On Tue, Feb 13, 2018 at 2:59 PM, Subhash Sriram <subhash.sri...@gmail.com>

Hey Xavier,
> Within a consumer group, you can only have as many consumers as you have
> partitions in a topic. If you start more consumers than partitions within
> the same group, they will just be idle.

Excellent, I am reading the docs but cannot anticipate some scenarios with

I am thinking about situations involving two machines, for fault-tolerance,
deploy procedures without downtime, etc.

Let's say we have machines A and B, running consumers that belong to the
same consumer group.

I guess the broker is then going to send messages only to the one that
opened the TCP connection first, right?

I correct, let's assume it is A. The broker is going to accept a connection
from B, but there are no more partitions to balance, so B is idle and
sending heartbeats just fine. If there is a network issue between the
broker and A, and the socket of B is up, Kafka is then going to assign the
unique partition to B automatically right?

In that case, if the hiccup is solved one minute later and the connection
in A is restored, then A is going to become the idle instance?

If that is all correct, the only issue I foresee is committing offsets. If
the client commits offsets every 10 seconds and the network cut happens, I
believe the instance taking over is going to receive duplicated messages in
the general case, right?

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