core: split out detailed trie access metrics from insertion time (#19316)

* core: split out detailed trie access metrics from insertion time

* cmd, core, metrics: support expensive optional metrics

1 files changed, 24 insertions, 7 deletions

diff --git a/metrics/metrics.go b/metrics/metrics.go
index 5910fb073..6d14c8ecf 100644
--- a/metrics/metrics.go
+++ b/metrics/metrics.go
@@ -15,24 +15,41 @@ import (
 )
 
 // Enabled is checked by the constructor functions for all of the
-// standard metrics.  If it is true, the metric returned is a stub.
+// standard metrics. If it is true, the metric returned is a stub.
 //
 // This global kill-switch helps quantify the observer effect and makes
 // for less cluttered pprof profiles.
 var Enabled = false
 
-// MetricsEnabledFlag is the CLI flag name to use to enable metrics collections.
-const MetricsEnabledFlag = "metrics"
-const DashboardEnabledFlag = "dashboard"
+// EnabledExpensive is a soft-flag meant for external packages to check if costly
+// metrics gathering is allowed or not. The goal is to separate standard metrics
+// for health monitoring and debug metrics that might impact runtime performance.
+var EnabledExpensive = false
+
+// enablerFlags is the CLI flag names to use to enable metrics collections.
+var enablerFlags = []string{"metrics", "dashboard"}
+
+// expensiveEnablerFlags is the CLI flag names to use to enable metrics collections.
+var expensiveEnablerFlags = []string{"metrics.expensive"}
 
 // Init enables or disables the metrics system. Since we need this to run before
 // any other code gets to create meters and timers, we'll actually do an ugly hack
 // and peek into the command line args for the metrics flag.
 func init() {
 	for _, arg := range os.Args {
-		if flag := strings.TrimLeft(arg, "-"); flag == MetricsEnabledFlag || flag == DashboardEnabledFlag {
-			log.Info("Enabling metrics collection")
-			Enabled = true
+		flag := strings.TrimLeft(arg, "-")
+
+		for _, enabler := range enablerFlags {
+			if !Enabled && flag == enabler {
+				log.Info("Enabling metrics collection")
+				Enabled = true
+			}
+		}
+		for _, enabler := range expensiveEnablerFlags {
+			if !Enabled && flag == enabler {
+				log.Info("Enabling expensive metrics collection")
+				EnabledExpensive = true
+			}
 		}
 	}
 }