From 706f07bf75e34e5aa4e7acd9419e0e9cc80b2ad6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Giedrius=20Statkevi=C4=8Dius?=
 <giedrius.statkevicius@vinted.com>
Date: Wed, 30 Jun 2021 15:45:01 +0300
Subject: [PATCH] cache: make adjustments according to the comments
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Giedrius Statkevičius <giedrius.statkevicius@vinted.com>
---
 pkg/cache/inmemory.go      | 54 ++++++++++++++++++++------------------
 pkg/cache/inmemory_test.go |  6 ++---
 2 files changed, 32 insertions(+), 28 deletions(-)

diff --git a/pkg/cache/inmemory.go b/pkg/cache/inmemory.go
index e21b5c38f4b..b45c43da8b6 100644
--- a/pkg/cache/inmemory.go
+++ b/pkg/cache/inmemory.go
@@ -65,9 +65,9 @@ type InMemoryCache struct {
 	hitsExpired prometheus.Counter
 	// The input cache value would be copied to an inmemory array
 	// instead of simply using the one sent by the caller.
-	added             prometheus.Counter
-	current           prometheus.Gauge
-	singleflightsaved prometheus.Counter
+	added   prometheus.Counter
+	current prometheus.Gauge
+	sfSaved prometheus.Counter
 
 	currentSize      prometheus.Gauge
 	totalCurrentSize prometheus.Gauge
@@ -121,7 +121,7 @@ func NewInMemoryCacheWithConfig(name string, logger log.Logger, reg prometheus.R
 
 	if config.Singleflight {
 		c.subs = make(map[string]*pubsub)
-		c.singleflightsaved = promauto.With(reg).NewCounter(prometheus.CounterOpts{
+		c.sfSaved = promauto.With(reg).NewCounter(prometheus.CounterOpts{
 			Name:        "thanos_cache_inmemory_singleflight_saved_calls_total",
 			Help:        "Total number of calls saved by the singleflight mechanism.",
 			ConstLabels: prometheus.Labels{"name": name},
@@ -342,29 +342,33 @@ func (c *InMemoryCache) Fetch(ctx context.Context, keys []string) map[string][]b
 	for _, key := range keys {
 		if b, ok := c.get(key); ok {
 			results[key] = b
-		} else if c.singleFlight {
-			c.mu.Lock()
-			if c.subs[key] == nil {
+			continue
+		}
+		if !c.singleFlight {
+			continue
+		}
+
+		c.mu.Lock()
+		if c.subs[key] == nil {
+			c.subs[key] = &pubsub{originalCtx: ctx}
+			c.mu.Unlock()
+		} else {
+			if c.subs[key].originalCtx.Err() != nil {
 				c.subs[key] = &pubsub{originalCtx: ctx}
-				c.mu.Unlock()
-			} else {
-				if c.subs[key].originalCtx.Err() != nil {
-					c.subs[key] = &pubsub{originalCtx: ctx}
-				}
-				originalCtx := c.subs[key].originalCtx
-				respReceiver := make(chan []byte)
-				c.subs[key].listeners = append(c.subs[key].listeners, respReceiver)
-				c.mu.Unlock()
+			}
+			originalCtx := c.subs[key].originalCtx
+			respReceiver := make(chan []byte)
+			c.subs[key].listeners = append(c.subs[key].listeners, respReceiver)
+			c.mu.Unlock()
 
-				select {
-				case b := <-respReceiver:
-					results[key] = b
-					c.singleflightsaved.Inc()
-				case <-ctx.Done():
-					return results
-				case <-originalCtx.Done():
-					continue
-				}
+			select {
+			case b := <-respReceiver:
+				results[key] = b
+				c.sfSaved.Inc()
+			case <-ctx.Done():
+				return results
+			case <-originalCtx.Done():
+				continue
 			}
 		}
 	}
diff --git a/pkg/cache/inmemory_test.go b/pkg/cache/inmemory_test.go
index 887c2a348f7..281c1346e5f 100644
--- a/pkg/cache/inmemory_test.go
+++ b/pkg/cache/inmemory_test.go
@@ -55,7 +55,7 @@ single_flight: true
 
 	testutil.Ok(t, g.Wait())
 
-	testutil.Equals(t, 1.0, prom_testutil.ToFloat64(c.singleflightsaved))
+	testutil.Equals(t, 1.0, prom_testutil.ToFloat64(c.sfSaved))
 }
 
 // TestInmemorySingleflightMultipleKeys tests whether single-flight mechanism works
@@ -94,7 +94,7 @@ single_flight: true
 	cancel()
 
 	testutil.Ok(t, g.Wait())
-	testutil.Equals(t, 1.0, prom_testutil.ToFloat64(c.singleflightsaved))
+	testutil.Equals(t, 1.0, prom_testutil.ToFloat64(c.sfSaved))
 }
 
 // TestInmemorySingleflightInterrupted tests whether single-flight mechanism still works
@@ -133,7 +133,7 @@ single_flight: true
 
 	time.Sleep(1 * time.Second)
 	testutil.Ok(t, g.Wait())
-	testutil.Equals(t, 0.0, prom_testutil.ToFloat64(c.singleflightsaved))
+	testutil.Equals(t, 0.0, prom_testutil.ToFloat64(c.sfSaved))
 }
 
 func TestInmemoryCache(t *testing.T) {