Phoenix

Web servers, API backends, and distributed messaging systems

Phoenix is ergonomic way to build web interfaces

  • MVC framework, Ruby on Rails like

  • Real-time messaging Channels allowing pubsub and websockets out of the box

  • Easy to test with high productivity & performance(observer tool can be used in prod, to find bottlenecks just see which process has a big message queue)

  • Auto hot reloading, Postgres default

  • Presence lets you replicate data across clients easily like which users are online

Phoenix Layers

  • Endpoint - lib/hello_web/endpoint.ex

    • the start and end of the request lifecycle

    • uses Plugs to do stuff like serve static files, log info, parse bodys => then routes to router

  • Router - lib/hello_web/router.ex

    • parses incoming requests and dispatches them to the correct controller/action, passing parameters as needed

    • Pipelines - groups plugs that requests can go through

  • Controllers - lib/hello_web/controllers/page_controller.ex

    • provide functions, called actions, to handle requests

    • actions:

      • prepare data then render views

      • perform redirects

  • Views - lib/hello_web/views/page_view.ex

    • controllers render templates, and views called implicitly

    • define helper functions, available in templates, to decorate data for presentation

  • Templates - lib/hello_web/templates/page/index.html.eex.

    • files that will be served allowing dynamic data/code

    • nested in the app template found in app.html.eex

  • Channels

    • manage sockets for easy realtime communication

    • are analogous to controllers except that they allow bi-directional communication with persistent connections

  • PubSub

    • underlies the channel layer and allows clients to subscribe to topics

    • abstracts the underlying pubsub adapter for third-party pubsub integration

Other parts

Plug

simple abstraction for dealing with different web servers

  • Spec to create composable functions to build pipeline for requests to response

  • Plug.Conn struct gives function for working with connections, session, body etc(both req and res object)

  • Function Plugs -> recieves a connection and options and return connection

  • Module plug is a module that must export init and call, extension of function

Cowboy

most popular small, fast, modular HTTP server written in Erlang that underlies Phoenix

Ecto

A DSL for writing queries and interacting with databases

Contexts

Dedicated Modules that expose and group related functionality

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