Research and Design of LVS Cluster Technology in Agricultural Environment Information Acquisition System

. With the development of agricultural informatization, agricultural environment information acquisition platform needs to collect more and more data. And with the increase of the number of data acquisition terminal, a large number of concurrent data traffic is generated on the server. This will lead to the phenomenon of excessive load which directly affects the validity of the data. Therefore, based on LVS technology, this paper designed a solution for the agricultural environment information acquisition platform. Through the experiment we know that the LVS technology can guarantee the validity of the data acquisition, which lays the foundation for the development of precision agriculture.


Introduction
The IOT is through the sensor technology, the acquisition of a variety of sensor information, through the network to connect with each other, information exchange and communication [1,2].The application of the same thing in precision agriculture, making precision agriculture has been rapid development [3][4][5]. By the traditional manual collection of environmental information, and gradually turned to the IOT technology to gather information, Improve the degree of information. Accurate and effective crop environment information data, in the greenhouse plant cultivation, can effectively ensure that the crop is in the best growth state, to ensure the yield and quality of agricultural products [6][7][8][9][10].

Load balancing
Load balancing (Balance Load): load balancing is a dynamic balancing technology in the network. Through the analysis of the data packets in the network, the server can handle the task in a reasonable dynamic distribution. Can ensure the network structure does not change, directly increase the network bandwidth and server, effectively improve the ability of processing data in the network, make the network flexibility and availability significantly improve the stability of the service operation [14,15].

Cluster profile
Cluster is usually the abbreviation of a system. This system is composed of many computers, as a whole, and provides services to the outside. At the same time, it can increase, modify or delete nodes in the cluster. Compared with the traditional single server, the cluster has the advantages of high stability, fast calculation speed and easy management [16,17].

LVS
LVS full name is Virtual Server Linux, which is sponsored by China's Linux programmer, Dr. Zhang Wensong (who is responsible for the development of the core software) and the free software project, which is based on Linux system. LVS is a cluster based on load balancing technology. In the LVS, there must be a master server, and more than 2 true Real-server. Master server according to the scheduling algorithm to control the server Real-server, Real-is responsible for providing services. The client only needs to communicate with a IP address provided by the cluster. The cluster is just a single server, and the structure of the cluster is not an invisible to the client [18]. Server Real-can provide a variety of common services such as FTP, DNS, Telnet, SMTP, etc.. Master control server is responsible for the control of server Real-. When the client sends a service request to the LVS, the server is specified by a server Realto receive a request from the client and respond to its request, for the client to communicate with a fixed IP.

Keepalived
Keepalived is a software that works like a switch. It can detect the status of the server.
When the server appears to restart, the keepalived will remove the server from the existing system. When the server is back to normal, it will resume to the system.

LVS working mode
LVS has three working modes, VS/NAT, VS/TUN, VS/DR. This paper chooses VS/TUN mode. The mode of the client to send the data packets, a two package, add a new destination IP address, and send it to the destination IP address corresponding to the real-server, it will be the results of the packet processing, directly returned to the client. The mode can effectively reduce the load of the pressure[19].

Firewall
In the network firewall usually refers to separate the internal network and external network and isolation, when two network for communication, according to certain rules, the communication of data conditional options, allowing data can freely in and out of the network, are not allowed to data, declined to its into the network, the maximum guarantee the safety of the network server. Linux operating system, also with a firewall, according to the different IP address and port to a certain degree of restriction. Because the system servers are used in the internal network, so close the Linux firewall can directly. The command: service iptables stop

TEST
The design goal of this paper is to realize the high load balance of agricultural environment information acquisition system. In the experiment, the client terminal is used to carry out concurrent access, and the data is sent to the server 500000, and the test data are as table 1. The test results show that the agricultural environment information acquisition system based on LVS technology can effectively improve the service capability, and Improve the service quality, which lays the foundation for the development of precision agriculture.

Conclusions
With the development of precision agriculture, the wide application of the IOT technology, the agricultural environment information acquisition system needs to provide uninterrupted service for 7X24 hours. In this paper, the load balance of the agricultural environment information acquisition system is realized by using LVS technology, and the stable operation of the data acquisition system is effectively guaranteed.