Add a hard timeout to stop the SQL processing of a too long query.

This will prevent from killing the MariaDB with bad queries.

Author: clems4ever

internal/database/mariadb.go

@@ -486,6 +486,12 @@ func (m *MariaDB) Query(ctx context.Context, query *query.QueryIL) (*knowledge.G
 		return nil, err
 	}
 
+	deadline, ok := ctx.Deadline()
+	// If there is a deadline, we make sure the query stops right after it has been reached.
+	if ok {
+		// Query can take 35 seconds max before being aborted...
+		sql.Query = fmt.Sprintf("SET STATEMENT max_statement_time=%f FOR %s", time.Until(deadline).Seconds()+5, sql.Query)
+	}
 	fmt.Println(sql.Query)
 
 	rows, err := m.db.QueryContext(ctx, sql.Query)
@@ -499,7 +505,6 @@ func (m *MariaDB) Query(ctx context.Context, query *query.QueryIL) (*knowledge.G
 		Projections: sql.ProjectionTypes,
 	}
 	res.Projections = sql.ProjectionTypes
-
 	return res, nil
 }
 

internal/knowledge/querier.go

@@ -40,12 +40,13 @@ func (q *Querier) Query(ctx context.Context, cypherQuery string) (*QuerierResult
 	s.Execution = MeasureDuration(func() {
 		res, err = q.GraphDB.Query(ctx, queryIL)
 	})
-	fmt.Printf("Found results in %dms\n", s.Execution/time.Millisecond)
 
 	if err != nil {
 		return nil, err
 	}
 
+	fmt.Printf("Found results in %dms\n", s.Execution/time.Millisecond)
+
 	result := &QuerierResult{
 		Cursor:      res.Cursor,
 		Projections: res.Projections,

internal/server/server.go

@@ -153,15 +153,15 @@ func postQuery(database knowledge.GraphDB) http.HandlerFunc {
 		}
 
 		querier := knowledge.NewQuerier(database)
-		ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 		defer cancel()
 
 		res, err := querier.Query(ctx, requestBody.Query)
-
 		if err != nil {
 			replyWithInternalError(w, err)
 			return
 		}
+		defer res.Cursor.Close()
 
 		columns := make([]ColumnType, 0)
 		for _, p := range res.Projections {