[jira] [Commented] (SOLR-13932) Review directory locking and Blob interactions

["Ilan Ginzburg (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-13932?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16987024#comment-16987024 ] 

Ilan Ginzburg commented on SOLR-13932:
--------------------------------------

[~mbwaheed] I agree with you about the generation being needed. I believe we could/should have done it differently, by identifying the segments_N coming from Blob and forcing that one to be picked for the new index, but I don't know if we can force Solr to use a given segments file, and otherwise it would require always switching the index directory (in order to remove the other segments_* files).

I've submitted a PR with the changes for this Jira.

> Review directory locking and Blob interactions
> ----------------------------------------------
>
>                 Key: SOLR-13932
>                 URL: https://issues.apache.org/jira/browse/SOLR-13932
>             Project: Solr
>          Issue Type: Sub-task
>            Reporter: Ilan Ginzburg
>            Priority: Major
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Review resolution of local index directory content vs Blob copy.
> There has been wrong understanding of following line acquiring a lock on index directory.
>  {{solrCore.getDirectoryFactory().get(indexDirPath, DirectoryFactory.DirContext.DEFAULT, solrCore.getSolrConfig().indexConfig.lockType);}}
> From Yonik:
> _A couple things about Directory locking.... the locks were only ever to prevent more than one IndexWriter from trying to modify the same index. The IndexWriter grabs a write lock once when it is created and does not release it until it is closed._ 
> _Directories are not locked on acquisition of the Directory from the DirectoryFactory. See the IndexWriter constructor, where the lock is explicitly grabbed._
> Review CorePushPull#pullUpdateFromBlob, ServerSideMetadata and other classes as relevant.
>  



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