tsmon: read hostname and region from config file

common/tsmon/iface.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 tsmon
 
 import (
         "fmt"
         "net/http"
         "net/url"
@@ skipping 81 matching lines @@
                 return err
         case mon == nil:
                 return nil // tsmon is disabled
         }
 
         // Monitoring is enabled, so get the expensive default values for hostname,
         // etc.
         if config.AutoGenHostname {
                 fl.Target.AutoGenHostname = true
         }
+        if config.Hostname != "" {
+                if fl.Target.DeviceHostname == "" {
+                        fl.Target.DeviceHostname = config.Hostname
+                }
+                if fl.Target.TaskHostname == "" {
+                        fl.Target.TaskHostname = config.Hostname
+                }
+        }
+        if config.Region != "" {
+                if fl.Target.DeviceRegion == "" {
+                        fl.Target.DeviceRegion = config.Region
+                }
+                if fl.Target.TaskRegion == "" {
+                        fl.Target.TaskRegion = config.Region
+                }
+        }
         fl.Target.SetDefaultsFromHostname()
         t, err := target.NewFromFlags(&fl.Target)
         if err != nil {
                 return err
         }
 
         Initialize(c, mon, store.NewInMemory(t))
 
         state := GetState(c)
         if state.Flusher != nil {
@@ skipping 93 matching lines @@
         case "":
                 // Let the Authenticator choose.
                 break
 
         default:
                 authOpts.Method = auth.ServiceAccountMethod
                 authOpts.ServiceAccountJSONPath = credentials
         }
         return auth.NewAuthenticator(ctx, auth.SilentLogin, authOpts).Client()
 }