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Dave Latham commented on HBASE-17178: ------------------------------------- The goal of both, from what I can tell is to limit the unavailability of regions during balancing. I'm happy to see the issue picked up again, and hope an implementation makes it in this time. > Add region balance throttling > ----------------------------- > > Key: HBASE-17178 > URL: https://issues.apache.org/jira/browse/HBASE-17178 > Project: HBase > Issue Type: Improvement > Components: Balancer > Reporter: Guanghao Zhang > Assignee: Guanghao Zhang > Attachments: HBASE-17178-v1.patch > > > Our online cluster serves dozens of tables and different tables serve for > different services. If the balancer moves too many regions in the same time, > it will decrease the availability for some table or some services. So we add > region balance throttling on our online serve cluster. > We introduce a new config hbase.balancer.max.balancing.regions, which means > the max number of regions in transition when balancing. > If we config this to 1 and a table have 100 regions, then the table will have > 99 regions available at any time. It helps a lot for our use case and it has > been running a long time > our production cluster. > But for some use case, we need the balancer run faster. If a cluster has 100 > regionservers, then it add 50 new regionservers for peak requests. Then it > need balancer run as soon as > possible and let the cluster reach a balance state soon. Our idea is compute > max number of regions in transition by the max balancing time and the average > time of region in transition. > Then the balancer use the computed value to throttling. > Examples for understanding. > A cluster has 100 regionservers, each regionserver has 200 regions and the > average time of region in transition is 1 seconds, we config the max > balancing time is 10 * 60 seconds. > Case 1. One regionserver crash, the cluster at most need balance 200 regions. > Then 200 / (10 * 60s / 1s) < 1, it means the max number of regions in > transition is 1 when balancing. Then the balancer can move region one by one > and the cluster will have high availability when balancing. > Case 2. Add other 100 regionservers, the cluster at most need balance 10000 > regions. Then 10000 / (10 * 60s / 1s) = 16.7, it means the max number of > regions in transition is 17 when balancing. Then the cluster can reach a > balance state within the max balancing time. > Any suggestions are welcomed. -- This message was sent by Atlassian JIRA (v6.3.4#6332)