Merge master into breakout_swarm

Signed-off-by: Alex Ellis <alexellis2@gmail.com>

gateway/vendor/github.com/prometheus/client_golang/prometheus/registry.go

@@ -80,7 +80,7 @@ func NewPedanticRegistry() *Registry {
 
 // Registerer is the interface for the part of a registry in charge of
 // registering and unregistering. Users of custom registries should use
-// Registerer as type for registration purposes (rather than the Registry type
+// Registerer as type for registration purposes (rather then the Registry type
 // directly). In that way, they are free to use custom Registerer implementation
 // (e.g. for testing purposes).
 type Registerer interface {
@@ -152,6 +152,38 @@ func MustRegister(cs ...Collector) {
 	DefaultRegisterer.MustRegister(cs...)
 }
 
+// RegisterOrGet registers the provided Collector with the DefaultRegisterer and
+// returns the Collector, unless an equal Collector was registered before, in
+// which case that Collector is returned.
+//
+// Deprecated: RegisterOrGet is merely a convenience function for the
+// implementation as described in the documentation for
+// AlreadyRegisteredError. As the use case is relatively rare, this function
+// will be removed in a future version of this package to clean up the
+// namespace.
+func RegisterOrGet(c Collector) (Collector, error) {
+	if err := Register(c); err != nil {
+		if are, ok := err.(AlreadyRegisteredError); ok {
+			return are.ExistingCollector, nil
+		}
+		return nil, err
+	}
+	return c, nil
+}
+
+// MustRegisterOrGet behaves like RegisterOrGet but panics instead of returning
+// an error.
+//
+// Deprecated: This is deprecated for the same reason RegisterOrGet is. See
+// there for details.
+func MustRegisterOrGet(c Collector) Collector {
+	c, err := RegisterOrGet(c)
+	if err != nil {
+		panic(err)
+	}
+	return c
+}
+
 // Unregister removes the registration of the provided Collector from the
 // DefaultRegisterer.
 //
@@ -169,6 +201,25 @@ func (gf GathererFunc) Gather() ([]*dto.MetricFamily, error) {
 	return gf()
 }
 
+// SetMetricFamilyInjectionHook replaces the DefaultGatherer with one that
+// gathers from the previous DefaultGatherers but then merges the MetricFamily
+// protobufs returned from the provided hook function with the MetricFamily
+// protobufs returned from the original DefaultGatherer.
+//
+// Deprecated: This function manipulates the DefaultGatherer variable. Consider
+// the implications, i.e. don't do this concurrently with any uses of the
+// DefaultGatherer. In the rare cases where you need to inject MetricFamily
+// protobufs directly, it is recommended to use a custom Registry and combine it
+// with a custom Gatherer using the Gatherers type (see
+// there). SetMetricFamilyInjectionHook only exists for compatibility reasons
+// with previous versions of this package.
+func SetMetricFamilyInjectionHook(hook func() []*dto.MetricFamily) {
+	DefaultGatherer = Gatherers{
+		DefaultGatherer,
+		GathererFunc(func() ([]*dto.MetricFamily, error) { return hook(), nil }),
+	}
+}
+
 // AlreadyRegisteredError is returned by the Register method if the Collector to
 // be registered has already been registered before, or a different Collector
 // that collects the same metrics has been registered before. Registration fails
@@ -243,7 +294,7 @@ func (r *Registry) Register(c Collector) error {
 	}()
 	r.mtx.Lock()
 	defer r.mtx.Unlock()
-	// Conduct various tests...
+	// Coduct various tests...
 	for desc := range descChan {
 
 		// Is the descriptor valid at all?
@@ -396,7 +447,7 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 
 	// Drain metricChan in case of premature return.
 	defer func() {
-		for range metricChan {
+		for _ = range metricChan {
 		}
 	}()
 
@@ -632,7 +683,7 @@ func (s metricSorter) Less(i, j int) bool {
 	return s[i].GetTimestampMs() < s[j].GetTimestampMs()
 }
 
-// normalizeMetricFamilies returns a MetricFamily slice with empty
+// normalizeMetricFamilies returns a MetricFamily slice whith empty
 // MetricFamilies pruned and the remaining MetricFamilies sorted by name within
 // the slice, with the contained Metrics sorted within each MetricFamily.
 func normalizeMetricFamilies(metricFamiliesByName map[string]*dto.MetricFamily) []*dto.MetricFamily {