receive: memoize exemplar/TSDB clients

We call this on each Series() so memoize the creation of this slice.

Signed-off-by: Giedrius Statkevičius <giedrius.statkevicius@vinted.com>

pkg/receive/multitsdb.go

@@ -64,6 +64,12 @@ type MultiTSDB struct {
 	allowOutOfOrderUpload bool
 	hashFunc              metadata.HashFunc
 	hashringConfigs       []HashringConfig
+
+	tsdbClients           []store.Client
+	tsdbClientsNeedUpdate bool
+
+	exemplarClients           map[string]*exemplars.TSDB
+	exemplarClientsNeedUpdate bool
 }
 
 // NewMultiTSDB creates new MultiTSDB.
@@ -84,17 +90,19 @@ func NewMultiTSDB(
 	}
 
 	return &MultiTSDB{
-		dataDir:               dataDir,
-		logger:                log.With(l, "component", "multi-tsdb"),
-		reg:                   reg,
-		tsdbOpts:              tsdbOpts,
-		mtx:                   &sync.RWMutex{},
-		tenants:               map[string]*tenant{},
-		labels:                labels,
-		tenantLabelName:       tenantLabelName,
-		bucket:                bucket,
-		allowOutOfOrderUpload: allowOutOfOrderUpload,
-		hashFunc:              hashFunc,
+		dataDir:                   dataDir,
+		logger:                    log.With(l, "component", "multi-tsdb"),
+		reg:                       reg,
+		tsdbOpts:                  tsdbOpts,
+		mtx:                       &sync.RWMutex{},
+		tenants:                   map[string]*tenant{},
+		labels:                    labels,
+		tsdbClientsNeedUpdate:     true,
+		exemplarClientsNeedUpdate: true,
+		tenantLabelName:           tenantLabelName,
+		bucket:                    bucket,
+		allowOutOfOrderUpload:     allowOutOfOrderUpload,
+		hashFunc:                  hashFunc,
 	}
 }
 
@@ -434,6 +442,8 @@ func (t *MultiTSDB) Prune(ctx context.Context) error {
 
 		level.Info(t.logger).Log("msg", "Pruned tenant", "tenant", tenantID)
 		delete(t.tenants, tenantID)
+		t.tsdbClientsNeedUpdate = true
+		t.exemplarClientsNeedUpdate = true
 	}
 
 	return merr.Err()
@@ -595,7 +605,16 @@ func (t *MultiTSDB) RemoveLockFilesIfAny() error {
 
 func (t *MultiTSDB) TSDBLocalClients() []store.Client {
 	t.mtx.RLock()
-	defer t.mtx.RUnlock()
+	if !t.tsdbClientsNeedUpdate {
+		t.mtx.RUnlock()
+		return t.tsdbClients
+	}
+
+	t.mtx.Lock()
+	if !t.tsdbClientsNeedUpdate {
+		return t.tsdbClients
+	}
+	defer t.mtx.Unlock()
 
 	res := make([]store.Client, 0, len(t.tenants))
 	for _, tenant := range t.tenants {
@@ -605,12 +624,25 @@ func (t *MultiTSDB) TSDBLocalClients() []store.Client {
 		}
 	}
 
-	return res
+	t.tsdbClientsNeedUpdate = false
+	t.tsdbClients = res
+
+	return t.tsdbClients
 }
 
 func (t *MultiTSDB) TSDBExemplars() map[string]*exemplars.TSDB {
 	t.mtx.RLock()
-	defer t.mtx.RUnlock()
+	if !t.exemplarClientsNeedUpdate {
+		t.mtx.RUnlock()
+		return t.exemplarClients
+	}
+	t.mtx.RUnlock()
+	t.mtx.Lock()
+	defer t.mtx.Unlock()
+
+	if !t.exemplarClientsNeedUpdate {
+		return t.exemplarClients
+	}
 
 	res := make(map[string]*exemplars.TSDB, len(t.tenants))
 	for k, tenant := range t.tenants {
@@ -619,7 +651,10 @@ func (t *MultiTSDB) TSDBExemplars() map[string]*exemplars.TSDB {
 			res[k] = e
 		}
 	}
-	return res
+
+	t.exemplarClientsNeedUpdate = false
+	t.exemplarClients = res
+	return t.exemplarClients
 }
 
 func (t *MultiTSDB) TenantStats(limit int, statsByLabelName string, tenantIDs ...string) []status.TenantStats {
@@ -695,6 +730,8 @@ func (t *MultiTSDB) startTSDB(logger log.Logger, tenantID string, tenant *tenant
 	if err != nil {
 		t.mtx.Lock()
 		delete(t.tenants, tenantID)
+		t.tsdbClientsNeedUpdate = true
+		t.exemplarClientsNeedUpdate = true
 		t.mtx.Unlock()
 		return err
 	}
@@ -743,6 +780,8 @@ func (t *MultiTSDB) getOrLoadTenant(tenantID string, blockingStart bool) (*tenan
 
 	tenant = newTenant()
 	t.tenants[tenantID] = tenant
+	t.tsdbClientsNeedUpdate = true
+	t.exemplarClientsNeedUpdate = true
 	t.mtx.Unlock()
 
 	logger := log.With(t.logger, "tenant", tenantID)