examples/traefik: Make pure

examples/traefik/arion-compose.nix

@@ -1,26 +1,47 @@
-{ pkgs, ... }: {
+/*
+ 
+  An example of
+   - traefik HTTP reverse proxy
+   - minimal images
+   - routing via docker labels
+
+  Run `arion up -d` and open http://nix-docs.localhost/
+
+ */
+{ lib, pkgs, ... }: {
 
   config.services = {
-    traefik.service = {
-      image = "traefik:v2.4";
-      container_name = "traefik";
-      command = [
+    traefik = {
+      image.command = [
+        "${pkgs.traefik}/bin/traefik"
         "--api.insecure=true"
         "--providers.docker=true"
         "--providers.docker.exposedbydefault=false"
         "--entrypoints.web.address=:80"
       ];
-      ports = [ "80:80" "8080:8080" ];
-      volumes = [ "/var/run/docker.sock:/var/run/docker.sock:ro" ];
+      service = {
+        container_name = "traefik";
+        stop_signal = "SIGINT";
+        ports = [ "80:80" "8080:8080" ];
+        volumes = [ "/var/run/docker.sock:/var/run/docker.sock:ro" ];
+      };
     };
 
-    whoami.service = {
-      image = "traefik/whoami";
-      container_name = "simple-service";
-      labels = {
+    nix-docs = {
+      image.command = ["${pkgs.writeScript "entrypoint" ''
+        #!${pkgs.bash}/bin/bash
+        cd ${pkgs.nix.doc}/share/doc/nix/manual
+        ${pkgs.python3}/bin/python -m http.server
+      ''}"];
+      service.container_name = "simple-service";
+      service.ports = [
+        "8000:8000" # host:container
+      ];
+      service.stop_signal = "SIGINT";
+      service.labels = {
         "traefik.enable" = "true";
-        "traefik.http.routers.whoami.rule" = "Host(`whoami.localhost`)";
-        "traefik.http.routers.whoami.entrypoints" = "web";
+        "traefik.http.routers.nix-docs.rule" = "Host(`nix-docs.localhost`)";
+        "traefik.http.routers.nix-docs.entrypoints" = "web";
       };
     };
   };