store: config file for commands to avoid disclosing passwords

store/charmd/main.go

 package main
 
 import (
         "fmt"
+        "io/ioutil"
+        "launchpad.net/goyaml"
         "launchpad.net/juju/go/log"
         "launchpad.net/juju/go/store"
         stdlog "log"
         "net/http"
         "os"
         "path/filepath"
 )
 
 func main() {
         log.Target = stdlog.New(os.Stdout, "", stdlog.LstdFlags)
         err := serve()
         if err != nil {
                 fmt.Fprintf(os.Stderr, "%v\n", err)
                 os.Exit(1)
         }
 }
 
-func goodArg(arg string) bool {
-        return len(arg) > 0 && arg[0] != '-'
+type config struct {
+        MongoURL string `yaml:"mongo-url"`
+        APIAddr string `yaml:"api-addr"`
+}
+
+func readConfig(path string, conf interface{}) error {
+        f, err := os.Open(path)
+        if err != nil {
+                return fmt.Errorf("opening config file: %v", err)
+        }
+        data, err := ioutil.ReadAll(f)
+        f.Close()
+        if err != nil {
+                return fmt.Errorf("reading config file: %v", err)
+        }
+        err = goyaml.Unmarshal(data, conf)
+        if err != nil {
+                return fmt.Errorf("processing config file: %v", err)
+        }
+        return nil
 }
 
 func serve() error {
-        if len(os.Args) != 3 || !goodArg(os.Args[1]) || !goodArg(os.Args[2]) {
-                return fmt.Errorf("usage: %s <mongo addr> <http addr>", filepath.Base(os.Args[0]))
+        var confPath string
+        if len(os.Args) == 2 {
+                if _, err := os.Stat(os.Args[1]); err == nil {
+                        confPath = os.Args[1]
+                }
         }
-        s, err := store.Open(os.Args[1])
+        if confPath == "" {
+                return fmt.Errorf("usage: %s <config path>", filepath.Base(os.Args[0]))
+        }
+        var conf config
+        err := readConfig(confPath, &conf)
         if err != nil {
                 return err
         }
+        if conf.MongoURL == "" || conf.APIAddr == "" {
+                return fmt.Errorf("missing mongo-url or api-addr in config file")
+        }
+        s, err := store.Open(conf.MongoURL)
+        if err != nil {
+                return err
+        }
         defer s.Close()
         server, err := store.NewServer(s)
         if err != nil {
                 return err
         }
-        return http.ListenAndServe(os.Args[2], server)
+        return http.ListenAndServe(conf.APIAddr, server)
 }