This patch should be applyed on 0.14.0 tag version

alertmanager-sort-feat.path

diff -rupN a/config/config.go b/config/config.go
--- a/config/config.go	2018-02-13 06:13:44.000000000 -0200
+++ b/config/config.go	2018-04-20 13:07:29.802965461 -0300
@@ -382,6 +382,7 @@ func (c *GlobalConfig) UnmarshalYAML(unm
 type Route struct {
 	Receiver string            `yaml:"receiver,omitempty" json:"receiver,omitempty"`
 	GroupBy  []model.LabelName `yaml:"group_by,omitempty" json:"group_by,omitempty"`
+	SortBy   []model.LabelName `yaml:"sort_by,omitempty" json:"sort_by,omitempty"`
 
 	Match    map[string]string `yaml:"match,omitempty" json:"match,omitempty"`
 	MatchRE  map[string]Regexp `yaml:"match_re,omitempty" json:"match_re,omitempty"`
@@ -424,6 +425,14 @@ func (r *Route) UnmarshalYAML(unmarshal
 		groupBy[ln] = struct{}{}
 	}
 
+	sortBy := map[model.LabelName]struct{}{}
+	for _, ln := range r.SortBy {
+		if _, ok := sortBy[ln]; ok {
+			return fmt.Errorf("duplicated label %q in sort_by", ln)
+		}
+		sortBy[ln] = struct{}{}
+	}
+
 	if r.GroupInterval != nil && time.Duration(*r.GroupInterval) == time.Duration(0) {
 		return fmt.Errorf("group_interval cannot be zero")
 	}
diff -rupN a/config/config_test.go b/config/config_test.go
--- a/config/config_test.go	2018-02-13 06:13:44.000000000 -0200
+++ b/config/config_test.go	2018-04-20 13:07:29.802965461 -0300
@@ -341,6 +341,10 @@ func TestEmptyFieldsAndRegex(t *testing.
 				"cluster",
 				"service",
 			},
+			SortBy: []model.LabelName{
+				"instance",
+				"severity",
+			},
 			Routes: []*Route{
 				{
 					Receiver: "team-X-mails",
diff -rupN a/config/testdata/conf.empty-fields.yml b/config/testdata/conf.empty-fields.yml
--- a/config/testdata/conf.empty-fields.yml	2018-02-13 06:13:44.000000000 -0200
+++ b/config/testdata/conf.empty-fields.yml	2018-04-20 13:07:29.802965461 -0300
@@ -15,6 +15,7 @@ templates:
 
 route:
   group_by: ['alertname', 'cluster', 'service']
+  sort_by: ['instance', 'severity']
 
   receiver: team-X-mails
   routes:
diff -rupN a/config/testdata/conf.good.yml b/config/testdata/conf.good.yml
--- a/config/testdata/conf.good.yml	2018-02-13 06:13:44.000000000 -0200
+++ b/config/testdata/conf.good.yml	2018-04-20 13:07:29.802965461 -0300
@@ -23,6 +23,10 @@ route:
   # multiple alerts coming in for cluster=A and alertname=LatencyHigh would
   # be batched into a single group.
   group_by: ['alertname', 'cluster', 'service']
+  
+  # The labels by which an notification inside a group would be sorted inside
+  # the group.
+  sort_by: ['instance', 'severity']
 
   # When a new group of alerts is created by an incoming alert, wait at
   # least 'group_wait' to send the initial notification.
diff -rupN a/config/testdata/conf.opsgenie-default-apikey.yml b/config/testdata/conf.opsgenie-default-apikey.yml
--- a/config/testdata/conf.opsgenie-default-apikey.yml	2018-02-13 06:13:44.000000000 -0200
+++ b/config/testdata/conf.opsgenie-default-apikey.yml	2018-04-20 13:07:29.802965461 -0300
@@ -3,6 +3,7 @@ global:
 
 route:
   group_by: ['alertname', 'cluster', 'service']
+  sort_by: ['instance', 'severity']
   group_wait: 30s
   group_interval: 5m
   repeat_interval: 3h
diff -rupN a/config/testdata/conf.opsgenie-no-apikey.yml b/config/testdata/conf.opsgenie-no-apikey.yml
--- a/config/testdata/conf.opsgenie-no-apikey.yml	2018-02-13 06:13:44.000000000 -0200
+++ b/config/testdata/conf.opsgenie-no-apikey.yml	2018-04-20 13:07:29.802965461 -0300
@@ -1,5 +1,6 @@
 route:
   group_by: ['alertname', 'cluster', 'service']
+  sort_by: ['instance', 'severity']
   group_wait: 30s
   group_interval: 5m
   repeat_interval: 3h
diff -rupN a/config/testdata/conf.victorops-default-apikey.yml b/config/testdata/conf.victorops-default-apikey.yml
--- a/config/testdata/conf.victorops-default-apikey.yml	2018-02-13 06:13:44.000000000 -0200
+++ b/config/testdata/conf.victorops-default-apikey.yml	2018-04-20 13:07:29.802965461 -0300
@@ -3,6 +3,7 @@ global:
 
 route:
   group_by: ['alertname', 'cluster', 'service']
+  sort_by: ['instance', 'severity']
   group_wait: 30s
   group_interval: 5m
   repeat_interval: 3h
diff -rupN a/config/testdata/conf.victorops-no-apikey.yml b/config/testdata/conf.victorops-no-apikey.yml
--- a/config/testdata/conf.victorops-no-apikey.yml	2018-02-13 06:13:44.000000000 -0200
+++ b/config/testdata/conf.victorops-no-apikey.yml	2018-04-20 13:07:29.802965461 -0300
@@ -1,5 +1,6 @@
 route:
   group_by: ['alertname', 'cluster', 'service']
+  sort_by: ['instance', 'severity']
   group_wait: 30s
   group_interval: 5m
   repeat_interval: 3h
diff -rupN a/dispatch/dispatch.go b/dispatch/dispatch.go
--- a/dispatch/dispatch.go	2018-02-13 06:13:44.000000000 -0200
+++ b/dispatch/dispatch.go	2018-04-20 13:07:29.802965461 -0300
@@ -424,6 +424,31 @@ func (ag *aggrGroup) flush(notify func(.
 		alertsSlice = append(alertsSlice, alert)
 	}
 
+	sortLabels := make([]model.LabelName, 0)
+	if ag.opts != nil {
+		sortLabels = (*ag.opts).SortBy
+	}
+
+	sort.SliceStable(alertsSlice, func(i, j int) bool {
+		// Look at labels on sort_by
+		for _, override_key := range sortLabels {
+			key_i, ok_i := alertsSlice[i].Labels[override_key]
+			if !ok_i {
+				return false
+			}
+			key_j, ok_j := alertsSlice[j].Labels[override_key]
+			if !ok_j {
+				return true
+			}
+
+			if key_i != key_j {
+				return key_i < key_j
+			}
+		}
+
+		return alertsSlice[i].Labels.Before(alertsSlice[j].Labels)
+	})
+
 	ag.mtx.Unlock()
 
 	level.Debug(ag.logger).Log("msg", "Flushing", "alerts", fmt.Sprintf("%v", alertsSlice))
diff -rupN a/dispatch/route.go b/dispatch/route.go
--- a/dispatch/route.go	2018-02-13 06:13:44.000000000 -0200
+++ b/dispatch/route.go	2018-04-20 13:07:29.802965461 -0300
@@ -34,6 +34,9 @@ var DefaultRouteOpts = RouteOpts{
 	GroupBy: map[model.LabelName]struct{}{
 		model.AlertNameLabel: struct{}{},
 	},
+	SortBy: []model.LabelName{
+		model.InstanceLabel,
+	},
 }
 
 // A Route is a node that contains definitions of how to handle alerts.
@@ -71,6 +74,9 @@ func NewRoute(cr *config.Route, parent *
 			opts.GroupBy[ln] = struct{}{}
 		}
 	}
+	if cr.SortBy != nil {
+		opts.SortBy = cr.SortBy
+	}
 	if cr.GroupWait != nil {
 		opts.GroupWait = time.Duration(*cr.GroupWait)
 	}
@@ -159,6 +165,7 @@ type RouteOpts struct {
 
 	// What labels to group alerts by for notifications.
 	GroupBy map[model.LabelName]struct{}
+	SortBy  []model.LabelName
 
 	// How long to wait to group matching alerts before sending
 	// a notificaiton
@@ -169,10 +176,14 @@ type RouteOpts struct {
 
 func (ro *RouteOpts) String() string {
 	var labels []model.LabelName
+	var sortLabels []model.LabelName
 	for ln := range ro.GroupBy {
 		labels = append(labels, ln)
 	}
-	return fmt.Sprintf("<RouteOpts send_to:%q group_by:%q timers:%q|%q>", ro.Receiver, labels, ro.GroupWait, ro.GroupInterval)
+	for _, ln := range ro.SortBy {
+		sortLabels = append(sortLabels, ln)
+	}
+	return fmt.Sprintf("<RouteOpts send_to:%q group_by:%q sort_by:%q timers:%q|%q>", ro.Receiver, labels, sortLabels, ro.GroupWait, ro.GroupInterval)
 }
 
 // MarshalJSON returns a JSON representation of the routing options.
@@ -180,11 +191,13 @@ func (ro *RouteOpts) MarshalJSON() ([]by
 	v := struct {
 		Receiver       string           `json:"receiver"`
 		GroupBy        model.LabelNames `json:"groupBy"`
+		SortBy         model.LabelNames `json:"sortBy"`
 		GroupWait      time.Duration    `json:"groupWait"`
 		GroupInterval  time.Duration    `json:"groupInterval"`
 		RepeatInterval time.Duration    `json:"repeatInterval"`
 	}{
 		Receiver:       ro.Receiver,
+		SortBy:         ro.SortBy,
 		GroupWait:      ro.GroupWait,
 		GroupInterval:  ro.GroupInterval,
 		RepeatInterval: ro.RepeatInterval,
diff -rupN a/dispatch/route_test.go b/dispatch/route_test.go
--- a/dispatch/route_test.go	2018-02-13 06:13:44.000000000 -0200
+++ b/dispatch/route_test.go	2018-04-20 13:07:29.802965461 -0300
@@ -40,6 +40,7 @@ routes:
 
     receiver: 'notify-testing'
     group_by: []
+    sort_by: []
 
   - match:
       env: "production"
@@ -64,6 +65,7 @@ routes:
     owner: 'team-(B|C)'
 
   group_by: ['foo', 'bar']
+  sort_by: ['lipsum']
   group_wait: 2m
   receiver: 'notify-BC'
 
@@ -110,6 +112,7 @@ routes:
 				{
 					Receiver:       "notify-A",
 					GroupBy:        def.GroupBy,
+					SortBy:         def.SortBy,
 					GroupWait:      def.GroupWait,
 					GroupInterval:  def.GroupInterval,
 					RepeatInterval: def.RepeatInterval,
@@ -126,6 +129,7 @@ routes:
 				{
 					Receiver:       "notify-A",
 					GroupBy:        def.GroupBy,
+					SortBy:         def.SortBy,
 					GroupWait:      def.GroupWait,
 					GroupInterval:  def.GroupInterval,
 					RepeatInterval: def.RepeatInterval,
@@ -141,6 +145,7 @@ routes:
 				{
 					Receiver:       "notify-BC",
 					GroupBy:        lset("foo", "bar"),
+					SortBy:         []model.LabelName{"lipsum"},
 					GroupWait:      2 * time.Minute,
 					GroupInterval:  def.GroupInterval,
 					RepeatInterval: def.RepeatInterval,
@@ -157,6 +162,7 @@ routes:
 				{
 					Receiver:       "notify-testing",
 					GroupBy:        lset(),
+					SortBy:         []model.LabelName{},
 					GroupWait:      def.GroupWait,
 					GroupInterval:  def.GroupInterval,
 					RepeatInterval: def.RepeatInterval,
@@ -173,6 +179,7 @@ routes:
 				{
 					Receiver:       "notify-productionA",
 					GroupBy:        def.GroupBy,
+					SortBy:         def.SortBy,
 					GroupWait:      1 * time.Minute,
 					GroupInterval:  def.GroupInterval,
 					RepeatInterval: def.RepeatInterval,
@@ -180,6 +187,7 @@ routes:
 				{
 					Receiver:       "notify-productionB",
 					GroupBy:        lset("job"),
+					SortBy:         def.SortBy,
 					GroupWait:      30 * time.Second,
 					GroupInterval:  5 * time.Minute,
 					RepeatInterval: 1 * time.Hour,
@@ -198,6 +206,7 @@ routes:
 				{
 					Receiver:       "notify-def",
 					GroupBy:        lset("role"),
+					SortBy:         def.SortBy,
 					GroupWait:      def.GroupWait,
 					GroupInterval:  def.GroupInterval,
 					RepeatInterval: def.RepeatInterval,
@@ -214,6 +223,7 @@ routes:
 				{
 					Receiver:       "notify-testing",
 					GroupBy:        lset("role"),
+					SortBy:         def.SortBy,
 					GroupWait:      def.GroupWait,
 					GroupInterval:  def.GroupInterval,
 					RepeatInterval: def.RepeatInterval,
@@ -231,6 +241,7 @@ routes:
 				{
 					Receiver:       "notify-testing",
 					GroupBy:        lset("role"),
+					SortBy:         def.SortBy,
 					GroupWait:      2 * time.Minute,
 					GroupInterval:  def.GroupInterval,
 					RepeatInterval: def.RepeatInterval,