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From "Mike Drob (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-9330) Race condition between core reload and statistics request
Date Thu, 22 Sep 2016 17:21:20 GMT

    [ https://issues.apache.org/jira/browse/SOLR-9330?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15513869#comment-15513869
] 

Mike Drob commented on SOLR-9330:
---------------------------------

{code}
    lst.add("searcherName", name);
    lst.add("caching", cachingEnabled);
    lst.add("openedAt", openTime);
    if (registerTime != null) lst.add("registeredAt", registerTime);
    lst.add("warmupTime", warmupTime);
{code}
Why not put these in the cached list as well? The first three are final and available before
your call to {{snapStatistics}}. The last two are set during {{register}} which should only
be called once, if I understand this correctly. Then the whole method becomes {{return readerStats;}}
-- much simpler and probably faster too!

{code}
+    // core.getInfoRegistry().remove(STATISTICS_KEY, this);
+    // decided to comment it, because it might upset users by showing stats, w/o "searcher"
entry
{code}
I don't think there is any reason to keep this in.

Other than those minor points, the patch looks good to me.

I've had a similar issue when calling {{/replication?command=details}}, but am not able to
reproduce it in this test, so I think we're fine to handle that later.

> Race condition between core reload and statistics request
> ---------------------------------------------------------
>
>                 Key: SOLR-9330
>                 URL: https://issues.apache.org/jira/browse/SOLR-9330
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>    Affects Versions: 5.5
>            Reporter: Andrey Kudryavtsev
>         Attachments: SOLR-9330.patch, SOLR-9390.patch, SOLR-9390.patch, SOLR-9390.patch,
SOLR-9390.patch, too_sync.patch
>
>
> Things happened that we execute this two requests consecutively in Solr 5.5:
> * Core reload: /admin/cores?action=RELOAD&core=_coreName_
> * Check core statistics: /_coreName_/admin/mbeans?stats=true
> And sometimes second request ends with this error:
> {code}
> ERROR org.apache.solr.servlet.HttpSolrCall - null:org.apache.lucene.store.AlreadyClosedException:
this IndexReader is closed
> 	at org.apache.lucene.index.IndexReader.ensureOpen(IndexReader.java:274)
> 	at org.apache.lucene.index.StandardDirectoryReader.getVersion(StandardDirectoryReader.java:331)
> 	at org.apache.lucene.index.FilterDirectoryReader.getVersion(FilterDirectoryReader.java:119)
> 	at org.apache.lucene.index.FilterDirectoryReader.getVersion(FilterDirectoryReader.java:119)
> 	at org.apache.solr.search.SolrIndexSearcher.getStatistics(SolrIndexSearcher.java:2404)
> 	at org.apache.solr.handler.admin.SolrInfoMBeanHandler.addMBean(SolrInfoMBeanHandler.java:164)
> 	at org.apache.solr.handler.admin.SolrInfoMBeanHandler.getMBeanInfo(SolrInfoMBeanHandler.java:134)
> 	at org.apache.solr.handler.admin.SolrInfoMBeanHandler.handleRequestBody(SolrInfoMBeanHandler.java:65)
> 	at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:155)
> 	at org.apache.solr.core.SolrCore.execute(SolrCore.java:2082)
> 	at org.apache.solr.servlet.HttpSolrCall.execute(HttpSolrCall.java:670)
> 	at org.apache.solr.servlet.HttpSolrCall.call(HttpSolrCall.java:458)
> 	at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:225)
> 	at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:183)
> {code}
> If my understanding of SolrCore internals is correct, it happens because of async nature
of reload request:
> * New searcher is "registered" in separate thread
> * Old searcher is closed in same separate thread and only after new one is registered
> * When old searcher is closing, it removes itself from map with MBeans 
> * If statistic requests happens before old searcher is completely removed from everywhere
- exception can happen. 
> What do you think if we will introduce new parameter for reload request which makes it
fully synchronized? Basically it will force it to call {code}  SolrCore#getSearcher(boolean
forceNew, boolean returnSearcher, final Future[] waitSearcher, boolean updateHandlerReopens)
{code} with waitSearcher!= null



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