Update librdkafka

[lukesteensen]

There was a report in discord of a strange Kafka error related to API protocol versions:

DEBUG librdkafka: librdkafka: PROTOERR [thrd:foo.cloudapp.net:]: my-kafka-broker:9092/1003: Protocol parse failure for ApiVersion v3 at 3/6 (rd_kafka_handle_ApiVersion:1915) (incorrect broker.version.fallback?)    
Dec 11 08:37:17.946 DEBUG librdkafka: librdkafka: PROTOERR [thrd:my-kafka-broker:]: my-kafka-broker:9092/1003: ApiArrayCnt -1 out of range

Our current version of rdkafka should work perfectly with their reported version of Kafka (2.1.1), but it's possible they're hitting a bug in the underlying library. I noticed that the latest version of librdkafka is 1.5.3 and our rdkafka crate is only on 1.4.2, with one entry in the changelog mentioning broker.version.fallback. It would be good to update to the lasest to ensure this isn't a bug that's been fixed upstream.

This will likely involve contributing the update to the rdkafka crate we use.

[jamtur01]

We're stuck on an rdkafka release here: fede1024/rust-rdkafka#299

[binarylogic]

It looks like a new version has been released: fede1024/rust-rdkafka#299 (comment)

[eeyun]

Worth mentioning that rdkafka 0.25.0 requires a tokio runtime of 1.x now. The latest release also includes librdkafka 1.6.0 so I think there's no need to contribute upstream, but it does put us in a predicament, unless I'm misunderstanding. We can't upgrade to rdkafk 0.25.0 a until we upgrade to tokio 1.x unless we write a compat layer. Since the work to make that migration is underway, I doubt it makes sense to do the compat here? Open to other's opinions of course.

[pablosichert]

The bump to rdkafka 0.26.0 has landed with #5872.