spec the server supports
>>>>> at its own endpoint. I think this avoids the future problem of having to
>>>>> classify new endpoints into a specific capability.
>>>>>
>>>>> You're right that this would be the most complete way to handle this,
>>>>> but it's really complicated and may require additional "handshake" calls
>>>>> even for small interactions with the catalog service. I think this puts a
>>>>> lot of onus on the client, when what we're describing is a set of
>>>>> endpoints
>>>>> that correspond to a capability.
>>>>>
>>>>> I think we also want to avoid relyance on server specific published
>>>>> OpenAPI as they may leak other options/parameters/etc. This may lead to
>>>>> confusion around what the canonical spec is and make clients incompatible
>>>>> if they're generated off of a non-standard spec document.
>>>>>
>>>>> All good points though, but I'm not aware of a standard way to handle
>>>>> this.
>>>>>
>>>>> I think versioning adds another level of complexity, but might be
>>>>> necessary since I expect these will evolve to some extent and may even
>>>>> require hitting versioned urls.
>>>>>
>>>>> -Dan
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Jun 24, 2024 at 12:03 AM Eduard Tudenhöfner <
>>>>> etudenhoef...@apache.org> wrote:
>>>>>
>>>>>> We had a separate discussion with Dan on the *oauth2* flag last week
>>>>>> and came to the same conclusion that removing the *oauth2*
>>>>>> capability is probably the best for now.
>>>>>> This is mainly because we can't really act on the *oauth2*
>>>>>> capability right now, because the */tokens* endpoint is called
>>>>>> before we hit the */config* endpoint.
>>>>>>
>>>>>> > Another option would be just list all endpoints (and maybe even
>>>>>> further which operations are supported) the server actually supports and
>>>>>> let clients take appropriate actions (i.e. grouping could happen on the
>>>>>> client side). This could be done by vending the OpenAPI spec the server
>>>>>> supports at its own endpoint. I think this avoids the future problem of
>>>>>> having to classify new endpoints into a specific capability.
>>>>>>
>>>>>> @Micah this sounds to me as if the client would then have to parse a
>>>>>> bunch of endpoints to figure out whether it's safe to e.g. call loading a
>>>>>> view or dropping a table on the given REST server. Rather than having a
>>>>>> dedicated endpoint we're just using the */config* endpoint to
>>>>>> provide information about what a server supports.
>>>>>>
>>>>>> Thanks
>>>>>> Eduard
>>>>>>
>>>>>> On Fri, Jun 21, 2024 at 8:27 PM Ryan Blue
>>>>>> <b...@databricks.com.invalid> <b...@databricks.com.invalid> wrote:
>>>>>>
>>>>>>> Let's remove the oauth2 tag for now until we figure out how to move
>>>>>>> forward there. That makes sense to me.
>>>>>>>
>>>>>>> On Fri, Jun 21, 2024 at 9:30 AM Dmitri Bourlatchkov
>>>>>>> <dmitri.bourlatch...@dremio.com.invalid>
>>>>>>> <dmitri.bourlatch...@dremio.com.invalid> wrote:
>>>>>>>
>>>>>>>> Hi Eduard,
>>>>>>>>
>>>>>>>> The capabilities PR looks good to me overall. I have a concern with
>>>>>>>> the "oauth2" tag name though.
>>>>>>>>
>>>>>>>> I also commented [1] in GH but the comment appears to be closed by
>>>>>>>> default :)
>>>>>>>>
>>>>>>>> I believe the term "oauth2" is confusing in this context with
>>>>>>>> respect to RFC 6749 [2] as discussed in depth on another thread [3]
>>>>>>>>
>>>>>>>> The functionality behind the /tokens endpoint is quite specific to
>>>>>>>> the Iceberg REST spec and as the other discussion highlights, there are
>>>>>>>> concerns with respect to OAuth2 interoperability with other OAuth2
>>>>>>>> servers.
>>>>>>>>
>>>>>>>> What do you think about using a different tag name for it, for
>>>>>>>> example "local-tokens" or "auth-tokens"?
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Dmitri.
>>>>>>>>
>>>>>>>> [1]
>>>>>>>> https://github.com/apache/iceberg/pull/9940/files/15c769a52b85ac4deff5659978c7ffa7802612b0#r1649173934
>>>>>>>> [2] https://www.rfc-editor.org/rfc/rfc6749
>>>>>>>> [3]
>>>>>>>> https://lists.apache.org/thread/twk84xx7v0xy5q5tfd9x5torgr82vv50
>>>>>>>>
>>>>>>>> On Thu, Jun 20, 2024 at 7:28 AM Eduard Tudenhoefner <
>>>>>>>> etudenhoef...@apache.org> wrote:
>>>>>>>>
>>>>>>>>> Hey everyone,
>>>>>>>>>
>>>>>>>>> I'd like to bring up the discussion around describing REST server
>>>>>>>>> capabilities via the */config* endpoint.
>>>>>>>>> There is PR #9940 <https://github.com/apache/iceberg/pull/9940> that
>>>>>>>>> describes the OpenAPI spec changes.
>>>>>>>>>
>>>>>>>>> Mainly we'd like to have a *capabilities* field in the
>>>>>>>>> *ConfigResponse* that allows servers to indicate to clients which
>>>>>>>>> capabilities are being supported.
>>>>>>>>>
>>>>>>>>> So far we have the following capabilities:
>>>>>>>>>
>>>>>>>>> - tables
>>>>>>>>> - views
>>>>>>>>> - remote-signing
>>>>>>>>> - vended-credentials
>>>>>>>>> - multi-table-commit
>>>>>>>>> - register-table
>>>>>>>>> - table-metrics
>>>>>>>>> - oauth2
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> The general idea behind a capability is that if e.g. a server
>>>>>>>>> supports *views*, then that server must implement all endpoints
>>>>>>>>> grouped under that capability.
>>>>>>>>> It's worth noting that the */config* endpoint is currently being
>>>>>>>>> implicit (meaning that every REST server would have to implement it).
>>>>>>>>>
>>>>>>>>> One discussion point that came up during review is how we want to
>>>>>>>>> handle capabilities and backwards compatibility and what the default
>>>>>>>>> capability would be, since older servers don't know anything about
>>>>>>>>> *capabilities* (in such a case we could assume that the default
>>>>>>>>> capabilities would be *oauth2* / *tables*).
>>>>>>>>>
>>>>>>>>> Are there any other capabilities that we'd like to include in the
>>>>>>>>> list?
>>>>>>>>>
>>>>>>>>> Eduard
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Ryan Blue
>>>>>>> Databricks
>>>>>>>
>>>>>> --
>> Robert Stupp
>> @snazy
>>
>>
