Question

我是Apache-Cassandra 0.8.2的新手。我试图插入一些数据，但得到这个例外。

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)

我的代码是：

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();
    }


}

有人可以帮我解释为什么会这样吗？

Answer 1

UnavailableException的原因是由于您的createKeySpace方法中的事实，您从未为密钥空间定义replication_factor指定KsDef。

2策略类NetworkTopologyStrategy和SimpleStrategy需要设置复制因子。在Cassandra 0.8及更高版本中，replication_factor中不再有KsDef字段，因此您必须自己添加它，就像这样（我已更新您的代码，但未经过测试。另外，请参阅我已将您的strategy_class更改为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);

对于NetworkTopologyStrategy，您需要为您创建的每个数据中心指定复制因子（请参阅说明here）。

有关详细信息，请查看我的Interfacing with Apache Cassandra 0.8 in Java博客。

Answer 2

请注意，我遇到了类似的问题（接收到许多不可用的异常），因为我在代码中创建了一个KsDef，当我在只有3个节点的集群上进行测试时，无意中将10个放在那里。

因此复制因子表示10因此尝试进行QUORUM读取或QUORUM写入总是会失败，因为永远无法达到QUORUM（即10/2 + 1 =至少6个节点。）

修复我的复制因子修复了QUORUM一致性级别的所有问题。

Apache-Cassandra 0.8.2中的UnavailableException（）

2 个答案: