Improve nginx performance to match listen backlog with net.core.somaxconn

controllers/nginx/nginx.tmpl

@@ -276,7 +276,7 @@ http {
 
     # default server, including healthcheck
     server {
-        listen 8080 default_server reuseport;
+        listen 8080 default_server reuseport backlog={{ .backlogSize }};
 
         location /healthz {
             access_log off;

controllers/nginx/nginx/template.go

@@ -61,6 +61,7 @@ func (ngx *Manager) loadTemplate() {
 
 func (ngx *Manager) writeCfg(cfg config.Configuration, ingressCfg IngressConfig) (bool, error) {
 	conf := make(map[string]interface{})
+	conf["backlogSize"] = sysctlSomaxconn()
 	conf["upstreams"] = ingressCfg.Upstreams
 	conf["servers"] = ingressCfg.Servers
 	conf["tcpUpstreams"] = ingressCfg.TCPUpstreams

controllers/nginx/nginx/utils.go

@@ -28,6 +28,7 @@ import (
 	"github.com/golang/glog"
 	"github.com/mitchellh/mapstructure"
 	"k8s.io/kubernetes/pkg/api"
+	"k8s.io/kubernetes/pkg/util/sysctl"
 
 	"k8s.io/contrib/ingress/controllers/nginx/nginx/config"
 )
@@ -220,3 +221,14 @@ func diff(b1, b2 []byte) (data []byte, err error) {
 	}
 	return
 }
+
+// sysctlSomaxconn returns the value of net.core.somaxconn, i.e.
+// maximum number of connections that can be queued for acceptance
+func sysctlSomaxconn() int {
+	maxConns, err := sysctl.GetSysctl("net.core.somaxconn")
+	if err != nil || maxConns < 512 {
+		return 511
+	}
+
+	return maxConns
+}