concept Argo CD in category kubernetes
This is an excerpt from Manning's book GitOps and Kuberentes MEAP V06 epub.
The book was organized to read all the chapters in sequential order. However, if there is a particular area of interest you’d like to jump into, we recommend you read the prerequisite chapters, as indicated in Figure 1.1. For example, if you would like to jump right into learning to use Argo CD, we recommend you read chapters 1, 2, 3, and 5 before reading chapter 9.
Argo CD is an open-source GitOps operator for Kubernetes[1]. The project is a part of the Argo family - a set of cloud-native tools for running and managing jobs and applications on Kubernetes. Along with Argo Workflows, Rollouts, and Events, Argo CD focuses on application delivery use cases and makes it easier to combine three modes of computing: services, workflows, and event-based processing.
The company behind Argo CD is Intuit - the creator of TurboTax and QuickBooks. In early 2018 Intuit decided to adopt Kubernetes to speed up cloud migration. At the time, the market already had several successful continuous deployment tools for Kubernetes, but none of them fully satisfied Intuit’s needs. So instead of adopting an existing solution, the company decided to invest in a new project and started working on Argo CD. So what is so special about Intuit's requirements? The answer to that question explains how Argo CD is different from other Kubernetes CD tools and explains the main project use cases.
The manifest generation in Argo CD is implemented by the “argocd-repo-server” component. This phase presents a whole set of challenges.
The manifests generation requires to download Git repository content and produce ready to use manifests YAML. First of all, it is too time-consuming to download the whole repository content every time when you need to retrieve expected resource manifests. Argo CD solves it by caching the repository content on local disk and using git fetch command to download only recent changes from the remote Git repository. The next challenge is related to memory usage. In real life, resources manifest are rarely stored as plain YAML files. In most cases, developers prefer to use a config management tool such as Helm or Kustomize. Every tool invocation causes a spike in memory usage. To handle the memory usage issues, Argo CD allows the user to limit the number of parallel manifest generations and scale up the number of “argocd-repo-server” instances to improve performance.
