16th June 2023

Coding⚑

Languages⚑

asyncio⚑

• New: Basic concepts of concurrency.

  Concurrency is best explained by an example stolen from Miguel Grinberg.

  Chess master Judit Polgár hosts a chess exhibition in which she plays multiple amateur players. She has two ways of conducting the exhibition: synchronously and asynchronously.

  Assumptions:

  • 24 opponents
  • Judit makes each chess move in 5 seconds
  • Opponents each take 55 seconds to make a move
  • Games average 30 pair-moves (60 moves total)

  Synchronous version: Judit plays one game at a time, never two at the same time, until the game is complete. Each game takes (55 + 5) * 30 == 1800 seconds, or 30 minutes. The entire exhibition takes 24 * 30 == 720 minutes, or 12 hours.

  Asynchronous version: Judit moves from table to table, making one move at each table. She leaves the table and lets the opponent make their next move during the wait time. One move on all 24 games takes Judit 24 * 5 == 120 seconds, or 2 minutes. The entire exhibition is now cut down to 120 * 30 == 3600 seconds, or just 1 hour.

  Async IO takes long waiting periods in which functions would otherwise be blocking and allows other functions to run during that downtime. (A function that blocks effectively forbids others from running from the time that it starts until the time that it returns.)

• New: Basic concepts.

  • AsyncIO is not easy
  • The async/await Syntax and Native Coroutines
  • The Rules of Async IO
  • Async IO Design Patterns
  • Chaining Coroutines
  • Using a Queue
  • async for and list comprehensions
  • Creating and gathering tasks
  • When and Why Is Async IO the Right Choice?
  • Async IO It Is, but Which One?
  • Testing

aiohttp⚑

• New: Introduce aiohttp.

  aiohttp is an asynchronous HTTP Client/Server for asyncio and Python. Think of it as the requests for asyncio.

  • Installation
  • How to make a request
  • Passing parameters in urls
  • Setting custom headers
  • Set custom cookies
  • Proxy support
  • How to use the ClientSession
  • An aiohttp adapter

Configure Docker to host the application⚑

• New: Add the contents of a directory to the docker.

  ADD ./path/to/directory /path/to/destination
  

DevOps⚑

Infrastructure as Code⚑

Ansible Snippets⚑

• New: Skip ansible-lint for some tasks.

  - name: Modify permissions
    command: >
      chmod -R g-w /home/user
    tags:
      - skip_ansible_lint
    sudo: yes
  

Infrastructure Solutions⚑

AWS Snippets⚑

• New: Get EC2 metadata from within the instance.

  The quickest way to fetch or retrieve EC2 instance metadata from within a running EC2 instance is to log in and run the command:

  Fetch metadata from IPv4:

  curl -s http://169.254.169.254/latest/dynamic/instance-identity/document
  

  You can also download the ec2-metadata tool to get the info:

  wget http://s3.amazonaws.com/ec2metadata/ec2-metadata
  
  chmod +x ec2-metadata
  
  ./ec2-metadata --all
  

Monitoring⚑

AlertManager⚑

• New: Alertmanager routes.

  A route block defines a node in a routing tree and its children. Its optional configuration parameters are inherited from its parent node if not set.

  Every alert enters the routing tree at the configured top-level route, which must match all alerts (i.e. not have any configured matchers). It then traverses the child nodes. If continue is set to false, it stops after the first matching child. If continue is true on a matching node, the alert will continue matching against subsequent siblings. If an alert does not match any children of a node (no matching child nodes, or none exist), the alert is handled based on the configuration parameters of the current node.

  A basic configuration would be:

  yaml route: group_by: [job, alertname, severity] group_wait: 30s group_interval: 5m repeat_interval: 12h receiver: 'email' routes: - match: alertname: Watchdog receiver: 'null'