Major Description
Currently the security context information such as the TlsContext, configuration tristates, and token information is attached to the Messenger. This means that a single Messenger can't be used to communicate with multiple clusters at the same time, or to act as multiple users at the same time.
This isn't currently a big deal since the client doesn't offer the ability to pool or reuse messengers, but that feature may become necessary in the future to improve Impala scalability for concurrent queries.