worker/peergrouper: implement worker

utils/voyeur/value.go

 // Copyright 2012, 2013 Canonical Ltd.
 // Licensed under the AGPLv3, see LICENCE file for details.
 
 // Package voyeur implements a concurrency-safe value that can be watched for
 // changes.
 package voyeur
 
 import (
         "sync"
 )
@@ skipping 46 matching lines @@
 // returns nil.
 func (v *Value) Close() error {
         v.mu.Lock()
         v.init()
         v.closed = true
         v.mu.Unlock()
         v.wait.Broadcast()
         return nil
 }
 
-// Get returns the current value. If the Value has been closed, ok will be
-// false.
-func (v *Value) Get() (val interface{}, ok bool) {
+// Closed reports whether the value has been closed.
+func (v *Value) Closed() bool {

[natefinch, 2014/02/26 21:10:29]

This is so much better, thanks.

         v.mu.RLock()
         defer v.mu.RUnlock()
-        if v.closed {
-                return v.val, false
-        }
-        return v.val, true
+        return v.closed
+}
+
+// Get returns the current value.
+func (v *Value) Get() interface{} {
+        v.mu.RLock()
+        defer v.mu.RUnlock()
+        return v.val
 }
 
 // Watch returns a Watcher that can be used to watch for changes to the value.
 func (v *Value) Watch() *Watcher {
         return &Watcher{value: v}
 }
 
 // Watcher represents a single watcher of a shared value.
 type Watcher struct {
         value   *Value
@@ skipping 49 matching lines @@
         w.closed = true
         w.value.mu.Unlock()
         w.value.wait.Broadcast()
 }
 
 // Value returns the last value that was retrieved from the watched Value by
 // Next.
 func (w *Watcher) Value() interface{} {
         return w.current
 }