About Jsonnet
What you'll learnUnderstand the benefits of using JsonnetLearn about all Jsonnet featuresStructure you Jsonnet code for flexibilityManage your jsonnet code and its dependencies in your source versioning systemUnderstand how Jsonnet is executedRequirementsProgramming experience is beneficialUnderstand how Jsonnet works, and be productive writing Jsonnet code. Based on real worl experience.Jsonnet is a programming language used to generate JSON and YAML content efficiently and with flexibility. JSON and YAML configuration formats are used pervasilvely. From docker-compose to Hashicorp tools like Vagrant and Terraform. Jsonnet is a tool of interest for anyone needing to generate JSON or YAML configuration. As such it is no surprise to see it is used by some tools helping to manage complex Kubernetes configurations.This training helps you get productive rapidly with the Jsonnet language. It covers from the basics to the advanced techniques:Syntax and data types: The Jsonnet syntax is close to JSON. Actually a JSON document is a valid Jsonnet program! Discover the syntax along with the data types supported by Jsonnet.Understanding the Jsonnet execution: When you know the syntax, it is tume to understand how Jsonnet code is executed. From Jsonnet expressions to JSON manifestationJsonnet functions: Learn to define and use function to avoid repetitions and modularize your codeJsonnet objects: Discover the power of combining objects, and more importantly, understand how it works. Learn about inheritances, and how to augment an object’s existing valueComprehension: Master array and object comprehension, allowing you to transform arrays to other arrays and even objectsParameterised runs: See how you can pass parameters to a Jsonnet programLibraries: Organise your code by authoring and using libraries. Manage your project’s dependencies with the Jsonnet Bundler, the package manager. Get tips on how to manage your Jsonnet with your source code versioning system.Generate errors: Learn how to interrupt the Jsonnet execution earlyWho this course is
Key features of the Jsonnet that are enabled through these drivers include:
- Jsonnet Pro - IntelliJ IDEs Plugin
- jsonnet/doc/learning/tutorial.html at master
- Jsonnet Training Course - GitHub Pages
- Newest 'jsonnet' Questions - Stack Overflow
- CertainLach/jrsonnet: Rust implementation of Jsonnet
- Jsonnet - IntelliJ IDEs Plugin - Marketplace
- Fractal Application (2/3) - Jsonnet
Jsonnet best practices we've found: For large templates (>10 parameters), avoid directly overriding internal fields when subclassing. Rather, define explicit constructors for templates using Jsonnet functions, which helps with readability and encourages modularity. Check your Jsonnet configurations into source control. Add pre-commit tests to make sure all checked in templates compile. This avoids inadvertent breakages when common templates are updated. You can also create "unit tests" using Jsonnet assert expressions that assert invariants over template variables. Consider also checking in the Jsonnet materialized JSON / YAML to make changes more visible during code review. Because common Jsonnet templates may be imported by many files, changing one file can affect the output of many. Fortunately, unintended changes can be detected at compile time if the materialized YAML is also included with the Jsonnet changes. Refactor often -- there's no risk of breakage. Since Jsonnet templates compile to concrete JSON / YAML files, it's possible to check the before and after outputs to ensure the refactoring was correct (i.e. zero net materialized diff). Push as much configuration to Jsonnet as possible. It may be tempting to introduce logic into services based on some environment flag (e.g. dev vs prod). We've found this to be an anti-pattern -- such configuration should be determined at template compile time rather than at runtime. This principle of hermetic configuration helps prevent surprises when services are deployed to new environments.For more detailed recommendations, check out our newly posted Jsonnet style guide. We also want to welcome any comments or contributions there from the community.ConclusionIn this blog post, we've shared our experience at Databricks using Jsonnet to simplify infrastructure management. As a unifying templating language that enables composition across a broad range of infrastructure and services, Jsonnet brings us one step closer to a totally declarative infrastructure. We've found Jsonnet easy to use and flexible enough to serve as our primary configuration language, and suggest you try it too!If you found this topic interesting, watch out for future blog posts on the tooling we've built around Jsonnet and Kubernetes. We're also hiring for Cloud platform, infrastructure, and Databricks Serverless.
