tree b8453ec2bab19975fd5c9a51fc9fb909cb1612bb
parent 6997e4d4e622e0af39e60f69417a4fe512b1b10c
author Ryan Blue <blue@apache.org> 1487716595 -0800
committer Luciano Resende <lresende@apache.org> 1496838313 -0700

TOREE-390: Lazily initialize spark sessions

This updates the kernel so that it lazily initializes
Spark sessions. This allows the user to configure and
start a session, or to wait until spark is first
referenced to start a session. This shortens the time
to the first interaction with Toree.

It also  adds a notification that Toree
is waiting for a Spark session to start when the
getOrCreate method takes more than 100ms.

Closes #109.