Cassandra连接 - 共享“群集”实例还是多个？

When using the Cassandra driver within a Java project, what is the best practice for managing connections? Specifically with respect to whether it's better practice to allow multiple threads to share a single Cluster instance or to allocate a separate Cluster instance for each thread that needs to talk to Cassandra.

在Java项目中使用Cassandra驱动程序时，管理连接的最佳做法是什么？特别是关于是否允许多个线程共享单个Cluster实例或为需要与Cassandra通信的每个线程分配单独的Cluster实例更好的做法。

I followed the example code and am setting up my Cluster instance like:

我按照示例代码设置了我的Cluster实例，如：

Cluster.builder().addContactPoint(HOST).withPort(PORT)
    .withCredentials(USER, PASS).build();

So what I'm asking is would the preferred approach be to do something like this (single shared Cluster instance):

所以我要问的是首选方法是做这样的事情（单个共享集群实例）：

private static Cluster _cluster = null;

public static Cluster connect() {
    if (_cluster != null && ! _cluster.isClosed()) {
        //return the cached instance
        return _cluster;
    }

    //create a new instance
    _cluster = Cluster.builder().addContactPoint(HOST).withPort(PORT)
                .withCredentials(USER, PASS).build();
    return _cluster;
}

...or is it best practice to return multiple Cluster instances? Like so:

...或者是返回多个Cluster实例的最佳做法？像这样：

public static Cluster connect() {
    //every caller gets their own Cluster instance
    return Cluster.builder().addContactPoint(HOST).withPort(PORT)
                .withCredentials(USER, PASS).build();
}

I guess the points at the core of this question are:

我想这个问题的核心点是：

Is building a new Cluster instance an expensive operation?
构建新的Cluster实例是一项昂贵的操作吗？
Will the Cluster object internally manage/pool connections to the backing datastore, or does it function more like an abstraction of a single connection?
Cluster对象是内部管理/池连接到后备数据存储区，还是更像是单个连接的抽象？
Is the Cluster object thread-safe?
Cluster对象是线程安全的吗？

1 个解决方案

#1

Is building a new Cluster instance an expensive operation?

构建新的Cluster实例是一项昂贵的操作吗？

Calling build to construct a Cluster instance does no networking IO, so it is a non-expensive operation.

调用构建来构建集群实例不会产生网络IO，因此它是一种非昂贵的操作。

Will the Cluster object internally manage/pool connections to the backing datastore, or does it function more like an abstraction of a single connection?

Cluster对象是内部管理/池连接到后备数据存储区，还是更像是单个连接的抽象？

What is expensive is calling cluster.init() which creates a single connection (control connection) to one of your contact points. cluster.connect() is even more expensive since it inits the Cluster (if it hasn't been already) and creates a Session which manages a connection pool (with pool size based on your PoolingOptions) to each discovered host. So yes, a Cluster has a 'control connection' to manage the state of hosts and each Session created via Cluster.connect() will have a connection pool to each host.

值得注意的是调用cluster.init（），它会为您的某个联系点创建一个连接（控制连接）。 cluster.connect（）因为它进入集群（如果它还没有）而更加昂贵，并创建一个Session来管理每个发现的主机的连接池（基于您的PoolingOptions的池大小）。所以，是的，集群有一个“控制连接”来管理主机的状态，通过Cluster.connect（）创建的每个Session都有一个连接池到每个主机。

Is the Cluster object thread-safe?

Cluster对象是线程安全的吗？

Put simply, yes :)

简单地说，是的:)

4 simple rules when using the DataStax drivers for Cassandra provides further guidance on this topic.

使用Cassandra的DataStax驱动程序时的4个简单规则提供了有关此主题的进一步指导。

#1