[jira] [Commented] (JENA-703) TDB - Ensure readers don't block writeback forever.

["Rob Vesse (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/JENA-703?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14018658#comment-14018658 ] 

Rob Vesse commented on JENA-703:
--------------------------------

It is worth noting that for scenarios like JENA-689 where the system has continuous high load the side effect of this change would be that queries may experience delays

> TDB - Ensure readers don't block writeback forever.
> ---------------------------------------------------
>
>                 Key: JENA-703
>                 URL: https://issues.apache.org/jira/browse/JENA-703
>             Project: Apache Jena
>          Issue Type: Improvement
>          Components: TDB
>    Affects Versions: Jena 2.11.1
>            Reporter: Andy Seaborne
>
> The commit queue can only be flushed when the main storage is quiet.  A stream of readers can lead to the main storage never being quiet.
> One possibility is to place a maximum (quite high) on the number of readers allowed after the decision to flush the journal to main storage. If exceeded,  then lock readers for a while, flush and resume.



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