PB138 presents

YAML and Containers

presented by Lukas Grolig

Yaml

YAML (a recursive acronym for "YAML Ain't Markup Language") is a human-readable data-serialization language. It is commonly used for configuration files and in applications where data is being stored or transmitted.  

YAML targets many of the same communications applications as Extensible Markup Language (XML) but has a minimal syntax which intentionally differs from SGML.

YAML

IS USED BY MANY MODERN APPS

Basics

  • YAML files should end with .yaml

  • YAML is case sensitive

  • YAML does not allow the use of tabs. Spaces are used instead as tabs are not universally supported.

Data Types

  • scalars (strings / numbers)

  • sequences (arrays / lists)

  • mappings (hashes / dictionaries)

Scalar types

They store single value

integer: 25
string: "25"
float: 25.0
boolean: true

Scalar types

They store single value

integer: 25
string: "25"
float: 25.0
boolean: true

Note: 

Yaml is supporting  single ' or double " quotation marks. Double quotation marks allow you to use escapings to represent ASCII and Unicode characters.

Sequences

aka your old friend list

- Cat
- Dog
- Goldfish
-
  - Cat
  - Dog
  - Goldfish
-
  - Python
  - Lion
  - Tiger

One dimensional

Multi dimensional

Sequences

we can do also inline sequences

npcflag: [GOSSIP, VENDOR]

Mappings

most probably you have seen dictionary

animal: pets

Mappings

we can assign sequence to the mapping

units:
 - Footman
 - Grunt
 - Knight
 - Ogre

Mappings

or use complex keys

? ["Tower", "Tier 1 Unit"]
: "Gremlin"

Sets

they are special case of mapping

set:
  ? item1
  ? item2
  ? item3

Sequence of Mappings

they are special case of mapping

-
  name: Mark McGwire
  points:   65
  grade:  "A"
-
  name: Sammy Sosa
  points:   63
  grade:  "B"

Sequence of Sequences

- [name        , hr, avg  ]
- [Mark McGwire, 65, 0.278]
- [Sammy Sosa  , 63, 0.288]

Mapping of Mappings

Mark McGwire: {hr: 65, avg: 0.278}
Sammy Sosa: {
    hr: 63,
    avg: 0.288
  }

Anchors

---
hr:
  - Mark McGwire
  # Following node labeled SS
  - &SS Sammy Sosa
rbi:
  - *SS # Subsequent occurrence
  - Ken Griffey

When you want avoid duplicities. It is pointer and reference.

One comlex example 

--- 
invoice: 34843
date   : 2001-01-23
bill-to: &id001
    given  : Chris
    family : Dumars
    address:
        lines: |
            458 Walkman Dr.
            Suite #292
        city    : Royal Oak
        state   : MI
        postal  : 48046
ship-to: *id001
product:
    - sku         : BL394D
      quantity    : 4
      description : Basketball
      price       : 450.00
    - sku         : BL4438H
      quantity    : 1
      description : Super Hoop
      price       : 2392.00
tax  : 251.42
total: 4443.52
comments:
    Late afternoon is best.
    Backup contact is Nancy
    Billsmer @ 338-4338.

Sometimes we have problems with types

Pluto is a planet: false

Do we assign string or boolean here?

Pluto is a planet: !!bool false

Like this it is clear

- true          # boolean
- "true"        # string, because it's quoted
- !!str true    # string, because of !!str
- !!bool "true" # boolean, because of !!bool

That's it for YAML

Now let's talk about containers

Before we start with Docker

HTTP

some infrastructure refreshments

Client

Server

Well, not realy

More realistic

Browser

DNS Server

CDN

Proxy

App Server 1

App Server 2

App Server 3

Database

Cache (eg. Redis)

Your infrasturcture

1.

2.

3.

Server

  • Can be bare metal
  • Can be Virtual Machine
  • Can be Container

 

  • And we have also "serverless" architecture

Comparison between bare metal and VM

Hardware

Hardware

OS

App

App

Hypervisor

OS

OS

App

App

Docker

Automates the deployment of software applications inside containers by providing an additional layer of abstraction and automation of OS-level virtualization.

Containers vs VMs

The industry standard today is to use Virtual Machines (VMs) to run software applications. VMs run applications inside a guest Operating System, which runs on virtual hardware powered by the server’s host OS

VMs are great at providing full process isolation for applications: there are very few ways a problem in the host operating system can affect the software running in the guest operating system, and vice-versa. But this isolation comes at great cost — the computational overhead spent virtualizing hardware for a guest OS to use is substantial.

Containers take a different approach: by leveraging the low-level mechanics of the host operating system, containers provide most of the isolation of virtual machines at a fraction of the computing power.

 

They have their own user space but share host's kernel

Why use containers?

  • You have the same environment on deployment machines as on dev machines. No more works on my machine

  • You can utilize you machines much more

  • You define your infrastructure in easy readable text format. You can version it!

How to get started?

  • Install Docker for Desktop (Windows and Mac). Windows users need Pro version. It is available to you from our faculty.

Let's take a look on basic commands

docker pull helloworld

You must pull image from Docker Hub

Is that image now available on my machine?

docker images

Let's take a look on basic commands

docker run helloworld

Ok, now I can run it

BTW if it is not pulled, it will be pulled when runned.

More commands

docker ps
docker ps -a

How to check what images are running?

Sometimes we must cleanup

docker kill container_id # kills running container
docker rm container_id   # remove cotainer image from your machine

More commands

docker run -p 8888:80 containerName

Often you must map ports

Or you can run deamon

docker run -d --name nodeapp -p 8888:5000 mywebsite/nodeapp

Until now we used existing containers

Dockerfile

When you want to create your own image with running system and some application, your create Dockerfile (recommended name) and build it.

FROM node:13.10.1-alpine3.11

After creating file specify base image

Next time to define what should happen.

Like defining work directory.

WORKDIR /usr/src/website

Dockerfile

COPY . .

Copy files to container

And run some custom commands

In this stage you have application build.

RUN npm install
RUN npm run build

Expose port to outside:

EXPOSE 5000

Dockerfile

CMD [“node”, “./“build/index.js]

And setup run command

Result

FROM node:13.10.1-alpine3.11

WORKDIR /usr/src/website

COPY . .

RUN npm install
RUN npm run build

EXPOSE 5000

CMD [“node”, “./“build/index.js]

And now build it

docker build -t mywebsite/nodeapp .

Now move to multiple containers for 1 app

Docker Compose

Docker Compose helps you setup multiple containers at once. Let’s say you want to have a web server, database, and application running. You would have to write lot of Shell code without Compose.

Compose offers simple way to define such architecture in human friendly way.

Docker Compose

Start by creating docker-compose.yml (or any other yml file)

Yes, it's YAML file!

Docker Compose

version: '3.1'

services:

  wordpress:
    image: wordpress
    restart: always
    ports:
      - 8080:80
    environment:
      WORDPRESS_DB_HOST: db
      WORDPRESS_DB_USER: exampleuser
      WORDPRESS_DB_PASSWORD: examplepass
      WORDPRESS_DB_NAME: exampledb
    volumes:
      - wordpress:/var/www/html

  db:
    image: mysql:5.7
    restart: always
    environment:
      MYSQL_DATABASE: exampledb
      MYSQL_USER: exampleuser
      MYSQL_PASSWORD: examplepass
      MYSQL_RANDOM_ROOT_PASSWORD: '1'
    volumes:
      - db:/var/lib/mysql

volumes:
  wordpress:
  db:

And run it

docker stack deploy -c docker-compose.yml wordpress 
# or
docker-compose -f docker-compose.yml up

That's it for today.

Any questions?

See you next time :)

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