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dokku

Published 2025-07-22, last edit 2025-08-12 #clojure

dokku is a PaaS (“platform as a service” or heroku-like) I’d heard about off and on over the years, but awhile back I got the chance to use it and it just worked so hard I completely forgot about it, even though it’s been running for a year.

It looks like I took notes at the time on the setup (on a debian box hosted on vultr) - named the “app” muffin, after my cat:

domain=app.neeasade.net
app_name=muffin

# on server
wget -NP . https://dokku.com/install/v0.35.7/bootstrap.sh
sudo DOKKU_TAG=v0.35.7 bash bootstrap.sh
dokku domains:set-global "$domain"
cat ~/.ssh/authorized_keys | dokku ssh-keys:add admin
dokku apps:create '$app_name'
# don't forget to open ports: 80, 443

# on your computer/from repo
# ... add Procfile, then:
git remote add dokku "dokku@$domain:$app_name"
git push dokku main

As soon as you run git push, dokku runs the Procfile! That’s all there is to it.

links:

edit: want SSL? docs

on server:

# self signed cert option:
dokku certs:generate "$app_name" key

or, Let’s Encrypt:

dokku plugin:install https://github.com/dokku/dokku-letsencrypt.git
dokku letsencrypt:cron-job --add # <- To enable auto-renew

dokku letsencrypt:set "$app_name" email your@email.tld
dokku letsencrypt:enable "$app_name"

∗ ∗ ∗

usecase:

The ct.el readme needs a few hundred color images for it’s documentation (colors are visual!), so I setup a little clojure service to send back smol square svgs. The entire source is below:

./src/muffin/handler.clj:


(ns muffin.handler
  (:require [compojure.core :refer :all]
            [compojure.route :as route]
            [ring.util.response :as resp]
            [ring.middleware.defaults :refer [wrap-defaults site-defaults]]))

(defn svg-response [svg-content]
  (-> (resp/response svg-content)
      (resp/content-type "image/svg+xml")
      (resp/header "Cache-Control" "public, max-age=31536000, immutable")))

(defn color-block
  ([color] (color-block color 16))
  ([color width]
   (when (re-matches #"[a-f0-9]{6}" color)
     (format "<svg xmlns='http://www.w3.org/2000/svg' width='%s' height='%s'>
  <rect width='%s' height='%s' fill='#%s'/>
</svg>" width width width width color))))

(defroutes app-routes
  (GET "/" [] "But why? -_-")
  (GET "/colorsquare/:color.svg" [color] (svg-response (color-block color)))
  (route/not-found "Not Found"))

(def app (wrap-defaults app-routes site-defaults))

./project.clj:

(defproject muffin "0.1.0-SNAPSHOT"
  :min-lein-version "2.0.0"
  :dependencies [[org.clojure/clojure "1.10.0"]
                 [compojure "1.6.1"]
                 [ring/ring-defaults "0.3.2"]]
  :plugins [[lein-ring "0.12.5"]]
  :ring {:handler muffin.handler/app}
  :profiles {:dev {:dependencies [[javax.servlet/servlet-api "2.5"]
                                  [ring/ring-mock "0.3.2"]]}})

./Procfile:

web: lein ring server-headless