From 34361c6f827679284d306aafcd4795d17dc08799 Mon Sep 17 00:00:00 2001
From: Mike Poindexter <staticsnow@gmail.com>
Date: Thu, 29 Aug 2024 23:08:54 -0700
Subject: [PATCH] Fix FKs on sqlite migrations (#2083)

---
 hscontrol/db/db.go | 79 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 69 insertions(+), 10 deletions(-)

diff --git a/hscontrol/db/db.go b/hscontrol/db/db.go
index 99c3aa68..accf439e 100644
--- a/hscontrol/db/db.go
+++ b/hscontrol/db/db.go
@@ -123,21 +123,16 @@ func NewHeadscaleDatabase(
 						}
 					}
 
-					// Only run automigrate Route table if it does not exist. It has only been
-					// changed once, when machines where renamed to nodes, which is covered
-					// further up. This whole initial integration is a mess and if AutoMigrate
-					// is ran on a 0.22 to 0.23 update, it will wipe all the routes.
+					// Remove any invalid routes associated with a node that does not exist.
 					if tx.Migrator().HasTable(&types.Route{}) && tx.Migrator().HasTable(&types.Node{}) {
 						err := tx.Exec("delete from routes where node_id not in (select id from nodes)").Error
 						if err != nil {
 							return err
 						}
 					}
-					if !tx.Migrator().HasTable(&types.Route{}) {
-						err = tx.AutoMigrate(&types.Route{})
-						if err != nil {
-							return err
-						}
+					err = tx.AutoMigrate(&types.Route{})
+					if err != nil {
+						return err
 					}
 
 					err = tx.AutoMigrate(&types.Node{})
@@ -421,7 +416,7 @@ func NewHeadscaleDatabase(
 		},
 	)
 
-	if err = migrations.Migrate(); err != nil {
+	if err := runMigrations(cfg, dbConn, migrations); err != nil {
 		log.Fatal().Err(err).Msgf("Migration failed: %v", err)
 	}
 
@@ -545,6 +540,70 @@ func openDB(cfg types.DatabaseConfig) (*gorm.DB, error) {
 	)
 }
 
+func runMigrations(cfg types.DatabaseConfig, dbConn *gorm.DB, migrations *gormigrate.Gormigrate) error {
+	// Turn off foreign keys for the duration of the migration if using sqllite to
+	// prevent data loss due to the way the GORM migrator handles certain schema
+	// changes.
+	if cfg.Type == types.DatabaseSqlite {
+		var fkEnabled int
+		if err := dbConn.Raw("PRAGMA foreign_keys").Scan(&fkEnabled).Error; err != nil {
+			return fmt.Errorf("checking foreign key status: %w", err)
+		}
+		if fkEnabled == 1 {
+			if err := dbConn.Exec("PRAGMA foreign_keys = OFF").Error; err != nil {
+				return fmt.Errorf("disabling foreign keys: %w", err)
+			}
+			defer dbConn.Exec("PRAGMA foreign_keys = ON")
+		}
+	}
+
+	if err := migrations.Migrate(); err != nil {
+		return err
+	}
+
+	// Since we disabled foreign keys for the migration, we need to check for
+	// constraint violations manually at the end of the migration.
+	if cfg.Type == types.DatabaseSqlite {
+		type constraintViolation struct {
+			Table           string
+			RowID           int
+			Parent          string
+			ConstraintIndex int
+		}
+
+		var violatedConstraints []constraintViolation
+
+		rows, err := dbConn.Raw("PRAGMA foreign_key_check").Rows()
+		if err != nil {
+			return err
+		}
+
+		for rows.Next() {
+			var violation constraintViolation
+			if err := rows.Scan(&violation.Table, &violation.RowID, &violation.Parent, &violation.ConstraintIndex); err != nil {
+				return err
+			}
+
+			violatedConstraints = append(violatedConstraints, violation)
+		}
+		_ = rows.Close()
+
+		if len(violatedConstraints) > 0 {
+			for _, violation := range violatedConstraints {
+				log.Error().
+					Str("table", violation.Table).
+					Int("row_id", violation.RowID).
+					Str("parent", violation.Parent).
+					Msg("Foreign key constraint violated")
+			}
+
+			return fmt.Errorf("foreign key constraints violated")
+		}
+	}
+
+	return nil
+}
+
 func (hsdb *HSDatabase) PingDB(ctx context.Context) error {
 	ctx, cancel := context.WithTimeout(ctx, time.Second)
 	defer cancel()