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From "Matteo Bertozzi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13260) Bootstrap Tables for fun and profit
Date Mon, 27 Apr 2015 19:44:41 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14514809#comment-14514809
] 

Matteo Bertozzi commented on HBASE-13260:
-----------------------------------------

{quote}I did not see an order of magnitude difference, it was the other way around before
we discovered HBASE-13529. Let me verify with the latest code.{quote}
that's correct, before HBASE-13529 the proc-wal was way slower. I avoided to post my result
to allow to have a run with tunings you may know and decide. 
I've a test with both proc-wal and region-store that you can run. it is based on your test,
but you can run it with mvn clean test -Dsurefire.timeout=5400 -Dtest= ProcedureStoreTest
and it will show you the result 
https://github.com/matteobertozzi/hbase/blob/7222e6a16430b8f1909b0197f21958ad2728d9e0/hbase-server/src/test/java/org/apache/hadoop/hbase/procedure2/ProcedureStoreTest.java

> 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_bench.patch, 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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