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Re: Backwards compatibility for REST API


Looked some more into it, as of _right now_ a 1.5.X client will not work against 1.6.0 cluster since the submission body was extended. But we could add a guard against this.

On 24.07.2018 17:27, Chesnay Schepler wrote:
Note that the changes made to the REST API will in the long-term reduce friction between versions, as we no longer have to submit data through the blob service, which is another internal API.

On 24.07.2018 17:25, Chesnay Schepler wrote:
/Will it be possible to submit a job graph built by 1.5.1 client (that does not contain any connectors or operators that depend on internal API) to 1.6.x job manager?/

Probably yes, but generally there's no guarantee.

The JobGraph is not a public API and thus may change in ways that could
cause serialization failures if the client and server versions do not match.

On 24.07.2018 17:12, Thomas Weise wrote:
I would expect more external dependencies on the REST API and suggest to
consider versioning and compatibility guarantees.

The particular issue is from Beam and tracked here:
https://issues.apache.org/jira/browse/BEAM-4842

I would be surprised if that is the only instance besides Flink CLI trying
to use the REST API for job submission. In the case of Beam, it is
problematic to assume that the job service that contains the Flink client
will always be upgraded lock step with the server.

What other factors prevent interoperability between Flink versions? Will it
be possible to submit a job graph built by 1.5.1 client (that does not
contain any connectors or operators that depend on internal API) to 1.6.x
job manager?

Thanks,
Thomas


On Tue, Jul 24, 2018 at 7:58 AM Chesnay Schepler <chesnay@xxxxxxxxxx> wrote:

Effectively there are no guarantees for backwards compatibility,
although we try to maintain it.

There are plans to version the REST API
(https://issues.apache.org/jira/browse/FLINK-7551) but no definitive
timeline.

The change you mentioned in particular primarily affects internal code
(since the removed endpoint is usually only used by the flink CLI).
Note we do not provide any guarantee that Flink components interact
properly if the versions don't exactly match, so you should always upgrade
the clients anyway.

On 24.07.2018 16:43, Thomas Weise wrote:
Hi,

Are there any compatibility guarantees for the Flink REST API or plans to
establish the same?

I'm asking since I noticed that the 1.5.1 release has an incompatible
change that prevents a 1.5.0 client to submit a job to 1.5.0 server
(FLINK-9280, removed endpoint /blobserver/port).

Such change is especially unexpected in a patch release, but even if it
was
in 1.6.x, it is still problematic because it forces clients to upgrade.

Thanks,
Thomas