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© 2019 – The symbIoTe Consortium
Building IoT Middleware with Microservices
Mario Kušek, University of Zagreb, FER
Javantura v6, 23 Feb 2019, Zagreb
Grant Agreement No 688156

© 2019 – The symbIoTe Consortium2
Who am I?
@MarioKusek
mario.kusek@fer.hr
University of Zagreb
Faculty of Electrical Engineering and Computing
Department of Telecommunications
IoT Laboratory

• What is a ”thing”?
– Object from physical world (physical object with
build in sensors and/or actuators) or virtual object
– Internet Connected Object (ICO)
• Has unique identifier and is connected to the Internet
• Communicates and generate data (reading from
environment)
• Can receive data/commands from network
• Can execute commands – actuate (electrical or
mechanical)
• Can receive data from other ICO, process them and
send for processing to cloud
Internet of Things - IoT

• IoT platforms integrate „things” and continuously
acquire data
– Large distributed system
– Processing large amount of data (often in real time)
– Integrates and saves data from different sources
– For application developers offer:
• Searching for things (sensors/actuators)
• Access to data
• There are more then 400 platforms
– Mostly specialised for one area
How to integrate „things” and provide user applications?

Architecture of IoT System
User
IoT
Platform
Gateway
IoT
Application
Smart spaceCloudUser

• Can not easily create cross domain applications!
• Interoperability:
– Data structures are different
– Different measurement units
– Vertical domain specific platforms
• Project: symbIoTe
– Symbiosis of smart objects across IoT environments
– H2020 project: 2016-2018 (3 years)
– 15 EU partners (universities, institutes, SMEs)
Some Challenges

The symbIoTe approach
Core Services
IoT
Platform A
IoT
Platform B
AdaptorAdaptor
Domain
Enabler
Application
Adaptor
IoT
Platform A
IoT
Platform C
Adaptor
Adaptor
IoT
Platform D
Adaptor
IoT
Platform B
Adaptor
Application
Agent
IoT
Gateway A
IoT
Gateway B Smart
Device
Smart Space Gateway
Agent Agent
L1
L2
L3L4
roaming
Smart Space A
Core Services
Smart Device
Smart Space B
Smart Space GatewaySmart Space Gateway
Smart Device

• Development
– Agile process (iterations) – planned 4 week releases
– Weekly meetings of all developers (video conference)
– One or two weeks for internal component releases
– Programming language is Java
– Unit testing: >70% code coverage
• Tools:
– Attlasian Jira as the feature planning tool
– github.com as code repository tool
– Git as versioning and code revisioning tool
– Travis CI as Continuous Integration server
Project organisation

High-level Architecture

Putting it all together: L1 compliance
Components for
semantic and
syntactic
interoperability +
security

• Each component is one microservice
– Has a component owner
– One microservice – mostly implemented by one
organisation
– One repository
• Frameworks:
– SpringBoot, Spring Cloud
– Communication between microservices:
RabbitMQ
Microservices – Decisions

• Spring Cloud Config – configuration
• Zipkin – distributed tracing system
• Spring Cloud Gateway – did not exist then
– We used NGINX
• Spring Cloud Netflix:
– Eureka – service registration
– Ribbon – REST client that uses Eureka
– Feign – declarative HTTP client
• For accessing core services
Spring Cloud

• Microservices were not divided by domains
• Frequent changing of messages
– Hard integration testing, lots of communication
between teams
• RabbitMQ
– Most of communication is request/response
• Design not appropriate for messaging
– No message (API) versioning
– Late arrival of Spring Cloud Contract (v1.0.0 Sep
2016)
• Not so good support for messages (documentation and
examples)
Problems

• Lots of microservices need to implement the
same data objects:
– Put data objects in library: SymbIoTeLibraries
• Put all libraries in Jitpack (https://jitpack.io)
• Problems with versions of library:
– Start using semantic versioning (https://semver.org)
• All components need to contact AAM
(Authentication Authorization Manager)
component
– Created SymbIoTeSecurity library
• SymbIoTeLibraries has dependency to it
Problems/decisions

• Each IoT platform needs to deploy cloud
components
– No automatic deployment
• 3 stages/ways of deployment:
– 1. From sources:
• Support web page (github wiki)
• Problems:
– Complex  automatization
– Slow  automatization
– Hard to configure  configuration generator (web page
similar to https://start.spring.io)
Deployment (1)

• 2. From jars:
– Created a script for downloading, configuring,
starting and stopping
– Problems:
• Microservices have startup dependencies
– Solved by putting small class in main method to wait for some
service (host:port)
• If it doesn’t work first time you need to dive into details
– Similar to SpringBoot
• Bash script - problem on windows if someone just want
to try it
Deployment (2)

• 3. From dockers
– Easy startup
– Starting with docker-compose or docker swarm
– Config git repo is in docker image
• Problem of custom configuration
– Putting config in volume
– Different documentation for using docker directly
(linux) or in docker machine
• Problems with port mapping
Deployment (3)

• For testing, hackathons you run components
on machine that is in local network
• Cloud components need to have public IP,
DNS, and certificate (for https)
– Workaround is ngrok tunnelling
• Different NGINX configuration
Cloud components on dev machine

Memory Consumption – Problem
• 1.5GB on startup
• 2-3GB when working
• Future work:
– Java 11: new GC, String internals, netty, ACDS, …
– Problem: late release of SpringBoot 2.1 (Oct 2018)
and Spring Cloud (Greenwich)(Jan 2019)

• Distributed teams require lots of
communication
• Be careful in choosing technologies
• Divide features to microservices that are
independent and scalable (up/down)
• Versioning of API is important
• Dedicate time for building/testing automation
– Do it in the beginning of the project and maintain
Conclusions

© 2019 – The symbIoTe Consortium
www.symbiote-h2020.eu
middleware.symbiote-h2020.eu
info@symbiote-h2020.eu
@symbiote_h2020
H2020 symbIoTe
github.com/symbiote-h2020
Member of
Thank you!
Questions?
@MarioKusek
mario.kusek@fer.hr

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Building IoT Middleware with Microservices

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