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 Labs • Coming from Madrid 🇪🇸 • Developer since 2001 (Java ☕ stack) • Micronaut core developer since its inception (2017). • Author: Maven Plugin, Object Storage, Kubernetes, Cache. • Others: Core, Gradle, AWS, GCP, Azure, Security, Test, etc. • Currently at Oracle Labs: • Micronaut and Graal Cloud Native (GCN). • GraalVM Native Build Tools. • Speaker at conferences: Devoxx, GeeCON, JavaLand, JavaZone, jPrime, Codemotion, Commit Conf, etc. 🇪🇸 🇩🇪 🇮🇹 🇬🇧 🇺🇸 🇨🇿 🇵🇱 🇩🇰 🇧🇪 🇳🇴 🇷🇴 🇫🇷 🇱🇺 🇲🇦 🇷🇸 🇨🇭 🇧🇬 @alvaro_sanchez
3. #PleaseDon’tGo Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 3
4. https://github.com/alvarosanchez/micronaut-kubernetes-demo Demo code available on GitHub Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 4
5. Copyright © 2022, 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 © 2022, 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 Java Framework Micronaut has been designed from scratch in 2017, focused on modern architectures like microservices and serverless, and with the cloud in mind. It is completely OSS with an Apache 2 license.
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 © 2022, Oracle and/or its affiliates 7
8. 8 Any language, build tool, test framework, reactive library, cloud, … Copyright © 2022, Oracle and/or its affiliates
9. History Copyright © 2022, Oracle and/or its affiliates 9 2020 Q1 Q2 Q3 Q4 2.0 January 2020 2021 Q1 Q2 Q3 Q4 2022 Q1 Q2 Q3 Q4 2023 Q1 Q2 Q3 Q4 3.9.2 May 2023 3.0 August 2021 4.0 Q2 2023*
10. Micronaut features 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 Bean Validation API compliance. 4. AOP: Aspect-Oriented Programming. • Compile-time, reflection free. 10 Copyright © 2022, Oracle and/or its affiliates
11. Micronaut features: HTTP Server 11 Copyright © 2022, Oracle and/or its affiliates
12. Micronaut features: HTTP Client 12 Copyright © 2022, Oracle and/or its affiliates Implemented at compile time
13. Micronaut features: message-driven applications Kafka • Producers. • Consumers. • Kafka Streams. RabbitMQ • Producers. • Consumers. • RPC. MQTT • Publishers. • Subscribers. NATS • Producers. • Consumers. Copyright © 2022, Oracle and/or its affiliates 13
14. Micronaut features: data access 14 Copyright © 2022, Oracle and/or its affiliates
15. Micronaut features: data access 15 Copyright © 2022, 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
16. 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. 16 Copyright © 2022, Oracle and/or its affiliates
17. 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. 17 Copyright © 2022, Oracle and/or its affiliates
18. Getting Started: Micronaut Launch 18 Copyright © 2022, Oracle and/or its affiliates https:!//launch.micronaut.io
19. Getting Started: Micronaut CLI 19 Copyright © 2022, Oracle and/or its affiliates
20. Getting started: Intellij IDEA 20 Copyright © 2022, Oracle and/or its affiliates
21. Getting started: Visual Studio Code 21 Copyright © 2022, Oracle and/or its affiliates
22. Micronaut 4 sneak peak 1. Java 17 required. • Virtual threads support (Project Loom). • New HTTP 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. Micronaut Data v4 • Hibernate 6. 22 Copyright © 2022, Oracle and/or its affiliates
23. Micronaut 4 sneak peak 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. 4. Other features: • HTTP client/server filter methods: annotation-based and without reactive APIs. • Annotation-based CORS configuration. • HTTP/3 support. • Use of GraalVM metadata repository. • Prefer Micronaut Serialization over Jackson. • Disabled cloud environment deduction by default. 23 Copyright © 2022, Oracle and/or its affiliates
24. Micronaut 4 sneak peak 5. Compile-time expression language 24 Copyright © 2022, Oracle and/or its affiliates Checked at compile time Checked at compile time
25. Micronaut 4 sneak peak 5. Compile-time expression language 25 Copyright © 2022, Oracle and/or its affiliates
26. Micronaut 4 Control Panel 26 Copyright © 2022, Oracle and/or its affiliates
27. Copyright © 2022, Oracle and/or its affiliates 27 Kubernetes Support in Micronaut
28. Service discovery: without Micronaut support 28 Copyright © 2022, Oracle and/or its affiliates
29. Service discovery: with Micronaut support 29 Copyright © 2022, Oracle and/or its affiliates
30. 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. 30 Copyright © 2022, Oracle and/or its affiliates
31. Distributed configuration 31 Copyright © 2022, Oracle and/or its affiliates
32. 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). 32 Copyright © 2022, Oracle and/or its affiliates
33. Health checks 33 Copyright © 2022, 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.
34. Kubernetes Java Client 34 Copyright © 2022, Oracle and/or its affiliates io.kubernetes.client.openapi.apis.CoreV1Api dependency injected
35. 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. 35 Copyright © 2022, Oracle and/or its affiliates
36. 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). 36 Copyright © 2022, Oracle and/or its affiliates
37. Kubernetes Operator support: informers 37 Copyright © 2022, Oracle and/or its affiliates
38. Kubernetes Operator support: reconcilers 38 Copyright © 2022, Oracle and/or its affiliates
39. Copyright © 2022, Oracle and/or its affiliates 39
40. What is GraalVM 40 Copyright © 2022, Oracle and/or its affiliates
41. Native Image Goals Low Resource Usage Start Fast Compact Packaging Minimize Vulnerability Copyright © 2023, Oracle and/or its affiliates 41
42. Micronaut and GraalVM 6ms As low as startup time 18MB Consuming memory footprint >30% Increased throughput up to and reduced latency
43. 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 Extenstion Pack for Visual Studio Code. 43 Copyright © 2022, Oracle and/or its affiliates
44. Micronaut and GraalVM powering Disney+ 44 Copyright © 2022, Oracle and/or its affiliates https://aws.amazon.com/blogs/opensource/improving-developer-productivity-at-disney-with-serverless-and-open-source/
45. Micronaut and GraalVM powering Disney+ 45 Copyright © 2022, Oracle and/or its affiliates
46. Copyright © 2022, Oracle and/or its affiliates 46 Demo Kubernetes operator in Java
47. 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. 47 Copyright © 2022, Oracle and/or its affiliates
48. ABCDB Operator Deployed in the cluster, reconciles the state of the kind: AbcDb resources. 48 Copyright © 2022, Oracle and/or its affiliates
49. Copyright © 2023, Oracle and/or its affiliates 49 Q &A
50. Álvaro Sánchez-Mariscal @alvaro_sanchez