Walid AshrafResearcher , Software Developer, Instructor

about.me/WalidAshraf

INTRODUCTION TO DOCKER SWARM

Docker Swarm - Walid Ashraf

Docker Basic Architecture

Native Client

UCP Third party

Docker Swarm - Walid Ashraf

INTRODUCTION TO DOCKER SWARM

Docker Swarm - Walid Ashraf

Docker Swarm - Walid Ashraf

What is Swarm

Docker Swarm is native clustering for Docker.

• It turns a pool of Docker hosts into a single, virtual Docker host.

Docker Swarm serves the standard Docker API, any tool that already communicates with a Docker daemon can use Swarm to transparently scale to multiple hosts.

Docker Swarm - Walid Ashraf

Docker Swarm - Walid Ashraf

Docker Discovery ServiceA key Value store for configurations

• Consul• Etcd• ZooKeeper

Defaults to a hosted discovery service with Docker Swarm.

The service maintains a list of IPs in your cluster. This page describes the different types of hosted discovery available to you.

Discovery service replacements (Libkv abstraction):

Should be replicated

Docker Swarm - Walid Ashraf

Swarm Manager

It’s the cluster admin or master

• 1 Primary (the Actual Admin)• Multiple Secondary Managers (Transfers to primary)• In case of primary failure (leader election occurs)

All communications with nodes passes through it

Supports HA

Docker Swarm - Walid Ashraf

How this works

Docker Swarm - Walid Ashraf

Filtering:The ability to mask some of the nodes

Constraints

• node to refer to the node by ID or name• storagedriver• executiondriver• kernelversion• operatingsystem

Resources

• Containerslots Number of containers on a host• Port

Containers

• Affinity filters• container name or id• an image on the host• a custom label applied to the container

• Depencecy

Docker Swarm - Walid Ashraf

Scheduling

Random

• Default• Least no of containers• CPU and RAM aware

Spread

• Most no of containers• CPU and RAM aware

Binpack

Docker Swarm - Walid Ashraf

CREATING SWARM INFRASTRUCTURE

Docker Swarm - Walid Ashraf

1 – Create Masterdocker swarm init --advertise-addr <MANAGER-IP>$ docker swarm init --advertise-addr 192.168.99.100docker info

Swarm: activeNodeID: dxn1zf6l61qsb1josjja83ngzIs Manager: trueManagers: 1Nodes: 1

docker node lsID HOSTNAME STATUS AVAILABILITY MANAGER STATUSdxn1zf6l61qsb1josjja83ngz * manager1 Ready Active Leader

Docker Swarm - Walid Ashraf

2 – Add Nodes$ docker swarm join \ --token SWMTKN-1-49nj1cmql0jkz5s954yi3oex3nedyz0fb0xx14ie39trti4wxv-8vxv8rssmk743ojnwacrr2e7c \ 192.168.99.100:2377Docker node ls

ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS03g1y59jwfg7cf99w4lt0f662 worker2 Ready Active9j68exjopxe7wfl6yuxml7a7j worker1 Ready Activedxn1zf6l61qsb1josjja83ngz * manager1 Ready Active Leader

Docker Swarm - Walid Ashraf

DEPLOYING A SERVICE

Docker Swarm - Walid Ashraf

What is a serviceA service is a container in swarm mode.Examples of services might include an HTTP server, a database, or any other type of executable program that you wish to run in a distributed environment.Things to be configured in a service

The port where the swarm will make the service available outside the swarmAn overlay network for the service to connect to other services in the swarmCPU and memory limits and reservationsA rolling update policyThe number of replicas of the image to run in the swarm

Docker Swarm - Walid Ashraf

Docker Swarm - Walid Ashraf

Replicated and global services

Docker Swarm - Walid Ashraf

Creating a service$docker service create --replicas 1 --name helloworld alpine ping docker.com

• ID NAME SCALE IMAGE COMMAND• 9uk4639qpg7n helloworld 1/1 alpine ping docker.com

$ docker service ls• ID: 9uk4639qpg7npwf3fn2aasksr• Name: helloworld• Mode: REPLICATED• Replicas: 1• Placement:• UpdateConfig:• Parallelism: 1• ContainerSpec:• Image: alpine• Args: ping docker.com

$ docker service inspect --pretty helloworld

• ID NAME SERVICE IMAGE LAST STATE DESIRED STATE NODE• 8p1vev3fq5zm0mi8g0as41w35 helloworld.1 helloworld alpine Running 3 minutes Running worker2

$ docker service ps helloworld

Docker Swarm - Walid Ashraf

Scaling a service$ docker service scale helloworld=5$ docker service ps helloworld

ID NAME SERVICE IMAGE LAST STATE DESIRED STATE NODE8p1vev3fq5zm0mi8g0as41w35 helloworld.1 helloworld alpine Running 7 minutes Running worker2c7a7tcdq5s0uk3qr88mf8xco6 helloworld.2 helloworld alpine Running 24 seconds Running worker16crl09vdcalvtfehfh69ogfb1 helloworld.3 helloworld alpine Running 24 seconds Running worker1auky6trawmdlcne8ad8phb0f1 helloworld.4 helloworld alpine Running 24 seconds Accepted manager1ba19kca06l18zujfwxyc5lkyn helloworld.5 helloworld alpine Running 24 seconds Running worker2

Docker Swarm - Walid Ashraf

Delete a service$ docker service rm helloworld

helloworld

High AvailabilitySecurity

OTHER CONSIDERATIONS

Docker Swarm - Walid Ashraf

Thinking about High Availability

Docker Swarm - Walid Ashraf

HA over Multiple clouds

Docker Swarm - Walid Ashraf

Implementing High AvailabilityNote: Default Discovery service needs a key value configuration manager Manager1

swarm manage -H :4000 <tls-config-flags> --replication --advertise 192.168.42.200:4000 consul://192.168.42.10:8500/nodes

Manager 2swarm manage -H :4000 <tls-config-flags> --replication --advertise 192.168.42.201:4000 consul://192.168.42.10:8500/nodes

Docker Swarm - Walid Ashraf

TLS for Docker Swarm

Docker Swarm - Walid Ashraf

Referenceshttps://docs.docker.com/swarm/https://docs.docker.com/engine/swarm/swarm-tutorial

Docker Swarm - Walid Ashraf