ElixirDaze 2018

Notes and links from ElixirDaze 2018 held on March 1-2, 2018 in Denver, CO.

Website | Twitter | #ElixirDaze2018

Recorded Presentations from Confreaks are available at https://confreaks.tv/events/elixirdaze2018

Thursday

Keynote - Rob Conery

Video: http://confreaks.tv/videos/elixirdaze2018-keynote

Why Elixir Matters - Osa Gaius

Video: http://confreaks.tv/videos/elixirdaze2018-why-elixir-matters-a-genealogy-of-functional-programming
Slides: https://speakerdeck.com/osayame/why-elixir-matters-a-genealogy-of-functional-programming-lonestar-elixirconf-2018

• The rise in popularity of the internet and the need for non-interrupted availability of services has extended a class of problems that Erlang can solve - Joe Armstrong

• Explained History of functional programming including Lambda Calculus in the 30's, Lisp in 1960, Scheme in 1970, and Erlang in 1986 etc.

Making Noise - Ben Marx

Video: http://confreaks.tv/videos/elixirdaze2018-making-noise

• API Gateway Pros - Simple, Secure
• API Gateway single point of failure
  • change things in isolation not everything at once
  • coupled service dependencies
  • app fallback logic / how to function in degraded state
    • Task.await vs Task.yield for async calls
      • Task.await - known you want it to crash if error happens
      • Task.yield - use for unpredictable scenarios (3rd party)
    • prevent all or nothing response if possible, incremental response (progressive API design)
  • Fastly / varnish intercept and reduce load on actual gateway to make it more resilient for things not needed to go directly through gateway
• architecture - systems and people
  • system lifecycle
  • Wabi-Sabi - basically implies that things can be imperfect and unfinished, yet still beautiful
  • Systems
    • Plan > Code > QA > Deploy -- this doesn't actually work in life or in software development
    • Instead, you introduce, evaluate, adjust, and start again.
    • App Fallback Logic -- Things fall apart, not realistic for things to work at all times,
    • Using task.yield instead of task.await
  • People
    • People lifecycle uses introduce > evaluate > adjust schedule
    • Trusted Autonomy - Trust but Verify
    • Bidirectional Ideas
  • Using kafka with erlang drivers and elixer driver
    • elixir driver crashed server
    • didn't know whether to fix driver or switch services or what
    • ended up building ruby library
  • growth, decay, growth
    • test, docs, standards in place to prevent large periods of decay
    • Embrace idea of symmetry and dissonance and whatever you do now will decay in so many months
• introducing new technology
  • choose least worst option (works for now, periodically re-evaluate)
  • needs maintained - requires people
  • isolate experimentation

Consistent Distributed Elixir - Chris Keathley

Video: http://confreaks.tv/videos/elixirdaze2018-consistent-distributed-elixir
Raft: https://github.com/toniqsystems/raft

• everything is a process in erlang
• limit access to external resource
  • genserver for global lock
• run multiple nodes
  • GenServer.start_link with global lock
  • if node with global lock process goes away other node would start up new global process
  • if nodes cant talk due to network issue, multiple nodes could have processes that can be reached by clients
• have a way to consistently manage state in elixir other than databases
  • distributed systems - cap theorem
    • When a network is partitioned you can either be available or consistent
    • Some problems need consistency
    • available vs consistent
      • Available
        • Every request receives a response without guarantee that it contains the most recent write
      • Consistent
        • Every read receives the most recent write but may not always receive a response
      • AP - Available during partitions
      • CP - Consistent during partitions
    • paxos => raft
    • logs - linearized writes on top of rocksdb, replicated across all nodes
    • Leader/follower distributed system design

Crypto + Concurrency - Anna Neyzberg

Video: http://confreaks.tv/videos/elixirdaze2018-crypto-concurrency

• Big idea behind cryptocurrencies is a digital transfer over internet that isnt back by hard collateral
• semi anonymous and secure
• Cryptography
  • bitcoin uses proof-of-work from hashcash(earliest form of digital currency)
• How dows bitcoin work?
  • a decentralized cluster of nodes
  • each node has its own copy of the blockchain
  • blockchain is just ledger of transactions
  • each data point points to the previous data point
• How does relate to Elixir?
  • decentralized ledger
  • processes - message processing
    • light weight
    • ways to communicate between processes
      • send
      • receive
    • agents - agents manage state

Deep Dive into Hex - Todd Resudek

Video: http://confreaks.tv/videos/elixirdaze2018-a-deep-dive-into-hex
Slides: https://github.com/supersimple/deep-dive-into-hex-slides

• Hex is the pkg manager for erlang / elixir ecosystem
  • It is analagous to NPM for Node.js, or Gems for Ruby
  • Hex has about 6000 packages available compared to RubyGems 9200
  • Hex allows you to work fawster, prevent issues, debug quicker
• Available Packages
  • Hex - 6000
  • Rugy Games - 9200
  • Crates - 14000
  • NPM - 500000
• mix hex.info
  • mix hex.info packagename
  • mix hex.info packagename version
• mix hex.search term
  • finds packages
• mix hex.docs online packagename (hex 0.17.4)
  • loads up documentation for packagename
  • only compatible with > 0.17
• mix hex.docs online packagename version
• mix hex.docs fetch
  • (offline - downloads docs for all dependencies in your current app)
• mix hex.docs fetch packagename (outside of app)
• mix hex.docs offline packagename (will download if it isnt already fetched)
• use -latest flag to override
• mix hex.user register
  • mix hex.user reset_password local
  • mix hex.user reset_password account (hex.pm user)
  • mix hex.user key -lost
  • mix hex.user key -revoke keyname
  • mix hex.user key --revoke-all
  • mix hex.auth
  • mix hex.config
  • mix hex.config key
• mix hex.outdated (shows current, latest, update, update possible)
  • --all will list all
• mix hex.audit
  • shows retired packages that you have installed as dependencies
• mix hex.publish
  • can publish privately
  • watch out for pre-release dependencies
• mix hex.retire
  • signifies a package is no longer recommended
  • retirement must include a valid reason

Format Your Elixir Code Now - Jake Worth

Video: http://confreaks.tv/videos/elixirdaze2018-format-your-elixir-code-now
Slides: https://speakerdeck.com/jwworth/format-your-elixir-code-now

• Linting vs Autoformatting
  • Linter - recommends changes
  • Autoformatter - recommends/changes code
• languages provide a lot of different ways to do the same thing
• Pros of Autoformatting
  • productivity
    • gives more time for important decisions
  • consistency
    • friendliness to new comers to your code
    • helps relieve workload on manual code reviews
  • collective ownership
• Negs of Autoformatting
  • disregards any particular programmers preferred coding style
• Autoformatter for Elixir requireed after 1.6, forcing uniform code
• Distinct style guides separate us
  • Elixir should have consistent style
  • We need collective ownership
• CI run mix format --check-formated

Is Security on Your Nerves? - Paul Rogers

Video: http://confreaks.tv/videos/elixirdaze2018-is-security-on-your-nerves

• Security between Http based communication
• Https does not secure your network calls to be safe from ManInTheMiddle Attacks
• RSA
  • Both client and server have a piece of the puzzle besides the password and username
  • These pieces are not sent over the http request but instead used for calculations to determine if the other side is who they say they are.

Hardware without Hardware or Lightning without Lightning - Amos King

Video: http://confreaks.tv/videos/elixirdaze2018-hardware-without-hardware-or-lightning-without-lightning
Slides: https://github.com/BinaryNoggin/lightning_without_lightning
Code: https://github.com/adkron/grovepi/tree/lightning-sensor

Friday

Keynote: The Hitchhiker’s Guide to the Unexpected - Fred Hebert

Video: http://confreaks.tv/videos/elixirdaze2018-keynote-the-hitchhiker-s-guide-to-the-unexpected

• property based testing
• supervisors
  • permanent, transient, temporary
  • supervisors, boot order
  • know how it boots, how it fails, supervision tree

Taking Elixir to the Metal - Sonny Scroggin

Video: http://confreaks.tv/videos/elixirdaze2018-taking-elixir-to-the-metal
Rustler: https://github.com/hansihe/rustler

• elixir and outside world: ports, erl_interface, C Nodes, Port Drivers, NIFs
  • mix uses port to talk to git binary, jiffy uses NIF
  • Erlangs inet_drv port driver for networking
  • Jiffy JSON encoding/decoding
    • really fast json encoder
    • written in C
• NIFs - Native Implemented Functions
  • Usually implemented in C\C++
  • Reasons to write
    • Erlang was not designed for raw CPU throughput
    • Deal directly hardware
    • Interop w/ graphics
    • Functionality already exists in C code already exosts
  • called just like any erlang/elixir code
  • NIFs live in dynamically loaded libraries
  • NIFs replace erlang/elixir functions of the same name at module load time
  • Functionality
    • Read and write erlang terms
    • binaries
    • resource objects
    • lengthy work from NIF degrades resp of VM
    • Dont block the schedulers
      • blocked scheduler can't run other processess
      • NIF should never take over a scheduler for more than 1ms
      • options
        • chunking - repeated calls to nif
        • rescheduling (not in rustler at this time)
        • threaded NIFs
    • NIF Resource Objects
      • only real usage is to pass it back as an arg to a NIF
      • safe way to return pointers to native data structures
  • erl_nif.h in C
    • ErlEnv
      • Passed as the first argument to all NIFs
      • Represents an environment that can host erlang terms
      • contains info about calling erlang process
      • All terms in an environment are valid as long as the environment is valid
    • ERL_NIF_TERM
  • Rustler - lib for writing Erlang NIFs in Rust
    • https://github.com/hansihe/rustler
    • Handles encoding and decoding of erlang tems
    • Catches rust panics beffore they unwind to C
    • Provides faciliities for generating the bolilerplate for interacting with the Erlang VM
    • code you write in Rust NIF should never be able to crash the Erlang VM
  • Nif Resource Objects
    • safe way t oreturn pointers to native data strctures from a nIF
    • Can be stored and passed between processes on the same code
    • The only real end usage is to pass it back as an argument to a NIF
  • Rescheduling
    • Erlang NIF API provides a way for a NIF to reschedule itself directly with enif_schedule_nif
    • Combined with rustler::schedule::consume_timeslice allows all chunking to be done directly in the NIF
    • Not yet supported in Rustler due to safety conc=rns.
  • Thread NIFs
    • Spawn a separate OS thread to do the work
    • Send the result as a message to the calling process.
  • Dirty NIFs
    • allows you to call a NIF w/o worrying about blocking a normal scheduler
    • by default have same number of dirty schedulers as normal schedulers

Build your own web framework in Elixir - German Velasco

Video: http://confreaks.tv/videos/elixirdaze2018-build-your-very-own-web-framework-in-elixir
Slides: https://speakerdeck.com/germsvel/build-your-own-web-framework-in-elixir
Code: https://github.com/germsvel/daze

• Cowboy, Plug, EEx
• Basics
  • really quick step by step of getting started with Cowboy.
  • have to add plugs for routing and logging get requests etc
• Templates with EEx
  • require EEx
  • compiles template to a function by passing the template and variables
  • comes with smart engine out of the box
• Handling Forms
  • use plug parsers and define what kind of parser you want, (urlencoded, multipart)
  • connection construct has query params key, body params key, and params key
  • define the route and module
  • define all function to retrieve all posts
  • throw into supervision tree
• Sessions
  • Use Plug.session with cookie and a key for the cookie and define a signing salt
  • In order to access session, need secret_key_base
• Static Assets
  • use Plug.Static
  • going to look for static asset, if cant find it, it goes throught other plugs
  • can limit directories to look with only:
  • priv/static/css

Become a Test Whisperer: what are your tests are telling you? - Jeffrey Matthias

Video: https://confreaks.tv/videos/elixirdaze2018-become-a-test-whisperer-what-are-your-tests-are-telling-you
Slides: https://speakerdeck.com/idlehands/elixirdaze-become-a-test-whisperer-what-are-your-tests-telling-you

Purify your web development with Raxx - Peter Saxton

Video: https://confreaks.tv/videos/elixirdaze2018-purify-your-web-development-with-raxx
Talk: http://crowdhailer.me/2018-01-17/simple-web-services-with-ace/   Raxx: https://github.com/CrowdHailer/raxx
Ace: https://github.com/CrowdHailer/Ace

• HTTP interface for servers, frameworks
• Ace - server to run Raxx apps
  • HTTP/2 + HTTPS by default

Building beautiful systems with Phoenix contexts and Domain-Driven Design - Andrew Hao

Video: https://confreaks.tv/videos/elixirdaze2018-building-beautiful-systems-with-phoenix-contexts-and-domain-driven-design
Slides: https://speakerdeck.com/andrewhao/building-beautiful-systems-with-phoenix-contexts-and-ddd

• High Cohesion
  • Similar concepts belong together in code
• Loose Coupling
  • minimal dependencies on external systems
• Contexts
  • Elixir modules that group system functionality
  • mix phx.gen.html Identity User users name:string email:string
    • lib/my_app/identity/identity.ex
    • All web concerns live in web context
  • DDD
    • Design your software systems according your business domains by paying attention to the language you speak in the business
    • Context mapping
      • Get everyone in the room, put up on a wall
        • Nouns - entities
        • Verbs - events
      • Group like concepts and actions together
      • Core domain - primary area of focus of your business
      • Supporting Domain - subdomain - areas that play roles in makine the core domain happen
        • natural groupings will emerge
      • Ubiquitous language, make a glossary, consistently use same terms in code and in discussion
      • Anti-Corruption Layer
      • Aggregates
      • Publish facts (domain events) over a bus
        • Interested contexts can subscribe
        • https://github.com/otobus/event_bus

Abstract Alchemy: Monads, ADTs, and Parallelized Pipes - Brooklyn Zelenka

Video: https://confreaks.tv/videos/elixirdaze2018-don-t-let-it-crash-safe-and-convenient-error-handling-with-exceptional
Witchcraft - https://github.com/expede/witchcraft