KAFKA-13709: Add docs for exactly-once support in Connect

[C0urante]

Jira

Adds administrator- and developer-facing documentation on the features introduced in KIP-618.

Rebased on top of #12938 to fix recently-introduced compilation failures on trunk.

[C0urante]

@joel-hamill would you be interested in taking a look at this?

[tikimims]

@joel-hamill would you be interested in taking a look at this?

Hi @C0urante :) I spoke with @joel-hamill. I can take a look if you like. 👍

[C0urante]

That'd be great! Thanks @tikimims

[tikimims]

Suggested change

<p>If a sink connector supports exactly-once delivery, all that is necessary to enable exactly-once delivery at the Connect worker level is ensuring that its consumer group is configured to ignore records in aborted transactions. This can be done by setting the worker property <code>consumer.isolation.level</code> to <code>read_committed</code> or, if running a version of Kafka Connect that supports it, using a <a href="#connectconfigs_connector.client.config.override.policy">connector client config override policy</a> that allows the <code>consumer.override.isolation.level</code> property to be set to <code>read_committed</code> in individual connector configs. There are no additional ACL requirements.</p>

<p>If a sink connector supports exactly-once delivery and to enable exactly-once delivery at the Connect worker level, you must ensure its consumer group is configured to ignore records in aborted transactions. You can do this by setting the worker property <code>consumer.isolation.level</code> to <code>read_committed</code> or, if running a version of Kafka Connect that supports it, using a <a href="#connectconfigs_connector.client.config.override.policy">connector client config override policy</a> that allows the <code>consumer.override.isolation.level</code> property to be set to <code>read_committed</code> in individual connector configs. There are no additional ACL requirements.</p>

[C0urante]

This one I don't quite grasp--the change from

If a sink connector supports exactly-once delivery, all that is necessary to enable exactly-once delivery

to

If a sink connector supports exactly-once delivery and to enable exactly-once delivery

doesn't seem quite right. The rest of the suggestion makes sense.

@tikimims can you help me understand this part better? Was it an accident?

[C0urante]

(I've pushed the suggested changes here except for the bit described above)

[tikimims]

Recommend reordering this sentence to: "For more information on this feature, see the <a href..."

[tikimims]

Hi @C0urante I took a first pass and left some suggestions. :) Let me know if you'd like me to take another pass after any updates. 👍

[C0urante]

Thanks @tikimims! I've accepted all but one of the suggestions and asked for clarification on the other. I didn't realize how common usage of "you" and "your" in the docs were; switching to that wording really helps tidy things up!

[C0urante]

Hi @mimaison @tombentley would either of you have time to take a look at this?

[mimaison]

Thanks @C0urante, that's a great addition to the docs! I left a couple of small questions.

[mimaison]

LGTM

[C0urante]

Thanks Mickael!