Carvel Tools: Simplifying Kubernetes Application Deployment

Before Carvel, developers often struggled with managing the complexities of building, configuring, and deploying applications on Kubernetes using a variety of tools and scripts. This process was challenging due to conflicting configurations, manual integration efforts, and the overhead of tracking changes across multiple tools. Then Carvel entered the scene.

What is Carvel?

Carvel provides a set of reliable, single-purpose, composable tools that aid in application building, configuration, and deployment to Kubernetes.

In simpler terms, Carvel is an open-source tool that simplifies the deployment process by offering a cohesive suite of tools that work well together, following consistent principles. Carvel streamlines the development workflow, reduces complexity, and enhances the overall developer experience, ultimately reducing the challenges developers face when developing applications for the cloud.

History of Carvel

In boat building, the "carvel" technique involves placing hull planks next to each other without overlapping, creating a smooth and strong frame for the boat. This analogy extends to the software world, particularly in the realm of Carvel tools. Just like the seamless planks in boat building, Carvel tools work harmoniously together without unnecessary complexity.

The inception of Carvel came about when Dmitriy Kalinin and Nima Kaviani, dissatisfied with existing Kubernetes application deployment tools, decided to create a better solution. They found the existing tools to be cumbersome, error-prone, and challenging to rectify when issues arose. Carvel offers a different approach by consolidating common application settings into a central library, making them easily accessible for all applications.

Following the UNIX philosophy, each Carvel tool is designed to excel at one specific task, ensuring they work cohesively together. Developers have the flexibility to use individual tools or the entire suite, tailoring Carvel to their Kubernetes setup for optimal performance.

Initially owned by VMware/Broadcom, Carvel is now a Cloud Native Computing Foundation (CNCF) sandbox open-source software project.

Carvel Tools:

Within the Carvel suite, there are seven tools, including five command-line tools (CLI) and two controllers, each addressing specific challenges in the Kubernetes application development process. Let's delve into each tool:

1. YTT (YAML Templating Tool)
   Before the advent of YTT (YAML Templating Tool), managing complex configurations across multiple environments and Kubernetes objects was a daunting task. Imagine you are having three clusters for development and production, each with five components and three environments that's 50 objects in total! Writing and managing 15,000 lines of YAML code manually for each configuration was complex and error-prone. YTT was developed to simplify this process and bring magic to Kubernetes setups.

   YTT is a YAML-native programming language that transforms YAML into a powerful templating tool with built-in conditions like loops and overlays. Every YTT program is a valid YAML file, where templating logic is embedded within comments. These comments serve as programming constructs, enabling developers to add dynamic logic directly into YAML configurations. For instance, you can annotate YAML with conditional logic like "// if the data value is Google Cloud, then apply this configuration." These annotations empower developers to switch configurations seamlessly based on different environments, making YAML files more dynamic and adaptable.

   YTT revolutionizes YAML templating, turning it into a versatile tool for orchestrating deployments effortlessly. With YTT, complex configurations become manageable, and deployments become a breeze.

2. kbld:-
   Before the introduction of kbld by Carvel, developers faced significant toil when updating applications. Making even small changes required rebuilding container images, updating configurations in multiple places, and pushing the changes to registries, which was cumbersome and time-consuming kbld is a tool designed to simplify this process by updating Kubernetes manifests more efficiently, specifically targeting image tag updates using SHA digests. Here's how kbld works:

   1. Building Container Images: kbld integrates with your preferred build tool to generate container images directly from your source code specified in the configuration file.

   2. Pushing Images to Repository: After building the container image, kbld automatically pushes it to the designated image repository.

   3. Resolving and Updating Image Tags: Using resolve tags, kbld updates images in the configuration file based on their SHA digests.

With kbld, developers can streamline the process of updating Kubernetes manifests, reducing the manual effort required for rebuilding and pushing container images when making changes to applications. This tool simplifies the workflow, making it easier for developers to manage and deploy updates efficiently.

3. kapp :-
   Before the kapp tool, developers often struggled with understanding the status of Kubernetes resources and ensuring they were in the desired state. Managing relationships between different Kubernetes resources and applying them in the correct order was also challenging.

   kapp addresses these issues by providing a powerful deployment tool that simplifies Kubernetes resource management. kapp Often referred to as "kubectl on steroids," kapp accepts YAML manifests and deploys them to Kubernetes, ensuring resources are deployed in the correct order. It groups related resources, such as deployments, services, configs, and secrets, allowing you to manage or access them as a single unit.
   One unique aspect of kapp is its concept of "applications" in Kubernetes. While Kubernetes lacks a built-in application concept, kapp allows you to define and manage applications by mapping the deployed resources. Using kapp ls, you can list all resources associated with an application. Additionally, kapp provides real-time updates and status information for resources, making it easier to monitor and manage deployments effectively.

4. imgpkg:-
   Before the imgpkg tool from Carvel, developers encountered significant challenges in effectively managing container images and their dependencies throughout the development lifecycle. The absence of a dedicated image packaging tool led to difficulties in versioning, sharing, and tracking changes across various environments, resulting in deployment inconsistencies and errors.
   With imgpkg, developers can bundle all necessary artifacts into a single cohesive package.

   This tool combines YAML manifests with referenced images into an OCI-compliant package, allowing for easy transfer of the entire application manifest from one environment to another. imgpkg simplifies the process of packaging, sharing, and deploying containerized applications, ensuring consistency and reliability across development, testing, and production environments.

5. vendir :-

   The vendir tool is designed to address the challenge of managing and packaging complex applications that consist of multiple components and dependencies. Specifically, it helps solve the problem of capturing and versioning dependencies for Kubernetes applications, which can be composed of various resources like Helm charts, Kubernetes manifests, Docker images, and more.
   Vendir is a versatile tool designed to streamline dependency management for Kubernetes applications. By defining dependencies declaratively in YAML files, developers can specify exactly what resources to pull and from where, including Git repositories, Docker registries, or other sources. The vendir sync command then simplifies the process of pulling down these resources onto a local machine, ensuring configuration and dependencies are captured in a reproducible and consistent manner. Vendir offers a unified API for managing dependencies, making it straightforward to integrate into Kubernetes workflows and enabling developers to achieve declarative and reproducible dependency management for their applications.

6. Kapp-controller: A GitOps Tool and Package Management Tool for Kubernetes

Kapp-controller is a powerful tool within the Carvel suite designed to simplify application deployment and management on Kubernetes, leveraging GitOps principles and effective package management.

Key Concepts:

1. App CR (Custom Resource):

   • Definition: Application resources that encapsulate GitOps concepts.

   • Where to Fetch: Fetch resources from any location.

   • Template/Patch: Utilize Carvel's YAML templating tool, ytt, along with kbld, Helm templates, and CUE language for defining resources.

2. GitOps:

   • Custom Resources: Define and manage custom resources for GitOps workflows.

Deployment and Security:

• Deploying Applications:

  • Use Kapp for deploying applications to specific clusters.

• App Security:

  • Define service accounts within resources to assign identity and permissions for application deployment.

  • Utilize SOPS for encrypting secrets stored within YAML manifests, ensuring secure deployment practices.

Package Management:

• Package Management:

  • Leverage package management capabilities to encapsulate applications into deployable units.

  • Packages wrap applications, allowing for easy distribution and deployment.

kapp-controller empowers developers to adopt GitOps practices seamlessly within Kubernetes environments. By combining structured application resource definitions with robust security measures and efficient package management, kapp-controller streamlines the deployment and management of Kubernetes applications while enhancing security and reliability. With Carvel's suite of tools, developers can embrace modern deployment practices and simplify complex Kubernetes workflows with ease.

In conclusion, Carvel revolutionizes Kubernetes application development by offering a seamless toolkit that simplifies building, configuring, and deploying applications. Its focus on simplicity, flexibility, and integration enhances the developer experience, reduces complexities, and ensures consistency across environments, ultimately improving productivity in the cloud-native ecosystem.