some renaming and comments fixes.

remove some select state that is most likely obsoleete and hoepfully doesn't braje anything :)
merge targets will sort by Discoverer name so we can have consistent tests for the maps.

discovery/manager.go

@@ -16,7 +16,7 @@ package discovery
 import (
 	"context"
 	"fmt"
-	"time"
+	"sort"
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
@@ -64,7 +64,7 @@ func NewManager(ctx context.Context, logger log.Logger) *Manager {
 		logger:         logger,
 		actionCh:       make(chan func()),
 		syncCh:         make(chan map[string][]*config.TargetGroup),
-		endpoints:      make(map[string]map[string][]*config.TargetGroup),
+		targets:        make(map[string]map[string][]*config.TargetGroup),
 		discoverCancel: []context.CancelFunc{},
 	}
 }
@@ -76,7 +76,7 @@ type Manager struct {
 	syncCh         chan map[string][]*config.TargetGroup // map[targetSetName]
 	actionCh       chan func()
 	discoverCancel []context.CancelFunc
-	endpoints      map[string]map[string][]*config.TargetGroup // map[targetSetName]map[providerName]
+	targets        map[string]map[string][]*config.TargetGroup // map[targetSetName]map[providerName]
 }
 
 // Run starts the background processing
@@ -86,12 +86,13 @@ func (m *Manager) Run() error {
 		case f := <-m.actionCh:
 			f()
 		case <-m.ctx.Done():
+			m.cancelDiscoverers()
 			return m.ctx.Err()
 		}
 	}
 }
 
-// SyncCh returns a read only channel used by all DiscoveryProviders targetSet updates
+// SyncCh returns a read only channel used by all Discoverers to send target updates.
 func (m *Manager) SyncCh() <-chan map[string][]*config.TargetGroup {
 	return m.syncCh
 }
@@ -120,22 +121,6 @@ func (m *Manager) startProvider(jobName, provName string, worker Discoverer) {
 
 	go worker.Run(ctx, updates)
 	go func(provName string) {
-		select {
-		case <-ctx.Done():
-			// First set of all endpoints the provider knows.
-		case tgs, ok := <-updates:
-			// Handle the case that a target provider exits and closes the channel
-			// before the context is done.
-			if !ok {
-				break
-			}
-			m.syncCh <- m.mergeGroups(jobName, provName, tgs)
-		case <-time.After(5 * time.Second):
-			// Initial set didn't arrive. Act as if it was empty
-			// and wait for updates later on.
-		}
-
-		// Start listening for further updates.
 		for {
 			select {
 			case <-ctx.Done():
@@ -156,26 +141,37 @@ func (m *Manager) cancelDiscoverers() {
 	for _, c := range m.discoverCancel {
 		c()
 	}
-	m.endpoints = make(map[string]map[string][]*config.TargetGroup)
+	m.targets = make(map[string]map[string][]*config.TargetGroup)
 	m.discoverCancel = []context.CancelFunc{}
 }
 
 // mergeGroups adds a new target group for a given discovery provider and returns all target groups for a given target set
 func (m *Manager) mergeGroups(tsName, provName string, tg []*config.TargetGroup) map[string][]*config.TargetGroup {
-	if m.endpoints[tsName] == nil {
-		m.endpoints[tsName] = make(map[string][]*config.TargetGroup)
-	}
-	m.endpoints[tsName][provName] = []*config.TargetGroup{}
-
 	tset := make(chan map[string][]*config.TargetGroup)
+
 	m.actionCh <- func() {
-		if tg != nil {
-			m.endpoints[tsName][provName] = tg
+		if m.targets[tsName] == nil {
+			m.targets[tsName] = make(map[string][]*config.TargetGroup)
 		}
-		var tgAll []*config.TargetGroup
-		for _, prov := range m.endpoints[tsName] {
-			for _, tg := range prov {
-				tgAll = append(tgAll, tg)
+		m.targets[tsName][provName] = []*config.TargetGroup{}
+
+		if tg != nil {
+			m.targets[tsName][provName] = tg
+		}
+		tgAll := []*config.TargetGroup{}
+
+		// Sort the providers alphabetically.
+		// Maps cannot be sorted so need to extract the keys to a slice and sort the string slice.
+		var providerNames []string
+		for providerName := range m.targets[tsName] {
+			providerNames = append(providerNames, providerName)
+		}
+		sort.Strings(providerNames)
+		for _, prov := range providerNames {
+			for _, tg := range m.targets[tsName][prov] {
+				if tg.Source != "" { // Don't add empty targets.
+					tgAll = append(tgAll, tg)
+				}
 			}
 		}
 		t := make(map[string][]*config.TargetGroup)