replace state machine with mutex

retrieval/manager.go

@@ -15,6 +15,7 @@ package retrieval
 
 import (
 	"fmt"
+	"sync"
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
@@ -35,7 +36,6 @@ func NewScrapeManager(logger log.Logger, app Appendable) *ScrapeManager {
 	return &ScrapeManager{
 		append:        app,
 		logger:        logger,
-		actionCh:      make(chan func()),
 		scrapeConfigs: make(map[string]*config.ScrapeConfig),
 		scrapePools:   make(map[string]*scrapePool),
 		graceShut:     make(chan struct{}),
@@ -49,7 +49,7 @@ type ScrapeManager struct {
 	append        Appendable
 	scrapeConfigs map[string]*config.ScrapeConfig
 	scrapePools   map[string]*scrapePool
-	actionCh      chan func()
+	mtx           sync.RWMutex
 	graceShut     chan struct{}
 }
 
@@ -59,8 +59,6 @@ func (m *ScrapeManager) Run(tsets <-chan map[string][]*targetgroup.Group) error
 
 	for {
 		select {
-		case f := <-m.actionCh:
-			f()
 		case ts := <-tsets:
 			m.reload(ts)
 		case <-m.graceShut:
@@ -79,23 +77,21 @@ func (m *ScrapeManager) Stop() {
 
 // ApplyConfig resets the manager's target providers and job configurations as defined by the new cfg.
 func (m *ScrapeManager) ApplyConfig(cfg *config.Config) error {
-	done := make(chan struct{})
+	m.mtx.Lock()
-	m.actionCh <- func() {
+	defer m.mtx.Unlock()
 	c := make(map[string]*config.ScrapeConfig)
 	for _, scfg := range cfg.ScrapeConfigs {
 		c[scfg.JobName] = scfg
 	}
 	m.scrapeConfigs = c
-		close(done)
-	}
-	<-done
 	return nil
 }
 
 // TargetMap returns map of active and dropped targets and their corresponding scrape config job name.
 func (m *ScrapeManager) TargetMap() map[string][]*Target {
-	targetsMap := make(chan map[string][]*Target)
+	m.mtx.Lock()
-	m.actionCh <- func() {
+	defer m.mtx.Unlock()
+
 	targets := make(map[string][]*Target)
 	for jobName, sp := range m.scrapePools {
 		sp.mtx.RLock()
@@ -105,26 +101,25 @@ func (m *ScrapeManager) TargetMap() map[string][]*Target {
 		targets[jobName] = append(targets[jobName], sp.droppedTargets...)
 		sp.mtx.RUnlock()
 	}
-		targetsMap <- targets
+
-	}
+	return targets
-	return <-targetsMap
 }
 
 // Targets returns the targets currently being scraped.
 func (m *ScrapeManager) Targets() []*Target {
-	targets := make(chan []*Target)
+	m.mtx.Lock()
-	m.actionCh <- func() {
+	defer m.mtx.Unlock()
-		var t []*Target
+
+	var targets []*Target
 	for _, p := range m.scrapePools {
 		p.mtx.RLock()
 		for _, tt := range p.targets {
-				t = append(t, tt)
+			targets = append(targets, tt)
 		}
 		p.mtx.RUnlock()
 	}
-		targets <- t
+
-	}
+	return targets
-	return <-targets
 }
 
 func (m *ScrapeManager) reload(t map[string][]*targetgroup.Group) {