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The first thing we are going to do is run and examine a simple application. You are not expected to write any code, but we will be looking at Dockerfiles and Docker-Compose files. The purpose of the exercise is to help you understand the structure of the application, capture it using C4, and ask architecturally significant questions. |
01 The Monolith Application
Docker is an ideal tool for understanding the nature of monolithic applications without the need to have numerous physical nodes (a node is a piece of hardware)
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Containers can be considered lightweight VMs
They are self-contained
Hermetically sealed
They expose their services through ports
They can share a common network and volume
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02 Running the Monolith
Using the Gitbash terminal, navigate to
/c/workClone down the following projects
Start Docker
Open Windows' terminal in Admin mode (right-click on Windows Start, and select Terminal (Admin)
Navigate to
c:\work\vat_calculator_serviceEnter the command
mvn package, this will build the binary for the calculator service. A number of files will have been created in thetargetfolder. You will need the file calledvat_calculator_service-0.0.1-SNAPSHOT-spring-boot.jarNavigate to
c:\work\react_app-vat_calculator.Create a folder called
targetCopy the file
vat_calculator_service-0.0.1-SNAPSHOT-spring-boot.jarinto thetargetfolderRun the command
docker build --tag=vat_calculator_service:latest .the full stop is important
Run the command
docker run -p 3000:3000 -p 8080:8080 --name vatc_fe --rm vat_calculator_servicethis will create a single docker container containing the 3 applications that are all wired together
03 Understanding the Monolith
Run the following commands
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Model what you have learnt using C4. So what are the things that you notice and architecturally what are the PROs and CONs? |
04 Monolith Breakdown
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05 Monolith to Docker
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06 PROs and CONs of the Monolith
07 Breaking up the Monolith
We are now going to run each component of the system as separate services
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Make sure you are in the folder
c:\work\react_app_calculatorRun
docker-compose upWait until no more messages are being sent to the screen
Open another terminal window (the plus symbol next to the title of the current terminal window)
Run
docker ps -a, look at the services that are running. You should notice that there are two services; one is calledvatc-fe, and the other is calledvatc-serviceExamine the other fields that are displayed from the
docker ps -acommandIn your browser enter the URL
localhost:30003001, when the app is running select the Sales menu option, and you should see some dataIn your browser enter the URL
localhost:8080/api/v1/vatentries, you should see the same data from when you select the Sales optionFrom the terminal run
docker stop vatc-serviceIn your browser enter the URL
localhost:8080/api/v1/vatentries, you should see no data, this is because we have stopped the backend serverIn your browser enter the URL
localhost:30003001, when the app is running select the Sales menu option, and you should see no data, this is because the frontend runs as a separate service to the backend, we have isolated each service from the other.From the terminal run docker start vatc-service
In your browser enter the URL
localhost:8080/api/v1/vatentries, you should see the same data from when you select the Sales optionFrom the terminal run
docker stop vatc-feIn your browser enter the URL
localhost:30003001, it should fail to connect to the applicationIn your browser enter the URL
localhost:8080/api/v1/vatentries, you should see the same data from when you select the Sales option, so you can still access the data even though the frontend has been stopped
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Model what you have learnt using C4. |
08 Cloud Computing Architecture
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Cloud computing allows us to
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All the major cloud providers; Amazon Web Services, Google Cloud Platform, Microsoft Azure, Alibaba Cloud, IBM Cloud, DigitalOcean Cloud, Salesforce Cloud, Tencent Cloud, Oracle Cloud Infrastructure, Huawei Cloud (https://www.cloudzero.com/blog/cloud-service-providers/ ), provide the three core elements of cloud services
IaaS (Infrastructure as a Service)
PaaS (Platform as a Service)
SaaS (Software as a Service)
Giving you
Low capital outlay
Faster time to market
Agility
Optimal cloud delivery models
Pay-as-you-go pricing
Managed services
More opportunities to build better disaster recovery into your organisation’s day-to-day operations
More opportunities to build better business continuity into your organisation’s day-to-day operations
09 AWS Example with Docker Containers
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We could use a computer engine, but this would require us to select the OS (infrastructure platform) and then install all the necessary applications and libraries to run our container on that compute engine
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We’ve also highlighted Red Hat OpenShift as an alternative approach. OpenShift® gives a one-stop shop to access the services of any number of cloud providers, it’s a unified platform to build, modernize, and deploy applications at scale
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10 Quality of Service Attributes Gained
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There are clearly some gains to be had by splitting our applications into these micro-services
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10-01 Scaleability
When you ran the monolith VAT application one of the main issues was its inability to scale. Whether we wanted to scale it horizontally or vertically was an issue
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Here we we demonstrate horizontal scaling |
Vertical Scaling
Modify the Node by adding more RAM, Upgrading the CPU, and adding more Disk space. All of these options require the system to be shut down, the hardware to be installed and the system to be rebooted. After this, you could have too much capacity or too little capacity.
Horizontal Scaling
Replicate a service, and distribute the workload amongst the distributed services You would make use of something like a load balancer to ensure that traffic is evenly sent to all replicated nodes/services (the cluster).
10-01 Demo Time
The trainer will demonstrate a Docker Image being deployed onto an AWS container service. They will also show horizontal scaling at work.
10-02 Less Brittle Architecture
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We are going to steal a concept from the world of software engineering - “Brittle Code” The concept is very simple, how much collateral damage is there to a codebase being changed? The scope of that damage is relative. However, the scale of the effect of change should have been considered during the design and development of the codebase that’s being changed. Unfortunately, many of these design decisions are not captured in the completed codebase, leading to another issue; technical debt. In a sense, what we are describing here is risk and levels of risk. An example of this would be the very small change to the name of a field in a class. The surrounding codebase should have no knowledge of this change because access to this field should only be through setters and getters (encapsulation). Suppose a change to this field causes other classes to have to be modified. In that case, this is clearly brittle code (we’re not including the idea of refactoring to clean up the codebase, making names more readable and appropriate to their purpose). We can use the same idea in architecture. Does the change in one component or service require the complete rebuild of the entire system? We saw that with the monolith application. |
10-03 Maintainability
How much effort is required to maintain the system, modify it, and integrate it with other systems?
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If you have to butcher the code to make it realize new scenarios whilst continuing to be what it was intended for, then it’s not maintainable
10-04 Security
A system is the sum of its parts. If each service can have its level of security (different set of security constraints), it becomes easier to secure the whole. But if the whole is a monolith, inevitably it becomes more difficult to apply security constraints around the parts.
10-05 Performance
You tune the whole by tuning the parts. That’s a basic engineering principle.
Formula 1 teams spend vast amounts of money capturing data from all the components of the car, as well as the performance of the driver. The car and driver only hit optimal performance when everything is functioning in harmony.
10-06 Cost Efficiency
The problem with the monolithic approach is that you have to tune the whole even though your intention may be to only effect a part. It then becomes very difficult to target the tuning for a single part without affecting the whole. So you end up spending money where it’s not needed. The tuning and cost management becomes much easier by componentising the system and using a micro-service architecture.
10-07 More fault-tolerant
The requirement is to make the whole fault-tolerant, but each component has different requirements for achieving fault tolerance. By tackling each part, you are tackling the whole.
10-08 Higher availability
The requirement to make the entire system highly available can only be achieved by tuning thr parts and making them highly available. If you’re dealing with a monolith, then if one part fails, then the whole fails. But if we compartmentalise the system, and reduce the coupling, then if one part fails, strategies can be put in place to ensure that the whole is not compromised.
10-09 More extensible
A system is only extensible if it is designed to be extensible. If you have a monolithic piece of code, then by it’s very nature it is not extensible. Likewise if you have a system that is comprised of many parts but the coupling between those parts is tight, then a change in one component will impact on other components. Testing one component would require testing of adjacent components etc. This is a bad design.