From 3de5605ab2401c963647b63935049b1631121709 Mon Sep 17 00:00:00 2001
From: Vladimir Mihailenco <vladimir.webdev@gmail.com>
Date: Thu, 28 Dec 2017 16:41:05 +0200
Subject: [PATCH] Pick random node when command does not have keys

---
 cluster.go                  | 14 ++++++++++----
 cluster_test.go             | 26 ++++++++++++++++++++++++++
 command.go                  |  4 ++--
 internal/hashtag/hashtag.go |  8 ++++++--
 ring.go                     |  6 +++++-
 5 files changed, 49 insertions(+), 9 deletions(-)

diff --git a/cluster.go b/cluster.go
index c81fc1d..afaf3f3 100644
--- a/cluster.go
+++ b/cluster.go
@@ -533,16 +533,22 @@ func (c *ClusterClient) cmdInfo(name string) *CommandInfo {
 	return info
 }
 
+func cmdSlot(cmd Cmder, pos int) int {
+	if pos == 0 {
+		return hashtag.RandomSlot()
+	}
+	firstKey := cmd.stringArg(pos)
+	return hashtag.Slot(firstKey)
+}
+
 func (c *ClusterClient) cmdSlot(cmd Cmder) int {
 	cmdInfo := c.cmdInfo(cmd.Name())
-	firstKey := cmd.stringArg(cmdFirstKeyPos(cmd, cmdInfo))
-	return hashtag.Slot(firstKey)
+	return cmdSlot(cmd, cmdFirstKeyPos(cmd, cmdInfo))
 }
 
 func (c *ClusterClient) cmdSlotAndNode(state *clusterState, cmd Cmder) (int, *clusterNode, error) {
 	cmdInfo := c.cmdInfo(cmd.Name())
-	firstKey := cmd.stringArg(cmdFirstKeyPos(cmd, cmdInfo))
-	slot := hashtag.Slot(firstKey)
+	slot := cmdSlot(cmd, cmdFirstKeyPos(cmd, cmdInfo))
 
 	if cmdInfo != nil && cmdInfo.ReadOnly && c.opt.ReadOnly {
 		if c.opt.RouteByLatency {
diff --git a/cluster_test.go b/cluster_test.go
index 6f3677b..43f3261 100644
--- a/cluster_test.go
+++ b/cluster_test.go
@@ -536,6 +536,32 @@ var _ = Describe("ClusterClient", func() {
 			Expect(nodesList).Should(HaveLen(1))
 		})
 
+		It("should RANDOMKEY", func() {
+			const nkeys = 100
+
+			for i := 0; i < nkeys; i++ {
+				err := client.Set(fmt.Sprintf("key%d", i), "value", 0).Err()
+				Expect(err).NotTo(HaveOccurred())
+			}
+
+			var keys []string
+			addKey := func(key string) {
+				for _, k := range keys {
+					if k == key {
+						return
+					}
+				}
+				keys = append(keys, key)
+			}
+
+			for i := 0; i < nkeys*10; i++ {
+				key := client.RandomKey().Val()
+				addKey(key)
+			}
+
+			Expect(len(keys)).To(BeNumerically("~", nkeys, nkeys/10))
+		})
+
 		assertClusterClient()
 	})
 
diff --git a/command.go b/command.go
index 601a288..598ed98 100644
--- a/command.go
+++ b/command.go
@@ -82,13 +82,13 @@ func cmdFirstKeyPos(cmd Cmder, info *CommandInfo) int {
 		if cmd.stringArg(2) != "0" {
 			return 3
 		} else {
-			return -1
+			return 0
 		}
 	case "publish":
 		return 1
 	}
 	if info == nil {
-		return -1
+		return 0
 	}
 	return int(info.FirstKeyPos)
 }
diff --git a/internal/hashtag/hashtag.go b/internal/hashtag/hashtag.go
index 2866488..8c7ebbf 100644
--- a/internal/hashtag/hashtag.go
+++ b/internal/hashtag/hashtag.go
@@ -55,13 +55,17 @@ func Key(key string) string {
 	return key
 }
 
+func RandomSlot() int {
+	return rand.Intn(SlotNumber)
+}
+
 // hashSlot returns a consistent slot number between 0 and 16383
 // for any given string key.
 func Slot(key string) int {
-	key = Key(key)
 	if key == "" {
-		return rand.Intn(SlotNumber)
+		return RandomSlot()
 	}
+	key = Key(key)
 	return int(crc16sum(key)) % SlotNumber
 }
 
diff --git a/ring.go b/ring.go
index a30c321..0697b3e 100644
--- a/ring.go
+++ b/ring.go
@@ -343,7 +343,11 @@ func (c *Ring) shardByName(name string) (*ringShard, error) {
 
 func (c *Ring) cmdShard(cmd Cmder) (*ringShard, error) {
 	cmdInfo := c.cmdInfo(cmd.Name())
-	firstKey := cmd.stringArg(cmdFirstKeyPos(cmd, cmdInfo))
+	pos := cmdFirstKeyPos(cmd, cmdInfo)
+	if pos == 0 {
+		return c.randomShard()
+	}
+	firstKey := cmd.stringArg(pos)
 	return c.shardByKey(firstKey)
 }