From 6864ca2e75011bd8060232e16e57e2673a5a8989 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sybren=20A=2E=20St=C3=BCvel?= <sybren@blender.org>
Date: Mon, 30 May 2022 15:10:07 +0200
Subject: [PATCH] Manager: add CLI argument to add random delay to HTTP
 responses

add `-delay` CLI argument, which adds a random delay of around 250ms to
all HTTP responses.

The web interface is quite asynchronous in nature, and having more
randomness and more visible delays in there will help development.

This CLI argument should not be used in production.
---
 cmd/flamenco-manager/main.go | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/cmd/flamenco-manager/main.go b/cmd/flamenco-manager/main.go
index 15db8f78..ad6d4b58 100644
--- a/cmd/flamenco-manager/main.go
+++ b/cmd/flamenco-manager/main.go
@@ -7,6 +7,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"math/rand"
 	"net"
 	"net/http"
 	"net/url"
@@ -42,8 +43,9 @@ import (
 )
 
 var cliArgs struct {
-	version     bool
-	writeConfig bool
+	version        bool
+	writeConfig    bool
+	delayResponses bool
 }
 
 const developmentWebInterfacePort = 8081
@@ -191,6 +193,9 @@ func buildWebService(
 	// Ensure panics when serving a web request won't bring down the server.
 	e.Use(middleware.Recover())
 
+	// For development of the web interface, to get a less predictable order of asynchronous requests.
+	e.Use(randomDelayMiddleware)
+
 	// Disabled, as it causes issues with "204 No Content" responses.
 	// TODO: investigate & file a bug report. Adding the check on an empty slice
 	// seems to fix it:
@@ -324,6 +329,8 @@ func parseCliArgs() {
 	flag.BoolVar(&debug, "debug", false, "Enable debug-level logging.")
 	flag.BoolVar(&trace, "trace", false, "Enable trace-level logging.")
 	flag.BoolVar(&cliArgs.writeConfig, "write-config", false, "Writes configuration to flamenco-manager.yaml, then exits.")
+	flag.BoolVar(&cliArgs.delayResponses, "delay", false,
+		"Add a random delay to any HTTP responses. This aids in development of Flamenco Manager's web frontend.")
 
 	flag.Parse()
 
@@ -403,3 +410,20 @@ func corsOrigins(urls []url.URL) []string {
 	log.Debug().Str("origins", strings.Join(origins, " ")).Msg("accepted CORS origins")
 	return origins
 }
+
+// randomDelayMiddleware sleeps for a random period of time, as a development tool for frontend work.
+func randomDelayMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
+	return func(c echo.Context) error {
+		err := next(c)
+
+		// Delay the response a bit.
+		var duration int64 = int64(rand.NormFloat64()*250 + 125) // in msec
+		if duration > 0 {
+			if duration > 1000 {
+				duration = 1000 // Cap at one second.
+			}
+			time.Sleep(time.Duration(duration) * time.Millisecond)
+		}
+		return err
+	}
+}