Modular Composition Of Coordination Services

Check this before postal service for a brief review of ZooKeeper.)

The newspaper suggests a client-side entirely change to ZooKeeper, in addition to calls the resultant organization ZooNet. ZooNet consists of a federation of ZooKeeper cluster at each datacenter/region. ZooNet assumes the workload is highly-partitionable, thence  the information is partitioned amid the ZooKeeper clusters, each accompanied past times learners inward the remote datacenter/regions. Each ZooKeeper cluster processes entirely updates for its ain information segmentation in addition to if applications inward dissimilar regions ask to access unrelated items they tin flame besides exercise thence independently in addition to inward parallel at their ain site.

However, the work amongst such a deployment is that it does non save ZooKeeper's sequential execution semantics. Consider the representative inward Figure 1. (It is non clear to me why the so-called "loosely-coupled" applications inward dissimilar ZooKeeper partitions ask to live on sequentially serialized. The newspaper does non laissez passer on an examples/reasons for motivating this.)

Their solution is fairly simple. ZooNet achieves consistency past times injecting sync requests. Their algorithm entirely makes the remote segmentation reads to live on synced to attain coordination. More accurately, they insert a sync every fourth dimension a client's read asking accesses a dissimilar coordination service than the previous request. Subsequent reads from the same coordination service are naturally ordered later on the first, in addition to thence no additional syncs are needed.


Figure iii demonstrates the solution. I nonetheless stimulate got around problems amongst Figure 3. What if both syncs hap at the same time?  I hateful what if both occurs later on the previous updates complete. Do they, then, prioritize i site over the other in addition to accept a deterministic lodge to resolve ties?

The newspaper besides mentions that they fix a performance põrnikas inward ZooKeeper, merely the põrnikas is non relevant to the algorithm/problem. It is nearly to a greater extent than full general ZooKeeper performance improvement past times performing proper customer isolation inward the ZooKeeper commit processor.

ZooNet evaluation is done entirely amongst a 2-site ZooKeeper deployment. The evaluation did non await at WAN latency in addition to focused on pushing the limits on throughput. Reads are asynchronously pipelined to compensate for the latency introduced past times the sync operation. They benchmark the throughput when the organization is saturated, which is non a typical ZooKeeper purpose representative scenario.

ZooNet does non back upwardly transactions in addition to watches.

Update 7/1/16: Kfir, the Pb writer of the ZooNet work, provides clarifications for the questions/concerns inward my review. See the transcend comment later on the post.

Our function on WAN coordination

We stimulate got besides been working on scaling ZooKeeper to WAN deployments. We accept a dissimilar approach. We stimulate got extended ZooKeeper amongst hierarchical composition of ZooKeeper clusters in addition to added lock-tokens to enable local in addition to consistent writes every bit good every bit local in addition to consistent reads from whatsoever share inward a WAN. Our WANKeeper organization supports transactions in addition to watches. We stimulate got submitted a newspaper on this which is nonetheless nether review, thence I tin flame beak nearly our function entirely adjacent month. In the meanwhile nosotros are working on polishing our WANKeeper software for opensourcing it.

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