server: Test HashByRev values to make sure they don't change

Signed-off-by: Marek Siarkowicz <siarkowicz@google.com>

server/storage/mvcc/hash_test.go

@@ -0,0 +1,166 @@
+// Copyright 2022 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mvcc
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.etcd.io/etcd/pkg/v3/traceutil"
+	"go.etcd.io/etcd/server/v3/lease"
+	betesting "go.etcd.io/etcd/server/v3/storage/backend/testing"
+	"go.uber.org/zap/zaptest"
+)
+
+const (
+	// Use high prime
+	compactionCycle = 71
+)
+
+// Test HashByRevValue values to ensure we don't change the output which would
+// have catastrophic consequences. Expected output is just hardcoded, so please
+// regenerate it every time you change input parameters.
+func TestHashByRevValue(t *testing.T) {
+	b, _ := betesting.NewDefaultTmpBackend(t)
+	s := NewStore(zaptest.NewLogger(t), b, &lease.FakeLessor{}, StoreConfig{})
+
+	var totalRevisions int64 = 1210
+	assert.Less(t, int64(s.cfg.CompactionBatchLimit), totalRevisions)
+	assert.Less(t, int64(compactionCycle*10), totalRevisions)
+	var rev int64
+	var got []kvHash
+	for ; rev < totalRevisions; rev += compactionCycle {
+		putKVs(s, rev, compactionCycle)
+		hash := testHashByRev(t, s, rev+compactionCycle/2)
+		got = append(got, hash)
+	}
+	putKVs(s, rev, totalRevisions)
+	hash := testHashByRev(t, s, rev+totalRevisions/2)
+	got = append(got, hash)
+	assert.Equal(t, []kvHash{
+		{4082599214, -1, 35},
+		{2279933401, 35, 106},
+		{3284231217, 106, 177},
+		{126286495, 177, 248},
+		{900108730, 248, 319},
+		{2475485232, 319, 390},
+		{1226296507, 390, 461},
+		{2503661030, 461, 532},
+		{4155130747, 532, 603},
+		{106915399, 603, 674},
+		{406914006, 674, 745},
+		{1882211381, 745, 816},
+		{806177088, 816, 887},
+		{664311366, 887, 958},
+		{1496914449, 958, 1029},
+		{2434525091, 1029, 1100},
+		{3988652253, 1100, 1171},
+		{1122462288, 1171, 1242},
+		{724436716, 1242, 1883},
+	}, got)
+}
+
+func TestHashByRevValueZero(t *testing.T) {
+	b, _ := betesting.NewDefaultTmpBackend(t)
+	s := NewStore(zaptest.NewLogger(t), b, &lease.FakeLessor{}, StoreConfig{})
+
+	var totalRevisions int64 = 1210
+	assert.Less(t, int64(s.cfg.CompactionBatchLimit), totalRevisions)
+	assert.Less(t, int64(compactionCycle*10), totalRevisions)
+	var rev int64
+	var got []kvHash
+	for ; rev < totalRevisions; rev += compactionCycle {
+		putKVs(s, rev, compactionCycle)
+		hash := testHashByRev(t, s, 0)
+		got = append(got, hash)
+	}
+	putKVs(s, rev, totalRevisions)
+	hash := testHashByRev(t, s, 0)
+	got = append(got, hash)
+	assert.Equal(t, []kvHash{
+		{1913897190, -1, 73},
+		{224860069, 73, 145},
+		{1565167519, 145, 217},
+		{1566261620, 217, 289},
+		{2037173024, 289, 361},
+		{691659396, 361, 433},
+		{2713730748, 433, 505},
+		{3919322507, 505, 577},
+		{769967540, 577, 649},
+		{2909194793, 649, 721},
+		{1576921157, 721, 793},
+		{4067701532, 793, 865},
+		{2226384237, 865, 937},
+		{2923408134, 937, 1009},
+		{2680329256, 1009, 1081},
+		{1546717673, 1081, 1153},
+		{2713657846, 1153, 1225},
+		{1046575299, 1225, 1297},
+		{2017735779, 1297, 2508},
+	}, got)
+}
+
+func putKVs(s *store, rev, count int64) {
+	for i := rev; i <= rev+count; i++ {
+		s.Put([]byte(pickKey(i)), []byte(fmt.Sprint(i)), 0)
+	}
+}
+
+func testHashByRev(t *testing.T, s *store, rev int64) kvHash {
+	hash, currentRev, compactRev, err := s.HashByRev(rev)
+	assert.NoError(t, err, "error on rev %v", rev)
+
+	if rev == 0 {
+		rev = currentRev
+	}
+	_, err = s.Compact(traceutil.TODO(), rev)
+	assert.NoError(t, err, "error on compact %v", rev)
+	return kvHash{hash: hash, compactRevision: compactRev, revision: rev}
+}
+
+type kvHash struct {
+	hash            uint32
+	compactRevision int64
+	revision        int64
+}
+
+func pickKey(i int64) string {
+	if i%(compactionCycle*2) == 30 {
+		return "zenek"
+	}
+	if i%compactionCycle == 30 {
+		return "xavery"
+	}
+	// Use low prime number to ensure repeats without alignment
+	switch i % 7 {
+	case 0:
+		return "alice"
+	case 1:
+		return "bob"
+	case 2:
+		return "celine"
+	case 3:
+		return "dominik"
+	case 4:
+		return "eve"
+	case 5:
+		return "frederica"
+	case 6:
+		return "gorge"
+	default:
+		panic("Can't count")
+	}
+}