In this episode of Running in Production, Adam Conrad goes over building a Slack bot service with Phoenix and Elixir. It’s hosted with Gigalixir for about $50 / month and has been up and running since mid 2018.

Adam talks about the wonderful Elixir community along with how Elixir helps him manage a bunch of concurrent tasks for his service. He also goes over a number of features that you get from using Gigalixir to host your Elixir projects.

Topics Include

• 1:31 – Adam is the sole developer but he has a friend who helps him market the service
• 2:38 – The Slack bot asks you a number of questions, such as your music preference
• 6:01 – The public site uses Phoenix and the bot is written in Elixir
• 6:25 – What made Elixir a perfect fit for this application?
• 7:38 – Handling concurrency through tasks using Elixir’s standard library
• 9:16 – Several thousand questions are answered per day
• 10:23 – It’s all done through Slack webhooks using the Elixir-Slack library
• 11:28 – Slack bots are easy to start using but it gets complicated pretty quickly
• 12:26 – Unix timestamps vs Gregorian seconds
• 13:39 – The Elixir forums and Slack channel are great resources to get Elixir help
• 15:13 – Are you using the latest version of Phoenix? Not yet
• 17:50 – Phoenix is nice because it gently guides you into creating well structured apps
• 19:19 – The stripity_stripe library is used to handle Stripe payments
• 19:52 – The awesome-elixir repo on GitHub has a great list of libraries
• 21:25 – It was hard to find a good well maintained authentication library for Elixir
• 22:50 – The Elixir-Slack library was really helpful for Adam’s project
• 23:59 – Everything is stored in a PostgreSQL database
• 25:02 – Gigalixir is used for hosting and it’s well optimized for running Elixir in production
• 25:56 – Gigalixir has really good support
• 26:25 – Gigalixir’s team is mostly composed of ex-Google / ex-Stripe employees
• 27:50 – Gigalixir also has zero down time deploys for most deploys
• 28:42 – nginx isn’t being used and Gigalixir handles TLS too
• 30:20 – The push for HTTPS everywhere and Let’s Encrypt being easy but not that easy
• 31:15 – Accessing your logs on Gigalixir by tailing your logs on the command line
• 32:31 – Adam pays about $50 a month for everything on Gigalixir
• 33:59 – Metrics related to server health can be found in the Gigalixir dashboard
• 34:14 – Surviving the front page of HackerNews with an Elixir app on a hobby instance
• 35:22 – Depending on user feedback for error reporting
• 36:28 – It’s super nice to have a compiler warn you about flaws in your code
• 36:57 – Gigalixir lets you git push your code to get it from your dev box into production
• 38:04 – Code is also pushed to GitHub mainly for backup purposes
• 38:23 – Code is tested locally before being pushed but testing a Slack integration is hard
• 42:18 – Putting an app on the Slack app marketplace requires human review
• 44:30 – Managing secrets with Gigalixir is done through their CLI, similar to Heroku
• 45:03 – Database backups happen daily but the interval on Gigalixir can be configured
• 47:26 – Email alerts are sent out by Gigalixir if your app happens to go down
• 48:59 – Best tips? Leverage the Elixir community if you get stuck
• 49:24 – Enjoy a language that a bit of novelty to it since it’s still relatively young
• 50:37 – Getting help for basic things from the creator of Elixir on IRC
• 51:47 – Constantly looking at older code to see how it could be refactored
• 52:57 – Using the Credo library to help analyze your code base for best practices
• 55:07 – Check out their Slack app, follow Adam on Twitter @theadamconrad and GitHub

Links

• https://www.phoenixframework.org/blog/the-road-to-2-million-websocket-connections
• https://api.slack.com/messaging/webhooks
• https://adamconrad.dev/blog/verifying-request-signatures-in-elixir-phoenix/
• https://elixir-lang.slack.com/
• https://github.com/h4cc/awesome-elixir
• https://www.postgresql.org/
• https://twitter.com/josevalim

• phoenix →
• elixir →
• gigalixir →
• postgres →
• slack →
• stripe →

• https://github.com/BlakeWilliams/Elixir-Slack
• https://github.com/code-corps/stripity_stripe
• https://github.com/rrrene/credo

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