Use environment-uuid when interacting with MAAS

provider/maas/environprovider.go

 // Copyright 2013 Canonical Ltd.
 // Licensed under the AGPLv3, see LICENCE file for details.
 
 package maas
 
 import (
+        "errors"
         "os"
 
         "launchpad.net/loggo"
 
         "launchpad.net/juju-core/environs"
         "launchpad.net/juju-core/environs/config"
         "launchpad.net/juju-core/instance"
         "launchpad.net/juju-core/juju/osenv"
         "launchpad.net/juju-core/utils"
 )
@@ skipping 13 matching lines @@
 
 func (maasEnvironProvider) Open(cfg *config.Config) (environs.Environ, error) {
         logger.Debugf("opening environment %q.", cfg.Name())
         env, err := NewEnviron(cfg)
         if err != nil {
                 return nil, err
         }
         return env, nil
 }
 
+var errUUIDAlreadySet = errors.New(
+        "environment-uuid is already set; this should not be set by hand")
+
 func (p maasEnvironProvider) Prepare(cfg *config.Config) (environs.Environ, error) {
-        // TODO any attributes to prepare?
+        attrs := cfg.UnknownAttrs()

[thumper, 2013/10/15 21:38:03]

Didn't this bit land as r1984 on lp:juju-core?

+        uuid, found := attrs["environment-uuid"]
+        if found {
+                if uuid != "" {
+                        return nil, errUUIDAlreadySet
+                }
+        } else {
+                uuid, err := utils.NewUUID()
+                if err != nil {
+                        return nil, err
+                }
+                attrs["environment-uuid"] = uuid.String()
+        }
+        cfg, err := cfg.Apply(attrs)
+        if err != nil {
+                return nil, err
+        }
         return p.Open(cfg)
 }
 
 // Boilerplate config YAML.  Don't mess with the indentation or add newlines!
 var boilerplateYAML = `
 # https://juju.ubuntu.com/docs/config-maas.html
 maas:
     type: maas
 ··
     # maas-server specifies the location of the MAAS server. It must
@@ skipping 36 matching lines @@
 
 // PublicAddress is specified in the EnvironProvider interface.
 func (prov maasEnvironProvider) PublicAddress() (string, error) {
         return prov.hostname()
 }
 
 // PrivateAddress is specified in the EnvironProvider interface.
 func (prov maasEnvironProvider) PrivateAddress() (string, error) {
         return prov.hostname()
 }