Allow underscore in hostname

[Lukkie]

We're working with multiple zookeeper and kafka stacks in the same Docker Swarm network. In the configuration, we would like to distinguish between services of these stacks by calling them with their full Docker Swarm service name, which looks like [stack-name]_[service-name], so we would for instance have stack1_zookeeper:2181 and stack2_zookeeper:2181 which belong to different stacks.

We tried following config:

[zookeeper]
servers=[ "cluster1_zookeeper1:2181", "cluster1_zookeeper2:2181", "cluster1_zookeeper3:2181" ]
timeout=6

but received following error:
{"level":"panic","ts":1561966576.124533,"msg":"Failed to validate Zookeeper servers"}

[coveralls]

Coverage increased (+0.03%) to 74.736% when pulling 3e5e06d on Lukkie:master into a449cc4 on linkedin:master.

[Lukkie]

Anyone?

[bai]

Thanks for contributing 🙏