refactor(adapter)!: drop the valkey adapter in favor of redis

Valkey speaks the Redis protocol, so the redis adapter (go-redis) already
serves it. Dropping valkey-go removes a dependency and shrinks the stripped
binary by about 9 MB.

The redis adapter now also closes a client that failed to connect only once.

BREAKING CHANGE: `adapter: valkey` is no longer accepted. Use
`adapter: redis` with a redis:// or rediss:// URL instead of valkey:// or
valkeys://. The namespace option now applies to these services.

adapter/redis.go

@@ -20,6 +20,8 @@ func init() {
 	}
 }
 
+// redisAdapter serves every RESP-compatible store: Redis, Valkey, Dragonfly,
+// KeyDB, Garnet and their hosted variants.
 type redisAdapter struct {
 	client *redis.Client
 	url    string
@@ -31,15 +33,16 @@ func (a *redisAdapter) Connect(ctx context.Context) error {
 	if err != nil {
 		return err
 	}
-	a.client = redis.NewClient(opt)
-	if err := a.client.Ping(ctx).Err(); err != nil {
-		a.client.Close()
+	client := redis.NewClient(opt)
+	if err := client.Ping(ctx).Err(); err != nil {
+		client.Close()
 		return err
 	}
-	if err := a.client.SetNX(ctx, a.key, 0, 0).Err(); err != nil {
-		a.client.Close()
+	if err := client.SetNX(ctx, a.key, 0, 0).Err(); err != nil {
+		client.Close()
 		return err
 	}
+	a.client = client
 	return nil
 }
 

adapter/valkey.go

@@ -1,55 +0,0 @@
-package adapter
-
-import (
-	"context"
-
-	"github.com/valkey-io/valkey-go"
-)
-
-func init() {
-	Registry["valkey"] = func(cfg Config) (Adapter, error) {
-		url, err := cfg.Required("url")
-		if err != nil {
-			return nil, err
-		}
-		return &valkeyAdapter{
-			url: url,
-			key: cfg.Optional("counter_key", "counter"),
-		}, nil
-	}
-}
-
-type valkeyAdapter struct {
-	client valkey.Client
-	url    string
-	key    string
-}
-
-func (a *valkeyAdapter) Connect(ctx context.Context) error {
-	opt, err := valkey.ParseURL(a.url)
-	if err != nil {
-		return err
-	}
-	client, err := valkey.NewClient(opt)
-	if err != nil {
-		return err
-	}
-	a.client = client
-	if err := a.client.Do(ctx, a.client.B().Setnx().Key(a.key).Value("0").Build()).Error(); err != nil {
-		a.client.Close()
-		return err
-	}
-	return nil
-}
-
-func (a *valkeyAdapter) Increment(ctx context.Context) (int64, error) {
-	return a.client.Do(ctx, a.client.B().Incr().Key(a.key).Build()).AsInt64()
-}
-
-func (a *valkeyAdapter) Close(_ context.Context) error {
-	if a.client == nil {
-		return nil
-	}
-	a.client.Close()
-	return nil
-}