Details
Major Description
We observe once the cluster has 1000+ nodes and when hundreds of nodes abort and doing split log, the split is very very slow, and we find the regionserver and master wait on the zookeeper response, so we need to reduce zookeeper request and pressure for big cluster.
(1) Reduce request to rsZNode, every time calculateAvailableSplitters will get rsZNode's children from zookeeper, when cluster is huge, this is heavy. This patch reduce the request.
(2) When the regionserver has max split tasks running, it may still trying to grab task and issue zookeeper request, we should sleep and wait until we can grab tasks again.