在使用ycbs进行测试的时候，设置1000的并发，客户端收到下面的错误提示
com.mongodb.MongoWaitQueueFullException: Too many threads are already waiting for a connection. Max number of threads (maxWaitQueueSize) of 500 has been exceeded.
https://github.com/opencb/opencga/issues/468 MaxWaitQueueSize is defined as threadsAllowedToBlockForConnectionMultiplier * connectionsPerHost
在新版本中使用 waitQueueMultiple替代threadsAllowedToBlockForConnectionMultiplier
在客户端上设置 ./bin/ycsb run mongodb -threads 1000 -P workloads/workloada -p mongodb.url=mongodb://perftest:perftest@xxx.xxx.xx.xx:xxx/mongo_perf?waitQueueMultiple=100
