Add a garbage collection threshold (prebid#2081)

config/config.go

@@ -24,6 +24,10 @@ type Configuration struct {
 	CacheClient HTTPClient `mapstructure:"http_client_cache"`
 	AdminPort   int        `mapstructure:"admin_port"`
 	EnableGzip  bool       `mapstructure:"enable_gzip"`
+	// GarbageCollectorThreshold allocates virtual memory (in bytes) which is not used by PBS but
+	// serves as a hack to trigger the garbage collector only when the heap reaches at least this size.
+	// More info: https://github.com/golang/go/issues/48409
+	GarbageCollectorThreshold int `mapstructure:"garbage_collector_threshold"`
 	// StatusResponse is the string which will be returned by the /status endpoint when things are OK.
 	// If empty, it will return a 204 with no content.
 	StatusResponse    string          `mapstructure:"status_response"`
@@ -634,6 +638,7 @@ func SetupViper(v *viper.Viper, filename string) {
 	v.SetDefault("port", 8000)
 	v.SetDefault("admin_port", 6060)
 	v.SetDefault("enable_gzip", false)
+	v.SetDefault("garbage_collector_threshold", 0)
 	v.SetDefault("status_response", "")
 	v.SetDefault("auction_timeouts_ms.default", 0)
 	v.SetDefault("auction_timeouts_ms.max", 0)

config/config_test.go

@@ -289,6 +289,7 @@ external_url: http://prebid-server.prebid.org/
 host: prebid-server.prebid.org
 port: 1234
 admin_port: 5678
+garbage_collector_threshold: 1
 auction_timeouts_ms:
   max: 123
   default: 50
@@ -426,6 +427,7 @@ func TestFullConfig(t *testing.T) {
 	cmpStrings(t, "host", cfg.Host, "prebid-server.prebid.org")
 	cmpInts(t, "port", cfg.Port, 1234)
 	cmpInts(t, "admin_port", cfg.AdminPort, 5678)
+	cmpInts(t, "garbage_collector_threshold", cfg.GarbageCollectorThreshold, 1)
 	cmpInts(t, "auction_timeouts_ms.default", int(cfg.AuctionTimeouts.Default), 50)
 	cmpInts(t, "auction_timeouts_ms.max", int(cfg.AuctionTimeouts.Max), 123)
 	cmpStrings(t, "cache.scheme", cfg.CacheURL.Scheme, "http")

main.go

@@ -4,6 +4,7 @@ import (
 	"flag"
 	"math/rand"
 	"net/http"
+	"runtime"
 	"time"
 
 	"github.com/prebid/prebid-server/config"
@@ -28,6 +29,14 @@ func main() {
 		glog.Exitf("Configuration could not be loaded or did not pass validation: %v", err)
 	}
 
+	// Create a soft memory limit on the total amount of memory that PBS uses to tune the behavior
+	// of the Go garbage collector. In summary, `cfg.GarbageCollectorThreshold` serves as a fixed cost
+	// of memory that is going to be held garbage before a garbage collection cycle is triggered.
+	// This amount of virtual memory won’t translate into physical memory allocation unless we attempt
+	// to read or write to the slice below, which PBS will not do.
+	garbageCollectionThreshold := make([]byte, cfg.GarbageCollectorThreshold)
+	defer runtime.KeepAlive(garbageCollectionThreshold)
+
 	err = serve(cfg)
 	if err != nil {
 		glog.Exitf("prebid-server failed: %v", err)