Cassandra Java驱动冷至500毫秒热？

Question

我遇到一个冷到热（首次使用）的集群和会话到本地数据源（Cassandra）需要640ms。任何额外的连接需要80到100毫秒，所以第一个连接的开销约为500 + ms。这是正常的，有什么我可以做些什么来以某种方式得到这个数字？我使用T410（i5 2.5GHz）。

[更新]

23:27:11.453 [main] DEBUG c.d.driver.core.SystemProperties - com.datastax.driver.NEW_NODE_DELAY_SECONDS is undefined, using default value 1 
23:27:11.460 [main] DEBUG c.d.driver.core.SystemProperties - com.datastax.driver.NON_BLOCKING_EXECUTOR_SIZE is undefined, using default value 4 
23:27:11.463 [main] DEBUG c.d.driver.core.SystemProperties - com.datastax.driver.NOTIF_LOCK_TIMEOUT_SECONDS is undefined, using default value 60 
23:27:11.607 [main] DEBUG com.datastax.driver.core.Cluster - Starting new cluster with contact points [localhost/127.0.0.1:9042] 
23:27:11.905 [main] DEBUG com.datastax.driver.core.Connection - Connection[localhost/127.0.0.1:9042-1, inFlight=0, closed=false] Transport initialized and ready 
23:27:11.906 [main] DEBUG c.d.driver.core.ControlConnection - [Control connection] Refreshing node list and token map 
23:27:11.969 [main] DEBUG c.d.driver.core.ControlConnection - [Control connection] Refreshing schema 
23:27:12.016 [main] DEBUG c.d.driver.core.ControlConnection - [Control connection] Refreshing node list and token map 
23:27:12.051 [main] DEBUG c.d.driver.core.ControlConnection - [Control connection] Successfully connected to localhost/127.0.0.1:9042 
23:27:12.052 [main] INFO c.d.d.c.p.DCAwareRoundRobinPolicy - Using data-center name 'datacenter1' for DCAwareRoundRobinPolicy (if this is incorrect, please provide the correct datacenter name with DCAwareRoundRobinPolicy constructor) 
23:27:12.053 [main] INFO com.datastax.driver.core.Cluster - New Cassandra host localhost/127.0.0.1:9042 added 
23:27:12.076 [Cassandra Java Driver worker-0] DEBUG com.datastax.driver.core.Connection - Connection[localhost/127.0.0.1:9042-2, inFlight=0, closed=false] Transport initialized and ready 
23:27:12.077 [Cassandra Java Driver worker-0] DEBUG com.datastax.driver.core.Session - Added connection pool for localhost/127.0.0.1:9042 
23:27:12.097 [main] DEBUG com.datastax.driver.core.Connection - Connection[localhost/127.0.0.1:9042-2, inFlight=0, closed=true] closing connection 
23:27:12.103 [main] DEBUG com.datastax.driver.core.Cluster - Shutting down 
23:27:12.105 [main] DEBUG com.datastax.driver.core.Connection - Connection[localhost/127.0.0.1:9042-1, inFlight=0, closed=true] closing connection 
23:27:12.123 [main] DEBUG com.datastax.driver.core.Cluster - Starting new cluster with contact points [/127.0.0.1:9042] 
23:27:12.132 [main] DEBUG com.datastax.driver.core.Connection - Connection[/127.0.0.1:9042-1, inFlight=0, closed=false] Transport initialized and ready 
23:27:12.132 [main] DEBUG c.d.driver.core.ControlConnection - [Control connection] Refreshing node list and token map 
23:27:12.138 [main] DEBUG c.d.driver.core.ControlConnection - [Control connection] Refreshing schema 
23:27:12.168 [main] DEBUG c.d.driver.core.ControlConnection - [Control connection] Refreshing node list and token map 
23:27:12.192 [main] DEBUG c.d.driver.core.ControlConnection - [Control connection] Successfully connected to /127.0.0.1:9042 
23:27:12.192 [main] INFO c.d.d.c.p.DCAwareRoundRobinPolicy - Using data-center name 'datacenter1' for DCAwareRoundRobinPolicy (if this is incorrect, please provide the correct datacenter name with DCAwareRoundRobinPolicy constructor) 
23:27:12.192 [main] INFO com.datastax.driver.core.Cluster - New Cassandra host /127.0.0.1:9042 added 
23:27:12.201 [Cassandra Java Driver worker-0] DEBUG com.datastax.driver.core.Connection - Connection[/127.0.0.1:9042-2, inFlight=0, closed=false] Transport initialized and ready 
23:27:12.202 [Cassandra Java Driver worker-0] DEBUG com.datastax.driver.core.Session - Added connection pool for /127.0.0.1:9042 

正如人们所看到的第一个连接尝试使用多达600毫秒，更取决于一个会如何读的数字。

Answer 1

我的猜测是这与连接初始化有关。在所有当前发布的Java驱动程序版本中，连接都是同步初始化的。幸运的是，单个主机池并行初始化，但连接不是。如果您使用的是2.0.9，其默认的8个核心连接数可以解释您为什么看到初始化时间较慢。另外，如果您使用密码认证，那么这会使系统的运行速度降低很多（从每个连接约0-10ms到约60-120ms）。

在即将发布的java驱动程序2.0.10中，所有连接都是并行初始化的，这极大地改进了会话初始化。有关信息，请参阅JAVA-701。