Make the Watcher strip the prefix on keys

And remove the unused StringSet type.

coordination/watcher/watcher.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"log"
-	"math/rand"
 	"sync"
 	"time"
 
@@ -111,95 +110,9 @@ func NewNotifyWatchable(ctx context.Context, w Watchable) NotifyWatchable {
 	}
 }
 
-// A StringSet is a particular type of Watchable where we are only
-// interested in the entry values, not their keys. Furthermore, the
-// values are plain strings. This is useful, for instance, for a list
-// of IP addresses.
-//
-// The StringSet keeps track of the keys, so if an entry changes value
-// we can handle it correctly (the previous value is removed from the
-// set).
-//
-// All methods are goroutine-safe. The nil value represents an empty
-// but valid set.
-//
-type StringSet struct {
-	mx sync.Mutex
-	m  map[string]string
-	l  []string
-}
-
-// Reset the contents of the set. Implements the Watchable interface.
-func (s *StringSet) Reset(m map[string]string) {
-	s.mx.Lock()
-	s.m = m
-	s.l = nil
-	for _, value := range m {
-		s.l = append(s.l, value)
-	}
-	s.mx.Unlock()
-}
-
-// Add an entry to the set. Implements the Watchable interface.
-func (s *StringSet) Add(key, value string) {
-	s.mx.Lock()
-	if s.m == nil {
-		s.m = make(map[string]string)
-	}
-	oldValue, ok := s.m[key]
-	if ok {
-		s.deleteValue(oldValue)
-	}
-	s.m[key] = value
-	s.l = append(s.l, value)
-}
-
-// Delete an entry from the set. Implements the Watchable interface.
-func (s *StringSet) Delete(key string) {
-	s.mx.Lock()
-	defer s.mx.Unlock()
-
-	if s.m == nil {
-		return
-	}
-	oldValue, ok := s.m[key]
-	if !ok {
-		return
-	}
-	s.deleteValue(oldValue)
-	delete(s.m, key)
-}
-
-func (s *StringSet) deleteValue(oldValue string) {
-	var l []string
-	for _, value := range s.l {
-		if value != oldValue {
-			l = append(l, value)
-		}
-	}
-	s.l = l
-}
-
-// RandomEntry returns a random entry from those currently active. If
-// the list is empty, the empty string is returned.
-func (s *StringSet) RandomEntry() string {
-	s.mx.Lock()
-	defer s.mx.Unlock()
-	if len(s.l) == 0 {
-		return ""
-	}
-	return s.l[rand.Intn(len(s.l))]
-}
-
-// Values returns all the currently known values.
-func (s *StringSet) Values() []string {
-	s.mx.Lock()
-	defer s.mx.Unlock()
-	// Try to make a copy.
-	return append([]string{}, s.l...)
-}
-
 func watchOnce(ctx context.Context, cli *clientv3.Client, prefix string, target Watchable) error {
+	plen := len(prefix)
+
 	// First populate the target with a prefix-ranged Get and call
 	// Reset because we have all the authoritative data.
 	resp, err := cli.Get(ctx, prefix, clientv3.WithPrefix(), clientv3.WithSort(clientv3.SortByKey, clientv3.SortAscend))
@@ -208,7 +121,8 @@ func watchOnce(ctx context.Context, cli *clientv3.Client, prefix string, target
 	}
 	m := make(map[string]string)
 	for _, ev := range resp.Kvs {
-		m[string(ev.Key)] = string(ev.Value)
+		key := string(ev.Key)[plen:]
+		m[key] = string(ev.Value)
 	}
 	target.Reset(m)
 	rev := resp.Header.Revision
@@ -218,11 +132,12 @@ func watchOnce(ctx context.Context, cli *clientv3.Client, prefix string, target
 	for resp := range rch {
 		for _, ev := range resp.Events {
 			fmt.Printf("%s %q : %q\n", ev.Type, ev.Kv.Key, ev.Kv.Value)
+			key := string(ev.Kv.Key)[plen:]
 			switch ev.Type {
 			case clientv3.EventTypePut:
-				target.Set(string(ev.Kv.Key), string(ev.Kv.Value))
+				target.Set(key, string(ev.Kv.Value))
 			case clientv3.EventTypeDelete:
-				target.Delete(string(ev.Kv.Key))
+				target.Delete(key)
 			}
 		}
 	}