Ashish Singhi commented on HBASE-17178:
> Add region balance throttling
> Key: HBASE-17178
> URL: https://issues.apache.org/jira/browse/HBASE-17178
> Project: HBase
> Issue Type: Improvement
> Components: Balancer
> Affects Versions: 2.0.0, 1.4.0
> Reporter: Guanghao Zhang
> Assignee: Guanghao Zhang
> Attachments: HBASE-17178-branch-1.patch, HBASE-17178-v1.patch,
> HBASE-17178-v2.patch, HBASE-17178-v3.patch, HBASE-17178-v4.patch,
> HBASE-17178-v5.patch, HBASE-17178-v6.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.
> Review board: https://reviews.apache.org/r/54191/
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