Add DefaultUpstreamFlushInterval to replace magic time.Second value

pkg/apis/options/legacy_options.go

@@ -27,7 +27,7 @@ func NewLegacyOptions() *LegacyOptions {
 		LegacyUpstreams: LegacyUpstreams{
 			PassHostHeader:  true,
 			ProxyWebSockets: true,
-			FlushInterval:   time.Duration(1) * time.Second,
+			FlushInterval:   DefaultUpstreamFlushInterval,
 		},
 
 		LegacyHeaders: LegacyHeaders{
@@ -62,7 +62,7 @@ type LegacyUpstreams struct {
 func legacyUpstreamsFlagSet() *pflag.FlagSet {
 	flagSet := pflag.NewFlagSet("upstreams", pflag.ExitOnError)
 
-	flagSet.Duration("flush-interval", time.Duration(1)*time.Second, "period between response flushing when streaming responses")
+	flagSet.Duration("flush-interval", DefaultUpstreamFlushInterval, "period between response flushing when streaming responses")
 	flagSet.Bool("pass-host-header", true, "pass the request Host Header to upstream")
 	flagSet.Bool("proxy-websockets", true, "enables WebSocket proxying")
 	flagSet.Bool("ssl-upstream-insecure-skip-verify", false, "skip validation of certificates presented when using HTTPS upstreams")

pkg/apis/options/upstreams.go

@@ -1,5 +1,12 @@
 package options
 
+import "time"
+
+const (
+	// DefaultUpstreamFlushInterval is the default value for the Upstream FlushInterval.
+	DefaultUpstreamFlushInterval = 1 * time.Second
+)
+
 // Upstreams is a collection of definitions for upstream servers.
 type Upstreams []Upstream