Allow Discovery Manager and Scrape Manager metrics to come from outsi…

…de the "New" functions.

discovery/manager.go

@@ -81,6 +81,7 @@ func CreateAndRegisterSDMetrics(reg prometheus.Registerer) (map[string]Discovere
 }
 
 // NewManager is the Discovery Manager constructor.
+// If you want multiple managers to share the same metrics, set "registerer" to nil and use "SetMetrics" in "options".
 func NewManager(ctx context.Context, logger log.Logger, registerer prometheus.Registerer, sdMetrics map[string]DiscovererMetrics, options ...func(*Manager)) *Manager {
 	if logger == nil {
 		logger = log.NewNopLogger()
@@ -99,13 +100,15 @@ func NewManager(ctx context.Context, logger log.Logger, registerer prometheus.Re
 		option(mgr)
 	}
 
-	// Register the metrics.
-	// We have to do this after setting all options, so that the name of the Manager is set.
-	if metrics, err := NewManagerMetrics(registerer, mgr.name); err == nil {
-		mgr.metrics = metrics
-	} else {
-		level.Error(logger).Log("msg", "Failed to create discovery manager metrics", "manager", mgr.name, "err", err)
-		return nil
+	if mgr.metrics == nil {
+		// Register the metrics.
+		// We have to do this after setting all options, so that the name of the Manager is set.
+		if metrics, err := NewManagerMetrics(registerer, mgr.name); err == nil {
+			mgr.metrics = metrics
+		} else {
+			level.Error(logger).Log("msg", "Failed to create discovery manager metrics", "manager", mgr.name, "err", err)
+			return nil
+		}
 	}
 
 	return mgr
@@ -169,11 +172,22 @@ func (m *Manager) Providers() []*Provider {
 	return m.providers
 }
 
+// SetMetrics is useful if you want multiple managers to share the same metrics.
+func SetMetrics(metrics *Metrics) func(*Manager) {
+	return func(m *Manager) {
+		m.mtx.Lock()
+		defer m.mtx.Unlock()
+		m.metrics = metrics
+	}
+}
+
 // UnregisterMetrics unregisters manager metrics. It does not unregister
 // service discovery or refresh metrics, whose lifecycle is managed independent
 // of the discovery Manager.
 func (m *Manager) UnregisterMetrics() {
-	m.metrics.Unregister(m.registerer)
+	if m.registerer != nil && m.metrics != nil {
+		m.metrics.Unregister(m.registerer)
+	}
 }
 
 // Run starts the background processing.

scrape/manager.go

@@ -44,7 +44,7 @@ func NewManager(o *Options, logger log.Logger, app storage.Appendable, registere
 		logger = log.NewNopLogger()
 	}
 
-	sm, err := newScrapeMetrics(registerer)
+	sm, err := NewScrapeMetrics(registerer)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create scrape manager due to error: %w", err)
 	}
@@ -66,6 +66,31 @@ func NewManager(o *Options, logger log.Logger, app storage.Appendable, registere
 	return m, nil
 }
 
+func NewManagerWithMetrics(o *Options, logger log.Logger, app storage.Appendable, metrics *ScrapeMetrics) *Manager {
+	if o == nil {
+		o = &Options{}
+	}
+	if logger == nil {
+		logger = log.NewNopLogger()
+	}
+
+	m := &Manager{
+		append:        app,
+		opts:          o,
+		logger:        logger,
+		scrapeConfigs: make(map[string]*config.ScrapeConfig),
+		scrapePools:   make(map[string]*scrapePool),
+		graceShut:     make(chan struct{}),
+		triggerReload: make(chan struct{}, 1),
+		metrics:       metrics,
+		buffers:       pool.New(1e3, 100e6, 3, func(sz int) interface{} { return make([]byte, 0, sz) }),
+	}
+
+	m.metrics.setTargetMetadataCacheGatherer(m)
+
+	return m
+}
+
 // Options are the configuration parameters to the scrape manager.
 type Options struct {
 	ExtraMetrics  bool
@@ -108,7 +133,7 @@ type Manager struct {
 
 	triggerReload chan struct{}
 
-	metrics *scrapeMetrics
+	metrics *ScrapeMetrics
 }
 
 // Run receives and saves target set updates and triggers the scraping loops reloading.

scrape/metrics.go

@@ -19,7 +19,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-type scrapeMetrics struct {
+type ScrapeMetrics struct {
 	reg prometheus.Registerer
 	// Used by Manager.
 	targetMetadataCache     *MetadataMetricsCollector
@@ -54,8 +54,8 @@ type scrapeMetrics struct {
 	targetScrapeNativeHistogramBucketLimit prometheus.Counter
 }
 
-func newScrapeMetrics(reg prometheus.Registerer) (*scrapeMetrics, error) {
-	sm := &scrapeMetrics{reg: reg}
+func NewScrapeMetrics(reg prometheus.Registerer) (*ScrapeMetrics, error) {
+	sm := &ScrapeMetrics{reg: reg}
 
 	// Manager metrics.
 	sm.targetMetadataCache = &MetadataMetricsCollector{
@@ -257,12 +257,12 @@ func newScrapeMetrics(reg prometheus.Registerer) (*scrapeMetrics, error) {
 	return sm, nil
 }
 
-func (sm *scrapeMetrics) setTargetMetadataCacheGatherer(gatherer TargetsGatherer) {
+func (sm *ScrapeMetrics) setTargetMetadataCacheGatherer(gatherer TargetsGatherer) {
 	sm.targetMetadataCache.TargetsGatherer = gatherer
 }
 
 // Unregister unregisters all metrics.
-func (sm *scrapeMetrics) Unregister() {
+func (sm *ScrapeMetrics) Unregister() {
 	sm.reg.Unregister(sm.targetMetadataCache)
 	sm.reg.Unregister(sm.targetScrapePools)
 	sm.reg.Unregister(sm.targetScrapePoolsFailed)

scrape/scrape.go

@@ -89,7 +89,7 @@ type scrapePool struct {
 
 	noDefaultPort bool
 
-	metrics *scrapeMetrics
+	metrics *ScrapeMetrics
 }
 
 type labelLimits struct {
@@ -122,7 +122,7 @@ const maxAheadTime = 10 * time.Minute
 // returning an empty label set is interpreted as "drop".
 type labelsMutator func(labels.Labels) labels.Labels
 
-func newScrapePool(cfg *config.ScrapeConfig, app storage.Appendable, offsetSeed uint64, logger log.Logger, buffers *pool.Pool, options *Options, metrics *scrapeMetrics) (*scrapePool, error) {
+func newScrapePool(cfg *config.ScrapeConfig, app storage.Appendable, offsetSeed uint64, logger log.Logger, buffers *pool.Pool, options *Options, metrics *ScrapeMetrics) (*scrapePool, error) {
 	if logger == nil {
 		logger = log.NewNopLogger()
 	}
@@ -696,7 +696,7 @@ type targetScraper struct {
 	acceptHeader         string
 	acceptEncodingHeader string
 
-	metrics *scrapeMetrics
+	metrics *ScrapeMetrics
 }
 
 var errBodySizeLimit = errors.New("body size limit exceeded")
@@ -849,7 +849,7 @@ type scrapeLoop struct {
 	reportExtraMetrics  bool
 	appendMetadataToWAL bool
 
-	metrics *scrapeMetrics
+	metrics *ScrapeMetrics
 
 	skipOffsetting bool // For testability.
 }
@@ -880,7 +880,7 @@ type scrapeCache struct {
 	metaMtx  sync.Mutex
 	metadata map[string]*metaEntry
 
-	metrics *scrapeMetrics
+	metrics *ScrapeMetrics
 }
 
 // metaEntry holds meta information about a metric.
@@ -896,7 +896,7 @@ func (m *metaEntry) size() int {
 	return len(m.Help) + len(m.Unit) + len(m.Type)
 }
 
-func newScrapeCache(metrics *scrapeMetrics) *scrapeCache {
+func newScrapeCache(metrics *ScrapeMetrics) *scrapeCache {
 	return &scrapeCache{
 		series:        map[string]*cacheEntry{},
 		droppedSeries: map[string]*uint64{},
@@ -1133,7 +1133,7 @@ func newScrapeLoop(ctx context.Context,
 	appendMetadataToWAL bool,
 	target *Target,
 	passMetadataInContext bool,
-	metrics *scrapeMetrics,
+	metrics *ScrapeMetrics,
 	skipOffsetting bool,
 ) *scrapeLoop {
 	if l == nil {