Design And Implementation Of General Internet Of Things Middleware Based On Microservice Architecture

With the development of communication technologies and computing power,it is possible to share the sensing data of massive devices in the Internet of Things(IoT)and even its ability to sensing and actuating.At present,most IoT systems only focus on the sensing data from a limited number of devices in their domains,while ignoring the ability of those devices to provide sensing and actuating services.There is still a lack of a general IoT middleware,on the premise of ensuring access of heterogeneous devices,establish open services according to device's ability for the purpose of realizing cross-system and cross-domain IoT applications.By analyzing heterogeneous characteristics of IoT devices,this paper summarizes the commonalities of the processing required in device accessing,proposes an IoT device model and implements a general IoT middleware based on the microservice architecture which can access heterogeneous devices and establishes open services for them.The middleware uses a profile to access and manage devices,and provide a programming model with customizable rules to build applications through those services.The main work and highlights of this paper as follows:1.For the access of heterogeneous devices,three specific processes are separated: communication establishment,message parsing,and resource abstraction,and both of them are implemented as a scalable microservice.The device description mechanism is established to specify the combination of microservices and a corresponding model can be generated for IoT device,this model can accept heterogeneous communication protocols,support custom parsing and command encapsulating and provide RESTFul-style services based on specific resources of the device.2.For the use of IoT device model,considering the service invocation in high concurrency situations,propose an asynchronous request processing method,the message middleware is used to buffer the concurrent pressure,the distributed cache is used to coordinate the correct service invocation between multiple instances.Besides,a request priority judgment method based on service invocation role,request initiation time,request method and default message received order are proposed solving the conflict caused by multiparty control.In addition,the programmable model--virtual IoT device is proposed which can consume services provided by other models,and change the way data processing dynamically at runtime using the rule engine integrated.Together with the IoT device models,they provide open services and constitute the IoT service marketplace.3.For the implementation of the middleware,system functions are divided into four modules: basic service facilities,IoT device model,virtual IoT device and public services according to the microservice architecture.Most microservices in the module are designed as stateless services and deployed in Docker container,Kubernetes will deploy and manage those containerized microservices automatically and support scaling them fastly,which all make the middleware high availability.In the implementation phase,the rolling update mechanism of the deployment is used to refine the native service configuration in Kubernetes,a monitoring microservice is established to collect exception information from model's communication,data parsing and service invocation handling to practice circuit breaker design pattern and automatic expansion once the concurrency pressure exceeds the threshold.This paper achieves interoperability in the level of IoT device's service by establishing the general IoT middleware based on microservice architecture,which provides a reference for improving the interoperability and universality of IoT,and helps to perfect the ecosystem of the IoT.