A part of the documentation (http://samza.incubator.apache.org/learn/documentation/0.7.0/container/task-runner.html) suggests it ?might? be possible to change the number of containers allocated to a job: "Your Samza job might be unable to keep up with only one container, so you ask for a second YARN container to put some of the StreamTask partitions"
How does one ask for a second YARN container? Is it a matter of stoping the job, changing the configuration and starting a new job? or is there some way to do this without starting a job? sgg
