JacksonYao287 opened a new pull request #2676:
URL: https://github.com/apache/ozone/pull/2676
## What changes were proposed in this pull request?
when i test container balancer in k8s cluster, i use the command line :
./ozone admin containerbalancer start -i -1 -t 0.000001 -d 1 -s 500, and set
the contaienr size to 1G.
i found that balancer thread can not stop when the cluster is close to
balance.
in my cluster , i have three datanodes d1,d2,d3(disk usage are 67G, 67G,
68G), and the fourth d4 datanode's disk usage is 1G. when i start balancer, it
begin to balance and work well, many containers have been moved from d1,d2,d3
to d4. but when the cluster is close to balance(the disk usages of the four
datanodes are 50G,52G,50G,51G), the balancer is still running , it will move
container among those datanodes again and again.
let us see a general example. if we have two datanode d1 and d2, the disk
usage are 3G and 7G respectively, then the average usage is 5G. if we set the
threshold to 0.00001(close to 0), the lowerLimit and upperLimit is close to 5G.
if we set the container size to 4G, in the first iteraion, we can recognize
the over-utilized datanode d2 and the under-utilized datanode d1, then we
schedule a move option from d2 to d1 with a 4G container. after move option is
finished , d1 is 7G and d2 is 3G. so the balancer thread will go on for ever.
so we should let the balancer thread exit when the cluster can not be more
balanced
## What is the link to the Apache JIRA
https://issues.apache.org/jira/browse/HDDS-5757
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