Butler: export Coordinator host in environment.

logdog/client/butlerlib/bootstrap/bootstrap.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package bootstrap
 
 import (
         "errors"
         "fmt"
 
         "github.com/luci/luci-go/client/environ"
         "github.com/luci/luci-go/common/config"
         "github.com/luci/luci-go/logdog/client/butlerlib/streamclient"
         "github.com/luci/luci-go/logdog/common/types"
 )
 
 // ErrNotBootstrapped is returned by Get when the current process is not
 // bootstrapped.
 var ErrNotBootstrapped = errors.New("not bootstrapped")
 
-// Bootstrap contains information about the
+// Bootstrap contains information about the configured bootstrap environment.
+//
+// The bootstrap environment is loaded by probing the local application
+// environment for variables emitted by a bootstrapping Butler.
 type Bootstrap struct {
+        // CoordinatorHost is the name of the upstream Coordinator host.
+        //
+        // This is just the host name ("example.appspot.com"), not a full URL.
+        //
+        // If this instance is not configured using a production Coordinator Output,
+        // this will be empty.
+        CoordinatorHost string
+
         // Project is the Butler instance project name.
         Project config.ProjectName
         // Prefix is the Butler instance prefix.
         Prefix types.StreamName
 
         // Client is the streamclient for this instance, or nil if the Butler has no
         // streamserver.
         Client streamclient.Client
 }
 
 func getFromEnv(env environ.Environment, reg *streamclient.Registry) (*Bootstrap, error) {
         // Detect Butler by looking for EnvStreamPrefix in the envrironent.
         prefix, ok := env[EnvStreamPrefix]
         if !ok {
                 return nil, ErrNotBootstrapped
         }
 
         bs := &Bootstrap{
-                Prefix:  types.StreamName(prefix),
-                Project: config.ProjectName(env[EnvStreamProject]),
+                CoordinatorHost: env[EnvCoordinatorHost],
+                Prefix:          types.StreamName(prefix),
+                Project:         config.ProjectName(env[EnvStreamProject]),
         }
         if err := bs.Prefix.Validate(); err != nil {
                 return nil, fmt.Errorf("bootstrap: failed to validate prefix %q: %s", prefix, err)
         }
         if err := bs.Project.Validate(); err != nil {
                 return nil, fmt.Errorf("bootstrap: failed to validate project %q: %s", bs.Project, err)
         }
 
         // If we have a stream server attached; instantiate a stream Client.
         if p, ok := env[EnvStreamServerPath]; ok {
                 c, err := reg.NewClient(p)
                 if err != nil {
                         return nil, fmt.Errorf("bootstrap: failed to create stream client [%s]: %s", p, err)
                 }
                 bs.Client = c
         }
 
         return bs, nil
 }
 
 // Get loads a Bootstrap instance from the environment. It will return an error
 // if the bootstrap data is invalid, and will return ErrNotBootstrapped if the
 // current process is not bootstrapped.
 func Get() (*Bootstrap, error) {
         return getFromEnv(environ.Get(), streamclient.DefaultRegistry)
 }