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https://issues.apache.org/jira/browse/HBASE-5487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13614484#comment-13614484
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Jonathan Hsieh commented on HBASE-5487:
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Thanks for writing this up. I read the first two sections and haven't spent
time reading the details of the others yet. (already have a bunch of
quetsions).
So the only problem is that the assignment manager and ssh is difficult to
reason about? Is the assignment manager the only "master coordinated" task in
scope?
I think there are more problems than that that we should enumerate:
* Instead of asserting it is not clear if table (+region) locks scale, let's
find out.
* Master operations and processes can clash and we should understand where we
need concurrency control. (I'm working on a table -- here's an draft distilled
version [1], there exists an overly detailed version that I'll share once i get
it fixed)
* Should there be a notion of queuing operations? (locking, or an actual
queue) Should these operations be generically logged so they can complete if a
master goes down in the middle? (ex: master goes down during a "move" operation
after the close but before the open on the new rs).
The "design principles" is actually more of a proposed design.
Design principles::region record
* how do we deal with operations where we need "locks" on multiple region
because we are reading or modifying multiple regions -- e.g. splits, merges,
snapshots? [~mbertozzi] had suggested in another jira making a the meta row
per table, or maybe part of the solution is using the multi-row single meta
region transaction.
What are alternatives? why this approach vs others?
[1]
https://docs.google.com/spreadsheet/ccc?key=0AiVCAt6zRttFdDRVaG56RnpQZlNNZUNsRVJsSXM3YlE&usp=sharing
> Generic framework for Master-coordinated tasks
> ----------------------------------------------
>
> Key: HBASE-5487
> URL: https://issues.apache.org/jira/browse/HBASE-5487
> Project: HBase
> Issue Type: New Feature
> Components: master, regionserver, Zookeeper
> Affects Versions: 0.94.0
> Reporter: Mubarak Seyed
> Attachments: Region management in Master.pdf
>
>
> Need a framework to execute master-coordinated tasks in a fault-tolerant
> manner.
> Master-coordinated tasks such as online-scheme change and delete-range
> (deleting region(s) based on start/end key) can make use of this framework.
> The advantages of framework are
> 1. Eliminate repeated code in Master, ZooKeeper tracker and Region-server for
> master-coordinated tasks
> 2. Ability to abstract the common functions across Master -> ZK and RS -> ZK
> 3. Easy to plugin new master-coordinated tasks without adding code to core
> components
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