UnavailableException() in Apache-Cassandra 0.8.2

Question

I new to Apache-Cassandra 0.8.2. I am trying to insert some data but getting this exception.

Exception in thread "main" UnavailableException()
    at org.apache.cassandra.thrift.Cassandra$insert_result.read(Cassandra.java:14902)
    at org.apache.cassandra.thrift.Cassandra$Client.recv_insert(Cassandra.java:858)
    at org.apache.cassandra.thrift.Cassandra$Client.insert(Cassandra.java:830)
    at TestCassandra.main(TestCassandra.java:166)

My Code is:

public class TestCassandra {

    public static void createKeySpace( Cassandra.Client client,String ksname)
        throws TException, InvalidRequestException, UnavailableException, UnsupportedEncodingException, NotFoundException, TimedOutException, SchemaDisagreementException {

        KsDef ksdef = new KsDef();
        ksdef.name = ksname;
        ksdef.strategy_class = "NetworkTopologyStrategy";    
        List l = new ArrayList();        
        ksdef.cf_defs =l;   

        client.system_add_keyspace(ksdef); 
        System.out.println("KeySpace Created");


    }

    public static void createColumnFamily(Cassandra.Client client,String ksname,String cfname)
        throws TException, InvalidRequestException, UnavailableException, UnsupportedEncodingException, NotFoundException, TimedOutException, SchemaDisagreementException {

        CfDef cfd = new CfDef(ksname, cfname);
        client.system_add_column_family(cfd);
        System.out.println("ColumnFamily Created");

    }

    public static void main(String[] args)
            throws TException, InvalidRequestException, UnavailableException, UnsupportedEncodingException, NotFoundException, TimedOutException, SchemaDisagreementException {

        TTransport tr = new TFramedTransport(new TSocket("localhost", 9160));
        TProtocol proto = new TBinaryProtocol(tr);
        Cassandra.Client client = new Cassandra.Client(proto);
        tr.open();

       String keySpace = "Keyspace1";
       String columnFamily = "Users";

       //Drop the Keyspace 

       client.system_drop_keyspace(keySpace);

       //Creating keyspace


       KsDef ksdef = new KsDef();
       ksdef.name = keySpace;
       ksdef.strategy_class = "NetworkTopologyStrategy";    
       List l = new ArrayList();        
       ksdef.cf_defs =l;

       client.system_add_keyspace(ksdef); 
       System.out.println("KeySpace Created");

       //createKeySpace(client,keySpace);

       client.set_keyspace(keySpace);

       //Creating column Family

       CfDef cfd = new CfDef(keySpace, columnFamily);
       client.system_add_column_family(cfd);
       System.out.println("ColumnFamily Created");

       //createColumnFamily(client,keySpace,columnFamily);

       ColumnParent parent = new ColumnParent(columnFamily);

       Column description = new Column();
       description.setName("description".getBytes());
       description.setValue("I’m a nice guy".getBytes());
       description.setTimestamp(System.currentTimeMillis());

       ConsistencyLevel consistencyLevel = ConsistencyLevel.ONE;
       ByteBuffer rowid = ByteBuffer.wrap("0".getBytes());

//Line No. 166
       client.insert(rowid, parent, description, consistencyLevel);
       System.out.println("Record Inserted...");

       tr.flush();       
       tr.close();
    }


}

Can anybody help me why this is so?

Answer 1

The reason for the UnavailableException is due to the fact of in your createKeySpace method, you have never specified a replication_factor for your keyspace definition, KsDef.

The 2 Strategy class, NetworkTopologyStrategy and SimpleStrategy requires a replication factor to be set. In Cassandra 0.8 and higher, there is no more a replication_factor field in KsDef so you will have to add it yourself, like so (I've updated your code, but not tested. Also, see that I've changed your strategy_class to SimpleStrategy):

KsDef ksdef = new KsDef();
ksdef.name = ksname;
ksdef.strategy_class = SimpleStrategy.class.getName(); 

//Set replication factor
if (ksdef.strategy_options == null) {
    ksdef.strategy_options = new LinkedHashMap<String, String>();
}

//Set replication factor, the value MUST be an integer
ksdef.strategy_options.put("replication_factor", "1");

//Cassandra must now create the Keyspace based on our KsDef
client.system_add_keyspace(ksdef);

For NetworkTopologyStrategy, you will need to specify your replication factor to each datacentre you've created (See explanation here).

For more information, view my Interfacing with Apache Cassandra 0.8 in Java blog.

Answer 2

Note that I ran in a similar problem (receiving many Unavailable exceptions) because I created a KsDef by code and inadvertently put 10 in there when I was testing on a cluster with only 3 nodes.

So the replication factor said 10 and thus attempting to do a QUORUM read or a QUORUM write would always fail because the QUORUM could never be reached (i.e. 10 / 2 + 1 = at least 6 nodes.)

Fixing my replication factor fixed all the problems with the QUORUM consistency level.