use new unique package to reduce memory duplication of interned labels

when multiple remote writes are configured

Signed-off-by: Callum Styan <callumstyan@gmail.com>

go.mod

@@ -1,6 +1,6 @@
 module github.com/prometheus/prometheus
 
-go 1.21.0
+go 1.23.0
 
 toolchain go1.22.5
 

storage/remote/intern.go

@@ -20,6 +20,7 @@ package remote
 
 import (
 	"sync"
+	"unique"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
@@ -35,22 +36,20 @@ var noReferenceReleases = promauto.NewCounter(prometheus.CounterOpts{
 
 type pool struct {
 	mtx  sync.RWMutex
-	pool map[string]*entry
+	pool map[unique.Handle[string]]*entry
 }
 
 type entry struct {
 	refs atomic.Int64
-
-	s string
 }
 
-func newEntry(s string) *entry {
+func newEntry() *entry {
-	return &entry{s: s}
+	return &entry{}
 }
 
 func newPool() *pool {
 	return &pool{
-		pool: map[string]*entry{},
+		pool: map[unique.Handle[string]]*entry{},
 	}
 }
 
@@ -60,27 +59,28 @@ func (p *pool) intern(s string) string {
 	}
 
 	p.mtx.RLock()
-	interned, ok := p.pool[s]
+	h := unique.Make(s)
+	interned, ok := p.pool[h]
 	p.mtx.RUnlock()
 	if ok {
 		interned.refs.Inc()
-		return interned.s
+		return s
 	}
 	p.mtx.Lock()
 	defer p.mtx.Unlock()
-	if interned, ok := p.pool[s]; ok {
+	if interned, ok := p.pool[h]; ok {
 		interned.refs.Inc()
-		return interned.s
+		return s
 	}
-
+	p.pool[h] = newEntry()
-	p.pool[s] = newEntry(s)
+	p.pool[h].refs.Store(1)
-	p.pool[s].refs.Store(1)
 	return s
 }
 
 func (p *pool) release(s string) {
 	p.mtx.RLock()
-	interned, ok := p.pool[s]
+	h := unique.Make(s)
+	interned, ok := p.pool[h]
 	p.mtx.RUnlock()
 
 	if !ok {
@@ -98,5 +98,5 @@ func (p *pool) release(s string) {
 	if interned.refs.Load() != 0 {
 		return
 	}
-	delete(p.pool, s)
+	delete(p.pool, h)
 }

storage/remote/intern_test.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"testing"
 	"time"
+	"unique"
 
 	"github.com/stretchr/testify/require"
 )
@@ -30,7 +31,7 @@ func TestIntern(t *testing.T) {
 	interner := newPool()
 	testString := "TestIntern"
 	interner.intern(testString)
-	interned, ok := interner.pool[testString]
+	interned, ok := interner.pool[unique.Make(testString)]
 
 	require.True(t, ok)
 	require.Equal(t, int64(1), interned.refs.Load(), fmt.Sprintf("expected refs to be 1 but it was %d", interned.refs.Load()))
@@ -41,13 +42,13 @@ func TestIntern_MultiRef(t *testing.T) {
 	testString := "TestIntern_MultiRef"
 
 	interner.intern(testString)
-	interned, ok := interner.pool[testString]
+	interned, ok := interner.pool[unique.Make(testString)]
 
 	require.True(t, ok)
 	require.Equal(t, int64(1), interned.refs.Load(), fmt.Sprintf("expected refs to be 1 but it was %d", interned.refs.Load()))
 
 	interner.intern(testString)
-	interned, ok = interner.pool[testString]
+	interned, ok = interner.pool[unique.Make(testString)]
 
 	require.True(t, ok)
 	require.Equal(t, int64(2), interned.refs.Load(), fmt.Sprintf("expected refs to be 2 but it was %d", interned.refs.Load()))
@@ -58,13 +59,13 @@ func TestIntern_DeleteRef(t *testing.T) {
 	testString := "TestIntern_DeleteRef"
 
 	interner.intern(testString)
-	interned, ok := interner.pool[testString]
+	interned, ok := interner.pool[unique.Make(testString)]
 
 	require.True(t, ok)
 	require.Equal(t, int64(1), interned.refs.Load(), fmt.Sprintf("expected refs to be 1 but it was %d", interned.refs.Load()))
 
 	interner.release(testString)
-	_, ok = interner.pool[testString]
+	_, ok = interner.pool[unique.Make(testString)]
 	require.False(t, ok)
 }
 
@@ -73,7 +74,7 @@ func TestIntern_MultiRef_Concurrent(t *testing.T) {
 	testString := "TestIntern_MultiRef_Concurrent"
 
 	interner.intern(testString)
-	interned, ok := interner.pool[testString]
+	interned, ok := interner.pool[unique.Make(testString)]
 	require.True(t, ok)
 	require.Equal(t, int64(1), interned.refs.Load(), fmt.Sprintf("expected refs to be 1 but it was %d", interned.refs.Load()))
 
@@ -84,7 +85,7 @@ func TestIntern_MultiRef_Concurrent(t *testing.T) {
 	time.Sleep(time.Millisecond)
 
 	interner.mtx.RLock()
-	interned, ok = interner.pool[testString]
+	interned, ok = interner.pool[unique.Make(testString)]
 	interner.mtx.RUnlock()
 	require.True(t, ok)
 	require.Equal(t, int64(1), interned.refs.Load(), fmt.Sprintf("expected refs to be 1 but it was %d", interned.refs.Load()))