Devoxx PL 2022

Quick & Dirty (&Right)

• Tech debt == financial debt; There is this concept of good financial debt
• No credit cards == low credit score
• Personal note: "A person can quit == get rid of a tech debt. In real life this is not possible"
• Deliberate decisions: for example using a credit card. Debt == value sooner
• Plan to pay off !!!

Quick & Dirty (&Right)

• We life in the "throw-away code" age
• Example project with C++, designed to be there for > 70 years, simply replaced
• We upgrade tools just to be cool
• NEST is gone
• Unit tests is more close to AGILE than clean code - my fav :) 
• OODA

Quick & Dirty (&Right)

Quick & Dirty (&Right)

Quick & Dirty (&Right)

Quick & Dirty (&Right)

Context is king

• Doamne fereste :)
• I learned how to do a very very bad presentation

Diagrams as code

• https://structurizr.com/
• C4 model
• Problems: no rules, missing automation
• https://structurizr.com/help/lite - as Docker image
• Render tool independent!!!
• Content != presentation
• GitHub will support Mermaid diagrams within Markdown fields and files -> https://github.blog/2022-02-14-include-diagrams-markdown-files-mermaid/

Team topologies

• value stream mapping
• https://teamtopologies.com/

Team topologies

Security and service mesh

• Trust is exploitable
• KUMA (by https://konghq.com/) - another service mesh like Istio; Platform agnostic.
• https://github.com/kumahq/kuma
• mTLS - CP automates it 

Security and service mesh

Security and service mesh

Security and service mesh

Security and service mesh

We had fun :) 

Quarkus

• Continuation
• Dev mode...nice :) 
• Continuous testing
• Dev services
• It uses Vert.x
• Hibernate reactive - Panache
• https://quarkus.io/guides/hibernate-orm-panache

Istio lab

• Envoy proxy (C++): api based 
• K8S service == SD because it provides you a ClusterIP
• DNS == SD; Not because this...DNS can hold multiple records for the same domain name. DNS can return the list of IP addresses for the same domain name.
• SD promoted by Consul, Eureka etc is not SD :)
• https://en.wikipedia.org/wiki/Service_discovery
• Load balancer != SD (this is just half of a K8S Service)
• Blue/green deployment != rollout upgrades

Istio lab

• https://github.com/boredabdel/istio-workshop-gcp

OptaPlanner

• Solves problems like: vechile routing, employee rostering, task assignment
• https://en.wikipedia.org/wiki/Integer_programming
• https://github.com/dupliaka/2022-devoxx-poland-school-timetabling
• Score function must be scalable !!!
• If we also define constraints; then the score function can be calculated incrementally
• Better than OR Tools -> https://developers.google.com/optimization
• Do not work well for "percentages"
• Question about airplanes routing :) 
• https://www.optaplanner.org/

Service Mesh

• From CPU to Network communication
• Move communication concerns outside app
• Idea K8s plugin :) !
• IP tables rules that forwards traffic to proxy == The pod cannot be unintentionally called !!!
• Proxy calls directly == not load balancing == that's why it is called mesh

Service Mesh

Service Mesh

Service Mesh

Service Mesh

Service Mesh

Service Mesh

Service Mesh

Service Mesh

• Istio has a lot of features 
• Debugging very hard -> big problems; took years to learn and master it

K8S operators

• helm tests
• helm create
• resource policy keep
• Operator == human interaction knowledge or SRE
• Operator == K8S api extended
• Backups ??!!

We had fun :)

We had fun :)

https://fearlesschangepatterns.com/