fix: update lego.

vendor/go.opencensus.io/metric/metricproducer/manager.go

@@ -0,0 +1,78 @@
+// Copyright 2019, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metricproducer
+
+import (
+	"sync"
+)
+
+// Manager maintains a list of active producers. Producers can register
+// with the manager to allow readers to read all metrics provided by them.
+// Readers can retrieve all producers registered with the manager,
+// read metrics from the producers and export them.
+type Manager struct {
+	mu        sync.RWMutex
+	producers map[Producer]struct{}
+}
+
+var prodMgr *Manager
+var once sync.Once
+
+// GlobalManager is a single instance of producer manager
+// that is used by all producers and all readers.
+func GlobalManager() *Manager {
+	once.Do(func() {
+		prodMgr = &Manager{}
+		prodMgr.producers = make(map[Producer]struct{})
+	})
+	return prodMgr
+}
+
+// AddProducer adds the producer to the Manager if it is not already present.
+func (pm *Manager) AddProducer(producer Producer) {
+	if producer == nil {
+		return
+	}
+	pm.mu.Lock()
+	defer pm.mu.Unlock()
+	pm.producers[producer] = struct{}{}
+}
+
+// DeleteProducer deletes the producer from the Manager if it is present.
+func (pm *Manager) DeleteProducer(producer Producer) {
+	if producer == nil {
+		return
+	}
+	pm.mu.Lock()
+	defer pm.mu.Unlock()
+	delete(pm.producers, producer)
+}
+
+// GetAll returns a slice of all producer currently registered with
+// the Manager. For each call it generates a new slice. The slice
+// should not be cached as registration may change at any time. It is
+// typically called periodically by exporter to read metrics from
+// the producers.
+func (pm *Manager) GetAll() []Producer {
+	pm.mu.Lock()
+	defer pm.mu.Unlock()
+	producers := make([]Producer, len(pm.producers))
+	i := 0
+	for producer := range pm.producers {
+		producers[i] = producer
+		i++
+	}
+	return producers
+}