fix for converter relabel source_labels (#4708)

Signed-off-by: erikbaranowski <[email protected]>

CHANGELOG.md

@@ -62,6 +62,8 @@ Main (unreleased)
 
 ### Bugfixes
 
+- Update to config converter so default relabel `source_labels` are left off the river output. (@erikbaranowski)
+
 - Rename `GrafanaAgentManagement` mixin rules to `GrafanaAgentConfig` and update individual alerts to be more accurate. (@spartan0x117)
 
 - Fix potential goroutine leak in log file tailing in static mode. (@thampiotr)

converter/internal/prometheusconvert/relabel.go

@@ -67,9 +67,12 @@ func ToFlowRelabelConfigs(relabelConfigs []*prom_relabel.Config) []*flow_relabel
 
 	var metricRelabelConfigs []*flow_relabel.Config
 	for _, relabelConfig := range relabelConfigs {
-		sourceLabels := make([]string, len(relabelConfig.SourceLabels))
-		for i, sourceLabel := range relabelConfig.SourceLabels {
-			sourceLabels[i] = string(sourceLabel)
+		var sourceLabels []string
+		if len(relabelConfig.SourceLabels) > 0 {
+			sourceLabels = make([]string, len(relabelConfig.SourceLabels))
+			for i, sourceLabel := range relabelConfig.SourceLabels {
+				sourceLabels[i] = string(sourceLabel)
+			}
 		}
 
 		metricRelabelConfigs = append(metricRelabelConfigs, &flow_relabel.Config{

converter/internal/staticconvert/testdata/integrations.river

@@ -35,9 +35,8 @@ discovery.relabel "integrations_node_exporter" {
 	}
 
 	rule {
-		source_labels = []
-		target_label  = "__address__"
-		replacement   = "localhost:8099"
+		target_label = "__address__"
+		replacement  = "localhost:8099"
 	}
 }
 

converter/internal/staticconvert/testdata/prom_scrape.river

@@ -52,9 +52,8 @@ discovery.relabel "metrics_agent_promobee" {
 	}
 
 	rule {
-		source_labels = []
-		target_label  = "__address__"
-		replacement   = "localhost:8099"
+		target_label = "__address__"
+		replacement  = "localhost:8099"
 	}
 }