DOCKER SWARM 1.12

By Tanmay Mehra

DOCKER RECAP…• Docker is an open platform for developing, shipping, and

running applications.

• The lightweight nature of containers, which run without the extra load of a hypervisor, means you can get more out of your hardware.

• Docker daemon, docker client, docker Host and docker registry.

• Docker images, containers, networks and volumes.

DOCKER SWARM 1.12 • Docker (starting from version 1.12) can run in two modes, classical

and swarm mode.

• A swarm is a cluster of Docker engines, or nodes, where you deploy services.

• Docker Swarm provides native clustering capabilities to turn a group of Docker engines into a single, virtual Docker Engine.

• The Docker Engine CLI and API include commands to manage swarm nodes (e.g., add or remove nodes), and deploy and orchestrate services across the swarm.

APPLICATION, SERVICES AND NETWORKS

• In the context of Docker and Docker Swarm, an application is made up of one to many services running on one to multiple of software defined networks (SDN).

• Each service can be “attached” to one or many networks. The communication between the services happens over a network.

• Lets see the logical and the physical architecture of the application running on docker swarm nodes.

APPLICATION, SERVICES AND NETWORKSLogical View

APPLICATION, SERVICES AND NETWORKS

Physical View

DOCKER SWARM COMPONENTS• NODES : A node is an instance of Docker Engine participating in a

swarm.

• There are two types of nodes : Manager node and Worker Node.

• To deploy your application to a swarm, you submit a service definition to a manager node. The manager node dispatches units of work called tasks to worker nodes.

• Manager nodes also perform the orchestration and cluster management functions required to maintain the desired state of the swarm.

• Worker nodes receive and execute tasks dispatched from manager nodes.

DOCKER SWARM COMPONENTS• SERVICE : A service is the definition of the tasks to execute on the

worker nodes. It is the central structure of the swarm system and the primary root of user interaction with the swarm.

• In the replicated services model, the swarm manager distributes a specific number of replica tasks among the nodes based upon the scale you set in the desired state.

• For global services, the swarm runs one task for the service on every available node in the cluster.

• TASK : A task carries a Docker container and the commands to run inside the container. It is the atomic scheduling unit of swarm.

DOCKER SWARM 1.12 FEATURES• LOAD BALANCING : The swarm manager uses ingress load

balancing to expose the services you want to make available externally to the swarm.

• The swarm manager can automatically assign the service a PublishedPort or you can configure a PublishedPort for the service.

• Swarm mode has an internal DNS component that automatically assigns each service in the swarm a DNS entry.

• The swarm manager uses internal load balancing to distribute requests among services within the cluster based upon the DNS name of the service.

DOCKER SWARM 1.12 FEATURES• HIGH SCALABILITY AND PERFORMANCE : Swarm is production

ready and tested to scale up to one thousand (1,000) nodes and fifty thousand (50,000) containers with no performance degradation in spinning up incremental containers onto the node cluster.

• FAILOVER AND HIGH AVAILABILITY : Ensure a highly available Swarm Manager. Create multiple Swarm masters and specify policies on leader election in case the primary master experiences a failure.

• FLEXIBLE CONTAINER SCHEDULING : The built-in scheduler has several filters such as node tags, affinity and strategies like spread, binpack and many more.

SWARM DEMO• Create a master node• Create two worker nodes• Join nodes with master node• Create a docker service • Inspect a service• Access a service on published port• scale a docker service• Upgrade service image (Rolling updates)• Drain a node• stop a node• remove nodes

SWARM DEMO

• Running multiple service in Docker swarm• Create a docker network• Create service foo• Create service bar• Access service bar inside foo (Load Balancing)

Thank you for listening !!