[CASSANDRA-1487] Bug in calculating QUORUM

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 0.7 beta 2
• Severity: Normal
• Assignee: Jignesh Dhruv
• Reporter: Jignesh Dhruv

Authors

Jignesh Dhruv

Reviewers

Jonathan Ellis

• Created: 09/Sep/10 16:34
• Updated: 16/Apr/19 09:33
• Resolved: 11/Sep/10 01:00

Description

Hello,

It seems that there is a bug in calculating QUORUM in src/java/org/apache/cassandra/service/QuorumResponseHandler.java

Currently the QUORUM formula in place will return correct QUORUM if replication factor <= 3. However if you have a Replication Factor > 3, it will return incorrect result.

-----------------------
— src/java/org/apache/cassandra/service/QuorumResponseHandler.java (revision 995482)
+++ src/java/org/apache/cassandra/service/QuorumResponseHandler.java (working copy)
@@ -109,7 +109,7 @@
case ANY:
return 1;
case QUORUM:

• return (DatabaseDescriptor.getQuorum(table)/ 2) + 1;
  + return DatabaseDescriptor.getQuorum(table);
  case ALL:
  return DatabaseDescriptor.getReplicationFactor(table);
  default:
  -------------------
  In QuorumResponseHandler:determineBlockFor()
  DatabaseDescriptor.getQuorum(table) is already returning a quorum value which is further divided by 2 and a one is added.

So say if your RF=6, it is suppose to check 4 replicas, (6/2)+1=4 but it ends up checking only 3 replicas as DatabaseDescriptor.getQuorum returns 4, so determineBlockFor will return (4/2)+1=3.

Let me know if you have any questions.

Jignesh