Work around int32/64 counter overflows on the DB side, by casting to uint32/64 on the Go side. Fixes prometheus-community#2.

Author: ncabatoff

db/db.go

@@ -161,8 +161,8 @@ func dbStringToFloat64(s string, re *regexp.Regexp) (float64, bool) {
 	return result, true
 }
 
-// Convert database.sql types to float64s for Prometheus consumption. Null types are mapped to NaN. string and []byte
-// types are mapped as NaN and !ok
+// Convert database.sql types to float64s for Prometheus consumption. Null
+// types are mapped to NaN. string and []byte types are mapped as NaN and !ok
 func ToFloat64(t interface{}, r *regexp.Regexp) (float64, bool) {
 	switch v := t.(type) {
 	case int32:
@@ -187,6 +187,17 @@ func ToFloat64(t interface{}, r *regexp.Regexp) (float64, bool) {
 	}
 }
 
+func ToUnsignedFloat64(t interface{}, r *regexp.Regexp) (float64, bool) {
+	switch v := t.(type) {
+	case int32:
+		return float64(uint32(v)), true
+	case int64:
+		return float64(uint64(v)), true
+	default:
+		return ToFloat64(t, r)
+	}
+}
+
 // Convert database.sql to string for Prometheus labels. Null types are mapped to empty strings.
 func ToString(t interface{}) (string, bool) {
 	switch v := t.(type) {

dbms_exporter.go

@@ -116,7 +116,7 @@ func makeDescMap(metricName string, resultMap recipes.ResultMap, recipe recipes.
 				vtype: prometheus.CounterValue,
 				desc:  newDesc(columnName, columnMapping.Description),
 				conversion: func(in interface{}) (float64, bool) {
-					return db.ToFloat64(in, regexp)
+					return db.ToUnsignedFloat64(in, regexp)
 				},
 			}
 		case common.GAUGE: