fixup! Expose stats' relevant threshold expression symbols publicly

stats/thresholds.go

@@ -58,19 +58,9 @@ func newThreshold(src string, abortOnFail bool, gracePeriod types.NullDuration)
 }
 
 func (t *Threshold) runNoTaint(sinks map[string]float64) (bool, error) {
-	// Because aggregation method can either be a static keyword ("count", "rate", etc...),
-	// or a parametric expression ("p(somefloatingpointvalue)"), we need to handle this
-	// case specifically. If we encounter the percentile aggregation method token,
-	// we recompute the whole "p(value)" expression in order to look for it in the
-	// sinks.
-	sinkKey := t.Parsed.AggregationMethod
-	if t.Parsed.AggregationMethod == TokenPercentile {
-		sinkKey = fmt.Sprintf("%s(%g)", TokenPercentile, t.Parsed.AggregationValue.Float64)
-	}
-
 	// Extract the sink value for the aggregation method used in the threshold
 	// expression
-	lhs, ok := sinks[sinkKey]
+	lhs, ok := sinks[t.Parsed.SinkKey()]
 	if !ok {
 		return false, fmt.Errorf("unable to apply threshold %s over metrics; reason: "+
 			"no metric supporting the %s aggregation method found",

stats/thresholds_parser.go

@@ -74,6 +74,28 @@ func NewThresholdExpressionFrom(input string) (*ThresholdExpression, error) {
 	return parseThresholdExpression(input)
 }
 
+// SinkKey computes the key used to index a ThresholdExpression in the engine's sinks.
+//
+// During execution, the engine "sinks" metrics into a internal mapping, so that
+// thresholds can be tried against them. This method is a helper to normalize the
+// sink the threshold expression should be applied to.
+//
+// Because a theshold expression's aggregation method can either be
+// a static keyword ("count", "rate", etc...), or a parametric
+// expression ("p(somefloatingpointvalue)"), we need to handle this
+// case specifically. If we encounter the percentile aggregation method token,
+// we recompute the whole "p(value)" expression in order to look for it in the
+// sinks.
+func (te *ThresholdExpression) SinkKey() string {
+	//
+	sinkKey := te.AggregationMethod
+	if te.AggregationMethod == TokenPercentile {
+		sinkKey = fmt.Sprintf("%s(%g)", TokenPercentile, te.AggregationValue.Float64)
+	}
+
+	return sinkKey
+}
+
 // parseThresholdAssertion parses a threshold condition expression,
 // as defined in a JS script (for instance p(95)<1000), into a thresholdExpression
 // instance.