Function EngineQueryFunc

rules/manager.go:50–75

EngineQueryFunc returns a new query function that executes instant queries against the given engine. It converts scalar into vector results.

(engine promql.QueryEngine, q storage.Queryable)

// the given engine.
// It converts scalar into vector results.
func EngineQueryFunc(engine promql.QueryEngine, q storage.Queryable) QueryFunc {
	return func(ctx context.Context, qs string, t time.Time) (promql.Vector, error) {
		q, err := engine.NewInstantQuery(ctx, q, nil, qs, t)
		if err != nil {
			return nil, err
		}
		defer q.Close()

		res := q.Exec(ctx)
		if res.Err != nil {
			return nil, res.Err
		}
		switch v := res.Value.(type) {
		case promql.Vector:
			return v, nil
		case promql.Scalar:
			return promql.Vector{promql.Sample{
				T:      v.T,
				F:      v.V,
				Metric: labels.Labels{},
			}}, nil
		default:
			return nil, errors.New("rule result is not a vector or scalar")
		}
	}
}

// DefaultEvalIterationFunc is the default implementation of
// GroupEvalIterationFunc that is periodically invoked to evaluate the rules