This code can be used to benchmark throughput for a kafka cluster. Args:
groupId -- (str) kafka consumer group id, default: bench
concurrency -- (int) Number of worker threads to spawn, defaults to number of cpus on current host
duration -- (int) How long to run the benchmark for, default: 20s
topic -- (str) the kafka topic to consume from, defaults to observations.json
zk -- (str) zookeeper url, defaults to localhost:2181