Juju

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Juju is an open source application modelling tool. It allows you to deploy, configure, scale and operate your software on public and private clouds¹.

• juju charms like install node, django etc and connect to mongodb
• one charm to rule them all. Devops operations
• Configuration and deployment tool
• Juju by default stores its configuration and state locally in the ~/.local/share/juju directory

Juju can be used locally² using LXD.

How to connect new interfaces, services/instances when application is scaled up?

Juju excels at continue to upgrade the model once its deployed

• scaling application
• upgrading applications
• configuring applications while they are running

Things always change

Modelling software deployments?

Application is not a single server these days, its a plethora of interconnectedd services

charm

is a set of action and hooks

actions are programs

hooks are events and signals

Developers can simulate a production like real cloud instances/interconnected environment using lightweigt LXD

Juju also has a concept of Bundles. A Bundle is a portable specification for a model with charms, configuration, and relations all specified in a declarative YAML format

Relations and applications information os provided in YAML descriptor file

sudo snap install juju --edge --classic

fish_update_completions
juju whoami
juju list-controllers

# Initializes a cloud environment.
juju bootstrap

controller

A Juju controller is the management node of a Juju cloud environment. It houses the database and keeps track of all the models in that environment.

juju bootstrap localhost lxd-local
juju controllers --refresh
juju whoami
juju deploy cs:bundle/mediawiki-single
juju status
juju destroy-model default
juju add-model default
juju gui --browser
juju deploy cs:bundle/openstack-base-61

• Documentation³
• Stop spending time on Configuration MAnagement - use prebuilt charms
• A software is stuff connected to other stuff
• Hosting Environment
  • Machines
  • Providers
  • Clouds
• Juju Architecture
  • Bundles
  • Charmes
    • Layers
  • Client
  • Controller
  • Agents
• SOftware Medelling
  • Applications
  • Models
  • Units
  • Relations

The Juju controller will manage:

• Multiple models
• All VMs in all your running models
• Scale out, config and placement
• User accounts and identification
• Sharing and access

• Reactive Programming
  • For example, in an imperative programming setting, {\displaystyle a:=b+c}a:=b+c would mean that {\displaystyle a}a is being assigned the result of {\displaystyle b+c}b+c in the instant the expression is evaluated, and later, the values of {\displaystyle b}b and {\displaystyle c}c can be changed with no effect on the value of {\displaystyle a}a. On the other hand, in reactive programming, the value of {\displaystyle a}a is automatically updated whenever the values of {\displaystyle b}b or {\displaystyle c}c change, without the program having to re-execute the statement {\displaystyle a:=b+c}a:=b+c to determine the presently assigned value of a
• deploy OS, event handling based interface management
• Bundles
  • Charms
  • Layers charm layers
• built in layers, anologous to docker layers
• could be written in bash or python
• charm build
• reactive framework
  • juju hooks
  • def install()
  • relationship
• Components of a charm
• Charm store

• Relationships - Provides and Requires

  charm create vanilla
  juju add-unit -n5 ubuntu            # add 5 units
  juju deploy ubuntu mytestmachine1
  juju deploy ubuntu mytestmachine2
  
  juju add-model --verbose mediawiki
  juju deploy haproxy
  juju deploy my-web-app
  juju add-relation my-web-app:website haproxy:reverseproxy
  juju add-unit my-web-app
  juju destroy-model --verbose mediawiki
  
  juju switch avi-os
  

• HAProxy

  • Layer 4 or Layer 7 load balancing
  • Algorithms
  • Round robin
  • Least connections *

Footnotes