Winning the Lottery with Spring: A Microservices Case Study for the Dutch Lotteries



Joris Kuipers as CTO, Trifork






English 🇺🇸





  • ✅ Great use-case talk, especially about technology and know-how of using custom Spring Boot autoconfiguration and replacing Spring Netflix.

  • ⛔ Lack of time for a more detailed API gateway description and circuit breaker solution.

"Microservices architecture built using state-of-the-art Spring Boot and Cloud components."

Case study

A case study of the integration platform developed for the Dutch Lotteries

Architecture: Separate domains (verticals - specific games, subscriptions, players…​) and service types (horizontals).

Project Setup: Every service is Spring Boot or Cloud app running on AWS EKS as AWS proprietary Docker orchestrator (K8S) using blocking HTTP for inter-service communication (started at the end of 2017, but too early for reactive programming as Spring was starting too, even though it would have been a good fit since asynchronous non-blocking is the bread and butter of building gateways and integrated solutions).

Currently around 30 services ad a bunch of libraries are inside a single GIT repository with a single Gradle build that produces all the actual Docker images because it is easy to build shared libraries used by a variety of services so no artifactory is needed.

  • libs module contains only Java libraries (not Dockerized services): accoung-status-store-client, auto-parameter-store-config, common-error-handling, common-potcodeservice-client, encryption, experience-web-shared, gateway-logging, gateway-monitoring, gateway-specification, gateway-testing, gateway-utils, http-client-autoconfiguer, open-api-specifications, sqs, etc…​

  • inlane, marketing, players (sample submodules: player-experience, player-experience-spec, player-igaming, player-process, player-specs, player-system, player-system-client, etc…​).

Autoconfiguration for the people

Spring Boot autoconfiguration is the main and most visible feature used extensively within the framework but not restricted to Spring Boot itself.

Although it seems like a black box or magic it is nothing more than conditional configuration classes providing beans that may or may not be initiated at startup based on certain conditions (classpath presence, something defined…​), automatically applied and listed in META-INF/spring.factories.

Custom autoconfiguration benefits in encapsulation and dynamic configuration (conditions, overridable defaults) and making components auto-configurable with default properties enable configuration options discovery (@ConfigurationProperties allows IDE auto-completion).

Key concepts: @Configuration, @PropertySource(value=""), @Import(HttpConnectionPoolHealthIndicaor.class), @ConfigurationProperties("http.client" on the properties POJO class, and @Bean definitions including @Primary, @ConfitionalOnMissingBean and @Order.

Examples: Custom JSON marshaling configuration, error handling (involves JSON response parsing), authentication (OAuth bearer token, basic auth), etc…​

Observability for messaging

  • Distributed Tracking is allowed by Spring Sleuth that propagates correlation ID per logical request called Trace ID and is instrumented by many Spring components out of the box.

    • Spring Cloud AWS for SQS integration (point-to-point solution - templates for sending, listener container for receiving) + Sleuth integration for message headers = To correlate asynchronous logging as a port of regular flow and provide Admin tool to link error logs for dead-lettered messages.

Spring Cloud Netflix

Part of the start of Spring Cloud allowed Netflix OSS stack to be used with Spring Boot (Eureka, Zuul, Ribbon, Hystrix…​), but Netflix has stopped maintenance, and Spring support announced to stop as well providing alternatives.

Experience APIProcess APISystem API - sometimes the Process API needed to do actual work and sometimes, however, just proxy through so they wanted to have an automatic way of doing that proxy which is what Zuul did.

With replacing deprecating Zuul they were forced to call Experience APISystem API directly in some cases, but they needed something to proxy 3rd party libraries, so they used Spring Cloud Gateway MVC (not Spring Cloud Gateway) which is a simple RestTemplate wrapper (`ProxyExchange passed to controller method allows for adding headers & query params, changing path and making the actual request) with Spring MVC integration for building proxies supporting reactive as well.