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Swarm with Gluster

Objective: Deploy a Docker Swarm from scratch on AWS where

  • there is persistent storage via GlusterFS.
  • there is secrets management via Vault.

Plan

  • Get connection to newly created AWS account, output availability zones, etc.
  • Provision two Ubuntu EC2s in default VPC with Terraform.
  • Provision a cluster of two Ubuntu machines with Ansible so that they run a Swarm cluster.
  • Be able to deploy a hello-world service and Swarm Visualizer on the swarm.
  • Provision a separate GlusterFS as underlying data store.
  • Make sure that the system is resilient to taking arbitrary nodes down.
  • It must be possible to scale up by just adding a new Swarm node (eg. EC2 instance).
  • It must be possible to scale down by removing a Swarm node.
  • It must be possible to incrementally upgrade the size of Swarm nodes and/or the Gluster bricks.
  • Provision a docker container that can simulate backup of files from a whitelist.

Creating a cluster

$ cd terraform
$ export AWS_PROFILE=lundogbendsen
$ terraform apply

Copy the cluster-nodes from the Terraform output to ../ansible/inventory.ini, the first host as master, the rest as workers:

$ cd ../ansible
$ edit inventory.ini

To avoid specifying the key all the time, put the location of the private key in ansible/ansible.cfg like

[defaults]
private_key_file = /Users/jps/.ssh/ec2-lundogbendsen-jp.pem

Prepare shared data storage:

$ export ANSIBLE_HOST_KEY_CHECKING=False
$ ansible-playbook -i inventory.ini staging-01-prepare-shared-data-storage.yml

Connect the nodes into a Trusted Storage Pool and start the cluster:

$ ansible-playbook -i inventory.ini staging-11-create-swarm-master.yml

Copy the token and IP from the output into group_vars/staging-workers. Then start all workers:

$ ansible-playbook -i inventory.ini staging-12-create-swarm-workers.yml

To see that it is working, make a SSH tunnel (in a new terminal) to one of the nodes:

$ ssh -i ~/.ssh/ec2-lundogbendsen-jp.pem -N -L 2375:/var/run/docker.sock ubuntu@ec2-xx-xx-xx-xx.eu-west-1.compute.amazonaws.com

And check that the cluster is running:

$ cd ..
$ export DOCKER_HOST=tcp://localhost:2375
$ docker node ls

Creating a stack

$ docker stack deploy -c docker-compose.yml mytest

Taking down the stack

$ docker stack rm mytest

Scaling up

Increase the number of nodes in terraform/variables.tf and run terraform plan to verify that everything looks ok. Then terraform apply to actually create the new instance.

Add the IPs of the newly created instance to ansible/inventory.ini group staging-new-workers: (It should be empty initially)

$ cd ../ansible
$ edit inventory.ini

Then provision only the new instance:

$ ansible-playbook -i inventory.ini -l staging-new-workers staging-01-prepare-shared-data-storage.yml
$ ansible-playbook -i inventory.ini staging-11-add-worker-to-existing-swarm.yml

Now that the new host is ready to be a worker, copy it in ansible/inventory.ini from group staging-new-workers to group staging-workers, and add it (only) to the swarm:

$ ansible-playbook -i inventory.ini -l staging-new-workers staging-12-create-swarm-workers.yml

Finally remove the new hosts from ansible/inventory.ini group staging-new-workers.

Scaling down

Start by changing the Terraform spec and do a terraform plan to find out which host would be taken down if applied. Them use that host in the following.

First drain the swarm node:

$ docker node ls
$ docker node update --availability drain 0hl18vnlus36szv9cvafpiwze

Then SSH into that particular node, and make it leave the swarm: $ ssh ... $ docker swarm leave $ exit

Remove the stopped node from the swarm:

$ docker node rm 0hl18vnlus36szv9cvafpiwze

Then, remove the brick from the Gluster volume:

$ ssh ...
$ sudo gluster volume remove-brick swarm replica 2 ec2-34-244-9-221.eu-west-1.compute.amazonaws.com:/data/gluster/swarm/brick0 force

Finally take the server down.

Todo

  • On each host: sudo touch /var/lib/cloud/instance/locale-check.skip
  • Only open
  • How to bypass host fingerprint warning from Ansible? ANSIBLE_HOST_KEY_CHECKING=False
  • Check out ansible --with-registry-auth.
  • Ansible role for common Apt stuff: HTTPS, update.

Trouble shooting

To see the state of services:

$ docker service ls

To see full error messages

$ docker service ps --no-trunc mytest_visualizer

Gluster

$ sudo gluster peer status
$ sudo gluster volume info myvol
$ sudo gluster volume status myvol
$ sudo gluster volume status myvol detail
$ sudo gluster volume heal myvol info
$ sudo gluster volume start swarm force

"Already part of a volume": https://www.jamescoyle.net/how-to/2234-glusterfs-error-volume-add-brick-failed-pre-validation-failed-on-brick-is-already-part-of-a-volume