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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13260) Bootstrap Tables for fun and profit
Date Tue, 17 Mar 2015 05:12:39 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14364591#comment-14364591
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stack commented on HBASE-13260:
-------------------------------

Seems heavyweight for keeping around edits but then, as you say, Region should just 'work'
by now.

Looking at patch, I think I like it -- not much code and we have 'working' store.  Would be
interested in [~mbertozzi] take.

Region has enough configuration knobs, we should be able to configure it to suit. Can we age
out whole hfiles at a time or is that not done yet? Or will Master be doing heavyweight compacting
when a fat assign dumps a bunch of hfiles under one of these system regions? I am against
Master hosting Regions (because it puts Master in the write path, etc.) but having these little
oddballs hosted in Master only seems like a nice boundary to put on them.

On the patch, are we opening the region each time we scan it?

Not you, but it is kinda odd that we have to have a 'table' associated.



> Bootstrap Tables for fun and profit 
> ------------------------------------
>
>                 Key: HBASE-13260
>                 URL: https://issues.apache.org/jira/browse/HBASE-13260
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 2.0.0, 1.1.0
>
>         Attachments: hbase-13260_prototype.patch
>
>
> Over at the ProcV2 discussions(HBASE-12439) and elsewhere I was mentioning an idea where
we may want to use regular old regions to store/persist some data needed for HBase master
to operate. 
> We regularly use system tables for storing system data. acl, meta, namespace, quota are
some examples. We also store the table state in meta now. Some data is persisted in zk only
(replication peers and replication state, etc). We are moving away from zk as a permanent
storage. As any self-respecting database does, we should store almost all of our data in HBase
itself. 
> However, we have an "availability" dependency between different kinds of data. For example
all system tables need meta to be assigned first. All master operations need ns table to be
assigned, etc. 
> For at least two types of data, (1) procedure v2 states, (2) RS groups in HBASE-6721
we cannot depend on meta being assigned since "assignment" itself will depend on accessing
this data. The solution in (1) is to implement a custom WAL format, and custom recover lease
and WAL recovery. The solution in (2) is to have the table to store this data, but also cache
it in zk for bootrapping initial assignments. 
> For solving both of the above (and possible future use cases if any), I propose we add
a "boostrap table" concept, which is: 
>  - A set of predefined tables hosted in a separate dir in HDFS. 
>  - A table is only 1 region, not splittable 
>  - Not assigned through regular assignment 
>  - Hosted only on 1 server (typically master)
>  - Has a dedicated WAL. 
>  - A service does WAL recovery + fencing for these tables. 
> This has the benefit of using a region to keep the data, but frees us to re-implement
caching and we can use the same WAL / Memstore / Recovery mechanisms that are battle-tested.

>  



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