Flagger is a progressive delivery tool that automates the release process for applications deployed on Kubernetes. It uses a service mesh interface to manage traffic routing and canary deployments, ensuring that new versions of an application are gradually rolled out and thoroughly tested before they become the primary version.
This article will delve into the intricacies of Flagger, containerization, and orchestration, providing a comprehensive understanding of these concepts and their interplay. We will explore the history, use cases, and specific examples to provide a holistic view of these critical components in modern software development.
Definition of Key Terms
Before we delve into the specifics of Flagger, it is crucial to understand the key terms associated with it. These terms include containerization, orchestration, service mesh, and progressive delivery.
Containerization is a lightweight alternative to full machine virtualization that involves encapsulating an application in a container with its own operating environment. This provides many of the benefits of loading an application onto a virtual machine, as the application can be run on any suitable physical machine without any worries about dependencies.
Orchestration
Orchestration in the context of computing refers to the automated configuration, coordination, and management of computer systems, applications, and services. Orchestration helps in managing complex systems and services efficiently and delivers faster and more reliable services.
In the context of containerization, orchestration involves coordinating and managing the lifecycle of containers in large, dynamic environments. Kubernetes is a popular tool for container orchestration.
Service Mesh
A service mesh is a dedicated infrastructure layer for facilitating service-to-service communication in a microservices architecture. It's responsible for the reliable delivery of requests through the complex topology of services that comprise a modern, cloud-native application.
In a service mesh, each service instance is paired with an instance of a reverse proxy server, known as a sidecar. The sidecar manages inter-service communications, monitoring, and security-related concerns—anything that can be abstracted away from the individual services.
History of Flagger
Flagger was developed by Weaveworks, a company known for creating tools that help developers and DevOps teams build and operate powerful containerized applications. It was designed to automate the promotion of canary deployments in Kubernetes using a service mesh, thereby reducing the risk of app downtime.
Flagger was built to leverage the power of service mesh technology to provide advanced deployment strategies such as canary releases, A/B testing, and blue-green deployments. Since its inception, Flagger has become a popular tool for progressive delivery in a Kubernetes environment.
Integration with Service Mesh
Flagger was designed to work seamlessly with service mesh technology. It supports several service mesh providers, including Istio, Linkerd, and App Mesh. This integration allows Flagger to control the traffic routing for canary deployments, gradually shifting traffic to the new version of the application.
By integrating with a service mesh, Flagger can also leverage the observability features of the service mesh. It can monitor the metrics of the new version of the application, automatically rolling back the deployment if it detects anomalies.
Use Cases of Flagger
Flagger is primarily used to automate the process of gradually releasing new versions of an application in a Kubernetes environment. It automates the steps of a canary deployment, reducing the risk of introducing a new version of an application.
Another use case for Flagger is in A/B testing. Flagger can route a subset of users to a new version of an application, allowing developers to test how the new version performs with a live audience. If the new version performs well, Flagger can gradually increase the number of users routed to the new version.
Automated Rollbacks
One of the key features of Flagger is its ability to automatically roll back a deployment if it detects problems. Flagger monitors the metrics of the new version of the application and if it detects anomalies, it can automatically reroute traffic back to the old version, preventing users from experiencing the problematic version.
This feature is particularly useful in a continuous delivery environment, where new versions of an application are frequently deployed. It reduces the risk of a bad deployment causing downtime or a poor user experience.
Examples of Flagger in Action
Flagger has been used in a variety of real-world scenarios to automate the release process and reduce the risk of app downtime. For instance, a company might use Flagger to automate the rollout of a new version of their web application.
In this scenario, the company would deploy the new version of the application alongside the old version. Flagger would gradually shift traffic to the new version, monitoring the application metrics to ensure that the new version is performing as expected. If Flagger detects any problems, it would automatically shift traffic back to the old version, preventing users from experiencing the problematic new version.
Flagger in a Microservices Architecture
Flagger is particularly useful in a microservices architecture, where an application is made up of many small, independent services. In this scenario, Flagger can be used to manage the deployment of each service, ensuring that new versions are gradually rolled out and thoroughly tested before they become the primary version.
By automating the release process, Flagger can help to reduce the risk of a problematic service causing issues for the entire application. It can also help to ensure that each service is able to handle the load of traffic before it becomes the primary version.
Conclusion
Flagger is a powerful tool for automating the release process in a Kubernetes environment. By leveraging the power of a service mesh, Flagger can manage traffic routing for canary deployments, gradually rolling out new versions of an application and monitoring their performance.
Whether you're deploying a monolithic application or a complex microservices architecture, Flagger can help to reduce the risk of app downtime and ensure that your new versions are thoroughly tested before they become the primary version. With its support for automated rollbacks and A/B testing, Flagger is a valuable tool for any team deploying applications on Kubernetes.