Coding Kata: Site Heartbeat in Elixir and Golang

Our today coding kata is a website heartbeat system. It checks the correct <title> for a bunch of domains. If a site is down, or the title is wrong, it should send a email. Of course it will do the job in parallel.

I’ll try it with Elixir and Go for fun and learning - and to have a bit of monitoring my sites.


Code on GitHub: ronnyhartenstein/site-heartbeat-elixir


  • build mix targets using Mix.Task
  • prepare stuff for escript (cli.ex) and use it for one-file-deployment (mix
  • read a text (the domains and titles) file as a stream with
  • parallel processing with
  • fetch sites body with HTTPoison.get
  • parse <title> using
  • tried to send mails with Mailer.compose_email but failed
  • try hard to do it the functional way!


Code on GitHub: ronnyhartenstein/site-heartbeat-golang


  • read a plain text file (the domains and titles) with ioutil.ReadFile
  • use goroutines for parallel processing and sync it with sync.WaitGroup
  • fetch and parse sites body with goquery - a jQuery like lib
  • use regexp to check the <title> string with regexp.MatchString
  • read a JSON config (the mailer config) as a Go struct with json.Unmarshal
  • send a mail TLS secured with net/mail, net/smtp and crypto/tls
  • for program organisation it is a good practise to split it into some files, but each is in package “main”
  • cross compile for linux from a mac via env GOOS=linux GOARCH=386 go build
  • try hard to do it the pragmatic getting-stuff-done-way


This kata was quite a lot of fun! I’m surprised how many diffent things I could touch on this small use case. Working with files, parsing configs, query websites, parsing body, sending mails, dealing with errors.