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From "Sean Busbey (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-3842) [UMBRELLA] Remove non-transient data from ZooKeeper
Date Fri, 22 May 2015 19:57:17 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3842?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14556735#comment-14556735
] 

Sean Busbey commented on ACCUMULO-3842:
---------------------------------------

{quote}
What we should really have to mimic the API we present is a strongly consistent means to update
configurations. ZooKeeper doesn't keep us from accomplishing this. We would need to write
code to actually get the strong consensus for ourselves. I know this is very hand-wavy at
this point, but I think we're at the point where this is a problem we need to start thinking
about because it's been a repeated problem for ourselves just in writing reasonable tests
for Accumulo for ~2years now.
{quote}

Once it's finalized, could we leverage the recent HBase procedure store for this (ref HBASE-12439)?

> [UMBRELLA] Remove non-transient data from ZooKeeper
> ---------------------------------------------------
>
>                 Key: ACCUMULO-3842
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3842
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: client, tserver
>            Reporter: Josh Elser
>             Fix For: 1.8.0
>
>
> Wanted to start brainstorming about this.
> We store a lot of persistent data in ZooKeeper that would better stored in something
backed by HDFS. ZooKeeper can be a very convenient place to store persisted data so that it's
available to all nodes, but it comes at a price and often must be asynchronously accessed
to achieve good performance.
> * Table/Namespace configuration
> * Users/Authorizations
> * Problem reports (maybe?)
> * System configuration overrides (maybe?)
> Some benefits we'd see from this:
> * Loss of ZooKeeper doesn't lose table configuration and users.
> * Greatly reduce zookeeper watchers (assume watchers=50*num_tables*num_tservers)
> * Consistent updates of table constraints and all other table properties
> The last note is the most important one IMO. The number of test issues alone that we've
had with constraints not being seen on all servers are bound to affect users.



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