feat(redis): add namespace counter key

README.md

@@ -18,6 +18,7 @@ services:
   - adapter: redis
     config:
       url: redis://default@redis-a.example.com:6379
+      namespace: keepalive
 
   - adapter: mongodb
     config:
@@ -43,7 +44,7 @@ services:
 
 | `adapter`    | Driver                              | `config` keys |
 | ------------ | ----------------------------------- | ------------- |
-| `redis`      | `github.com/redis/go-redis/v9`      | `url` |
+| `redis`      | `github.com/redis/go-redis/v9`      | `url`, optional `namespace` |
 | `valkey`     | `github.com/valkey-io/valkey-go`    | `url` |
 | `postgresql` | `github.com/lib/pq`                 | `url` |
 | `mysql`      | `github.com/go-sql-driver/mysql`    | `dsn` |
@@ -88,7 +89,8 @@ go run .
 
 On startup each adapter initializes the minimum resource it owns, then every tick performs the cheapest write that proves the cluster is alive. `counter_key` selects the key/doc ID and defaults to `counter`.
 
-- **Redis/Valkey** — initialize with `SETNX key 0`, then `INCR key`
+- **Redis** — initialize with `SETNX key 0`, then `INCR key`. When `namespace` is empty, the key is `counter`; when `namespace: keepalive`, the key is `keepalive:counter`.
+- **Valkey** — initialize with `SETNX key 0`, then `INCR key`
 - **PostgreSQL** — `CREATE TABLE IF NOT EXISTS keepalive`, seed `key`, then `UPDATE ... RETURNING`
 - **MySQL** — `CREATE TABLE IF NOT EXISTS keepalive`, seed `key`, then `UPDATE` + `SELECT`
 - **MongoDB** — upsert `{_id: key, count: 0}` on connect, then `FindOneAndUpdate({_id: key}, {$inc: {count: 1}}, upsert)`

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
+}

config.example.yml

@@ -6,6 +6,7 @@ services:
   - adapter: redis
     config:
       url: redis://default@redis-a.example.com:6379
+      namespace: keepalive
 
   - adapter: redis
     config: