It wasn’t confusing to me given we know the internals, but I can see why it would be.
In my mind, what existed for a long time was ‘internal reservation of resources for individual containers within an application’ and the newer feature is about user-driven reservation of resources at application / workload granularity. For the newer metrics if/when we add, we should just make the distinction explicit - for e.g. numUserReservedResources. Agreeing with others, this doesn’t warrant us to break existing metrics even in the next major release. Thanks +Vinod On Aug 5, 2015, at 10:16 AM, Carlo Curino <[email protected]<mailto:[email protected]>> wrote: +1 on keeping the name "reservation" for the user-visible (2). On top of the external/internal argument that Chris makes (which I completely agree with), I noticed the following: While developing (2) we spoke with lots and lots of folks both in industry and academia, and the term "reservation" was very evocative and intuitive. Within seconds people were using it to refer to the functionality and easily grasping the idea. On the other hand, every time I spoke about (1) using the keyword "reservation", I had to add a bunch of context, expand, explain, and even then people were naturally drawn to refer to it as "hoarding of resources for large containers", or "large container management". Other alternative names for (1) could be: "hoarded" or "prefecthed" resources. My 2 cents... Cheers, Carlo -----Original Message----- From: Karthik Kambatla [mailto:[email protected]] Sent: Wednesday, August 5, 2015 8:20 AM To: [email protected]<mailto:[email protected]> Subject: Re: "Reservation" ambiguity Inline. On Tue, Aug 4, 2015 at 6:48 PM, Chris Douglas <[email protected]<mailto:[email protected]>> wrote: How visible are (1) reservations? They're an internal, implementation detail exposed in metrics only to explain the edge cases they create. Are users typically aware of them? This is internal, and I don't think users are aware of the mechanics. However, they do see metrics for "reserved" resources. SLA reservations (2) are user-visible, and express the contract with users/operators symmetrically. While (1) is a concept, renaming (2) would require user-breaking code changes. Yes, I don't think we should rename (2). Unless you're discussing the intersection- the effect of reservations (1) on a reservation (2)- it's usually clear from context... I'd rather avoid breaking anyone listening to the metrics in Hadoop-3. I propose to add new metrics holdMB, holdCores for reservedMB, reseveredCores. Could we deprecate the older metrics in Hadoop-2 and Hadoop-3, and remove them in Hadoop-4? Maybe reservations (2) could have been named "sessions", but that collided with applications that already used it for a similar concept. -C On Wed, Jul 29, 2015 at 10:37 AM, Karthik Kambatla <[email protected]<mailto:[email protected]>> wrote: Hi folks We use the word "reservation" to mean both (1) reservations on nodes to avoid starvation of big container asks, and (2) the recent SLA work. This is confusing both to developers and end-users. I was wondering if people are open to calling the first one a "hold" and the second one a "reservation". We can change the terminology in the code and add new metrics for hold in branch-2 and remove the metrics for reserved* in Hadoop-3? Thoughts?
