使用 datastax java 驱动程序连接到本地 cassandra 节点? [英] connect to local cassandra nodes using datastax java driver?

问题描述

我使用 datastax java 驱动程序 3.1.0 连接到 cassandra 集群，我的 cassandra 集群版本是 2.0.10.

I am using datastax java driver 3.1.0 to connect to cassandra cluster and my cassandra cluster version is 2.0.10.

下面是我用来连接到 cassandra 集群的单例类.

Below is the singleton class I am using to connect to cassandra cluster.

public class CassUtil {
  private static final Logger LOGGER = Logger.getInstance(CassUtil.class);

  private Session session;
  private Cluster cluster;

  private static class Holder {
    private static final CassUtil INSTANCE = new CassUtil();
  }

  public static CassUtil getInstance() {
    return Holder.INSTANCE;
  }

  private CassUtil() {
    List<String> servers = TestUtils.HOSTNAMES;
    String username =
        TestUtils.loadCredentialFile().getProperty(TestUtils.USERNAME);
    String password =
        TestUtils.loadCredentialFile().getProperty(TestUtils.PASSWORD);

    // is this right setting?
    PoolingOptions poolingOptions = new PoolingOptions();
    poolingOptions.setConnectionsPerHost(HostDistance.LOCAL, 4, 10).setConnectionsPerHost(
        HostDistance.REMOTE, 2, 4);

    Builder builder = Cluster.builder();
    cluster =
        builder
            .addContactPoints(servers.toArray(new String[servers.size()]))
            .withRetryPolicy(DowngradingConsistencyRetryPolicy.INSTANCE)
            .withPoolingOptions(poolingOptions)
            .withReconnectionPolicy(new ConstantReconnectionPolicy(100L))
            .withLoadBalancingPolicy(
                DCAwareRoundRobinPolicy
                    .builder()
                    .withLocalDc(
                        !TestUtils.isProduction() ? "DC2" : TestUtils.getCurrentLocation()
                            .get().name().toLowerCase()).build())
            .withCredentials(username, password).build();

    try {
      session = cluster.connect("testkeyspace");
      StringBuilder sb = new StringBuilder();
      Set<Host> allHosts = cluster.getMetadata().getAllHosts();
      for (Host host : allHosts) {
        sb.append("[");
        sb.append(host.getDatacenter());
        sb.append(host.getRack());
        sb.append(host.getAddress());
        sb.append("]");
      }
      LOGGER.logInfo("connected: " + sb.toString());
    } catch (NoHostAvailableException ex) {
      LOGGER.logError("error= ", ExceptionUtils.getStackTrace(ex));
    } catch (Exception ex) {
      LOGGER.logError("error= " + ExceptionUtils.getStackTrace(ex));
    }
  }

  public void shutdown() {
    LOGGER.logInfo("Shutting down the whole cassandra cluster");
    if (null != session) {
      session.close();
    }
    if (null != cluster) {
      cluster.close();
    }
  }

  public Session getSession() {
    if (session == null) {
      throw new IllegalStateException("No connection initialized");
    }
    return session;
  }

  public Cluster getCluster() {
    return cluster;
  }
}

我需要使用什么设置来首先连接到本地 cassandra 节点，如果它们关闭，则只与远程节点通信.另外，我在上面的代码中使用的池配置选项就在这里?

What is the settings I need to use to connect to local cassandra nodes first and if they are down, then only talk to remote nodes. Also my pooling configuration options is right here which I am using in the above code?

推荐答案

默认情况下，datastax 驱动程序只会连接到本地 DC 中的节点.如果您不使用 withLocalDc，它将尝试从它能够连接到的接触点的 DC 中辨别本地数据中心.

By default the datastax drivers will only connect to nodes in the local DC. If you do not use withLocalDc it will attempt to discern the local datacenter from the DC of the contact point it is able to connect to.

如果您希望驱动程序故障转移到远程数据中心的主机，您应该使用 withUsedHostsPerRemoteDc，即:

If you want the driver to fail over to host in remote data center(s) you should use withUsedHostsPerRemoteDc, i.e.:

cluster.builder()        
  .withLoadBalancingPolicy(DCAwareRoundRobinPolicy.builder()
    .withLocalDc("DC1")
    .withUsedHostsPerRemoteDc(3).build())

使用此配置，驱动程序将与每个远程 DC 中的 3 个主机建立连接，并且仅在本地数据中心的所有主机都关闭时才向它们发送查询.

With this configuration, the driver will establish connections to 3 hosts in each remote DC, and only send queries to them if all hosts in the local datacenter is down.

故障转移到远程数据中心还有其他策略.例如，您可以在与 C* 数据中心相同的每个物理数据中心运行您的应用程序客户端，然后当一个物理数据中心出现故障时，您可以在更高级别(例如您的负载平衡器)进行故障转移.

There are other strategies for failover to remote data centers. For example, you could run your application clients in each same physical data center as your C* data centers, and then when a physical data center fails, you can fail over at a higher level (like your load balancer).

还有我在上面的代码中使用的池配置选项吗?

Also my pooling configuration options is right here which I am using in the above code?

我认为你所拥有的很好.默认值也很好.

I think what you have is fine. The defaults are fine too.

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