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Assignment: Create A Multi-Service Multi-Node Web App

Goal: create networks, volumes, and services for a web-based "cats vs. dogs" voting app.

Here is a basic diagram of how the 5 services will work:

diagram

  • All images are on Docker Hub, so you should use editor to craft your commands locally, then paste them into swarm shell (at least that's how I'd do it)
  • a backend and frontend overlay network are needed. Nothing different about them other than that backend will help protect database from the voting web app. (similar to how a VLAN setup might be in traditional architecture)
  • The database server should use a named volume for preserving data. Use the new --mount format to do this: --mount type=volume,source=db-data,target=/var/lib/postgresql/data

docker network create -d overlay backend docker network create -d overlay frontend

Services (names below should be service names)

  • vote

    • bretfisher/examplevotingapp_vote
    • web front end for users to vote dog/cat
    • ideally published on TCP 80. Container listens on 80
    • on frontend network
    • 2+ replicas of this container docker service create --name vote -p 80:80 --network frontend --replicas 2 dockersamples/examplevotingapp_vote
  • redis

    • redis:3.2
    • key/value storage for incoming votes
    • no public ports
    • on frontend network
    • 1 replica NOTE VIDEO SAYS TWO BUT ONLY ONE NEEDED docker service create --name redis --network frontend redis:3.2
  • worker

    • bretfisher/examplevotingapp_worker
    • backend processor of redis and storing results in postgres
    • no public ports
    • on frontend and backend networks
    • 1 replica docker service create --name worker --network frontend --network backend dockersamples/examplevotingapp_worker
  • db

    • postgres:9.4
    • one named volume needed, pointing to /var/lib/postgresql/data
    • on backend network
    • 1 replica
    • remember set env for password-less connections -e POSTGRES_HOST_AUTH_METHOD=trust docker service create --name db --network backend -e POSTGRES_HOST_AUTH_METHOD=trust --mount type=volume,source=db-data,target=/var/lib/postgresql/data postgres:9.4
  • result

    • bretfisher/examplevotingapp_result
    • web app that shows results
    • runs on high port since just for admins (lets imagine)
    • so run on a high port of your choosing (I choose 5001), container listens on 80
    • on backend network
    • 1 replica docker service create --name result --network backend -p 5001:80 dockersamples/examplevotingapp_result