Panic Integer Divide by Zero when dividePartitionsBetweenConsumers about kafka

[jdness]

I ran into this overnight last night. Mine was in a slightly different context, during a rebalance operation while system was idle:

[Sarama] 2015/07/13 02:02:13 client/metadata fetching metadata for all topics from broker 192.168.1.8:9095
[Sarama] 2015/07/13 02:12:13 client/metadata fetching metadata for all topics from broker 192.168.1.8:9095
[Sarama] 2015/07/13 02:22:13 client/metadata fetching metadata for all topics from broker 192.168.1.8:9095
[Sarama] 2015/07/13 04:05:10 [backend/30dccfbe8daf] Triggering rebalance due to consumer list change
[Sarama] 2015/07/13 04:05:10 [backend/30dccfbe8daf] VeraTopic/3 :: Stopping partition consumer at offset -1
[Sarama] 2015/07/13 04:05:10 [backend/30dccfbe8daf] VeraTopic/0 :: Stopping partition consumer at offset -1
[Sarama] 2015/07/13 04:05:10 [backend/30dccfbe8daf] VeraTopic/1 :: Stopping partition consumer at offset -1
[Sarama] 2015/07/13 04:05:10 [backend/30dccfbe8daf] VeraTopic/2 :: Stopping partition consumer at offset 25199
[Sarama] 2015/07/13 04:05:10 client/metadata fetching metadata for all topics from broker 192.168.1.8:9095
[Sarama] 2015/07/13 04:05:10 consumer/broker/0 closed dead subscription to VeraTopic/3
[Sarama] 2015/07/13 04:05:10 consumer/broker/2 closed dead subscription to VeraTopic/1
[Sarama] 2015/07/13 04:05:10 consumer/broker/1 closed dead subscription to VeraTopic/0
[Sarama] 2015/07/13 04:05:10 consumer/broker/3 closed dead subscription to VeraTopic/2
[Sarama] 2015/07/13 04:05:11 [backend/30dccfbe8daf] VeraTopic :: Stopped topic consumer
[Sarama] 2015/07/13 04:05:12 [backend/30dccfbe8daf] Currently registered consumers: 0
[Sarama] 2015/07/13 04:05:12 [backend/30dccfbe8daf] VeraTopic :: Started topic consumer
panic: runtime error: integer divide by zero
[signal 0x8 code=0x7 addr=0xfa3af pc=0xfa3af]
goroutine 120 [running]:
runtime.panic(0x407d80, 0x6a8df9)
    /usr/local/go/src/pkg/runtime/panic.c:279 +0xf5
github.com/wvanbergen/kafka/consumergroup.dividePartitionsBetweenConsumers(0x6ad198, 0x0, 0x0, 0xc20865a100, 0x4, 0x4, 0x0)
    /Users/jness/v/gocode/src/github.com/wvanbergen/kafka/consumergroup/utils.go:39 +0x15f
github.com/wvanbergen/kafka/consumergroup.(*ConsumerGroup).topicConsumer(0xc2080523c0, 0x475c10, 0x9, 0xc208011b00, 0xc208012400, 0xc208406420)
    /Users/jness/v/gocode/src/github.com/wvanbergen/kafka/consumergroup/consumer_group.go:310 +0x5e1
created by github.com/wvanbergen/kafka/consumergroup.(*ConsumerGroup).topicListConsumer
    /Users/jness/v/gocode/src/github.com/wvanbergen/kafka/consumergroup/consumer_group.go:260 +0x340

[wvanbergen]

Yeah, I think just sleeping for a bit and retrying might be the best approach when this happens.

[nemosupremo]

@wvanbergen I've created a PR with the fix we applied @ #68