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https://issues.apache.org/jira/browse/ACCUMULO-2801?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14026951#comment-14026951
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Jonathan Park commented on ACCUMULO-2801:
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[~keith_turner] what are your thoughts on not calling sync for define tablet
and instead relying on the sync for a data write to ensure that it exists?
It will make it possible for there to be a metadata table entry for the WAL
without there being an associated DEFINE_TABLET in the WAL which I think
recovery will currently ignore (looking at 1.5.1). It might change our recovery
semantics (I'm not fully familiar with what our current guarantees are) in the
case of log rollovers/defines.
> define tablet syncs walog for each tablet in a batch
> ----------------------------------------------------
>
> Key: ACCUMULO-2801
> URL: https://issues.apache.org/jira/browse/ACCUMULO-2801
> Project: Accumulo
> Issue Type: Bug
> Affects Versions: 1.5.0, 1.5.1, 1.6.0
> Reporter: Keith Turner
>
> When the batch writer sends a batch of mutations for N tablets that were not
> currently using a walog, then define tablet will be called for each tablet.
> Define tablet will sync the walog. In hadoop 2 hsync is used, which is much
> slower than hadoop1 sync calls. If hsync takes 50ms and there are 100
> tablets, then this operation would take 5 secs. The calls to define tablet
> do not occur frequently, just when walogs switch or tablets are loaded so the
> cost will be amortized. Ideally there could be one walog sync call for all
> of the tablets in a batch of mutations.
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