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https://issues.apache.org/jira/browse/HBASE-22618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16909906#comment-16909906
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Hudson commented on HBASE-22618:
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Results for branch master
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> Provide a way to have Heterogeneous deployment
> ----------------------------------------------
>
> Key: HBASE-22618
> URL: https://issues.apache.org/jira/browse/HBASE-22618
> Project: HBase
> Issue Type: Improvement
> Affects Versions: 3.0.0, 2.2.0, 2.2.1, 2.1.6, 1.4.11, 2.1.7
> Reporter: Pierre Zemb
> Assignee: Pierre Zemb
> Priority: Major
> Attachments: HBASE-22618.master.001.patch
>
>
> Hi,
> We wouls like to open the discussion about bringing the possibility to have
> regions deployed on {color:#222222}Heterogeneous deployment{color}, i.e Hbase
> cluster running different kind of hardware.
> h2. Why?
> * Cloud deployments means that we may not be able to have the same hardware
> throughout the years
> * Some tables may need special requirements such as SSD whereas others
> should be using hard-drives
> * {color:#222222} {color}*in our usecase*{color:#222222}(single table,
> dedicated HBase and Hadoop tuned for our usecase, good key
> distribution){color}*, the number of regions per RS was the real limit for
> us*{color:#222222}.{color}
> h2. Our usecase
> We found out that *in our usecase*(single table, dedicated HBase and Hadoop
> tuned for our usecase, good key distribution)*, the number of regions per RS
> was the real limit for us*.
> Over the years, due to historical reasons and also the need to benchmark new
> machines, we ended-up with differents groups of hardware: some servers can
> handle only 180 regions, whereas the biggest can handle more than 900.
> Because of such a difference, we had to disable the LoadBalancing to avoid
> the {{roundRobinAssigmnent}}. We developed some internal tooling which are
> responsible for load balancing regions across RegionServers. That was 1.5
> year ago.
> h2. Our Proof-of-concept
> We did work on a Proof-of-concept
> [here|https://github.com/PierreZ/hbase/blob/dev/hbase14/balancer/hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/HeterogeneousBalancer.java],
> and some early tests
> [here|https://github.com/PierreZ/hbase/blob/dev/hbase14/balancer/hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/HeterogeneousBalancer.java],
>
> [here|https://github.com/PierreZ/hbase/blob/dev/hbase14/balancer/hbase-server/src/test/java/org/apache/hadoop/hbase/master/balancer/TestHeterogeneousBalancerBalance.java],
> and
> [here|https://github.com/PierreZ/hbase/blob/dev/hbase14/balancer/hbase-server/src/test/java/org/apache/hadoop/hbase/master/balancer/TestHeterogeneousBalancerRules.java].
> We wrote the balancer for our use-case, which means that:
> * there is one table
> * there is no region-replica
> * good key dispersion
> * there is no regions on master
> A rule file is loaded before balancing. It contains lines of rules. A rule is
> composed of a regexp for hostname, and a limit. For example, we could have:
>
> {quote}rs[0-9] 200
> rs1[0-9] 50
> {quote}
>
> RegionServers with hostname matching the first rules will have a limit of
> 200, and the others 50. If there's no match, a default is set.
> Thanks to the rule, we have two informations: the max number of regions for
> this cluster, and the rules for each servers. {{HeterogeneousBalancer}} will
> try to balance regions according to their capacity.
> Let's take an example. Let's say that we have 20 RS:
> * 10 RS, named through {{rs0}} to {{rs9}} loaded with 60 regions each, and
> each can handle 200 regions.
> * 10 RS, named through {{rs10}} to {{rs19}} loaded with 60 regions each, and
> each can support 50 regions.
> Based on the following rules:
>
> {quote}rs[0-9] 200
> rs1[0-9] 50
> {quote}
>
> The second group is overloaded, whereas the first group has plenty of space.
> We know that we can handle at maximum *2500 regions* (200*10 + 50*10) and we
> have currently *1200 regions* (60*20). {{HeterogeneousBalancer}} will
> understand that the cluster is *full at 48.0%* (1200/2500). Based on this
> information, we will then *try to put all the RegionServers to ~48% of load
> according to the rules.* In this case, it will move regions from the second
> group to the first.
> The balancer will:
> * compute how many regions needs to be moved. In our example, by moving 36
> regions on rs10, we could go from 120.0% to 46.0%
> * select regions with lowest data-locality
> * try to find an appropriate RS for the region. We will take the lowest
> available RS.
> h2. Other implementations and ideas
> Clay Baenziger proposed this idea on the dev ML:
> {quote}{color:#222222}Could it work to have the stochastic load balancer use
> [pluggable cost functions instead of this static list of cost
> functions|[https://github.com/apache/hbase/blob/baf3ae80f5588ee848176adefc9f56818458a387/hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/StochasticLoadBalancer.java#L198]]?
> Then, could this type of a load balancer be implemented simply as a new cost
> function which folks could choose to load and mix with the others?{color}
> {quote}
> {color:#222222}I think this could be an interesting way to include
> user-functions in the mix. As you know your hardawre and the pattern access,
> you can easily know which metrics is important for balancing, for us, it will
> only be the number of regions, but we could mix-it with the incoming
> writes!{color}
>
> bhupendra.jain proposed also the ideas of "labels"
>
> {quote}{color:#222222}Internally, we are also having discussion to develop
> similar solution. In our approach, We were also thinking of adding "RS Label"
> Feature similar to Hadoop Node Label feature. {color}
> {color:#222222}Each RS can have a label to denote its capabilities /
> resources . When user create table, there can be extra attributes with its
> descriptor. The balancer can decide to host region of table based on RS label
> and these attributes further. {color}
> {color:#222222}With RS label feature, Balancer can be more intelligent.
> Example tables with high read load needs more cache backed by SSDs , So such
> table regions should be hosted on RS having SSDs ... {color}
> {quote}
> {color:#222222}I love the idea, but I think Clay's idea is better for a
> better and faster first set of commits on the subject! What do you think?
> {color}
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