Make database boot process storage provider agonistic

Moved database queries into provider specific object to ensure database checking, installation, upgrade procedures are pluggable.

core/database/lock.go

@@ -0,0 +1,110 @@
+// Copyright 2016 Documize Inc. <legal@documize.com>. All rights reserved.
+//
+// This software (Documize Community Edition) is licensed under
+// GNU AGPL v3 http://www.gnu.org/licenses/agpl-3.0.en.html
+//
+// You can operate outside the AGPL restrictions by purchasing
+// Documize Enterprise Edition and obtaining a commercial license
+// by contacting <sales@documize.com>.
+//
+// https://documize.com
+
+package database
+
+import (
+	"crypto/rand"
+	"time"
+
+	"github.com/documize/community/core/env"
+	"github.com/jmoiron/sqlx"
+)
+
+// Lock will try to lock the database instance to the running process.
+// Uses a "random" delay as a por man's database cluster-aware process.
+// We skip delay if there are no scripts to process.
+func Lock(runtime *env.Runtime, scriptsToProcess int) (bool, error) {
+	// Wait for random period of time.
+	b := make([]byte, 2)
+	_, err := rand.Read(b)
+	if err != nil {
+		return false, err
+	}
+	wait := ((time.Duration(b[0]) << 8) | time.Duration(b[1])) * time.Millisecond / 10 // up to 6.5 secs wait
+
+	// Why delay if nothing to process?
+	if scriptsToProcess > 0 {
+		time.Sleep(wait)
+	}
+
+	// Start transaction fotr lock process.
+	tx, err := runtime.Db.Beginx()
+	if err != nil {
+		runtime.Log.Error("Database: unable to start transaction", err)
+		return false, err
+	}
+
+	// Lock the database.
+	_, err = tx.Exec(runtime.StoreProvider.QueryStartLock())
+	if err != nil {
+		runtime.Log.Error("Database: unable to lock tables", err)
+		return false, err
+	}
+
+	// Unlock the database at the end of this function.
+	defer func() {
+		_, err = tx.Exec(runtime.StoreProvider.QueryFinishLock())
+		if err != nil {
+			runtime.Log.Error("Database: unable to unlock tables", err)
+		}
+		tx.Commit()
+	}()
+
+	// Try to record this process as leader of database migration process.
+	_, err = tx.Exec(runtime.StoreProvider.QueryInsertProcessID())
+	if err != nil {
+		runtime.Log.Info("Database: marked as slave process awaiting upgrade")
+		return false, nil
+	}
+
+	// We are the leader!
+	runtime.Log.Info("Database: marked as database upgrade process leader")
+	return true, err
+}
+
+// Unlock completes process that was started with Lock().
+func Unlock(runtime *env.Runtime, tx *sqlx.Tx, err error, amLeader bool) error {
+	if amLeader {
+		defer func() {
+			doUnlock(runtime)
+		}()
+
+		if tx != nil {
+			if err == nil {
+				tx.Commit()
+				runtime.Log.Info("Database: is ready")
+				return nil
+			}
+			tx.Rollback()
+		}
+
+		runtime.Log.Error("Database: install/upgrade failed", err)
+
+		return err
+	}
+
+	return nil // not the leader, so ignore errors
+}
+
+// Helper method for defer function called from Unlock().
+func doUnlock(runtime *env.Runtime) error {
+	tx, err := runtime.Db.Beginx()
+	if err != nil {
+		return err
+	}
+	_, err = tx.Exec(runtime.StoreProvider.QueryDeleteProcessID())
+	if err != nil {
+		return err
+	}
+
+	return tx.Commit()
+}