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From Fredrik L Stigbäck <fredrik.l.stigb...@sitevision.se>
Subject Hinted handoff bug?
Date Thu, 01 Dec 2011 09:03:19 GMT
Hi,
We,re running cassandra 1.0.3.
I've done some testing with 2 nodes (node A, node B), replication factor 2.
I take node A down, writing some data to node B and then take node A up.
Sometimes hints aren't delivered when node A comes up.

I've done some debugging in org.apache.cassandra.db.HintedHandOffManager 
and sometimes node B ends up in a strange state in method
org.apache.cassandra.db.HintedHandOffManager.deliverHints(final 
InetAddress to), where 
org.apache.cassandra.db.HintedHandOffManager.queuedDeliveries already 
has node A in it's Set and therefore no hints will ever be delivered to 
node A.
The only reason for this that I can see is that in 
org.apache.cassandra.db.HintedHandOffManager.deliverHintsToEndpoint(InetAddress 
endpoint) the hintStore.isEmpty() check returns true and the endpoint 
(node A)  isn't removed from 
org.apache.cassandra.db.HintedHandOffManager.queuedDeliveries. Then no 
hints will ever be delivered again until node B is restarted.
During what conditions will hintStore.isEmpty() return true?
Shouldn't the hintStore.isEmpty() check be inside the try {} finally{} 
clause, removing the endpoint from queuedDeliveries in the finally block?

public void deliverHints(final InetAddress to)
{
         logger_.debug("deliverHints to {}", to);
*if (!queuedDeliveries.add(to))*
             return;
         .......
}

private void deliverHintsToEndpoint(InetAddress endpoint) throws 
IOException, DigestMismatchException, InvalidRequestException, 
TimeoutException,
{
         ColumnFamilyStore hintStore = 
Table.open(Table.SYSTEM_TABLE).getColumnFamilyStore(HINTS_CF);
*   if (hintStore.isEmpty())*
             return; // nothing to do, don't confuse users by logging a 
no-op handoff
     try
     {
         ......
     }
     finally
     {
*queuedDeliveries.remove(endpoint);*
     }
}

Regards
/Fredrik

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