Question

我是Cassandra的新手我想在Cassandra做一个CRUD操作。我可以从java类连接Cassandra。但现在当我做CRUD它不工作时。这是我的代码..

import com.datastax.driver.core.Cluster;
import com.datastax.driver.core.Host;
import com.datastax.driver.core.Metadata;
import com.datastax.driver.core.Row;
import com.datastax.driver.core.Session;

public class AnotherClient {

private Session session;

private Cluster cluster;

public void connect(String node) {
    cluster = Cluster.builder().addContactPoint(node).build();
    Metadata metadata = cluster.getMetadata();
    System.out.println("Cassandra connection established");
    System.out.printf("Connected to cluster: %s\n",
            metadata.getClusterName());
    for (Host host : metadata.getAllHosts()) {
        System.out.printf("Datatacenter: %s; Host: %s; Rack: %s \n",
                host.getDatacenter(), host.getAddress(), host.getRack());
        session = cluster.connect();

    }
}

public void createSchema() {
    session.execute("CREATE KEYSPACE simplex WITH replication "
            + "= {'class':'SimpleStrategy', 'replication_factor':3};");

    session.execute("CREATE TABLE simplex.songs (" + "id uuid PRIMARY KEY,"
            + "title text," + "album text," + "artist text,"
            + "tags set<text>," + "data blob" + ");");
    session.execute("CREATE TABLE simplex.playlists (" + "id uuid,"
            + "title text," + "album text, " + "artist text,"
            + "song_id uuid," + "PRIMARY KEY (id, title, album, artist)"
            + ");");

}

public void loadData() {
    session.execute("INSERT INTO simplex.songs (id, title, album, artist, tags) "
            + "VALUES ("
            + "756716f7-2e54-4715-9f00-91dcbea6cf50,"
            + "'La Petite Tonkinoise',"
            + "'Bye Bye Blackbird',"
            + "'Joséphine Baker'," + "{'jazz', '2013'})" + ";");
    session.execute("INSERT INTO simplex.playlists (id, song_id, title, album, artist) "
            + "VALUES ("
            + "2cc9ccb7-6221-4ccb-8387-f22b6a1b354d,"
            + "756716f7-2e54-4715-9f00-91dcbea6cf50,"
            + "'La Petite Tonkinoise',"
            + "'Bye Bye Blackbird',"
            + "'Joséphine Baker'" + ");");
}

public void close() {
    cluster.shutdown();
}

public static void main(String[] args) {
    AnotherClient client = new AnotherClient();
    client.connect("127.0.0.1");

    client.createSchema();
    client.close();
}

}

连接已正确建立。但方法createSchema（）无法正常工作。这是我的错误日志。

Cassandra connection established
Connected to cluster: Test Cluster
Datatacenter: datacenter1; Host: /127.0.0.1; Rack: rack1 
Exception in thread "main" com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: [])
    at com.datastax.driver.core.exceptions.NoHostAvailableException.copy(NoHostAvailableException.java:61)
    at com.datastax.driver.core.ResultSetFuture.extractCauseFromExecutionException(ResultSetFuture.java:234)
    at com.datastax.driver.core.ResultSetFuture.getUninterruptibly(ResultSetFuture.java:165)
    at com.datastax.driver.core.Session.execute(Session.java:106)
    at com.datastax.driver.core.Session.execute(Session.java:75)
    at com.example.cassandra.AnotherClient.createSchema(AnotherClient.java:30)
    at com.example.cassandra.AnotherClient.main(AnotherClient.java:81)
Caused by: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: [])
    at com.datastax.driver.core.RequestHandler.sendRequest(RequestHandler.java:93)
    at com.datastax.driver.core.Session$Manager.execute(Session.java:393)
    at com.datastax.driver.core.Session$Manager.executeQuery(Session.java:429)
    at com.datastax.driver.core.Session.executeAsync(Session.java:146)
    ... 4 more

Answer 1

为什么您的主机“/127.0.0.1”而不只是“127.0.0.1”？

线程“main”中的异常com.datastax.driver.core.exceptions。 NoHostAvailableException

错误告诉您连接未正确建立，因为驱动程序无法连接到您提供的任何提供的节点（String节点）。

为了让它变得非常简单 ...尝试：

cluster = Cluster.builder().addContactPoint("127.0.0.1").build();

Answer 2

问题由以下原因引起：Caused by: com.datastax.driver.core.exceptions.NoHostAvailableException

@Lyuben Todorov，问题不是由/127.0.0.1中的前导斜杠引起的。根据此question，在IP之前存在前导/的原因是记录器隐式调用toString的{{1}}。

我认为原因可能是Cassandra远程设置或Cassandra设置的防火墙设置。

对于Cassandra设置：更改InetAddress并重新启动Cassandra：

/etc/cassandra/cassandra.yaml
对于防火墙设置：

rpc_address: 0.0.0.0 broadcast_rpc_address: {YOUR_SERVER_ID_HERE}

有关详细信息，请参阅此question

Answer 3

我遇到了与OP相同的问题。这会发生什么，如果我从命令行运行cassandra-stress，我得到输出为 Datatacenter：datacenter1;主持人：localhost / 127.0.0.1;机架：rack1 即，您可以看到主机被指定为localhost或127.0.0.1。当我使用Eclipse运行测试时，我看到正斜杠出现了。所以现在，读取节点参数并截断正斜杠可能是个更好的主意。

如何使用java Class在Cassandra中创建KEYSPACE

3 个答案: