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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-13260) Bootstrap Tables for fun and profit
Date Tue, 17 Mar 2015 01:32:39 GMT

     [ https://issues.apache.org/jira/browse/HBASE-13260?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Enis Soztutar updated HBASE-13260:
----------------------------------
    Attachment: hbase-13260_prototype.patch

Here is a patch to demonstrate what I propose. 

{{BootstrapTableService}} implements a set of known tables, together with a separate WAL directory
and data directory. WAL recovery is not implemented yet, but should be straightforward to
implement. These regions are not "assigned", but opened instead. We can make it so that they
share the same resources with the rest of the RS running inside master (periodic memstore
flusher, global memstore tracker, etc). 

{{RegionProcedureStore}} is an implementation of {{ProcedureStore}} and can be used instead
of {{WALProcedureStore}} on top of the patch in HBASE-13202. 

Let me know what do you think? I can pursue this approach, and polish / harden it for Procv2
and RS groups. If you think that this is not a good idea, now would be the best time to say
so. 

> 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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