[receiver/expvar] Fix bug where measurement is recorded into wrong me…

…tric. (#13172)

Noticed a bug where the mSpanSys value was higher than it should be. Turns out we were recording to mCacheSys value to that metric as well. This resulted in no mCacheSys metric and an incorrect mSpanSys metric. This PR fixes the issue.

receiver/expvarreceiver/scraper.go

@@ -101,7 +101,7 @@ func (e *expVarScraper) scrape(ctx context.Context) (pmetric.Metrics, error) {
 	e.mb.RecordProcessRuntimeMemstatsMspanInuseDataPoint(now, int64(memStats.MSpanInuse))
 	e.mb.RecordProcessRuntimeMemstatsMspanSysDataPoint(now, int64(memStats.MSpanSys))
 	e.mb.RecordProcessRuntimeMemstatsMcacheInuseDataPoint(now, int64(memStats.MCacheInuse))
-	e.mb.RecordProcessRuntimeMemstatsMspanSysDataPoint(now, int64(memStats.MCacheSys))
+	e.mb.RecordProcessRuntimeMemstatsMcacheSysDataPoint(now, int64(memStats.MCacheSys))
 	e.mb.RecordProcessRuntimeMemstatsBuckHashSysDataPoint(now, int64(memStats.BuckHashSys))
 	e.mb.RecordProcessRuntimeMemstatsGcSysDataPoint(now, int64(memStats.GCSys))
 	e.mb.RecordProcessRuntimeMemstatsOtherSysDataPoint(now, int64(memStats.OtherSys))

receiver/expvarreceiver/testdata/metrics/expected_all_metrics.json

@@ -244,7 +244,17 @@
                     "startTimeUnixNano": "1653023581589787000",
                     "timeUnixNano": "1653023581592037000",
                     "asInt": "81600"
-                  },
+                  }
+                ],
+                "aggregationTemporality": "AGGREGATION_TEMPORALITY_CUMULATIVE"
+              }
+            },
+            {
+              "name": "process.runtime.memstats.mcache_sys",
+              "description": "Bytes of memory obtained from the OS for mcache structures.",
+              "unit": "By",
+              "sum": {
+                "dataPoints": [
                   {
                     "startTimeUnixNano": "1653023581589787000",
                     "timeUnixNano": "1653023581592037000",

unreleased/expvar-bug-fix-#13172.yaml

@@ -0,0 +1,4 @@
+change_type: bug_fix
+component: expvarreceiver
+note: "Fixes an bug where the mSpanSys value was recorded into the mCacheSys metric."
+issues: [13171]