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.

Elixir

Code on GitHub: ronnyhartenstein/site-heartbeat-elixir

Learnings:

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

Go

Code on GitHub: ronnyhartenstein/site-heartbeat-golang

Learnings:

• 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 github.com/ronnyhartenstein/site-heartbeat-golang
• try hard to do it the pragmatic getting-stuff-done-way

Conclusion

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.