Docker Swarm is native clustering for Docker. It allows you create and access to a pool of Docker hosts using the full suite of Docker tools. Because 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 has a Manager, a pre-defined Docker Host, and is a single point for all administration. Swarm manager orchestrates and schedules containers on the entire cluster, and can be configured in High Availability. The containers are deployed on Nodes that are additional Docker Hosts.
Swarm talks to a hosted Discovery Service that maintains a list of IPs in your cluster. For development, its easy to use the default discovery service hosted on Docker Hub. Complete instructions for that are available in Install and Create Docker Swarm. This blog will show how to setup Docker Swarm Cluster using Consul.
Lets get started!
Create Consul Discovery Service
- Create a Machine that will host discovery service:0102030405060708091011
docker-machine create -d=virtualbox consul-machineRunning pre-create checks...Creating machine...Waitingformachine to be running, this may take a few minutes...Machine is running, waitingforSSH to be available...Detecting operating system of created instance...Provisioning created instance...Copying certs to thelocalmachine directory...Copying certs to the remote machine...Setting Docker configuration on the remote daemon...To see how to connect Docker to this machine, run: docker-machineenvconsul-machine - Connect to this Machine:1
eval$(docker-machineenvconsul-machine) - Run Consul service using the following Compose file:1234567
myconsul:image: progrium/consulrestart: alwayshostname: consulports:- 8500:8500command:"-server -bootstrap"This file is also available at github.com/arun-gupta/docker-images/tree/master/consul. The service is started as:
010203040506070809101112131415161718192021222324docker-compose up -dPulling myconsul (progrium/consul:latest)...latest: Pulling from progrium/consul3b4d28ce80e4: Pull completee5ab901dcf2d: Pull complete30ad296c0ea0: Pull complete3dba40dec256: Pull completef2ef4387b95e: Pull complete53bc8dcc4791: Pull complete75ed0b50ba1d: Pull complete17c3a7ed5521: Pull complete8aca9e0ecf68: Pull complete4d1828359d36: Pull complete46ed7df7f742: Pull completeb5e8ce623ef8: Pull complete049dca6ef253: Pull completebdb608bc4555: Pull complete8b3d489cfb73: Pull completec74500bbce24: Pull complete9f3e605442f6: Pull completed9125e9e799b: Pull completeDigest: sha256:8cc8023462905929df9a79ff67ee435a36848ce7a10f18d6d0faba9306b97274Status: Downloaded newer imageforprogrium/consul:latestCreating consul_myconsul_1Started container can be verified as:
123dockerpsCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMESf05d8dd11e7f progrium/consul"/bin/start -server -"30 seconds ago Up 29 seconds 53/tcp, 53/udp, 8300-8302/tcp, 8400/tcp, 0.0.0.0:8500->8500/tcp, 8301-8302/udpconsul_myconsul_1
Create Docker Swarm Cluster using Consul
Swarm is fully integrated with Machine, and so is the easiest way to get started.
- Create a Swarm Master using the Consul discovery service:010203040506070809101112
docker-machine create -d virtualbox --swarm --swarm-master --swarm-discovery="consul://$(docker-machine ip consul-machine):8500"--engine-opt="cluster-store=consul://$(docker-machine ip consul-machine):8500"--engine-opt="cluster-advertise=eth1:2376"swarm-masterRunning pre-create checks...Creating machine...Waitingformachine to be running, this may take a few minutes...Machine is running, waitingforSSH to be available...Detecting operating system of created instance...Provisioning created instance...Copying certs to thelocalmachine directory...Copying certs to the remote machine...Setting Docker configuration on the remote daemon...Configuring swarm...To see how to connect Docker to this machine, run: docker-machineenvswarm-masterThree options to look here:
--swarm-discoverydefines address of the discovery service--cluster-advertiseadvertise the machine on the network--cluster-storedesignate a distributed k/v storage backend for the cluster
In addition,
--swarmconfigures the Machine with Swarm,--swarm-masterconfigures the created Machine to be Swarm master. - Connect to this newly created master and find some information about it:12
eval"$(docker-machine env swarm-master)"docker infoThis will show the output as:
01020304050607080910111213141516171819202122232425262728293031docker infoContainers: 2Images: 8Server Version: 1.9.0Storage Driver: aufsRoot Dir:/mnt/sda1/var/lib/docker/aufsBacking Filesystem: tmpfsDirs: 12Dirperm1 Supported:trueExecution Driver: native-0.2Logging Driver: json-fileKernel Version: 4.1.12-boot2dockerOperating System: Boot2Docker 1.9.0 (TCL 6.4); master : 16e4a2a - Tue Nov 3 19:49:22 UTC 2015CPUs: 1Total Memory: 996.2 MiBName: swarm-masterID: 2EDA:WPOD:YVWO:GGLZ:ZUHY:WCBU:ZERW:OWBE:6MPQ:IPXN:BS2V:QCSIDebug mode (server):trueFile Descriptors: 30Goroutines: 67System Time: 2015-11-29T02:08:10.636829121ZEventsListeners: 1Init SHA1:Init Path:/usr/local/bin/dockerDocker Root Dir:/mnt/sda1/var/lib/dockerUsername: arunguptaRegistry: https://index.docker.io/v1/Labels:provider=virtualboxCluster store: consul://192.168.99.109:8500Cluster advertise: 192.168.99.111:2376 - Create a new Machine to be part of this Swarm cluster:010203040506070809101112
docker-machine create -d virtualbox --swarm --swarm-discovery="consul://$(docker-machine ip consul-machine):8500"--engine-opt="cluster-store=consul://$(docker-machine ip consul-machine):8500"--engine-opt="cluster-advertise=eth1:2376"swarm-node-01Running pre-create checks...Creating machine...Waitingformachine to be running, this may take a few minutes...Machine is running, waitingforSSH to be available...Detecting operating system of created instance...Provisioning created instance...Copying certs to thelocalmachine directory...Copying certs to the remote machine...Setting Docker configuration on the remote daemon...Configuring swarm...To see how to connect Docker to this machine, run: docker-machineenvswarm-node-01Machine talks to the Discovery Service using
--swarm-discovery. - Create a second node in this cluster:010203040506070809101112
docker-machine create -d virtualbox --swarm --swarm-discovery="consul://$(docker-machine ip consul-machine):8500"--engine-opt="cluster-store=consul://$(docker-machine ip consul-machine):8500"--engine-opt="cluster-advertise=eth1:2376"swarm-node-02Running pre-create checks...Creating machine...Waitingformachine to be running, this may take a few minutes...Machine is running, waitingforSSH to be available...Detecting operating system of created instance...Provisioning created instance...Copying certs to thelocalmachine directory...Copying certs to the remote machine...Setting Docker configuration on the remote daemon...Configuring swarm...To see how to connect Docker to this machine, run: docker-machineenvswarm-node-02 - List all the created Machines:1234567
docker-machinelsNAME ACTIVE DRIVER STATE URL SWARMconsul-machine - virtualbox Running tcp://192.168.99.109:2376default - virtualbox Running tcp://192.168.99.100:2376swarm-master * virtualbox Running tcp://192.168.99.111:2376 swarm-master (master)swarm-node-01 - virtualbox Running tcp://192.168.99.112:2376 swarm-masterswarm-node-02 - virtualbox Running tcp://192.168.99.113:2376 swarm-masterThe machines that are part of the cluster have cluster’s name in the SWARM column, blank otherwise. For example, “
default” and “consul-machine” are standalone machines where as all other machines are part of the “swarm-master” cluster. The Swarm master is also identified by (master) in the SWARM column. - Connect to the Swarm cluster and find some information about it:12
eval"$(docker-machine env --swarm swarm-master)"docker infoThe main difference here is
--swarmwhen finding information about Swarm cluster as opposed to a single Machine.This shows the output as:
01020304050607080910111213141516171819202122232425docker infoContainers: 4Images: 3Role: primaryStrategy: spreadFilters: health, port, dependency, affinity, constraintNodes: 3swarm-master: 192.168.99.111:2376└ Containers: 2└ Reserved CPUs: 0 / 1└ Reserved Memory: 0 B / 1.021 GiB└ Labels: executiondriver=native-0.2, kernelversion=4.1.12-boot2docker, operatingsystem=Boot2Docker 1.9.0 (TCL 6.4); master : 16e4a2a - Tue Nov 3 19:49:22 UTC 2015, provider=virtualbox, storagedriver=aufsswarm-node-01: 192.168.99.112:2376└ Containers: 1└ Reserved CPUs: 0 / 1└ Reserved Memory: 0 B / 1.021 GiB└ Labels: executiondriver=native-0.2, kernelversion=4.1.12-boot2docker, operatingsystem=Boot2Docker 1.9.0 (TCL 6.4); master : 16e4a2a - Tue Nov 3 19:49:22 UTC 2015, provider=virtualbox, storagedriver=aufsswarm-node-02: 192.168.99.113:2376└ Containers: 1└ Reserved CPUs: 0 / 1└ Reserved Memory: 0 B / 1.021 GiB└ Labels: executiondriver=native-0.2, kernelversion=4.1.12-boot2docker, operatingsystem=Boot2Docker 1.9.0 (TCL 6.4); master : 16e4a2a - Tue Nov 3 19:49:22 UTC 2015, provider=virtualbox, storagedriver=aufsCPUs: 3Total Memory: 3.064 GiBName: 10edc606d097There are 3 nodes – one Swarm master and 2 Swarm _worker_ nodes. There is a total of 4 containers running in this cluster – one Swarm agent on master and each node, and there is an additional swarm-agent-master running on the master. This can be verified by connecting to the master and listing all the containers.
- List nodes in the cluster with the following command:1234
docker run swarm list consul://$(docker-machine ip consul-machine):8500192.168.99.111:2376192.168.99.112:2376192.168.99.113:2376
Subsequent blog will explain how to deploy applications to this Docker Swarm Cluster.
Enjoy!
| Reference: | Docker Swarm Cluster using Consul from our JCG partner Arun Gupta at the Miles to go 2.0 … blog. |
