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From Apache Wiki <>
Subject [Cassandra Wiki] Update of "FAQ" by AaronMorton
Date Sun, 07 Aug 2011 03:55:12 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Cassandra Wiki" for change notification.

The "FAQ" page has been changed by AaronMorton:

   * [[#max_key_size|What's the maximum key size permitted?]]
   * [[#ubuntu_hangs|I'm using Ubuntu with JNA, and holy crap weird things keep hanging and
stalling and printing scary tracebacks in dmesg!]]
   * [[#schema_disagreement|How do I fix schema disagreement errors?]]
+  * [[#dropped_messages|Why do I see "... messages dropped.." in the logs?]]
@@ -509, +510 @@

  To confirm everything is on the same schema, use the cassandra-cli to confirm 'describe
cluster;' only returns one schema version.
+ <<Anchor(dropped_messages)>>
+ == Why do I see "... messages dropped.." in the logs? ==
+ Internode messages which are received by a node, but do not get not to be processed within
rpc_timeout are dropped rather than processed. As the coordinator node will no longer be waiting
for a response. If the Coordinator node does not receive Consistency Level responses before
the rpc_timeout it will return a TimedOutExcpetion to the client. If the coordinator receives
Consistency Level responses it will return success to the client. 
+ For MUTATION messages this means that the mutation was not applied to all replicas it was
sent to. The inconsistency will be repaired by Read Repair or Anti Entropy Repair. 
+ For READ messages this means a read request may not have completed. 
+ Load shedding is part of the Cassandra architecture, if this is a persistent issue it is
generally a sign of an overloaded node or cluster. 

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