add test to experiment with Redis cluster slot distribution

centrifugal · Nov 9, 2023 · 1de89f2 · 1de89f2
1 parent 9597830
commit 1de89f2
Showing 1 changed file with 134 additions and 0 deletions.
diff --git a/broker_redis_test.go b/broker_redis_test.go
@@ -1695,3 +1695,137 @@ func BenchmarkPubSubThroughput(b *testing.B) {
 		})
 	}
 }
+
+var tab = [256]uint16{
+	0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
+	0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
+	0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
+	0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
+	0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
+	0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
+	0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
+	0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
+	0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
+	0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
+	0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
+	0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
+	0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
+	0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
+	0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
+	0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
+	0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
+	0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
+	0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
+	0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
+	0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
+	0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
+	0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
+	0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
+	0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
+	0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
+	0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
+	0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
+	0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
+	0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
+	0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
+	0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
+}
+
+// numSlots is the number of slots keys are sharded into in a redis cluster
+const numSlots = 16384
+
+// crc16 returns checksum for a given set of bytes based on the crc algorithm
+// defined for hashing redis keys in a cluster setup
+func crc16(buf []byte) uint16 {
+	crc := uint16(0)
+	for _, b := range buf {
+		index := byte(crc>>8) ^ b
+		crc = (crc << 8) ^ tab[index]
+	}
+	return crc
+}
+
+// Slot returns the cluster slot the given key will fall into, taking into
+// account curly braces within the key as per the spec.
+func redisSlot(key string) uint16 {
+	if start := strings.Index(key, "{"); start >= 0 {
+		if end := strings.Index(key[start+1:], "}"); end > 0 {
+			key = key[start+1 : start+1+end]
+		}
+	}
+	return crc16([]byte(key)) % numSlots
+}
+
+type shardedSlotsTestCase struct {
+	numRedisNodes   int
+	numShards       int
+	clusterPartFunc clusterFuncWrapper
+}
+
+func detectRedisNodeIndex(slot uint16, numNodes int) int {
+	slotsPerRedis := 16384 / numNodes
+	s := 0
+	for i := 0; i < numNodes; i++ {
+		s += slotsPerRedis
+		if int(slot) < s {
+			return i
+		}
+	}
+	return numNodes - 1
+}
+
+type clusterPartFunc func(string) string
+
+type clusterFuncWrapper struct {
+	name string
+	fn   clusterPartFunc
+}
+
+// TestPreShardedSlots allows experimenting with Redis slots and its distribution.
+func TestPreShardedSlots(t *testing.T) {
+	t.Skip()
+	redisNodesChoices := []int{3, 5, 8, 16}
+	numShardsChoices := []int{32}
+
+	clusterPartFuncChoices := []clusterFuncWrapper{
+		{
+			name: "simple_number",
+			fn: func(idx string) string {
+				return "{" + idx + "}"
+			},
+		},
+		{
+			name: "repeat_number",
+			fn: func(idx string) string {
+				return "{" + idx + "," + idx + "," + idx + "," + idx + "}"
+			},
+		},
+	}
+
+	var testCases []shardedSlotsTestCase
+
+	for _, fw := range clusterPartFuncChoices {
+		for _, rn := range redisNodesChoices {
+			for _, sc := range numShardsChoices {
+				testCases = append(testCases, shardedSlotsTestCase{
+					numRedisNodes:   rn,
+					numShards:       sc,
+					clusterPartFunc: fw,
+				})
+			}
+		}
+	}
+
+	for _, tc := range testCases {
+		t.Run(fmt.Sprintf("%s_%d_nodes_%d_shards", tc.clusterPartFunc.name, tc.numRedisNodes, tc.numShards), func(t *testing.T) {
+			nodeIndexCounts := make([]int, tc.numRedisNodes)
+			for i := 0; i < tc.numShards; i++ {
+				ch := tc.clusterPartFunc.fn(strconv.Itoa(i))
+				slot := redisSlot(ch)
+				nodeIndex := detectRedisNodeIndex(slot, tc.numRedisNodes)
+				nodeIndexCounts[nodeIndex]++
+			}
+			t.Logf("%s: %v", t.Name(), nodeIndexCounts)
+		})
+	}
+}