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From "Matteo Bertozzi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13260) Bootstrap Tables for fun and profit
Date Wed, 29 Apr 2015 06:49:08 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14518846#comment-14518846
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Matteo Bertozzi commented on HBASE-13260:
-----------------------------------------

[~ndimiduk] for 1.1 is probably ok having a slow proc-store (keep in mind that currently proc-wal
is using hsync and the performance are really different from the bench above done with hflush
only, instead of 15sec for 1M ops I get 200sec for 10k ops)

what I'd like to know from you is what do you have in mind for upgrading?
let say we can't get perf improvement on the region, and from the above "With increased concurrency,
the region performs worse (>10 threads)". for the assignment we need a better throughput
and shortcut on the replay will help too.

in my mind, I always had the different "stores" for groups of operations (e.g. the DDL goes
on its own wal, the assignment for sys-ns goes on its own wal and so on). but using this we
can even do DDL still uses the region-store and assignment uses the proc-wal, and avoid any
migration.
but I'd like to know what is your upgrade story in case the region patch can't be improved.
(can we get the full bench with 10, 30, 50 threads too, just for reference?)

> 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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