深入浅出Zookeeper之四Create请求和处理

客户端接口

public String create(final String path,
byte data[], List<ACL> acl,
CreateMode createMode)
throws KeeperException, InterruptedException
{
final String clientPath = path;
PathUtils.validatePath(clientPath, createMode.isSequential());

final String serverPath = prependChroot(clientPath);
//请求头
RequestHeader h = new RequestHeader();
h.setType(ZooDefs.OpCode.create);
//请求体
CreateRequest request = new CreateRequest();
//CREATE请求需要server端响应
CreateResponse response = new CreateResponse();
request.setData(data);
//node类型
request.setFlags(createMode.toFlag());
request.setPath(serverPath);
if (acl != null && acl.size() ==
0) {
throw new KeeperException.InvalidACLException();
}
request.setAcl(acl);
//同步提交
ReplyHeader r = cnxn.submitRequest(h, request, response, 
null);
//异常情况
if (r.getErr() != 0) {
throw KeeperException.create(KeeperException.Code.get(r.getErr()),
clientPath);
}
//真实路径，对于SEQUENTIAL NODE后面会加上序号
if (cnxn.chrootPath == null) {
return response.getPath();
} else {
return response.getPath().substring(cnxn.chrootPath.length());
}
}

public String create(final String path, byte data[], List<ACL> acl,
            CreateMode createMode)
        throws KeeperException, InterruptedException
    {
        final String clientPath = path;
        PathUtils.validatePath(clientPath, createMode.isSequential());

        final String serverPath = prependChroot(clientPath);
	//请求头
        RequestHeader h = new RequestHeader();
        h.setType(ZooDefs.OpCode.create);
	//请求体
        CreateRequest request = new CreateRequest();
	//CREATE请求需要server端响应
        CreateResponse response = new CreateResponse();
        request.setData(data);
	//node类型
        request.setFlags(createMode.toFlag());
        request.setPath(serverPath);
        if (acl != null && acl.size() == 0) {
            throw new KeeperException.InvalidACLException();
        }
        request.setAcl(acl);
	//同步提交
        ReplyHeader r = cnxn.submitRequest(h, request, response, null);
        //异常情况
	if (r.getErr() != 0) {
            throw KeeperException.create(KeeperException.Code.get(r.getErr()),
                    clientPath);
        }
	//真实路径，对于SEQUENTIAL NODE后面会加上序号
        if (cnxn.chrootPath == null) {
            return response.getPath();
        } else {
            return response.getPath().substring(cnxn.chrootPath.length());
        }
    }

请求提交过程和之前的exists一样，都是通过sendthread写出去，都会进入pengding队列等待server端返回。

server端处理也是一样，变化的只是RequestProcessor的业务逻辑。也就是说transport层是通用的，变化的是上层的业务层。

server端执行处理链，PrepRequestProcessor

switch (request.type) {
case OpCode.create:
//反序列化的对象
CreateRequest createRequest = new CreateRequest();
//zxid递增
pRequest2Txn(request.type, zks.getNextZxid(), request, createRequest, 
true);
break;
......
request.zxid = zks.getZxid();
nextProcessor.processRequest(request);