DevOps

DevOps is a Culture

It depends who you ask

• Automation
• Repeatability
• Feedback
• Operations

What do we model?

Self-contained

Application

What do we model?

Self-contained

Application

Configuration

A Simple Example

Django Application

• Web application using Django
• PostgreSQL database

Django Application

• For the database, django needs
  • Database credentials
  • Database created for the application
  • Connection URL - where is the DB server

Production Deployment

• Web application using Django
• PostgreSQL database

• gunicorn as an efficient WSGI HTTP Server
• nginx as efficient static file server

Gunicorn

• Python environment
• WSGI configuration
• Port to listen on

Nginx

• Hostname
• Static files path extension
• Static files file location
• Port to forward non-static calls to

Scale Out

• Highly available database - 2 or 3 nodes
• Multiple web application servers
• HA proxy

Extend and Monitor

• Add celery for asynchronous tasks
• Now we need redis or rabbitMQ
• Monitor with nagios

Juju

and

Charms

Juju

• An Open Source tool
  • github.com/juju/juju
• Manages the deployment and operation of charms
• Provides the modelling abstraction
  • Can think more about the applications and their relationships rather than machines

Charms are

Encapsulated DevOps

• Installation and configuration
• Relationship management
• Operational activities
• Can become projects in their own right

A Charm

• It is just a ZIP file
• Metadata defined in YAML
• Hooks are executed at specific times of change

Installation and Configuration

• install, config-changed, and upgrade-charm
• start, stop, update-status
• leader-elected, leader-settings-changed

Relationship Management

• Relations between software using agreed "protocols"
• For example, "pgsql" for PostgreSQL information
• Protocol goes something like this:
  • django establishes relationship with postgresql
  • django says my app is "foo"
  • postgresql creates a database "foo", a user "fooish" and a password, and sets these values
  • django picks up those settings and saves them for its configuration

Operational Activities

• A charm can also define any number of named actions
• These actions can be invoked by an operator at any time
• For example:
  • backup / restore
  • quiesce
  • update content

Deployment Targets

• Juju also abstracts the deployment target being used
• Kubernetes - for container workloads
• Public clouds:
  • AWS, Azure, GCE, Joyent, Oracle cloud
• Private clouds:
  • OpenStack, VMWare, MAAS, LXD, Manual

Modelling Requirements

• Some software has more defined needs
  • High IOPS
  • GPU
  • Attached storage
• Networks
  • Extra layer 2 devices, VLANs, subnets
  • Spaces - multiple connected subnets with same ingress and egress rules, e.g. DMZ

Simple Repeatability

• Bundles are YAML documents
• Lists the applications to deploy
  • Charm and Configuration
  • Target Constraints
  • Relationships