feat(redis): add namespace counter key

adapter/redis.go

@@ -2,6 +2,7 @@ package adapter
 
 import (
 	"context"
+	"strings"
 
 	"github.com/redis/go-redis/v9"
 )
@@ -14,7 +15,7 @@ func init() {
 		}
 		return &redisAdapter{
 			url: url,
-			key: cfg.Optional("counter_key", "counter"),
+			key: redisCounterKey(cfg.Optional("counter_key", "counter"), cfg.Optional("namespace", "")),
 		}, nil
 	}
 }
@@ -52,3 +53,11 @@ func (a *redisAdapter) Close(_ context.Context) error {
 	}
 	return a.client.Close()
 }
+
+func redisCounterKey(counterKey, namespace string) string {
+	namespace = strings.TrimSpace(namespace)
+	if namespace == "" {
+		return counterKey
+	}
+	return namespace + ":" + counterKey
+}

adapter/redis_test.go

@@ -0,0 +1,52 @@
+package adapter
+
+import "testing"
+
+func TestRedisFactoryUsesRootCounterKeyWithoutNamespace(t *testing.T) {
+	got := newRedisAdapterForTest(t, Config{
+		"url":         "redis://cache.example.com:6379",
+		"counter_key": "counter",
+	})
+
+	if got.key != "counter" {
+		t.Fatalf("key = %q, want %q", got.key, "counter")
+	}
+}
+
+func TestRedisFactoryPrefixesCounterKeyWithNamespace(t *testing.T) {
+	got := newRedisAdapterForTest(t, Config{
+		"url":         "redis://cache.example.com:6379",
+		"counter_key": "counter",
+		"namespace":   "keepalive",
+	})
+
+	if got.key != "keepalive:counter" {
+		t.Fatalf("key = %q, want %q", got.key, "keepalive:counter")
+	}
+}
+
+func TestRedisFactoryTreatsBlankNamespaceAsRoot(t *testing.T) {
+	got := newRedisAdapterForTest(t, Config{
+		"url":         "redis://cache.example.com:6379",
+		"counter_key": "counter",
+		"namespace":   "  ",
+	})
+
+	if got.key != "counter" {
+		t.Fatalf("key = %q, want %q", got.key, "counter")
+	}
+}
+
+func newRedisAdapterForTest(t *testing.T, cfg Config) *redisAdapter {
+	t.Helper()
+
+	adapterValue, err := Registry["redis"](cfg)
+	if err != nil {
+		t.Fatalf("redis factory returned error: %v", err)
+	}
+	got, ok := adapterValue.(*redisAdapter)
+	if !ok {
+		t.Fatalf("redis factory returned %T, want *redisAdapter", adapterValue)
+	}
+	return got
+}