Jackson Chung created CASSANDRA-4675:
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             Summary: NPE in NTS when using LQ against a node (DC) that doesn't 
have replica
                 Key: CASSANDRA-4675
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4675
             Project: Cassandra
          Issue Type: Bug
            Reporter: Jackson Chung
            Priority: Minor


in a NetworkTopologyStrategy where there are 2 DC:

{panel}
Address         DC          Rack        Status State   Load            Owns    
Token                                       
                                                                               
85070591730234615865843651857942052864      
127.0.0.1       dc1         r1          Up     Normal  115.78 KB       50.00%  
0                                           
127.0.0.2       dc2         r1          Up     Normal  129.3 KB        50.00%  
85070591730234615865843651857942052864  
{panel}
I have a KS that has replica is 1 of the dc (dc1):

{panel}
[default@unknown] describe Keyspace3;                                           
                                                                          
Keyspace: Keyspace3:
  Replication Strategy: org.apache.cassandra.locator.NetworkTopologyStrategy
  Durable Writes: true
    Options: [dc1:1]
  Column Families:
    ColumnFamily: testcf
{panel}

But if I connect to a node in dc2, using LOCAL_QUORUM, I get NPE in the 
Cassandra node's log:

{panel}
[default@unknown] consistencylevel as LOCAL_QUORUM;                       
Consistency level is set to 'LOCAL_QUORUM'.
[default@unknown] use Keyspace3;                                          
Authenticated to keyspace: Keyspace3
[default@Keyspace3] get testcf[utf8('k1')][utf8('c1')];                     
Internal error processing get
org.apache.thrift.TApplicationException: Internal error processing get
        at 
org.apache.thrift.TApplicationException.read(TApplicationException.java:108)
        at 
org.apache.cassandra.thrift.Cassandra$Client.recv_get(Cassandra.java:511)
        at org.apache.cassandra.thrift.Cassandra$Client.get(Cassandra.java:492)
        at org.apache.cassandra.cli.CliClient.executeGet(CliClient.java:648)
        at 
org.apache.cassandra.cli.CliClient.executeCLIStatement(CliClient.java:209)
        at 
org.apache.cassandra.cli.CliMain.processStatementInteractive(CliMain.java:220)
        at org.apache.cassandra.cli.CliMain.main(CliMain.java:348)
{panel}

node2's log:
{panel}
ERROR [Thrift:3] 2012-09-17 18:15:16,868 Cassandra.java (line 2999) Internal 
error processing get
java.lang.NullPointerException
        at 
org.apache.cassandra.locator.NetworkTopologyStrategy.getReplicationFactor(NetworkTopologyStrategy.java:142)
        at 
org.apache.cassandra.service.DatacenterReadCallback.determineBlockFor(DatacenterReadCallback.java:90)
        at 
org.apache.cassandra.service.ReadCallback.<init>(ReadCallback.java:67)
        at 
org.apache.cassandra.service.DatacenterReadCallback.<init>(DatacenterReadCallback.java:63)
        at 
org.apache.cassandra.service.StorageProxy.getReadCallback(StorageProxy.java:775)
        at 
org.apache.cassandra.service.StorageProxy.fetchRows(StorageProxy.java:609)
        at org.apache.cassandra.service.StorageProxy.read(StorageProxy.java:564)
        at 
org.apache.cassandra.thrift.CassandraServer.readColumnFamily(CassandraServer.java:128)
        at 
org.apache.cassandra.thrift.CassandraServer.internal_get(CassandraServer.java:383)
        at 
org.apache.cassandra.thrift.CassandraServer.get(CassandraServer.java:401)
        at 
org.apache.cassandra.thrift.Cassandra$Processor$get.process(Cassandra.java:2989)
        at 
org.apache.cassandra.thrift.Cassandra$Processor.process(Cassandra.java:2889)
        at 
org.apache.cassandra.thrift.CustomTThreadPoolServer$WorkerProcess.run(CustomTThreadPoolServer.java:187)
        at 
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at 
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
{panel}

I could workaround it by adding dc2:0 to the option:

{panel}
[default@Keyspace3] describe Keyspace3;                                         
  
Keyspace: Keyspace3:
  Replication Strategy: org.apache.cassandra.locator.NetworkTopologyStrategy
  Durable Writes: true
    Options: [dc2:0, dc1:1]
  Column Families:
    ColumnFamily: testcf
{panel}

Now you get UA:

{panel}
[default@Keyspace3] get testcf[utf8('k1')][utf8('c1')];                         
  
null
UnavailableException()
        at 
org.apache.cassandra.thrift.Cassandra$get_result.read(Cassandra.java:6506)
        at 
org.apache.cassandra.thrift.Cassandra$Client.recv_get(Cassandra.java:519)
        at org.apache.cassandra.thrift.Cassandra$Client.get(Cassandra.java:492)
        at org.apache.cassandra.cli.CliClient.executeGet(CliClient.java:648)
        at 
org.apache.cassandra.cli.CliClient.executeCLIStatement(CliClient.java:209)
        at 
org.apache.cassandra.cli.CliMain.processStatementInteractive(CliMain.java:220)
        at org.apache.cassandra.cli.CliMain.main(CliMain.java:348)
{panel}


On a side note, is there a thought on having a CL.LOCAL_ONE? Ie if local node 
(wrt the dc) does not have replica, on a LOCAL_ONE, it won't try to go across 
DC to try to get it. It would be similar to LOCAL_QUORUM.

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