Alexander Lapin created IGNITE-15389:
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             Summary: org.apache.ignite.internal.metastorage.client.CursorImpl 
has potential deadlock inside
                 Key: IGNITE-15389
                 URL: https://issues.apache.org/jira/browse/IGNITE-15389
             Project: Ignite
          Issue Type: Improvement
         Environment: [link title|http://example.com][link 
title|http://example.com]
            Reporter: Alexander Lapin


The initiating cursor operation can be processed in the same thread as the 
cursor.hasNext() cursor.next(), etc, which, due to its synchronous nature, can 
block the processing of the response from the server that should complete the 
initiating operation. 

In other words:

 
{code:java}
metaStorageMgr.range(...)
{code}
internally will call 
org.apache.ignite.raft.client.service.impl.RaftGroupServiceImpl#sendWithRetry

 

where raft command response within

 
{code:java}
fut0.whenComplete(...){code}
could be blocked with upcomming

cursor.hasNext(), cursor.next(), cursor.close() if it's processed within same 
thread.

Below, there is snippet of hasNext() where we await future result here 
synchronously.

 
{code:java}
initOp.thenCompose(
    cursorId -> metaStorageRaftGrpSvc.run(new 
CursorCloseCommand(cursorId))).get();
{code}
 

Similar issue is https://issues.apache.org/jira/browse/IGNITE-15272

It worth to mention that Cursor extends Iterator that has synchronous 
operations by design.

 

 



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