hbase-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Himanshu Vashishtha (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10378) Divide HLog interface into User and Implementor specific interfaces
Date Tue, 21 Jan 2014 06:17:19 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10378?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13877251#comment-13877251
] 

Himanshu Vashishtha commented on HBASE-10378:
---------------------------------------------

Yes, hiding the impl specific details from HRS is one big point of this feature. Looks like
we both are on same page re getWAL() api? That is, hiding the details in the impl.

Re: rollWriter()
bq. ... called from admin. Currently it returns set of regions that were flushed on calling
rollWriter.
No, it doesn't flush any region. It just returns regions which the caller should flush in
order to archive the oldest WAL file. Actually, this return value is never used by the shell.

Anyway, though rolling is an internal stuff, we have exposed it as an API in shell. I would
again go the same route and let WAL impl decide how to deal with it. For example, TableGroupWALImpl
could roll the logs for all tables. Since it requires user's input, we can also overload the
API as per WAL requirement?
As mentioned in the parent jira, I will take a stab at it once basic switching is done.

> Divide HLog interface into User and Implementor specific interfaces
> -------------------------------------------------------------------
>
>                 Key: HBASE-10378
>                 URL: https://issues.apache.org/jira/browse/HBASE-10378
>             Project: HBase
>          Issue Type: Sub-task
>          Components: wal
>            Reporter: Himanshu Vashishtha
>         Attachments: 10378-1.patch
>
>
> HBASE-5937 introduces the HLog interface as a first step to support multiple WAL implementations.
This interface is a good start, but has some limitations/drawbacks in its current state, such
as:
> 1) There is no clear distinction b/w User and Implementor APIs, and it provides APIs
both for WAL users (append, sync, etc) and also WAL implementors (Reader/Writer interfaces,
etc). There are APIs which are very much implementation specific (getFileNum, etc) and a user
such as a RegionServer shouldn't know about it.
> 2) There are about 14 methods in FSHLog which are not present in HLog interface but are
used at several places in the unit test code. These tests typecast HLog to FSHLog, which makes
it very difficult to test multiple WAL implementations without doing some ugly checks.
> I'd like to propose some changes in HLog interface that would ease the multi WAL story:
> 1) Have two interfaces WAL and WALService. WAL provides APIs for implementors. WALService
provides APIs for users (such as RegionServer).
> 2) A skeleton implementation of the above two interface as the base class for other WAL
implementations (AbstractWAL). It provides required fields for all subclasses (fs, conf, log
dir, etc). Make a minimal set of test only methods and add this set in AbstractWAL.
> 3) HLogFactory returns a WALService reference when creating a WAL instance; if a user
need to access impl specific APIs (there are unit tests which get WAL from a HRegionServer
and then call impl specific APIs), use AbstractWAL type casting,
> 4) Make TestHLog abstract and let all implementors provide their respective test class
which extends TestHLog (TestFSHLog, for example).



--
This message was sent by Atlassian JIRA
(v6.1.5#6160)

Mime
View raw message