Implement authentication mechanism

[kmaehashi]

Currently JubaQL Gateway does not support any kind of authentication.
This means that privileges of the user who runs JubaQL gateway is used to submit jobs to YARN cluster (and to access HDFS resources.)

To support the true multi-tenancy, JubaQL gateway should implement authentication mechanism.
hadoop-auth library, which is a servlet filter used to support simple / Kerberos authentication against HTTP API / Web UI of Hadoop components, seems like a reasonable choice.
Gateway can then impersonate another user using proxy user feature of Hadoop.

Now I'm working on migrating the unfiltered backend from Netty to Jetty to use servlet filter.
Any concerns?

cc: @tgpfeiffer

[tgpfeiffer]

I am not very familiar with Hadoop authentication, so I can't comment on that. Regarding the Netty/Jetty change in the gateway I don't see any particular problem. (In the JubaQL Processor, touching anything that involves netty will probably lead to dependency issues, though.)

[kmaehashi]

Thanks for the followup!