Cassandra java驱动协议版本和连接限制不匹配

Question

我使用的是java驱动版本：2.1.4
Cassandra 版本：dsc-cassandra-2.1.10
cql 的输出如下

cqlsh 5.0.1 | Cassandra 2.1.10 | CQL spec 3.2.1 | Native protocol v3

我是协议 V3。但是当我尝试将其设置为每个连接超过 128 个请求时，它会引发异常。这似乎是 V2 中的一个限制。解释如下：

以下代码块：

PoolingOptions poolingOptions = new PoolingOptions();
poolingOptions.setCoreConnectionsPerHost(HostDistance.LOCAL, 8);

Cluster cluster = Cluster.builder()
                         .addContactPoints(x.x.x.x)
                         .withPoolingOptions(poolingOptions)
                         .withProtocolVersion(ProtocolVersion.V3)
                         .build();

System.out.println("Protocol version = "+myCurrentVersion);
System.out.println("LOCAL CORE = "+poolingOptions.getCoreConnectionsPerHost(HostDistance.LOCAL));
System.out.println("LOCAL MAX = "+poolingOptions.getMaxConnectionsPerHost(HostDistance.LOCAL));
System.out.println("Max sim requests = "+poolingOptions.getMaxSimultaneousRequestsPerConnectionThreshold(HostDistance.LOCAL));
System.out.println("Max sim requests per host = "+poolingOptions.getMaxSimultaneousRequestsPerHostThreshold(HostDistance.LOCAL));

 poolingOptions
.setMaxSimultaneousRequestsPerHostThreshold(HostDistance.LOCAL, 3000);

 poolingOptions
.setMaxSimultaneousRequestsPerConnectionThreshold(HostDistance.LOCAL, 128);         

System.out.println("LOCAL CORE = "+poolingOptions.getCoreConnectionsPerHost(HostDistance.LOCAL));
System.out.println("LOCAL MAX = "+poolingOptions.getMaxConnectionsPerHost(HostDistance.LOCAL));
System.out.println("Max sim requests = "+poolingOptions.getMaxSimultaneousRequestsPerConnectionThreshold(HostDistance.LOCAL));
System.out.println("Max sim requests per host = "+poolingOptions.getMaxSimultaneousRequestsPerHostThreshold(HostDistance.LOCAL));

输出是：

Protocol version = V3
LOCAL CORE = 1
LOCAL MAX = 8
Max sim requests = 100
Max sim requests per host = 1024
Exception in thread "main" java.lang.IllegalArgumentException: Max simultaneous requests per connection for LOCAL hosts must be in the range (0, 128)
    at com.datastax.driver.core.PoolingOptions.checkRequestsPerConnectionRange(PoolingOptions.java:370)
    at com.datastax.driver.core.PoolingOptions.setMaxSimultaneousRequestsPerConnectionThreshold(PoolingOptions.java:175)
    at ca.txio.pricehistoryservice.main.ConnectionOptionTest.main(ConnectionOptionTest.java:38)

根据 Cassandra 文档 https://docs.datastax.com/en/developer/java-driver/2.1/manual/native_protocol/ 和 http://docs.datastax.com/en/developer/java-driver/2.1/manual/pooling/

我是协议 V3。但是为什么我限制每个连接 128 个请求。这似乎是 V2 中的一个限制。有人可以解释一下如何找到我的实际版本，如果确实是 V3，为什么我不能同时拥有超过 128 个连接？

Answer 1

使用 ProtocolVersion#V3 或更高版本，每个连接最多有 32768 个请求，并且池默认为固定大小 1。您通常会通过允许每个连接更多同时请求来提高最大容量（setMaxRequestsPerConnection(HostDistance, int))

参考：http://docs.datastax.com/en/drivers/java/2.1/com/datastax/driver/core/PoolingOptions.html#setMaxRequestsPerConnection-com.datastax.driver.core.HostDistance-int-