main.go

package main

import (
	"fmt"
	"os"
	"strconv"
	"text/template"
)

var tmpl = `
# {{.Service}}.uss-lib-staging.uoregon.edu
upstream {{.Service}}.uss-lib-staging.uoregon.edu {
  server 127.0.0.1:{{.Port}};
}
server {
  server_name {{.Service}}.uss-lib-staging.uoregon.edu;
  listen 80;
  access_log /var/log/nginx/access.log vhost;
  return 301 https://$host$request_uri;
}
server {
  server_name {{.Service}}.uss-lib-staging.uoregon.edu;
  listen 443 ssl http2;
  access_log /var/log/nginx/access.log vhost;
  ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
  ssl_ciphers 'ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:!DSS';
  ssl_prefer_server_ciphers on;
  ssl_session_timeout 5m;
  ssl_session_cache shared:SSL:50m;
  ssl_session_tickets off;
  ssl_certificate /etc/nginx/certs/default.crt;
  ssl_certificate_key /etc/nginx/certs/default.key;
  add_header Strict-Transport-Security "max-age=31536000";
  location / {
    proxy_pass http://{{.Service}}.uss-lib-staging.uoregon.edu;
  }
}
`

type Definition struct {
	Service string
	Port    int
}

func main() {
	var service = os.Getenv("SERVICE")
	var port = os.Getenv("PORT")
	var errs []string
	if service == "" {
		errs = append(errs, "SERVICE environment variable must be set")
	}
	var pnum, _ = strconv.Atoi(port)
	if pnum < 1 {
		errs = append(errs, "PORT environment variable must be set to a positive number")
	}
	if len(errs) > 0 {
		fmt.Fprintln(os.Stderr, "Cannot generate config:")
		for _, e := range errs {
			fmt.Fprintln(os.Stderr, "  - "+e)
		}
		fmt.Fprintln(os.Stderr)
		fmt.Fprintln(os.Stderr, "Usage example:")
		fmt.Fprintln(os.Stderr)
		fmt.Fprintf(os.Stderr, "SERVICE=foo PORT=18333 %s\n", os.Args[0])
		fmt.Fprintln(os.Stderr)
		os.Exit(1)
	}

	var t = template.Must(template.New("conf").Parse(tmpl))
	var data = Definition{Service: service, Port: pnum}

	var fname = service+"-"+port+".conf"
	var f, err = os.Create(fname)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Unable to create config file %q: %s\n", fname, err)
		os.Exit(1)
	}
	defer f.Close()
	err = t.Execute(f, data)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Unable to process config template: %s\n", err)
		os.Exit(1)
	}

	fmt.Printf("Config file %q created. Copy this to /etc/nginx/conf.d/%s, then reload nginx\n", fname, fname)
}