[
https://issues.apache.org/jira/browse/HBASE-24528?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17130895#comment-17130895
]
Andrew Kyle Purtell commented on HBASE-24528:
---------------------------------------------
Regards filtering, a list of 100 or 1000 items isn’t overly large, so could be
implemented as presentation options in the shell commands or UI. This doesn’t
preclude filtering as part of the API but it isn’t essential I think.
Regards persistence, we could maintain a cache of this history in zk, or in a
table. It’s a good point. We implemented persistence for the online slow log
and arguably an item in this history is more useful than an individual slow log
entry. However I’m proposing to capture balancer decisions not region
assignment trace. It’s relatively safe to have the balancer write trace
somewhere. It isn’t the end of the world if it is temporarily slowed by that.
> Improve balancer decision observability
> ---------------------------------------
>
> Key: HBASE-24528
> URL: https://issues.apache.org/jira/browse/HBASE-24528
> Project: HBase
> Issue Type: New Feature
> Components: Admin, Balancer, Operability, shell, UI
> Reporter: Andrew Kyle Purtell
> Priority: Major
>
> We provide detailed INFO and DEBUG level logging of balancer decision
> factors, outcome, and reassignment planning, as well as similarly detailed
> logging of the resulting assignment manager activity. However, an operator
> may need to perform online and interactive observation, debugging, or
> performance analysis of current balancer activity. Scraping and correlating
> the many log lines resulting from a balancer execution is labor intensive and
> has a lot of latency (order of ~minutes to acquire and index, order of
> ~minutes to correlate).
> The balancer should maintain a rolling window of history, e.g. the last 100
> region move plans, or last 1000 region move plans submitted to the assignment
> manager. This history should include decision factor details and weights and
> costs. The rsgroups balancer may be able to provide fairly simple decision
> factors, like for example "this table was reassigned to that regionserver
> group". The underlying or vanilla stochastic balancer on the other hand,
> after a walk over random assignment plans, will have considered a number of
> cost functions with various inputs (locality, load, etc.) and multipliers,
> including custom cost functions. We can devise an extensible class structure
> that represents explanations for balancer decisions, and for each region move
> plan that is actually submitted to the assignment manager, we can keep the
> explanations of all relevant decision factors alongside the other details of
> the assignment plan like the region name, and the source and destination
> regionservers.
> This history should be available via API for use by new shell commands and
> admin UI widgets.
> The new shell commands and UI widgets can unpack the representation of
> balancer decision components into human readable output.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
