What are Kubernetes Workloads?
A Kubernetes workload is an application that runs on Kubernetes. A workload can be composed of a single component or multiple components working together, but it must run within a set of pods. In Kubernetes, each pod has a defined lifecycle, and it represents a collection of running containers.
Managing each pod individually can be time-consuming and inefficient. To simplify this process, Kubernetes makes it possible to employ workload resources to manage a set of pods. Workload resources use controllers to match the number and type of running pods with a specified state.
In this article:
Kubernetes Workload Basic Concepts
When you run workloads on Kubernetes, you will use several Kubernetes mechanisms. Here are the most important ones.
A pod is the smallest and simplest unit in the Kubernetes object model. It represents a single instance of a running process in your application and can contain one or more containers.
A ReplicaSet ensures that a specified number of pods are running at any given time. It acts as a self-healing mechanism, automatically replacing failed or deleted pods. ReplicaSets provide basic scaling and availability features.
Deployments are higher-level abstractions over ReplicaSets and provide more advanced features for managing and updating your applications. They provide declarative updates for pods and ReplicaSets and allow for easy rollback in case of failures. Deployments also allow you to perform rolling updates and rollbacks, which means you can update your application without any downtime.
DaemonSets ensure that a single instance of a pod runs on every node in a cluster. They are useful for running system-level services such as logging, monitoring, and backups. For other use cases, you will likely use Deployments.
StatefulSets provide guarantees around the ordering and unique identity of pods in a set. They are used to manage stateful applications such as databases, where each pod in a set must have a unique identity and persistent storage. StatefulSets are a better option than Deployments for managing workloads with databases like MySQL, MongoDB, Cassandra, Etcd, or PostgreSQL.
Jobs are used to run a finite number of pods to completion, for example, to run a batch process or performing a one-time task. Jobs ensure that a specified number of pods run to completion, and clean up after themselves. Jobs can run multiple pods in parallel, allowing you to distribute the workload and process data faster.
CronJobs allow you to run a Job on a schedule, such as running a Job every hour. They provide a way to run Jobs at specific times or on a recurring schedule.
How Kubernetes Workloads Work
When you create a workload in Kubernetes, it has a desired state, such as the number of replicas of a pod that should be running. Based on the workload configurations, such as a Deployment or a StatefulSet, Kuberenets monitors the current state of the cluster and compares it to the desired state. If the current state does not match the desired state, the controller takes action to bring the cluster into compliance.
Kubernetes also handles other operations such as scaling, rolling updates, and self-healing. For example, when a Deployment is scaled up, the controller creates new replicas and updates the desired state. When a rolling update is performed, the controller updates the desired state of the pods in a gradual way and ensures that the application continues to be available during the update.
Securing Kubernetes Workloads
Workload security management refers to the process of ensuring the security and integrity of applications running in a Kubernetes cluster. It involves implementing security controls and monitoring to prevent unauthorized access, data breaches, and other security incidents. System admins must have access to monitoring, logging, and network management tools to manage containers and clusters.
The Build, Deploy, Run Approach
This is a common method for managing changes in Kubernetes clusters, which consists of the following steps:
- Build: Compile the code and build the containers that make up the application.
- Deploy: Deploy the containers to a testing environment for testing and validation.
- Run: After the application has been validated, deploy it to the production environment.
This approach allows for changes to be thoroughly tested before being deployed to production, reducing the risk of introducing bugs or security vulnerabilities into the production environment.
Using a GitOps development method, where changes are made to the source code and automatically applied through a CI/CD pipeline, provides a secure and auditable way to manage changes to the cluster. The advantage of this approach is that it creates a unified work environment to keep everyone in sync.
Kubernetes Security Tools
A security tool designed specifically for Kubernetes environments can provide security capabilities for various aspects of the Kubernetes cluster, including network security, runtime security, secret management, and compliance management. Some examples of Kubernetes-specific security solutions include:
- Network policies: Kubernetes network policies allow administrators to specify the communication rules between pods, providing a way to secure the network communication in the cluster.
- Runtime security: Kubernetes runtime security solutions such as Falco or Aqua Security provide real-time monitoring and enforcement of security policies, such as detecting and preventing container breakouts.
- Secret management: Kubernetes secret management solutions such as Hashicorp Vault or Jetstack’s cert-manager provide a secure way to manage secrets, such as passwords, certificates, and other sensitive information.
Compliance management: Kubernetes compliance management solutions such as Open Policy Agent (OPA) or Anchore provide a way to automate policy enforcement, ensuring that the cluster and its workloads are in compliance with regulations, standards, and best practices.