More metric tests and fix reconnect

* more metric test and fix reconnect

* remove build-devjmstest as dependency

vendor/github.com/prometheus/client_golang/prometheus/metric.go

@@ -79,12 +79,20 @@ type Opts struct {
 	// with the same fully-qualified name must have the same label names in
 	// their ConstLabels.
 	//
-	// ConstLabels are only used rarely. In particular, do not use them to
-	// attach the same labels to all your metrics. Those use cases are
-	// better covered by target labels set by the scraping Prometheus
-	// server, or by one specific metric (e.g. a build_info or a
-	// machine_role metric). See also
-	// https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels,-not-static-scraped-labels
+	// Note that in most cases, labels have a value that varies during the
+	// lifetime of a process. Those labels are usually managed with a metric
+	// vector collector (like CounterVec, GaugeVec, UntypedVec). ConstLabels
+	// serve only special purposes. One is for the special case where the
+	// value of a label does not change during the lifetime of a process,
+	// e.g. if the revision of the running binary is put into a
+	// label. Another, more advanced purpose is if more than one Collector
+	// needs to collect Metrics with the same fully-qualified name. In that
+	// case, those Metrics must differ in the values of their
+	// ConstLabels. See the Collector examples.
+	//
+	// If the value of a label never changes (not even between binaries),
+	// that label most likely should not be a label at all (but part of the
+	// metric name).
 	ConstLabels Labels
 }
 
@@ -127,6 +135,20 @@ func (s LabelPairSorter) Less(i, j int) bool {
 	return s[i].GetName() < s[j].GetName()
 }
 
+type hashSorter []uint64
+
+func (s hashSorter) Len() int {
+	return len(s)
+}
+
+func (s hashSorter) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+func (s hashSorter) Less(i, j int) bool {
+	return s[i] < s[j]
+}
+
 type invalidMetric struct {
 	desc *Desc
 	err  error