From fe9ec398f909506040f68d813163ced013815ace Mon Sep 17 00:00:00 2001
From: matt durham <mattdurham@ppog.org>
Date: Thu, 5 Oct 2023 09:12:03 -0400
Subject: [PATCH] Add caching back in.

---
 collector/collector.go | 27 ++++++++++++++++++---------
 collector/config.go    |  3 ++-
 node_exporter.go       |  1 +
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/collector/collector.go b/collector/collector.go
index 224ebfa6..73313f99 100644
--- a/collector/collector.go
+++ b/collector/collector.go
@@ -50,11 +50,13 @@ const (
 )
 
 var (
-	factories            = make(map[string]func(config *NodeCollectorConfig, logger log.Logger) (Collector, error))
-	collectorStateGlobal = make(map[string]bool)
-	collectorFlagState   = make(map[string]*bool)
-	availableCollectors  = make([]string, 0)
-	forcedCollectors     = map[string]bool{} // collectors which have been explicitly enabled or disabled
+	factories              = make(map[string]func(config *NodeCollectorConfig, logger log.Logger) (Collector, error))
+	initiatedCollectorsMtx = sync.Mutex{}
+	initiatedCollectors    = make(map[string]Collector)
+	collectorStateGlobal   = make(map[string]bool)
+	collectorFlagState     = make(map[string]*bool)
+	availableCollectors    = make([]string, 0)
+	forcedCollectors       = map[string]bool{} // collectors which have been explicitly enabled or disabled
 )
 
 func GetDefaults() map[string]bool {
@@ -140,15 +142,22 @@ func NewNodeCollector(config *NodeCollectorConfig, logger log.Logger, filters ..
 	}
 	collectors := make(map[string]Collector)
 
+	initiatedCollectorsMtx.Lock()
+	defer initiatedCollectorsMtx.Unlock()
 	for key, enabled := range config.Collectors {
 		if !enabled || (len(f) > 0 && !f[key]) {
 			continue
 		}
-		collector, err := factories[key](config, log.With(logger, "collector", key))
-		if err != nil {
-			return nil, err
+		if collector, ok := initiatedCollectors[key]; ok && config.AllowCachingOfCollectors {
+			collectors[key] = collector
+		} else {
+			collector, err := factories[key](config, log.With(logger, "collector", key))
+			if err != nil {
+				return nil, err
+			}
+			collectors[key] = collector
+			initiatedCollectors[key] = collector
 		}
-		collectors[key] = collector
 	}
 	return &NodeCollector{Collectors: collectors, logger: logger}, nil
 }
diff --git a/collector/config.go b/collector/config.go
index 3cb907fe..32cbba8d 100644
--- a/collector/config.go
+++ b/collector/config.go
@@ -43,7 +43,8 @@ type NodeCollectorConfig struct {
 	VmStat                VmStatConfig
 	Wifi                  WifiConfig
 
-	Collectors map[string]bool
+	Collectors               map[string]bool
+	AllowCachingOfCollectors bool
 }
 
 type WifiConfig struct {
diff --git a/node_exporter.go b/node_exporter.go
index 2d5d11e6..ec7b4256 100644
--- a/node_exporter.go
+++ b/node_exporter.go
@@ -189,6 +189,7 @@ func main() {
 	runtime.GOMAXPROCS(*maxProcs)
 	level.Debug(logger).Log("msg", "Go MAXPROCS", "procs", runtime.GOMAXPROCS(0))
 	collectorConfig.Collectors = collector.GetFlagDefaults()
+	collectorConfig.AllowCachingOfCollectors = true
 	http.Handle(*metricsPath, newHandler(!*disableExporterMetrics, *maxRequests, collectorConfig, logger))
 	if *metricsPath != "/" {
 		landingConfig := web.LandingConfig{