Updated details on VM builds

docs/ha-docker-swarm/design.md

@@ -1,7 +1,64 @@
-The "private cloud" platform is:
+# Introduction
 
-* **Highly-available** (can tolerate the failure of a single component)
-* **Scalable** (can add resource or capacity as required)
-* **Portable** (run it on your garage server today, run it in AWS tomorrow)
-* **Secure** (access protected with LetsEncrypt certificates)
-* **Automated** (requires minimal care and feeding)
+In the design described below, the "private cloud" platform is:
+
+* **Highly-available** (_can tolerate the failure of a single component_)
+* **Scalable** (_can add resource or capacity as required_)
+* **Portable** (_run it on your garage server today, run it in AWS tomorrow_)
+* **Secure** (_access protected with LetsEncrypt certificates_)
+* **Automated** (_requires minimal care and feeding_)
+
+## Design Decisions
+
+**Where possible, services will be highly available.**
+
+This means that:
+
+* At least 3 docker swarm manager nodes are required, to provide fault-tolerance of a single failure.
+* GlusterFS is employed for share filesystem, because it too can be made tolerant of a single failure.
+
+**Where multiple solutions to a requirement exist, preference will be given to the most portable solution.**
+
+This means that:
+
+* Services are defined using docker-compose v3 YAML syntax
+* Services are portable, meaning a particular stack could be shut down and moved to a new provider with minimal effort.
+
+## High availability
+
+### Normal function
+
+Assuming 3 nodes, under normal circumstances the following is illustrated:
+
+* All 3 nodes provide shared storage via GlusterFS, which is provided by a docker container on each node. (i.e., not running in swarm mode)
+* All 3 nodes participate in the Docker Swarm as managers.
+* The various containers belonging to the application "stacks" deployed within Docker Swarm are automatically distributed amongst the swarm nodes.
+* Persistent storage for the containers is provide via GlusterFS mount.
+* The **traefik** service (in swarm mode) receives incoming requests (on http and https), and forwards them to individual containers. Traefik knows the containers names because it's able to access the docker socket.
+* All 3 nodes run keepalived, at different priorities. Since traefik is running as a swarm service and listening on TCP 80/443, requests made to the keepalived VIP and arriving at **any** of the swarm nodes will be forwarded to the traefik container (no matter which node it's on), and then onto the target backend.
+
+![HA function](images/docker-swarm-ha-function.png)
+
+### Node failure
+
+In the case of a failure (or scheduled maintenance) of one of the nodes, the following is illustrated:
+
+* The failed node no longer participates in GlusterFS, but the remaining nodes provide enough fault-tolerance for the cluster to operate.
+* The remaining two nodes in Docker Swarm achieve a quorum and agree that the failed node is to be removed.
+* The (possibly new) leader manager node reschedules the containers known to be running on the failed node, onto other nodes.
+* The **traefik** service is either restarted or unaffected, and as the backend containers stop/start and change IP, traefik is aware and updates accordingly.
+* The keepalived VIP continues to function on the remaining nodes, and docker swarm continues to forward any traffic received on TCP 80/443 to the appropriate node.
+
+![HA function](images/docker-swarm-node-failure.png)
+
+### Node restore
+
+When the failed (or upgraded) host is restored to service, the following is illustrated:
+
+* GlusterFS regains full redundancy
+* Docker Swarm managers become aware of the recovered node, and will use it for scheduling **new** containers
+* Existing containers which were migrated off the node are not migrated backend
+* Keepalived VIP regains full redundancy
+
+
+![HA function](images/docker-swarm-node-restore.png)

docs/ha-docker-swarm/docker.md

@@ -12,8 +12,9 @@ We start building our cloud with virtual machines. You could use bare-metal mach
 
 ## Preparation
 
-1. Install Virtual machines
-
-* Hosts must be within the same subnet, and connected on a low-latency link (i.e., no WAN links)
-
-2. Setup super-user access for your admin user, as a member of the "docker" group
+### Install latest docker
+```
+systemctl disable docker --now
+systemctl enable docker-latest --now
+sed -i '/DOCKERBINARY/s/^#//g' /etc/sysconfig/docker
+```

docs/ha-docker-swarm/vms.md

@@ -1,28 +1,41 @@
 # Introduction
 
-We start building our cloud with virtual machines. You could use bare-metal machines as well, the configuration would be the same. Given that most readers (myself included) will be using virtual infrastructure, from now on I'll be referring strictly to VMs.
+Let's start building our cloud with virtual machines. You could use bare-metal machines as well, the configuration would be the same. Given that most readers (myself included) will be using virtual infrastructure, from now on I'll be referring strictly to VMs.
+
+I chose the "[Atomic](https://www.projectatomic.io/)" CentOS/Fedora image for the VM layer because:
+
+1. I want less responsibility for maintaining the system, including ensuring regular software updates and reboots. Atomic's idempotent nature means the OS is largely real-only, and updates/rollbacks are "atomic" (haha) procedures, which can be easily rolled back if required.
+2. For someone used to administrating servers individually, Atomic is a PITA. You have to employ [tricky](atomic-trick2) [tricks](atomic-trick1) to get it to install in a non-cloud environment. It's not designed for tweaking or customizing beyond what cloud-config is capable of. For my purposes, this is good, because it forces me to change my thinking - to consider every daemon as a container, and every config as code, to be checked in and version-controlled. Atomic forces this thinking on you.
+3. I want the design to be as "portable" as possible. While I run it on VPSs now, I may want to migrate it to a "cloud" provider in the future, and I'll want the most portable, reproducible design.
+
+[atomic-trick1]:https://spinningmatt.wordpress.com/2014/01/08/a-recipe-for-starting-cloud-images-with-virt-install/
+[atomic-trick2]:http://blog.oddbit.com/2015/03/10/booting-cloud-images-with-libvirt/
 
 ## Ingredients
 
 3 x Virtual Machines, each with:
+
 * CentOS/Fedora Atomic
 * At least 1GB RAM
-* At least 20GB disk space (but it'll be tight)
-* Connectivity to each other within the same subnet, and on a low-latency link (i.e., no WAN links)
+* At least 20GB disk space (_but it'll be tight_)
+* Connectivity to each other within the same subnet, and on a low-latency link (_i.e., no WAN links_)
 
 ## Preparation
 
 ### Install Virtual machines
 
-1. Install Virtual machines
-2. Setup super-user access for your admin user, as a member of the "docker" group
+1. Install / launch virtual machines.
+2. The default username on CentOS atomic is "centos", and you'll have needed to supply your SSH key during the build process. If you're not using a platform with cloud-init support (i.e., you're building a VM manually, not provisioning it through a cloud provider), you'll need to refer to [trick #1][atomic-trick1] and [#2][atomic-trick2] for a means to override the automated setup, apply a manual password to the CentOS account, and enable SSH password logins.
 
 
-I chose the "Atomic" CentOS/Fedora image because:
+### Upgrade Atomic
 
-1. I want less responsibility for maintaining the system, including ensuring regular software updates and reboots. Atomic's idempotent nature means the OS is largely real-only, and updates/rollbacks are "atomic" (haha) procedures, which can be easily rolled back if required.
-2. For someone used to administrating servers individually, Atomic is a PITA. You have to employ [tricky](http://blog.oddbit.com/2015/03/10/booting-cloud-images-with-libvirt/) [tricks](https://spinningmatt.wordpress.com/2014/01/08/a-recipe-for-starting-cloud-images-with-virt-install/) to get it to install in a non-cloud environment. It's not designed for tweaking or customizing beyond what cloud-config is capable of. For my purposes, this is good, because it forces me to change my thinking - to consider every daemon as a container, and every config as code, to be checked in and version-controlled. Atomic forces this thinking on you.
-3. I want the design to be as "portable" as possible. While I run it on VPSs now, I may want to migrate it to a "cloud" provider in the future, and I'll want the most portable, reproducible design.
+Run ```atomic host upgrade```, and reboot if necessary.
 
 
-atomic host upgrade
+## Serving
+
+After completing the above, you should have:
+
+* [X] 3 fresh atomic instances, at the latest releases
+* [X] A user belonging to the docker group for administration

mkdocs.yml

@@ -20,7 +20,7 @@ pages:
     - HA Docker Swarm:
       - Index: ha-docker-swarm/index.md
       - Design: ha-docker-swarm/design.md
-      - VMs: ha-docker-swarm/design.md
+      - VMs: ha-docker-swarm/vms.md
       - Persistent Storage: beginner/beginner.md
       - Keepalived: advanced/keepalived.md
       - Docker Swarm Mode: advanced/keepalived.md