How Microservices Run in Kubernetes and why this combination is so effective?
What Are Microservices?
Microservices are an approach to designing software systems as a collection of loosely coupled services. Each service is responsible for a specific functionality and can be developed, deployed, and scaled independently. This approach offers several benefits:
- Scalability: Services can be scaled independently based on demand.
- Dev Stack Flexibility: Different services can be written in different programming languages and use different technologies.
- Resilience: If one service fails, it doesn’t bring down the entire system.
Introduction to Kubernetes
Kubernetes is an open-source platform designed to automate the deployment, scaling, and operation of containerized applications. It provides a robust set of features for managing applications in a clustered environment, including:
- Pod Scheduling: Efficiently schedules containers based on resource requirements and constraints.
- Self-healing: Automatically restarts failed containers and replaces and reschedules containers on other nodes if a running node dies.
- Horizontal Pod Scaling: Automatically scales applications up and down based on CPU utilization or other metrics.
- Service discovery and load balancing: Automatically assigns IP addresses and a single DNS name for a set of containers and distributes traffic across them.
Running Microservices in Kubernetes
Running microservices in Kubernetes involves several key components and concepts:
1. Containers and Pods
Microservices are typically packaged as containers, which are lightweight, portable, and consistent environments for running applications. In Kubernetes, containers are encapsulated in Pods, the smallest deployable units. A Pod can contain one or more containers that share the same network namespace and storage.
2. Deployments
Deployments in Kubernetes manage the desired state of your application. They ensure that the specified number of replicas of your microservice are always running. If a container crashes, the Deployment controller will automatically replace it.
3. Services
Kubernetes Services provide a stable endpoint for accessing a set of Pods. They enable load balancing and service discovery, ensuring that traffic is evenly distributed across the available replicas of a microservice.
4. ConfigMaps and Secrets
ConfigMaps and Secrets are used to manage configuration data and sensitive information, respectively. They decouple configuration from the application code, making it easier to manage and update configurations without redeploying the application.
5. Ingress
Ingress resources in Kubernetes manage external access to the services within a cluster. They provide load balancing, SSL termination, and name-based virtual hosting, making it easier to expose microservices to the outside world.
Benefits of Running Microservices in Kubernetes
Combining microservices with Kubernetes, we can achieve several advantages:
- Improved Resource Utilization: Kubernetes efficiently schedules and manages resources, ensuring optimal utilization.
- Enhanced Resilience: Kubernetes’ self-healing capabilities ensure that microservices remain available even in the face of failures.
- Simplified Scaling: Kubernetes’ horizontal scaling features make it easy to scale microservices up or down based on demand.
- Deployment Strategies: Kubernetes offers several deployment strategies to manage and scale applications. We can achieve zero downtime with the implementation of deployment strategies. Here are some of the most common ones:
1. Rolling Update
This is the default deployment strategy in Kubernetes. Gradually replacing the old versions of the application replicas with new ones, ensuring that some pods of the old version are always running until the new version is fully deployed. Using rolling update strategy, we can bring applications downtime almost zero but not actually zero because the new version of replica pods might take some times to communicate with the other microservices
2. Canary Deployment
We can implement this model of deployment using ingress controller in Kubernetes. In this model of deployment, gradually rolls out the new version to a small subset of users before rolling it out to the entire infrastructure. We can fully control how many percentages of users will send to old version of replicas and how many percentages of users will send to newer versions. The Canary model of deployment is allowing us to perform tests on the production environment with real-time data. That’s why this model of deployment is very powerful.
3. Blue-Green Deployment
Runs two identical environments (blue and green). The new version is deployed to the blue environment, and once it’s verified, traffic is switched from the blue environment to the green one. This model of deployment is useful for minimizing downtime and ensuring a smooth transition.
Conclusion
Microservices and Kubernetes are a powerful combination for building and managing modern applications. By leveraging Kubernetes’ robust orchestration capabilities, developers can ensure that their microservices are scalable, resilient, and easy to manage.