int ping = 11; 限流 客户端验证与服务端是连接的

int ping = 11;

ZooKeeper Programmer's Guide https://zookeeper.apache.org/doc/r3.1.2/zookeeperProgrammers.html

The session is kept alive by requests sent by the client. If the session is idle for a period of time that would timeout the session, the client will send a PING request to keep the session alive. This PING request not only allows the ZooKeeper server to know that the client is still active, but it also allows the client to verify that its connection to the ZooKeeper server is still active. The timing of the PING is conservative enough to ensure reasonable time to detect a dead connection and reconnect to a new server.

https://github.com/apache/zookeeper/blob/master/zookeeper-server/src/main/java/org/apache/zookeeper/server/Request.java#L124

public boolean isThrottlable() {
	return this.type != OpCode.ping
	&& this.type != OpCode.closeSession
	&& this.type != OpCode.createSession;
	}

zookeeper/ZooDefs.java at master · apache/zookeeper https://github.com/apache/zookeeper/blob/master/zookeeper-server/src/main/java/org/apache/zookeeper/ZooDefs.java

public interface OpCode {
	int notification = 0;
	int create = 1;
	int delete = 2;
	int exists = 3;
	int getData = 4;
	int setData = 5;
	int getACL = 6;
	int setACL = 7;
	int getChildren = 8;
	int sync = 9;
	int ping = 11;
	int getChildren2 = 12;
	int check = 13;
	int multi = 14;
	int create2 = 15;
	int reconfig = 16;
	int checkWatches = 17;
	int removeWatches = 18;
	int createContainer = 19;
	int deleteContainer = 20;
	int createTTL = 21;
	int multiRead = 22;
	int auth = 100;
	int setWatches = 101;
	int sasl = 102;
	int getEphemerals = 103;
	int getAllChildrenNumber = 104;
	int setWatches2 = 105;
	int addWatch = 106;
	int createSession = -10;
	int closeSession = -11;
	int error = -1;
	}