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C4 models allow us to visualize software architecture by decomposition in containers and components. Viewpoints are organized in hierarchical levels: Context Diagrams (Level 1) Container Diagrams (Level 2) Component Diagrams (Level 3) Code Diagrams (Level 4) C4-PlantUML offers a variety of macros and stereotypes that make modeling fun. An example in PlantUML: sample.puml @startuml !include <c4/C4_Context.puml> !include <c4/C4_Container.puml> left to right direction Person(user, "User") System_Ext(auth, "AuthService", "Provides authentication and authorization via OIDC") System_Boundary(zone1, "Some system boundary") { System(lb, "Load Balancer") System_Boundary(az, "App Cluster") { System(app, "App Servers") { Container(app1, "App1", "Docker", "Does stuff") Container(app2, "App1", "Docker", "Does stuff") ContainerDb(dbSess, "Session DB", "Redis") ContainerDb(db1, "RBMS 1", "AWS RDS Postgres") ContainerDb(db2, "RBMS 2", "AWS RDS Postgres") ' both app servers sync sessions via redis Rel(app1, dbSess, "Uses", "Sync Session") Rel(app2, dbSess, "Uses", "Sync Session") ' both app servers persist data in RDBMS Rel(app1, db1, "Uses", "Persist/query relational data") Rel(app2, db2, "Uses", "Persist/query relational data") } } } Rel(user, lb, "call") Rel(lb, app1, "delegate") Rel(lb, app2, "delegate") Rel(app1, auth, "Verify", "User auth") Rel(app2, auth, "Verify", "User auth") SHOW_FLOATING_LEGEND() @enduml ...

The following hack allows us to draw a diagram in a diagram in a table in a legend :D example-diagram.puml @startuml skinparam legendBackgroundColor transparent skinparam legendBorderColor transparent actor Editor as editor queue Queue as "Message\nQueue" editor -> [Component] : call [Component] --> Queue : publish legend right {{ scale 0.7 skinparam defaultFontSize 14 skinparam BackGroundColor transparent skinparam defaultBackgroundColor white !procedure $entry($type, $label, $scale=1) {{\nscale $scale \nskinparam backgroundcolor transparent\nlabel " " as A\nlabel " " as B\n $type \n}} => $label !endprocedure map "<b>Legend</b>" as legend #white { $entry(":Editor:","\nEditor for Data xyz", 0.6) $entry("[Component]","\nSome Component", 0.8) $entry("queue Queue","\nKafka-Topic", 1) $entry("A -> B","Data-Flow") } }} endlegend @enduml ...

Remote Debug a Pod’s Java Process Simple steps for remote debugging a Java process running on a k8 pod: Edit deployment and add the following parameters to the Java start line: -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=127.0.0.1:5005 Also add the following port mapping at the section container → ports in the deployment: - containerPort: 5005 protocol: TCP Safe, wait for the new pods and then add a port forward for port 5005 for this pod: kubectl port-forward podname 5005 ...

Checks / Exit Conditions Instead of writing something like if !condition throw …​ we may use require and check for quick exit conditions: val num = 1; require(num > 1){ // ... } val num = 1; require(num > 1){ // .. } Pluralize Strings Adding pluralization as extension function fun String.pluralize(count:Int):String { return if (count > 1){ this + 's' } else { this } } Use it like this ...