Require migration to run Horizon version successfully (fixes #778) (#808

)

* first pass

* extracted data structures for set comparing migrations

* migration set differencing

* remove debug printing

* minor review comments

* simplified logic for down migrations

* further review comments

* fix out of date comment

* fix spacing

services/horizon/internal/db2/schema/main.go

@@ -3,6 +3,7 @@ package schema
 import (
 	"database/sql"
 	"errors"
+	stdLog "log"
 
 	migrate "github.com/rubenv/sql-migrate"
 	"github.com/stellar/go/support/db"
@@ -68,3 +69,53 @@ func Migrate(db *sql.DB, dir MigrateDir, count int) (int, error) {
 		return 0, errors.New("Invalid migration direction")
 	}
 }
+
+// GetMigrationsUp returns a list of names of any migrations needed in the
+// "up" direction (more recent schema versions).
+func GetMigrationsUp(dbUrl string) (migrationIds []string) {
+	// Get a DB handle
+	db, dbErr := sql.Open("postgres", dbUrl)
+	if dbErr != nil {
+		stdLog.Fatal(dbErr)
+	}
+
+	// Get the possible migrations
+	possibleMigrations, _, migrateErr := migrate.PlanMigration(db, "postgres", Migrations, migrate.Up, 0)
+	if migrateErr != nil {
+		stdLog.Fatal(migrateErr)
+	}
+
+	// Extract a list of the possible migration names
+	for _, m := range possibleMigrations {
+		migrationIds = append(migrationIds, m.Id)
+	}
+
+	return migrationIds
+}
+
+// GetNumMigrationsDown returns the number of migrations to apply in the
+// "down" direction to return to the older schema version expected by this
+// version of Horizon. To keep the code simple, it does not provide a list of
+// migration names.
+func GetNumMigrationsDown(dbUrl string) (nMigrations int) {
+	// Get a DB handle
+	db, dbErr := sql.Open("postgres", dbUrl)
+	if dbErr != nil {
+		stdLog.Fatal(dbErr)
+	}
+
+	// Get the set of migrations recorded in the database
+	migrationRecords, recordErr := migrate.GetMigrationRecords(db, "postgres")
+	if recordErr != nil {
+		stdLog.Fatal(recordErr)
+	}
+
+	// Get the list of migrations needed by this version of Horizon
+	allNeededMigrations, _, migrateErr := migrate.PlanMigration(db, "postgres", Migrations, migrate.Down, 0)
+	if migrateErr != nil {
+		stdLog.Fatal(migrateErr)
+	}
+
+	// Return the size difference between the two sets of migrations
+	return len(migrationRecords) - len(allNeededMigrations)
+}

services/horizon/main.go

@@ -10,7 +10,9 @@ import (
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 	"github.com/stellar/go/network"
-	"github.com/stellar/go/services/horizon/internal"
+	horizon "github.com/stellar/go/services/horizon/internal"
+	"github.com/stellar/go/services/horizon/internal/db2/schema"
+	apkg "github.com/stellar/go/support/app"
 	"github.com/stellar/go/support/log"
 	"github.com/throttled/throttled"
 )
@@ -244,6 +246,21 @@ func initConfig() {
 		stdLog.Fatal("Invalid config: network-passphrase is blank.  Please specify --network-passphrase on the command line or set the NETWORK_PASSPHRASE environment variable.")
 	}
 
+	migrationsToApplyUp := schema.GetMigrationsUp(viper.GetString("db-url"))
+	if len(migrationsToApplyUp) > 0 {
+		stdLog.Printf(`There are %v migrations to apply in the "up" direction.`, len(migrationsToApplyUp))
+		stdLog.Printf("The necessary migrations are: %v", migrationsToApplyUp)
+		stdLog.Printf("A database migration is required to run this version (%v) of Horizon. Run \"horizon db migrate up\" to update your DB. Consult the Changelog (https://github.com/stellar/horizon/blob/master/CHANGELOG.md) for more information.", apkg.Version())
+		os.Exit(1)
+	}
+
+	nMigrationsDown := schema.GetNumMigrationsDown(viper.GetString("db-url"))
+	if nMigrationsDown > 0 {
+		stdLog.Printf("A database migration DOWN to an earlier version of the schema is required to run this version (%v) of Horizon. Consult the Changelog (https://github.com/stellar/horizon/blob/master/CHANGELOG.md) for more information.", apkg.Version())
+		stdLog.Printf("In order to migrate the database DOWN, using the HIGHEST version number of Horizon you have installed (not this binary), run \"horizon db migrate down %v\".", nMigrationsDown)
+		os.Exit(1)
+	}
+
 	ll, err := logrus.ParseLevel(viper.GetString("log-level"))
 
 	if err != nil {