Top-level: move Go runtime params earlier in initialization

E.g. if a module starting up looks at GOMAXPROCS to size something, we
need to have set it already.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

cmd/prometheus/main.go

@@ -617,7 +617,31 @@ func main() {
 	if cfgFile.StorageConfig.TSDBConfig != nil {
 		cfg.tsdb.OutOfOrderTimeWindow = cfgFile.StorageConfig.TSDBConfig.OutOfOrderTimeWindow
 	}
+
+	// Set Go runtime parameters before we get too far into initialization.
 	updateGoGC(cfgFile, logger)
+	if cfg.maxprocsEnable {
+		l := func(format string, a ...interface{}) {
+			logger.Info(fmt.Sprintf(strings.TrimPrefix(format, "maxprocs: "), a...), "component", "automaxprocs")
+		}
+		if _, err := maxprocs.Set(maxprocs.Logger(l)); err != nil {
+			logger.Warn("Failed to set GOMAXPROCS automatically", "component", "automaxprocs", "err", err)
+		}
+	}
+
+	if cfg.memlimitEnable {
+		if _, err := memlimit.SetGoMemLimitWithOpts(
+			memlimit.WithRatio(cfg.memlimitRatio),
+			memlimit.WithProvider(
+				memlimit.ApplyFallback(
+					memlimit.FromCgroup,
+					memlimit.FromSystem,
+				),
+			),
+		); err != nil {
+			logger.Warn("automemlimit", "msg", "Failed to set GOMEMLIMIT automatically", "err", err)
+		}
+	}
 
 	// Now that the validity of the config is established, set the config
 	// success metrics accordingly, although the config isn't really loaded
@@ -765,29 +789,6 @@ func main() {
 		ruleManager *rules.Manager
 	)
 
-	if cfg.maxprocsEnable {
-		l := func(format string, a ...interface{}) {
-			logger.Info(fmt.Sprintf(strings.TrimPrefix(format, "maxprocs: "), a...), "component", "automaxprocs")
-		}
-		if _, err := maxprocs.Set(maxprocs.Logger(l)); err != nil {
-			logger.Warn("Failed to set GOMAXPROCS automatically", "component", "automaxprocs", "err", err)
-		}
-	}
-
-	if cfg.memlimitEnable {
-		if _, err := memlimit.SetGoMemLimitWithOpts(
-			memlimit.WithRatio(cfg.memlimitRatio),
-			memlimit.WithProvider(
-				memlimit.ApplyFallback(
-					memlimit.FromCgroup,
-					memlimit.FromSystem,
-				),
-			),
-		); err != nil {
-			logger.Warn("automemlimit", "msg", "Failed to set GOMEMLIMIT automatically", "err", err)
-		}
-	}
-
 	if !agentMode {
 		opts := promql.EngineOpts{
 			Logger:                   logger.With("component", "query engine"),