presto-mongodb/src/main/java/io/prestosql/plugin/mongodb/MongoClientConfig.java/MongoClientConfig/setConnectionsPerHost
class MongoClientConfig:    @Config("mongodb.connections-per-host")
    public MongoClientConfig setConnectionsPerHost(int connectionsPerHost)
    {
        this.connectionsPerHost = connectionsPerHost;
        return this;
    }