HiveServer2 today maintains Tez sessions ( when running with perimeter security i.e Ranger/Sentry ) and re-uses the session across queries.
Tez AM recovery works for the most part. It will try to recover completed tasks of the last running DAG and complete the one that did not complete or were still running. It does not handle cases where the committer was in the middle of a commit though so those dags will abort when trying to recover. Given the complexity of recovery, there are probably bugs that we may not have discovered yet but for the most part, it does function well. There are a few issues you should consider when trying to use a single AM: - on secure clusters, the delegation token max lifetime is 7 days so you will need to re-cycle apps on a weekly basis. - YARN does not clean up data/logs for an app until the app completes so this can add space pressure on the yarn local dirs. That said, there is some work happening as part of TEZ-3334 to help clean up intermediate data on a regular basis. There have been a couple of other jiras filed recently too to look at being able to clean up data more frequently. thanks — Hitesh > On Oct 20, 2016, at 2:35 PM, Madhusudan Ramanna <[email protected]> wrote: > > Ok, no worries. I agree that this single AM model would be very close to a > mini-job tracker. One of the options we're investigating having 1 yarn Tez > AM running all our DAGs. Given this AM already has all the > resources/containers, we were thinking this could save on the cost of AM, and > container initialization. > > We haven't looked into tez recovery as well. Durability is one of our big > concerns as well. > > > On Thursday, October 20, 2016 12:44 PM, Hitesh Shah <[email protected]> wrote: > > > Not supported as of now. There are multiple aspects to supporting this > properly. One of the most important issues to address would be to do proper > QoS across various DAGs i.e. what kind of policies would need to be built out > to run multiple DAGs to completion within a limited amount of resources. The > model would become close to a mini-jobtracker or a spark-standalone cluster. > > Could you provide more details on what you are trying to achieve? We could > try and provide different viewpoints on trying to get you to a viable > solution. > > — Hitesh > > > On Oct 20, 2016, at 10:52 AM, Madhusudan Ramanna <[email protected]> > > wrote: > > > > Hello Folks, > > > > http://hortonworks.com/blog/introducing-tez-sessions/ > > > > From the above post it seems like DAGs can only be executed serially. > > Could DAGs be executed in parallel on one Tez AM ? > > > > thanks, > > Madhu > >
