watchtower: build channel to sessionIDs index

In this commit, a migration is added that adds an index from channel to
sessionIDs (using the DB-assigned session IDs). This will make it easier
in future to know which sessions have updates for which channels.

watchtower/wtdb/migration7/client_db_test.go

@@ -0,0 +1,191 @@
+package migration7
+
+import (
+	"testing"
+
+	"github.com/lightningnetwork/lnd/channeldb/migtest"
+	"github.com/lightningnetwork/lnd/kvdb"
+)
+
+var (
+	// preDetails is the expected data of the channel details bucket before
+	// the migration.
+	preDetails = map[string]interface{}{
+		channelIDString(100): map[string]interface{}{
+			string(cChannelSummary): string([]byte{1, 2, 3}),
+		},
+		channelIDString(222): map[string]interface{}{
+			string(cChannelSummary): string([]byte{4, 5, 6}),
+		},
+	}
+
+	// preFailCorruptDB should fail the migration due to no channel summary
+	// being found for a given channel ID.
+	preFailCorruptDB = map[string]interface{}{
+		channelIDString(30): map[string]interface{}{},
+	}
+
+	// channelIDIndex is the data in the channelID index that is used to
+	// find the mapping between the db-assigned channel ID and the real
+	// channel ID.
+	channelIDIndex = map[string]interface{}{
+		uint64ToStr(10): channelIDString(100),
+		uint64ToStr(20): channelIDString(222),
+	}
+
+	// sessions is the expected data in the sessions bucket before and
+	// after the migration.
+	sessions = map[string]interface{}{
+		sessionIDString("1"): map[string]interface{}{
+			string(cSessionAckRangeIndex): map[string]interface{}{
+				uint64ToStr(10): map[string]interface{}{
+					uint64ToStr(30): uint64ToStr(32),
+					uint64ToStr(34): uint64ToStr(34),
+				},
+				uint64ToStr(20): map[string]interface{}{
+					uint64ToStr(30): uint64ToStr(30),
+				},
+			},
+			string(cSessionDBID): uint64ToStr(66),
+		},
+		sessionIDString("2"): map[string]interface{}{
+			string(cSessionAckRangeIndex): map[string]interface{}{
+				uint64ToStr(10): map[string]interface{}{
+					uint64ToStr(33): uint64ToStr(33),
+				},
+			},
+			string(cSessionDBID): uint64ToStr(77),
+		},
+	}
+
+	// postDetails is the expected data in the channel details bucket after
+	// the migration.
+	postDetails = map[string]interface{}{
+		channelIDString(100): map[string]interface{}{
+			string(cChannelSummary): string([]byte{1, 2, 3}),
+			string(cChanSessions): map[string]interface{}{
+				uint64ToStr(66): string([]byte{1}),
+				uint64ToStr(77): string([]byte{1}),
+			},
+		},
+		channelIDString(222): map[string]interface{}{
+			string(cChannelSummary): string([]byte{4, 5, 6}),
+			string(cChanSessions): map[string]interface{}{
+				uint64ToStr(66): string([]byte{1}),
+			},
+		},
+	}
+)
+
+// TestMigrateChannelToSessionIndex tests that the MigrateChannelToSessionIndex
+// function correctly builds the new channel-to-sessionID index to the tower
+// client DB.
+func TestMigrateChannelToSessionIndex(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name         string
+		shouldFail   bool
+		preDetails   map[string]interface{}
+		preSessions  map[string]interface{}
+		preChanIndex map[string]interface{}
+		postDetails  map[string]interface{}
+	}{
+		{
+			name:         "migration ok",
+			shouldFail:   false,
+			preDetails:   preDetails,
+			preSessions:  sessions,
+			preChanIndex: channelIDIndex,
+			postDetails:  postDetails,
+		},
+		{
+			name:        "fail due to corrupt db",
+			shouldFail:  true,
+			preDetails:  preFailCorruptDB,
+			preSessions: sessions,
+		},
+		{
+			name:       "no sessions",
+			shouldFail: false,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			// Before the migration we have a channel details
+			// bucket, a sessions bucket, a session ID index bucket
+			// and a channel ID index bucket.
+			before := func(tx kvdb.RwTx) error {
+				err := migtest.RestoreDB(
+					tx, cChanDetailsBkt, test.preDetails,
+				)
+				if err != nil {
+					return err
+				}
+
+				err = migtest.RestoreDB(
+					tx, cSessionBkt, test.preSessions,
+				)
+				if err != nil {
+					return err
+				}
+
+				return migtest.RestoreDB(
+					tx, cChanIDIndexBkt, test.preChanIndex,
+				)
+			}
+
+			after := func(tx kvdb.RwTx) error {
+				// If the migration fails, the details bucket
+				// should be untouched.
+				if test.shouldFail {
+					if err := migtest.VerifyDB(
+						tx, cChanDetailsBkt,
+						test.preDetails,
+					); err != nil {
+						return err
+					}
+
+					return nil
+				}
+
+				// Else, we expect an updated details bucket
+				// and a new index bucket.
+				return migtest.VerifyDB(
+					tx, cChanDetailsBkt, test.postDetails,
+				)
+			}
+
+			migtest.ApplyMigration(
+				t, before, after, MigrateChannelToSessionIndex,
+				test.shouldFail,
+			)
+		})
+	}
+}
+
+func sessionIDString(id string) string {
+	var sessID SessionID
+	copy(sessID[:], id)
+	return sessID.String()
+}
+
+func channelIDString(id uint64) string {
+	var chanID ChannelID
+	byteOrder.PutUint64(chanID[:], id)
+	return string(chanID[:])
+}
+
+func uint64ToStr(id uint64) string {
+	b, err := writeUint64(id)
+	if err != nil {
+		panic(err)
+	}
+
+	return string(b)
+}