extract promql query from variable in grafana collector

README.md

@@ -131,10 +131,7 @@ perses_collector:
 
 ### Grafana Collector
 
-This collector gets the list of dashboards using the HTTP API of Grafana. Then it extracts the metric used in the different panels. 
-
-> [!IMPORTANT]
-> Extraction from variable still needs to be done.
+This collector gets the list of dashboards using the HTTP API of Grafana. Then it extracts the metric used in the different panels.
 
 #### Configuration
 

source/grafana/grafana.go

@@ -17,6 +17,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"regexp"
 	"strings"
 
 	"github.com/go-openapi/strfmt"
@@ -33,15 +34,23 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
-var variableReplacer = strings.NewReplacer(
-	"$__interval", "5m",
-	"$interval", "5m",
-	"$resolution", "5m",
-	"$__rate_interval", "15s",
-	"$rate_interval", "15s",
-	"$__range", "1d",
-	"${__range_s:glob}", "15",
-	"${__range_s}", "15",
+var (
+	labelValuesRegexp            = regexp.MustCompile(`(?s)label_values\((.+),.+\)`)
+	labelValuesNoQueryRegexp     = regexp.MustCompile(`(?s)label_values\((.+)\)`)
+	queryResultRegexp            = regexp.MustCompile(`(?s)query_result\((.+)\)`)
+	variableRangeQueryRangeRegex = regexp.MustCompile(`\[\$?\w+?]`)
+	variableSubqueryRangeRegex   = regexp.MustCompile(`\[\$?\w+:\$?\w+?]`)
+	variableReplacer             = strings.NewReplacer(
+		"$__interval", "5m",
+		"$interval", "5m",
+		"$resolution", "5m",
+		"$__rate_interval", "15s",
+		"$rate_interval", "15s",
+		"$__range", "1d",
+		"${__range_s:glob}", "15",
+		"${__range_s}", "15",
+		"${__range_ms}", "15",
+	)
 )
 
 func NewCollector(db database.Database, cfg config.GrafanaCollector) (async.SimpleTask, error) {
@@ -113,8 +122,8 @@ func (c *grafanaCollector) extractMetricUsage(metricUsage map[string]*modelAPIV1
 	c.extractMetricUsageFromPanels(metricUsage, dashboard.Panels, dashboard)
 	for _, r := range dashboard.Rows {
 		c.extractMetricUsageFromPanels(metricUsage, r.Panels, dashboard)
-		// TODO extract metric usage from variable
 	}
+	c.extractMetricUsageFromVariables(metricUsage, dashboard.Templating.List, dashboard)
 }
 
 func (c *grafanaCollector) extractMetricUsageFromPanels(metricUsage map[string]*modelAPIV1.MetricUsage, panels []panel, dashboard *simplifiedDashboard) {
@@ -132,6 +141,40 @@ func (c *grafanaCollector) extractMetricUsageFromPanels(metricUsage map[string]*
 	}
 }
 
+func (c *grafanaCollector) extractMetricUsageFromVariables(metricUsage map[string]*modelAPIV1.MetricUsage, variables []templateVar, dashboard *simplifiedDashboard) {
+	for _, v := range variables {
+		if v.Type != "query" {
+			continue
+		}
+		query, err := v.extractQueryFromVariableTemplating()
+		if err != nil {
+			logrus.WithError(err).Errorf("failed to extract query in a variable")
+			continue
+		}
+		// label_values(query, label)
+		if labelValuesRegexp.MatchString(query) {
+			sm := labelValuesRegexp.FindStringSubmatch(query)
+			if len(sm) > 0 {
+				query = sm[1]
+			} else {
+				continue
+			}
+		} else if labelValuesNoQueryRegexp.MatchString(query) {
+			// No query so no metric.
+			continue
+		} else if queryResultRegexp.MatchString(query) {
+			// query_result(query)
+			query = queryResultRegexp.FindStringSubmatch(query)[1]
+		}
+		metrics, err := prometheus.ExtractMetricNamesFromPromQL(replaceVariables(query))
+		if err != nil {
+			logrus.WithError(err).Errorf("failed to extract metric names from PromQL expression in variable %q for the dashboard %s/%s", v.Name, dashboard.Title, dashboard.UID)
+			continue
+		}
+		c.populateUsage(metricUsage, metrics, dashboard)
+	}
+}
+
 func (c *grafanaCollector) getDashboard(uid string) (*simplifiedDashboard, error) {
 	response, err := c.grafanaClient.Dashboards.GetDashboardByUID(uid)
 	if err != nil {
@@ -188,5 +231,8 @@ func (c *grafanaCollector) String() string {
 }
 
 func replaceVariables(expr string) string {
-	return variableReplacer.Replace(expr)
+	newExpr := variableReplacer.Replace(expr)
+	newExpr = variableRangeQueryRangeRegex.ReplaceAllLiteralString(newExpr, `[5m]`)
+	newExpr = variableSubqueryRangeRegex.ReplaceAllLiteralString(newExpr, `[5m:1m]`)
+	return newExpr
 }

source/grafana/model.go

@@ -13,6 +13,8 @@
 
 package grafana
 
+import "fmt"
+
 type target struct {
 	Expr string `json:"expr,omitempty"`
 }
@@ -34,6 +36,23 @@ type templateVar struct {
 	Query interface{} `json:"query"`
 }
 
+// extractQueryFromVariableTemplating will extract the PromQL expression from query.
+// Query can have two types.
+// It can be a string or the following JSON object:
+// { query: "up", refId: "foo" }
+// We need to ensure we are in one of the different cases.
+func (v templateVar) extractQueryFromVariableTemplating() (string, error) {
+	if query, ok := v.Query.(string); ok {
+		return query, nil
+	}
+	if queryObj, ok := v.Query.(map[string]interface{}); ok {
+		if query, ok := queryObj["query"].(string); ok {
+			return query, nil
+		}
+	}
+	return "", fmt.Errorf("query variable %q doesn't have the right type (string, or JSON object). It is of type %T", v.Name, v.Query)
+}
+
 type simplifiedDashboard struct {
 	UID        string  `json:"uid,omitempty"`
 	Title      string  `json:"title"`