Allow use of existing Redis client for checkpoint store (#96)

store/redis/options.go

@@ -0,0 +1,13 @@
+package redis
+
+import redis "github.com/go-redis/redis"
+
+// Option is used to override defaults when creating a new Redis checkpoint
+type Option func(*Checkpoint)
+
+// WithClient overrides the default client
+func WithClient(client *redis.Client) Option {
+	return func(c *Checkpoint) {
+		c.client = client
+	}
+}

store/redis/redis.go

@@ -10,24 +10,38 @@ import (
 const localhost = "127.0.0.1:6379"
 
 // New returns a checkpoint that uses Redis for underlying storage
-func New(appName string) (*Checkpoint, error) {
-	addr := os.Getenv("REDIS_URL")
-	if addr == "" {
-		addr = localhost
+func New(appName string, opts ...Option) (*Checkpoint, error) {
+	if appName == "" {
+		return nil, fmt.Errorf("must provide app name")
 	}
 
-	client := redis.NewClient(&redis.Options{Addr: addr})
+	c := &Checkpoint{
+		appName: appName,
+	}
+
+	// override defaults
+	for _, opt := range opts {
+		opt(c)
+	}
+
+	// default client if none provided
+	if c.client == nil {
+		addr := os.Getenv("REDIS_URL")
+		if addr == "" {
+			addr = localhost
+		}
+
+		client := redis.NewClient(&redis.Options{Addr: addr})
+		c.client = client
+	}
 
 	// verify we can ping server
-	_, err := client.Ping().Result()
+	_, err := c.client.Ping().Result()
 	if err != nil {
 		return nil, err
 	}
 
-	return &Checkpoint{
-		appName: appName,
-		client:  client,
-	}, nil
+	return c, nil
 }
 
 // Checkpoint stores and retreives the last evaluated key from a DDB scan

store/redis/redis_test.go

@@ -2,8 +2,28 @@ package redis
 
 import (
 	"testing"
+
+	"github.com/alicebob/miniredis"
+	redis "github.com/go-redis/redis"
 )
 
+func Test_CheckpointOptions(t *testing.T) {
+	s, err := miniredis.Run()
+	if err != nil {
+		panic(err)
+	}
+	defer s.Close()
+
+	client := redis.NewClient(&redis.Options{
+		Addr: s.Addr(),
+	})
+
+	_, err = New("app", WithClient(client))
+	if err != nil {
+		t.Fatalf("new checkpoint error: %v", err)
+	}
+}
+
 func Test_CheckpointLifecycle(t *testing.T) {
 	// new
 	c, err := New("app")