kafka with multiple zookeeper config

Question

A bit confused about clustering setup:

1. Zookeeper could be setup as a cluster by configuring myid (1,2,3...) in the file and having for example zookeeper1:2888:3888, zookeeper2:2889:3889 in the zoo.cfg file

2. For Kafka, in the server.properties file, is it must to specify the full list of zookeeper server for parameter zookeeper.connect, or just 1 is enough? Is there any differences? I've seen practices of specifying the full list of zookeeper server even when creating a topic, e.g. /opt/kafka/bin/kafka-topics.sh --create --zookeeper x.x.x.x:2181,x.x.x.x:2181,x.x.x.x:2181 --replication-factor 1 --partitions 1 --topic sample_test

---Production and DR setup (large latency is expected between production and dr)---

1. Let's say, having 1 Kafka (kafka1) and 1 zookeeper server (zookeeper1) in production, 1 kafka (kafka2) and 1 zookeeper server (zookeeper2) in DR, and form those 2 zookeepers into a cluster;

2. running uReplicator to replicate data in production to DR; from uReplicator example, it seems the configuration is like: kafka1 (in production) is connecting to "zookeeper1:2181/cluster1", and kafka2 (in DR) is connecting to "zookeeper1:2181/cluster2", what's the meaning of "/cluster1", "/cluster2"? what's the right config for this scenario, what's the idea of having kafka2 in DR connects to zookeeper1 in prod?

Answer 1

is it must to specify the full list of zookeeper server for parameter zookeeper.connect

It is good practice to put at least 3 or 5. If you only put one, and that goes down, Kafka will likely not work as expected, or fail out.

in DR, and form those 2 zookeepers into a cluster

It's not generally encouraged to share Zookeepers clusters between Kafka clusters, as Kafka puts a reasonable amount of load on Zookeeper for high volume Kafka clusters.

Though, as you point out

connecting to "zookeeper1:2181/cluster1", and kafka2 (in DR) is connecting to "zookeeper1:2181/cluster2", what's the meaning of "/cluster1", "/cluster2"?

This is called a Chroot in Zookeeper. Think of it like a directory, or namespace for each unique Kafka cluster within the Zookeeper cluster.

what's the idea of having kafka2 in DR connects to zookeeper1 in prod?

Well, you wouldn't. If Kafka2 has its own unique topic data that is not being replicated to Kafka1, then pointing at the Zookeeper data that says those topics existed on Kafka2, but not Kafka1 will only result in confusion and error.

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Also, I am unaware of how uReplicator works other than MirrorMaker, but you'll also want to prepare a DR strategy for Zookeeper, not only Kafka

Answer 2

You have two questions in there. I'll try to tackle the first one at least:

• Specifying only one zookeeper server:port is usually enough, but in production instances/properties, you always want to configure all of them. If one of the servers is down, but the cluster is still up and running (say, 2 out of 3 Zookeeper servers are up), Kafka will try the next server in the config, until it finds one it can talk to. However, if the only one you chose to put happens to be down at that exact time, the server won't be able to talk to Zookeeper at all. It's best to always include the entire list of zookeeper servers in configuration.