adds server lock package

pkg/infra/serverlock/serverlock.go

@@ -0,0 +1,111 @@
+package serverlock
+
+import (
+	"context"
+	"time"
+
+	"github.com/grafana/grafana/pkg/log"
+	"github.com/grafana/grafana/pkg/registry"
+	"github.com/grafana/grafana/pkg/services/sqlstore"
+)
+
+func init() {
+	registry.RegisterService(&ServerLockService{})
+}
+
+// ServerLockService allows servers in HA mode to execute function once over in the group
+type ServerLockService struct {
+	SQLStore *sqlstore.SqlStore `inject:""`
+	log      log.Logger
+}
+
+// Init this service
+func (sl *ServerLockService) Init() error {
+	return nil
+}
+
+// OncePerServerGroup try to create a lock for this server and only executes the
+// `fn` function when successful. This should not be used at low internal. But services
+// that needs to be run once every ex 10m.
+func (sl *ServerLockService) OncePerServerGroup(ctx context.Context, actionName string, maxEvery time.Duration, fn func()) error {
+	rowLock, err := sl.getOrCreate(ctx, actionName)
+	if err != nil {
+		return err
+	}
+
+	if rowLock.LastExecution != 0 {
+		lastExeuctionTime := time.Unix(rowLock.LastExecution, 0)
+		if lastExeuctionTime.Unix() > time.Now().Add(-maxEvery).Unix() {
+			return nil
+		}
+	}
+
+	acquiredLock, err := sl.acquireLock(ctx, rowLock, maxEvery)
+	if err != nil {
+		return err
+	}
+
+	if acquiredLock {
+		fn()
+	}
+
+	return nil
+}
+
+func (sl *ServerLockService) acquireLock(ctx context.Context, serverLock *serverLock, maxEvery time.Duration) (bool, error) {
+	var result bool
+
+	err := sl.SQLStore.WithDbSession(ctx, func(dbSession *sqlstore.DBSession) error {
+		newVersion := serverLock.Version + 1
+		sql := `UPDATE server_lock SET
+			version = ?,
+			last_execution = ?
+		WHERE
+			id = ? AND version = ?`
+
+		res, err := dbSession.Exec(sql, newVersion, time.Now().Unix(), serverLock.Id, serverLock.Version)
+		if err != nil {
+			return err
+		}
+
+		affected, err := res.RowsAffected()
+		result = affected == 1
+
+		return err
+	})
+
+	return result, err
+}
+
+func (sl *ServerLockService) getOrCreate(ctx context.Context, actionName string) (*serverLock, error) {
+	var result *serverLock
+
+	err := sl.SQLStore.WithTransactionalDbSession(ctx, func(dbSession *sqlstore.DBSession) error {
+		lockRows := []*serverLock{}
+		err := dbSession.Where("operation_uid = ?", actionName).Find(&lockRows)
+		if err != nil {
+			return err
+		}
+
+		if len(lockRows) > 0 {
+			result = lockRows[0]
+			return nil
+		}
+
+		lockRow := &serverLock{
+			OperationUid:  actionName,
+			LastExecution: 0,
+		}
+
+		_, err = dbSession.Insert(lockRow)
+		if err != nil {
+			return err
+		}
+
+		result = lockRow
+
+		return nil
+	})
+
+	return result, err
+}