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https://issues.apache.org/jira/browse/HBASE-8119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13605847#comment-13605847
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Enis Soztutar commented on HBASE-8119:
--------------------------------------
Quoting review at https://reviews.apache.org/r/9998/:
Attaching a patch for improving the running time of StochasticLoadBalancer 200x
times.
TestStochasticLoadBalancer#testMidCluster() Current impl:
//2013-03-15 17:28:25,495 DEBUG [main] balancer.StochasticLoadBalancer(256):
Finished computing new laod balance plan. Computation took 172526ms to try
15000 different iterations. Found a solution that moves 600 regions; Going
from a computed cost of 35.85000000000001 to a new cost of 23.481578947368426
With patch:
//2013-03-18 14:56:13,541 DEBUG [Thread-2]
balancer.StochasticLoadBalancer(436): Finished computing new laod balance plan.
Computation took 941ms to try 15000 different iterations. Found a solution
that moves 600 regions; Going from a computed cost of 35.85 to a new cost of
23.48157894736842
The improvements come from:
- Optimized array based data structures in Cluster class
- Getting rid of hashmaps
- Optimized region move and swap ops
- Removing most of the computation to cluster initialization, and state change
for the cluster, thus eliminating computing the same results over and over
- Some profiling
There should be further optimizations but this should be a good start. If we
ran into more problems, we can investigate further. There are a lof of TODO's
added in this patch. I'll create a jira for collecting some thoughts, but I
wont have the time to work on those for now.
There are (hopefully) minor semantic changes in the algo. I had to bump up
loadMultiplier, and decrease moveCostMultiplier. See comments at
TestStochasticLoadBalancer#testLargeCluster(). Please review carefully.
As noted in testLargeCluster(), this does not work for large clusters > 100000
regions, 1000 nodes. This can be solved by smt like
http://en.wikipedia.org/wiki/Simulated_annealing instead of random walk with
eager selection.
> Optimize StochasticLoadBalancer
> -------------------------------
>
> Key: HBASE-8119
> URL: https://issues.apache.org/jira/browse/HBASE-8119
> Project: HBase
> Issue Type: Bug
> Components: Region Assignment
> Affects Versions: 0.95.0
> Reporter: Enis Soztutar
> Fix For: 0.95.0
>
>
> On a 5 node trunk cluster, I ran into a weird problem with
> StochasticLoadBalancer:
> server1 Thu Mar 14 03:42:50 UTC 2013 0.0 33
> server2 Thu Mar 14 03:47:53 UTC 2013 0.0 34
> server3 Thu Mar 14 03:46:53 UTC 2013 465.0 42
> server4 Thu Mar 14 03:47:53 UTC 2013 11455.0 282
> server5 Thu Mar 14 03:47:53 UTC 2013 0.0 34
> Total:5 11920 425
> Notice that server4 has 282 regions, while the others have much less. Plus
> for one table with 260 regions has been super imbalanced:
> {code}
> Regions by Region Server
> Region Server Region Count
> http://server3:60030/ 10
> http://server4:60030/ 250
> {code}
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