[StackOverflow/kubernetes] Issue with Spring Boot/Webflux APIs on Kubernetes

### ROOT CAUSE The issue arises due to misconfigured environment variables in the Spring Boot/Webflux application when deployed on Kubernetes. Specifically, the `spring.cloud.gateway.route` configuration is not being properly injected via environment variables, leading to incorrect routing behavior or missing configurations. This is compounded by improper handling of `application.properties` files across different environments (dev, prod), causing classpath conflicts or missing dependencies. ### CODE FIX 1. **Environment Variables for Configuration**: - Use Kubernetes ConfigMaps and Secrets to inject environment-specific configurations (e.g., `spring.cloud.gateway.route`, database URLs). - Example `deployment.yaml` snippet: ```yaml env: - name: SPRING_GAMMA_GATEWAY_ROUTE value: "file=\"classpath:/routes.json\"" ``` - Reference in `application.properties`: ```properties spring.cloud.gateway.route[0]=$${SPRING_GAMMA_GATEWAY_ROUTE} ``` 2. **Docker Multi-Stage Build for Environment-Specific Layers**: - Split the build process to handle environment-specific files (e.g., `routes.json`) only at deployment time: ```dockerfile FROM eclipse-temurin:17-jdk AS builder COPY src/main/resources/routes.json /app/ RUN spring build --pack application --env $ENVIRONMENT FROM gcr.io/paketo-buildpacks/java COPY --from=builder /app.jar /app.jar ``` 3. **Kubernetes Liveness/Readiness Probes**: - Add probes to restart unhealthy pods and ensure endpoints are ready: ```yaml livenessProbe: httpGet: path: /actuator/health port: 8080 initialDelaySeconds: 15 periodSeconds: 20 ``` 4. **Webhook for Dynamic Route Updates**: - Deploy a Spring Boot webhook to update routes via `/actuator/gateway` endpoint: ```java @RestController public class RouteController { @PostMapping("/routes") public Mono updateRoutes(@RequestBody String configuration) { return ServerWebExchangeUtils.putRequestHeader( exchange.getRequest(), "SPRING_CLOUD_GATEWAY_CONFIGURATION_URI", configuration ).flatMap(exchange -> exchange.getResponse().ok().build()); } } ``` 5. **Helm Chart for Consistent Deployment**: - Use Helm to manage environment-specific values (e.g., `values-dev.yaml`): ```values-dev.yaml image: repository: my-repo tag: dev env: - name: SPRING_PROFILES_ACTIVE value: "dev" ``` **Additional Notes**: - Validate all environment variable names in Kubernetes deployment manifests against Java property names (e.g., `SPRING_CLOUD_GAMMA_ENABLED`). - Use `kubectl describe pod ` to check environment variables and pod logs (`kubectl logs `) for configuration errors. - Test gateway routes with `curl -X GET http://localhost:8080/gateway/routes` before deployment.