Introduce the null provider

provider/null/provider.go

+// Copyright 2013 Canonical Ltd.
+// Licensed under the AGPLv3, see LICENCE file for details.
+
+package null
+
+import (
+        "errors"
+        "fmt"
+
+        "launchpad.net/juju-core/environs"
+        "launchpad.net/juju-core/environs/config"
+        "launchpad.net/juju-core/provider"
+        "launchpad.net/juju-core/utils"
+)
+
+type nullProvider struct{}
+
+func init() {
+        environs.RegisterProvider(provider.Null, nullProvider{})
+}
+
+var errNoBootstrapHost = errors.New("bootstrap-host must be specified")
+
+func (p nullProvider) Prepare(cfg *config.Config) (environs.Environ, error) {
+        return p.Open(cfg)
+}
+
+func (p nullProvider) Open(cfg *config.Config) (environs.Environ, error) {
+        envConfig, err := p.validate(cfg, nil)
+        if err != nil {
+                return nil, err
+        }
+        return &nullEnviron{cfg: envConfig}, nil
+}
+
+func checkImmutableString(cfg, old *environConfig, key string) error {
+        if old.attrs[key] != cfg.attrs[key] {
+                return fmt.Errorf("cannot change %s from %q to %q", key, old.attrs[key], cfg.attrs[key])
+        }
+        return nil
+}
+
+func (p nullProvider) validate(cfg, old *config.Config) (*environConfig, error) {
+        // Check for valid changes for the base config values.
+        if err := config.Validate(cfg, old); err != nil {
+                return nil, err
+        }
+        validated, err := cfg.ValidateUnknownAttrs(configFields, configDefaults)
+        if err != nil {
+                return nil, err
+        }
+        envConfig := newEnvironConfig(cfg, validated)
+        if envConfig.bootstrapHost() == "" {
+                return nil, errNoBootstrapHost
+        }
+        // Check various immutable attributes.
+        if old != nil {
+                oldEnvConfig, err := p.validate(old, nil)
+                if err != nil {
+                        return nil, err
+                }
+                for _, key := range [...]string{
+                        "bootstrap-user",
+                        "bootstrap-host",
+                        "storage-listen-ip",
+                } {
+                        if err = checkImmutableString(envConfig, oldEnvConfig, key); err != nil {
+                                return nil, err
+                        }
+                }
+                oldPort, newPort := oldEnvConfig.storagePort(), envConfig.storagePort()
+                if oldPort != newPort {
+                        return nil, fmt.Errorf("cannot change storage-port from %q to %q", oldPort, newPort)
+                }
+        }
+        return envConfig, nil
+}
+
+func (p nullProvider) Validate(cfg, old *config.Config) (valid *config.Config, err error) {
+        envConfig, err := p.validate(cfg, old)
+        if err != nil {
+                return nil, err
+        }
+        return cfg.Apply(envConfig.attrs)
+}
+
+func (_ nullProvider) BoilerplateConfig() string {
+        return `
+    "null":
+        type: "null"
+        admin-secret: {{rand}}
+        ## set bootstrap-host to the host where the bootstrap machine agent
+        ## should be provisioned.
+        bootstrap-host:
+        ## set the login user to bootstrap the machine as. If left blank,
+        ## juju will connect to the bootstrap machine as the current user.
+        # bootstrap-user:
+        ## set the IP address for the bootstrap machine to listen on for
+        ## storage requests. If left blank, storage will be served on all
+        ## network interfaces.
+        # storage-listen-ip:
+        # storage-port: 8040
+`
+}
+
+func (_ nullProvider) SecretAttrs(cfg *config.Config) (map[string]interface{}, error) {
+        return make(map[string]interface{}), nil
+}
+
+func (_ nullProvider) PublicAddress() (string, error) {
+        // TODO(axw) 2013-09-10 bug #1222643
+        //
+        // eth0 may not be the desired interface for traffic to route
+        // through. We should somehow make this configurable, and
+        // possibly also record the IP resolved during manual bootstrap.
+        return utils.GetAddressForInterface("eth0")
+}
+
+func (p nullProvider) PrivateAddress() (string, error) {
+        return p.PublicAddress()
+}