I am all for self-reliance, but if you really want to influence someone else, you might want to include a link to the project, especially when the only word you share has a much more prevalent meaning.
Nope, it also stores topic metadata in ZK - it's not exactly going to store that in the (near) stateless brokers, or in Bookkeeper - and BK also relies on ZK, but it's common to reuse the ZK quorum between the brokers and the bookies.
It also needs an additional ZK for cluster replication.
For a lot a projects this is hardly a problem. On the other hand Kafka is more mature and has a huge ecosystem (Kafka Connect, Kafka Streams, KSQL, ...).
But one of those moving parts of Pulsar, BookKeeper, means that you're no longer storing data on message brokers. Worth the extra puzzle piece for a lot of use cases.
Pulsar is less mature but does provide functional equivalents to all of the above. Pulsar IO (Kafka Connect), Pulsar SQL (KSQL), Pulsar Functions (Kafka Streams).
Nah, Pulsar functions is nowhere near Kafka Streams - it's more like AWS lambda.
Example off the top of my head, is that you can't, in Pulsar Functions write the equivalent of "aggregate this stream across a 10 minute window and emit the results on window close".
But that's fine, it doesn't need to be like Kafka Streams, you can use Flink or Spark or Storm etc. to fill the same niche. In fact one of the founders of StreamNative (Pulsar's equivalent of Confluent) is a core committer on Flink.
Kafka is not more mature just more hyped. I just wish Aphyr jepsen test would also cover more scenario like
- what happen to your data if x+1 server permanently fail in the cluster with a replication factor of X.
- what happen if a single partition data size or request rate become 90% of the cluster capacity
- what happen in multi-tenancy scenario to other user throughput and latency when one user try to use all the capacity of the cluster
- ...
It's way more mature. I just spent a week evaluating Pulsar vs Kafka for a client and the fact Kafka has been open sourced for 10 years vs. Pulsar's 1.5 really shows in documentation, community support etc.
> what happen to your data if x+1 server permanently fail in the cluster with a replication factor of X.
It depends on how many in sync replica sets existed entirely within those X+1 servers. Their partitions will go offline, and other ISRs will have underreplicated partitions, and the alerting you've set up as a good engineer will have told you this was happening.
> what happen in multi-tenancy scenario to other user throughput and latency when one user try to use all the capacity of the cluster
Nothing because you're using ACL and have configured quotas appropriately.