Manager nodes – dispatch units of work called tasks to worker nodes.You can run one or more nodes on a single physical computer or cloud server, but production swarm deployments typically include Docker nodes distributed across multiple machines. Nodes – a swarm node is an individual Docker Engine participating in the swarm.When you create a service, you specify which container image to use and which commands to execute inside running containers. Service – a service is the definition of the tasks to execute on the manager or worker nodes.It can only run on the assigned node or fail. Once a task is assigned to a node, it cannot move to another node. A task carries a Docker container and the commands to run inside the container. Task – the swarm manager distributes a specific number of tasks among the nodes, based on the service scale you specify.Swarm – a swarm consists of multiple Docker hosts which run in swarm mode and act as managers and workers.Swarm's capabilities include coordination between containers, allocating tasks to groups of containers, health checks and lifecycle management of containers, redundancy and failover, scaling containers up and down based on load, and rolling updates. Others say that Swarm will continue to be relevant, as a simpler orchestration tool which is suitable for organizations with smaller container workloads. Some believe that with support for Kubernetes, Docker Swarm will become obsolete.
Note #2: As of the time of this writing in late 2017, Docker announced it will support both Swarm and Kubernetes as orchestration engines. Kubernetes or Docker Swarm work together with the Docker Container Engine - the former manage and orchestrate containers, and the Docker Engine runs the containers themselves. It is not accurate to compare Kubernetes to "docker", the Docker Container Engine, because they have different functions. Note #1: When people compare Kubernetes to Docker, they typically mean to compare it to Docker Swarm, the container orchestration engine offered within the Docker platform. You can use the Docker CLI to create a swarm, deploy application services to a swarm, and manage swarm behavior.
DOCKER SWARM VS KUBERNETES VS RANCHER UPDATE
Labels: Key-value pairs that can be used to find multiple objects within the Kubernetes cluster and update them in bulk.ĭocker swarm mode allows you to manage a cluster of Docker Engines, natively within the Docker platform.Services are the external point of contact for container workloads, accessible via an internal DNS server. A service round-robins requests between pods. Services: Endpoints that can be connected to pods using label selectors.Kubernetes supports service deployments, which enable scaling across multiple nodes. Deployments: Used to create and manage a group of pods.All the containers in a single pod run on the same node, and share resources on the physical host. Pods: Kubernetes deploys and schedules containers in groups called pods.Kubelet: Receives pod specifications from the API Server and manages running pods.Scheduler: This component places the workload on the appropriate node – in this case all workloads will be placed locally on your host.Controller Manager: Scales workloads up and down to ensure the cluster reaches its desired state.API Server: The management hub for the Kubernetes master node, allowing communication between other components.etcd: Stores configuration data, for access by the Kubernetes Master’s API Server.In Kubernetes, the master node places container workloads in user pods, on worker nodes or on the master node itself.Īdditional Kubernetes components include: The diagram below shows the Kubernetes architecture. Typically Kubernetes deployments use Docker as the underlying container engine, but can also be used with other container engines such as rkt.
It is a system that helps you manage containers. It's important to understand that unlike the popular Docker Engine, Kubernetes is not a container engine. Kubernetes was built by Google based on their experience running massive amount of containers in production. Kubernetes is a container orchestration system, which can be used to manage large numbers of containers on top of physical infrastructure.