Implementing Kubernetes operators in Java with Micronaut

Micronaut is a modern, JVM-based, full stack Java framework designed for building modular, easily testable JVM applications

Micronaut supports a wide range of technologies, one of which is Kubernetes, allowing application developers to write cloud-native applications that are to be deployed on a Kubernetes cluster, and can benefit from features such as distributed configuration and service discovery. One of the features of the Micronaut Kubernetes module is the built-in support for implementing Kubernetes operators.

In this talk, Micronaut committer and Micronaut Kubernetes author Álvaro Sánchez-Mariscal, will demonstrate how to implement Kubernetes operators in Java with Micronaut. There will be a demo that includes the following:

- An application written in Micronaut, whose purpose is being deployed with a Kubernetes operator itself.
- Another Micronaut application that contains the Kubernetes operator logic, and will create Kubernetes deployments of the above applications.
- A Kubernetes custom resource definition (CRD) that will be used to manage the deployment of the first application.

Transcript

1. Implementing Kubernetes operators in Java with the Micronaut® framework Álvaro Sánchez-Mariscal Principal Member of Technical Staff Oracle @alvaro_sanchez
2. Álvaro Sánchez-Mariscal Principal Member of Technical Staff, Oracle • Coming from Madrid • Developer since 2001 (Java stack) • Micronaut core developer since its inception (2017). • Author: Maven Plugin, Object Storage, Kubernetes, Cache, Control Panel. • Others: Core, Gradle, AWS, GCP, Azure, Security, Test, etc. • Currently at Oracle Labs: • Micronaut and Graal Development Kit for Micronaut (GDK). • GraalVM Native Build Tools. • Speaker at conferences: Devoxx, GeeCON, JavaLand, JavaZone, jPrime, Codemotion, Commit Conf, etc. @alvaro_sanchez
3. #PleaseDon’tGo Copyright © 2024, Oracle and/or its affiliates 3
4. Slides 4 Copyright © 2024, Oracle and/or its affiliates Demo
5. Copyright © 2024, Oracle and/or its affiliates. Micronaut® is a registered trademark of Object Computing, Inc. Use is for referential purposes and does not imply any endorsement or affiliation with any third-party product. 5
6. Introduction to Micronaut Copyright © 2024, Oracle and/or its affiliates 6 Micronaut is a complete solution for any type of application: microservices, message-driven producers or consumers, command-line apps, serverless functions, etc. All application types Micronaut leverages Java annotation processors and other optimisations to compute the framework infrastructure at compile-time, drastically reducing startup time and memory consumption. Highly optimised Modern, open-source Java Framework Micronaut has been designed from scratch in 2017, focused on modern architectures like microservices and serverless, and with the cloud in mind.
7. Micronaut computes at build time: • All dependency and configuration injection. • Annotation metadata (meta annotations) • AOP proxies. • Bean introspections. • All other framework infrastructure. At runtime: • No reflection. • No proxy generation. • No dynamic classloading. • No classpath scanning. AOT: Ahead Of Time Copyright © 2024, Oracle and/or its affiliates 7 Source code @Singleton class MySvc {} Bytecode class $MySvc$Definition {} class $MySvc$Definition$Reference {} Source code @Builder record Person() {} Source code @Generated class PersonBuilder() {} compilation compilation
8. 8 Any language, build tool, test framework, reactive library, cloud, … Copyright © 2024, Oracle and/or its affiliates
9. Micronaut Hello World 9 Copyright © 2024, Oracle and/or its affiliates
10. Micronaut features: HTTP Client 10 Copyright © 2024, Oracle and/or its affiliates Implemented at compile time
11. Micronaut features: message-driven applications Kafka • Producers. • Consumers. • Kafka Streams. RabbitMQ • Producers. • Consumers. • RPC. MQTT • Publishers. • Subscribers. NATS • Producers. • Consumers. Copyright © 2024, Oracle and/or its affiliates 11
12. Micronaut features: data access 12 Copyright © 2024, Oracle and/or its affiliates
13. Micronaut features: data access 13 Copyright © 2024, Oracle and/or its affiliates Interface implemented at compile time Query generated from the method name, compile-time validated Can have custom queries, inserts, etc
14. Micronaut features: security 1. Authentication providers. • Bult-in support for LDAP and OAuth 2.0 password grant flow. 2. Security rules. • Configuration or annotation-based. 3. Authorization strategies. • Basic auth, session, JWT (JWKS, JWS), X.509. 4. OAuth 2.0. • Authorization code, client credentials and password grants. • OpenID Connect. • Ease of integration with providers such as Okta, Auth0, AWS Cognito, Keycloak and more. 14 Copyright © 2024, Oracle and/or its affiliates
15. Micronaut features: Test Resources 1. Automatic provisioning of external resources needed during development or testing. • Containers, binaries, etc. 2. Built-in support: 3. Integrated with JUnit Platform (JUnit / Spock / Kotest) for zero-configuration Testcontainers. 15 Copyright © 2024, Oracle and/or its affiliates • MariaDB • MySQL • Oracle • PostgreSQL • SQL Server • Elasticsearch • Redis • MongoDB • Neo4j • Hashicorp Vault • Kafka • RabbitMQ • MQTT • Localstack
16. Micronaut features: Serialization 1. Drop-in replacement for Jackson Databind, compile-time and reflection free. 2. Supports (most of) Jackson, JSON-B and BSON annotations. 3. Why? • Memory performance: 10x smaller runtime footprint. • Security: serializable classes must be opt-in. • Type-safety: Micronaut Serialization performs checks at compile-time (vs Jackson runtime exceptions). • Runtime portability: Micronaut Serialization at runtime supports different annotation sets. 16 Copyright © 2024, Oracle and/or its affiliates
17. Micronaut features: misc 1. Dependency injection. • Can use JSR-330 (@Inject) or Spring (@Autowired) annotations. 2. Configuration. • Properties, YAML, TOML, Groovy, Config4K. 3. Validation support. • Built-in: reflection free, faster startup, smaller JAR, reduced memory. • Hibernate Validation: full Jakarta Validation API compliance. 4. AOP: Aspect-Oriented Programming. • Compile-time, reflection free. 17 Copyright © 2024, Oracle and/or its affiliates
18. Micronaut features: misc 1. Distributed Tracing. • Zipkin, Jaegger. 2. Service Discovery and Distributed Configuration. • Consul, Eureka, Kubernetes. 3. Monitoring. • Micrometer, JMX, Elasticsearch. 4. API development. • GraphQL, GRPC, Open API. 5. Containers. • Docker, Kubernetes, Testcontainers. 6. Cache. • Jcache, Redis, Ehcache, Hazelcast, Infinispan, Oracle Coherence. 7. Email. 8. Error handling. 18 Copyright © 2024, Oracle and/or its affiliates
19. Getting Started: Micronaut Guides 19 Copyright © 2024, Oracle and/or its affiliates https://guides.micronaut.io
20. Getting Started: Micronaut Launch 20 Copyright © 2024, Oracle and/or its affiliates https://launch.micronaut.io
21. Getting Started: Micronaut CLI 21 Copyright © 2024, Oracle and/or its affiliates
22. Getting Started: IntelliJ IDEA 22 Copyright © 2024, Oracle and/or its affiliates
23. Getting Started: Visual Studio Code 23 Copyright © 2024, Oracle and/or its affiliates
24. Micronaut 4: what’s new 1. Java 17 required. • Virtual threads support (Project Loom). • @Client implementation based on java.net.http.HttpClient (JEP 321) • For older versions of Java use Micronaut 3.x. • Other languages • Kotlin 1.8, KSP support. • Apache Groovy 4. 2. GraalVM improvements. • Reachability metadata enabled. • Improved build times and reduced memory consumption. 3. Micronaut Data v4 • Hibernate 6. 24 Copyright © 2024, Oracle and/or its affiliates
25. Micronaut 4: what’s new 3. Smaller, lighter runtime. • Performance closer to raw Netty (~200ms startup). • Some modules spun off core: Service Discovery, Retry, Session, Validation, Websocket. • Some dependencies now optional: Jackson, SnakeYAML, Caffeine. 4. Other features: • HTTP client/server filter methods: annotation-based and without reactive APIs. • Annotation-based CORS configuration. • HTTP/3 support. • Prefer Micronaut Serialization over Jackson. • Disabled cloud environment deduction by default. 25 Copyright © 2024, Oracle and/or its affiliates
26. Micronaut 4: what’s new 5. Compile-time expression language 26 Copyright © 2024, Oracle and/or its affiliates Checked at compile time Checked at compile time
27. Micronaut 4: what’s new 6. Bean mappers: built-in, type-safe alternative to MapStruct for type mapping built on EL. 27 Copyright © 2024, Oracle and/or its affiliates
28. Micronaut 4 Control Panel 28 Copyright © 2024, Oracle and/or its affiliates
29. Micronaut 4 coming soon: source generation 29 Copyright © 2024, Oracle and/or its affiliates Generates PersonBuilder at compile-time
30. Copyright © 2024, Oracle and/or its affiliates 30 Kubernetes Support in Micronaut
31. Service discovery: without Micronaut support 31 Copyright © 2024, Oracle and/or its affiliates
32. Service discovery: with Micronaut support 32 Copyright © 2024, Oracle and/or its affiliates
33. Service discovery 1. Allows Micronaut HTTP clients to discover Kubernetes services (kind: Service) 2. Micronaut will query the Kubernetes API to fetch the list of services and watch for changes. • By default, will search in the current namespace, but can be configured to look in different ones. • If the service is a Multi-port one, the client can be configured to use one specific port. • Available services can be filtered by using includes/excludes lists or labels. 3. Service discovery modes: • Endpoint (default): reads from kind: Endpoints objects to compute a list of instances that are load balanced by the Micronaut HTTP client. • Service: uses the ClusterIP from the service. Load balancing is handled by Kubernetes’ kube-proxy. 33 Copyright © 2024, Oracle and/or its affiliates
34. Distributed configuration 34 Copyright © 2024, Oracle and/or its affiliates
35. Distributed configuration 1. Reads Kubernetes kind: ConfigMap and kind: Secret, and makes them available as PropertySource’s 2. Micronaut will query the Kubernetes API to fetch the list of config maps / secrets, and watch for changes. • By default, will search in the current namespace, but can be configured to look in different ones. • Available objects can be filtered by using includes/excludes lists or labels. 3. Config maps / secrets can also be read from mounted volumes (no Kubernetes API). 35 Copyright © 2024, Oracle and/or its affiliates
36. Health checks 36 Copyright © 2024, Oracle and/or its affiliates 1. Probes communication with the Kubernetes API. 2. Provides some additional information about the pod where the application is running from. 3. Lists all the services discovered and their resolved URL endpoints.
37. Kubernetes Java Client 37 Copyright © 2024, Oracle and/or its affiliates io.kubernetes.client.openapi.apis.CoreV1Api dependency injected
38. Kubernetes Java Client 1. Allows you to use dependency injection to get a ready-to-use client object from the Official Kubernetes Java client library. 2. Supports multiple authentication options. It works out-of-the-box. Can be programmatically customised. 3. Micronaut implements reactive variants with Reactor or RxJava 2/3. 4. The underlying HTTP client can be programmatically customised if needed. 38 Copyright © 2024, Oracle and/or its affiliates
39. Kubernetes Operator support 1. Micronaut allows you to implement the following Kubernetes operators building blocks: • Informers. • Reconcilers. • Leader election. 2. Allows you to work with both core and custom resource definitions (CRD). 39 Copyright © 2024, Oracle and/or its affiliates
40. Kubernetes Operator support: informers 40 Copyright © 2024, Oracle and/or its affiliates
41. Kubernetes Operator support: reconcilers 41 Copyright © 2024, Oracle and/or its affiliates
42. Graal A full stack for the development and deployment of high performance Java cloud native applications
43. Copyright © 2024, Oracle and/or its affiliates 43
44. What is Graal Development Kit for Micronaut? Copyright © 2024, Oracle and/or its affiliates 44 BUILT FOR GRAALVM NATIVE IMAGE Easily compile ahead-of-time with GraalVM Native Image into small executables that start instantly, and use less memory/CPU. CLOUD-AGNOSTIC MODULES A curated set of Micronaut modules that provide platform-independent support for core cloud services – object store, secrets, streaming, and more. DEV TOOLS AND VS CODE EXTENSIONS Dev tools to generate multicloud application starter templates. VS Code extensions for local development and cloud deployment.
46. 46 Copyright © 2024, Oracle and/or its affiliates
47. 47 Copyright © 2024, Oracle and/or its affiliates
48. Copyright © 2024, Oracle and/or its affiliates 48
49. What is GraalVM 49 Copyright © 2024, Oracle and/or its affiliates
50. Native Image Goals Low Resource Usage Start Fast Compact Packaging Minimize Vulnerability Copyright © 2024, Oracle and/or its affiliates 50
51. Micronaut and GraalVM 6ms As low as startup time 18MB Consuming memory footprint >30% Increased throughput up to and reduced latency
52. Micronaut and GraalVM 1. The best integration possibly, supported by teams working together at Oracle Labs. • GraalVM EE includes optimisations for Micronaut for increased performance and throughput. • GraalVM EE license included in Oracle Cloud. 2. Micronaut is ready for GraalVM Native Image since day 1. • No reflection, no runtime proxies, no bytecode generation, no dynamic classloading. 3. GraalVM tooling for Visual Studio Code and Intellij IDEA. 52 Copyright © 2024, Oracle and/or its affiliates
53. GraalVM Reachability Metadata Repository Community-driven collection of GraalVM reachability metadata for open-source libraries. • Actively maintained by a collective effort of VMware, Oracle and others. • Enabled in GraalVM Native Build Tools (Maven and Gradle plugins). • Integrated by default in Spring Boot and Micronaut. 53 Copyright © 2024, Oracle and/or its affiliates
54. Micronaut is the fastest to startup 54 Copyright © 2024, Oracle and/or its affiliates Source: https://speakerdeck.com/mraible/comparing-native-java-rest-api-frameworks-jchampions-conference-2024
55. Micronaut is the fastest to startup 55 Copyright © 2024, Oracle and/or its affiliates Source: https://speakerdeck.com/mraible/comparing-native-java-rest-api-frameworks-jchampions-conference-2024
56. Micronaut consumes the less memory 56 Copyright © 2024, Oracle and/or its affiliates Source: https://speakerdeck.com/mraible/comparing-native-java-rest-api-frameworks-jchampions-conference-2024
57. Micronaut and GraalVM powering Disney+ 57 Copyright © 2024, Oracle and/or its affiliates https://aws.amazon.com/blogs/opensource/improving-developer-productivity-at-disney-with-serverless-and-open-source/
58. Copyright © 2024, Oracle and/or its affiliates 58 Demo Kubernetes operator in Java
59. ABCDB: A Better Cool DataBase 1. Simple Micronaut application that pretends being a database product. 2. We want our customers to install it with a Kubernetes operator. • Instances will be created with a Custom Resource Definition 3. Packaged as a native executable inside a Docker image. 4. Can read configuration from a ConfigMap, and has a @Refreshable endpoint. 59 Copyright © 2024, Oracle and/or its affiliates
60. ABCDB Operator Deployed in the cluster, reconciles the state of the kind: AbcDb resources. 60 Copyright © 2024, Oracle and/or its affiliates
61. Copyright © 2024, Oracle and/or its affiliates 61 Q &A
62. Álvaro Sánchez-Mariscal @alvaro_sanchez