fix for panic with snmp exporter from the recent version upgrade (#6921)

* fix for panic with snmp exporter from the recent version upgrade

Signed-off-by: erikbaranowski <39704712+erikbaranowski@users.noreply.github.com>

---------

Signed-off-by: erikbaranowski <39704712+erikbaranowski@users.noreply.github.com>

CHANGELOG.md

@@ -50,6 +50,10 @@ Main (unreleased)
 
 ### Bugfixes
 
+- Fix panic for `prometheus.exporter.snmp` and snmp_exporter integration
+  introduced in v0.40.5 with a version upgrade. This was due to an
+  uninitialized new metric for the exporter. (@erikbaranowski)
+
 - Fix an issue where JSON string array elements were not parsed correctly in `loki.source.cloudflare`. (@thampiotr)
 
 - Fix SSRF vulnerability in `faro.receiver` by disabling source map download. (@hainenber)

static/integrations/snmp_exporter/snmp_exporter.go

@@ -155,6 +155,13 @@ func NewSNMPMetrics(reg prometheus.Registerer) collector.Metrics {
 				Help:      "Number of SNMP packet retries.",
 			},
 		),
+		SNMPInflight: promauto.With(reg).NewGauge(
+			prometheus.GaugeOpts{
+				Namespace: namespace,
+				Name:      "request_in_flight",
+				Help:      "Current number of SNMP scrapes being requested.",
+			},
+		),
 	}
 }