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 .
下面是我用来连接cassandra集群的单例类 .
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;
}
}
我需要首先连接到本地cassandra节点的设置是什么,如果它们关闭,那么只能与远程节点通信 . 我的池配置选项就在这里,我在上面的代码中使用它?
1 回答
默认情况下,数据存储驱动程序仅连接到本地DC中的节点 . 如果您不使用
withLocalDc
,它将尝试从其能够连接的联系点的DC识别本地数据中心 .如果您希望驱动程序故障转移到远程数据中心托管,您应该使用withUsedHostsPerRemoteDc,即:
使用此配置,驱动程序将 Build 与每个远程DC中3个主机的连接,并且只有在本地数据中心中的所有主机都关闭时才向它们发送查询 .
还有其他策略可以故障转移到远程数据中心 . 例如,您可以在与C *数据中心相同的物理数据中心中运行应用程序客户端,然后当物理数据中心发生故障时,您可以在更高级别进行故障转移(如负载均衡器) .
我觉得你有什么好 . 默认值也很好 .