[jira] [Created] (SOLR-9330) Race condition between core reload and statistics request

["Andrey Kudryavtsev (JIRA)" <ji...@apache.org>]

Andrey Kudryavtsev created SOLR-9330:
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             Summary: 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


Things happened that we execute this two requests consequentially 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 make 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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