Docker Swarm
Contents Docker Swarm SwarmKit Open source tool kit to build multi-node systems Reusable library. Plumbing part of the Docker ecosystem. Adopted into Docker as Docker Swarm SwarmKit Features SwarmKit Concepts A cluster will be at least one node. A node can be a manager and/or a worker. A manager actively takes part in the Raft consensus and keeps the Raft log. One manager is elected as the leader; other manager merely forward requests to it. The managers expose the SwarmKit API. You can talk to a manager using the SwarmKit API. Using the API, you can indicate that you want to run a service. A service is specified by its desired state: which image, how many instances… The leader uses different subsystems to break down services into tasks: orchestrator, scheduler, allocator, dispatcher. A task corresponds to a specific container, assigned to a specific node. Nodes know which tasks should be running, and will start or stop containers accordingly. The workers get their instructions from the managers. Both workers and managers can run containers. Running Applications on Swarm This is to be done on FABRIC. Refresh your fabric-examples repository with git pull. Open 468_examples/docker_swarm and launch the docker_swarm.ipynb. CloudLab Setup This helps deploy Docker Swarm for your project.
Update CloudLab Git Repository Create a new branch called docker-swarm from your Docker branch . Update the profile.py in your docker-swarm branch with the content from this profile.py . Launch CloudLab profile Update your CloudLab profile to see the new branch. Instantiate the experiment. Fill in the parameters as follows: Node type: XenVM or RawPC: XenVM Number of nodes: 2 Number of cores in each node: 4 MB of RAM in each node: 4096 Deploying your swarm By default, SwarmKit features are asleep until you active Swarm mode Swarm Mode commands: docker swarm: enable Swarm mode, join Swarm, adjust Swarm’s parameters docker node: view nodes, promote/demote managers, manage nodes docker service: create and manage services. Run the following on head node:
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cd
docker swarm init --advertise-addr eth1:7777 --listen-addr eth1:7777
Read the output and use the provided commands on the worker nodes to have these nodes joining the swarm. On the head node, run the following command to view the swarm nodes Hands-on: Launching a registry inside Swarm Run the following on the head node
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docker service create --name registry --publish 5000:5000 registry
docker service ps registry
curl 127.0.0.1:5000/v2/_catalog
Test your registry This is a demo registry with no security!
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docker pull busybox
docker tag busybox 127.0.0.1:5000/busybox
docker push 127.0.0.1:5000/busybox
curl 127.0.0.1:5000/v2/_catalog
Hands-on: Deploying a service on Swarm
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git clone https://github.com/CSC468-WCU/ram_coin.git
cd ram_coin
Run the following to build and push the images into the local registry
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export REGISTRY = 127.0.0.1:5000
export TAG = v0.1
for SERVICE in hasher rng webui worker; do docker build -t $REGISTRY /$SERVICE :$TAG ./$SERVICE ; docker push $REGISTRY /$SERVICE :$TAG ; done
curl 127.0.0.1:5000/v2/_catalog
Launching the overlay network and other services
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docker network create --driver overlay ramcoins
docker service create --network ramcoins --name redis redis
for SERVICE in hasher rng webui worker; do docker service create --network ramcoins --detach = true --name $SERVICE $REGISTRY /$SERVICE :$TAG ; done
docker service ls
docker service update webui --publish-add 8000:80
docker service ls
Visit the head node at port 8000 to observe the application running. Try scaling up services using: docker service scale SERVICE_NAME=... 
