Naive string iterning for labes & values in the remote_write path.

Signed-off-by: Tom Wilkie <tom.wilkie@gmail.com>

storage/remote/codec.go

@@ -363,32 +363,12 @@ func labelProtosToLabels(labelPairs []prompb.Label) labels.Labels {
 	return result
 }
 
-func labelsetToLabelsProto(ls model.LabelSet) []prompb.Label {
-	result := make([]prompb.Label, 0, len(ls))
-	keys := make([]string, 0, len(ls))
-
-	for k := range ls {
-		keys = append(keys, string(k))
-	}
-	sort.Strings(keys)
-
-	for _, k := range keys {
-		ln := model.LabelName(k)
-		result = append(result, prompb.Label{
-			Name:  k,
-			Value: string(ls[ln]),
-		})
-	}
-
-	return result
-}
-
 func labelsToLabelsProto(labels labels.Labels) []prompb.Label {
 	result := make([]prompb.Label, 0, len(labels))
 	for _, l := range labels {
 		result = append(result, prompb.Label{
-			Name:  iterner.intern(l.Name),
-			Value: iterner.intern(l.Value),
+			Name:  interner.intern(l.Name),
+			Value: interner.intern(l.Value),
 		})
 	}
 	return result

storage/remote/intern.go

@@ -0,0 +1,65 @@
+// Copyright 2019 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Inspired / copied / modified from https://gitlab.com/cznic/strutil/blob/master/strutil.go,
+// which is MIT licensed, so:
+//
+// Copyright (c) 2014 The strutil Authors. All rights reserved.
+
+package remote
+
+import "sync"
+
+var interner = newPool()
+
+type pool struct {
+	mtx  sync.RWMutex
+	pool map[string]string
+}
+
+func newPool() *pool {
+	return &pool{
+		pool: map[string]string{},
+	}
+}
+
+func (p *pool) intern(s string) string {
+	if s == "" {
+		return ""
+	}
+
+	p.mtx.RLock()
+	interned, ok := p.pool[s]
+	p.mtx.RUnlock()
+	if ok {
+		return interned
+	}
+
+	p.mtx.Lock()
+	defer p.mtx.Unlock()
+	if interned, ok := p.pool[s]; ok {
+		return interned
+	}
+
+	s = pack(s)
+	p.pool[s] = s
+	return s
+}
+
+// StrPack returns a new instance of s which is tightly packed in memory.
+// It is intended for avoiding the situation where having a live reference
+// to a string slice over an unreferenced biger underlying string keeps the biger one
+// in memory anyway - it can't be GCed.
+func pack(s string) string {
+	return string([]byte(s))
+}