From 7bbab380b6374362e3fc055c9a754943b3614674 Mon Sep 17 00:00:00 2001
From: Marco Pracucci <marco@pracucci.com>
Date: Mon, 15 Mar 2021 15:05:47 +0100
Subject: [PATCH] Added tracing span to evaluator.eval()

Signed-off-by: Marco Pracucci <marco@pracucci.com>
---
 promql/engine.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/promql/engine.go b/promql/engine.go
index 9fba6c68b..f963f454b 100644
--- a/promql/engine.go
+++ b/promql/engine.go
@@ -19,6 +19,7 @@ import (
 	"context"
 	"fmt"
 	"math"
+	"reflect"
 	"regexp"
 	"runtime"
 	"sort"
@@ -1125,6 +1126,10 @@ func (ev *evaluator) eval(expr parser.Expr) (parser.Value, storage.Warnings) {
 	}
 	numSteps := int((ev.endTimestamp-ev.startTimestamp)/ev.interval) + 1
 
+	// Create a new span to help investigate inner evaluation performances.
+	span, _ := opentracing.StartSpanFromContext(ev.ctx, stats.InnerEvalTime.SpanOperation()+" eval "+reflect.TypeOf(expr).String())
+	defer span.Finish()
+
 	switch e := expr.(type) {
 	case *parser.AggregateExpr:
 		unwrapParenExpr(&e.Param)