hbase-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "nkeywal (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7590) Add a costless notifications mechanism from master to regionservers & clients
Date Wed, 06 Feb 2013 18:27:14 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7590?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13572644#comment-13572644
] 

nkeywal commented on HBASE-7590:
--------------------------------

Yep, but at the beginning, we're just waiting 1 second. It's only at the 8th tries that we're
getting serious and wait for 16 seconds: for a recovery, that usually takes a few 10th of
second, the seven first tries are not very useful. As well, there is still the risk of a herd
effect: you don't want 1000 servers to go immediately to the poor meta because they received
the same notification. And lastly, sometimes the 10 tries are consumed without going to the
right server, I need to understand why...

                
> Add a costless notifications mechanism from master to regionservers & clients
> -----------------------------------------------------------------------------
>
>                 Key: HBASE-7590
>                 URL: https://issues.apache.org/jira/browse/HBASE-7590
>             Project: HBase
>          Issue Type: Bug
>          Components: Client, master, regionserver
>    Affects Versions: 0.96.0
>            Reporter: nkeywal
>            Assignee: nkeywal
>
> t would be very useful to add a mechanism to distribute some information to the clients
and regionservers. Especially It would be useful to know globally (regionservers + clients
apps) that some regionservers are dead. This would allow:
> - to lower the load on the system, without clients using staled information and going
on dead machines
> - to make the recovery faster from a client point of view. It's common to use large timeouts
on the client side, so the client may need a lot of time before declaring a region server
dead and trying another one. If the client receives the information separatly about a region
server states, it can take the right decision, and continue/stop to wait accordingly.
> We can also send more information, for example instructions like 'slow down' to instruct
the client to increase the retries delay and so on.
>  Technically, the master could send this information. To lower the load on the system,
we should:
> - have a multicast communication (i.e. the master does not have to connect to all servers
by tcp), with once packet every 10 seconds or so.
> - receivers should not depend on this: if the information is available great. If not,
it should not break anything.
> - it should be optional.
> So at the end we would have a thread in the master sending a protobuf message about the
dead servers on a multicast socket. If the socket is not configured, it does not do anything.
On the client side, when we receive an information that a node is dead, we refresh the cache
about it.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

Mime
View raw message