feat: allow configuration of underlying http.Server (#199)

Fixes #194, which pointed out that we should allow configuring
additional relevant options on the underlying
[http.Server](https://pkg.go.dev/net/http#Server) without requiring
users to build and push their own images.

Author: mccutchen

README.md

@@ -92,6 +92,7 @@ variables (or a combination of the two):
 | Argument| Env var | Documentation | Default |
 | - | - | - | - |
 | `-allowed-redirect-domains` | `ALLOWED_REDIRECT_DOMAINS` | Comma-separated list of domains the /redirect-to endpoint will allow | |
+| `-exclude-headers` | `EXCLUDE_HEADERS` | Drop platform-specific headers. Comma-separated list of headers key to drop, supporting wildcard suffix matching. For example: `"foo,bar,x-fc-*"` | - |
 | `-host` | `HOST` | Host to listen on | "0.0.0.0" |
 | `-https-cert-file` | `HTTPS_CERT_FILE` | HTTPS Server certificate file | |
 | `-https-key-file` | `HTTPS_KEY_FILE` | HTTPS Server private key file | |
@@ -100,8 +101,10 @@ variables (or a combination of the two):
 | `-max-duration` | `MAX_DURATION` | Maximum duration a response may take | 10s |
 | `-port` | `PORT` | Port to listen on | 8080 |
 | `-prefix` | `PREFIX` | Prefix of path to listen on (must start with slash and does not end with slash) | |
+| `-srv-max-header-bytes` | `SRV_MAX_HEADER_BYTES` | Value to use for the http.Server's MaxHeaderBytes option | 16384 |
+| `-srv-read-header-timeout` | `SRV_READ_HEADER_TIMEOUT` | Value to use for the http.Server's ReadHeaderTimeout option | 1s |
+| `-srv-read-timeout` | `SRV_READ_TIMEOUT` | Value to use for the http.Server's ReadTimeout option | 5s |
 | `-use-real-hostname` | `USE_REAL_HOSTNAME` | Expose real hostname as reported by os.Hostname() in the /hostname endpoint | false |
-| `-exclude-headers` | `EXCLUDE_HEADERS` | Drop platform-specific headers. Comma-separated list of headers key to drop, supporting wildcard suffix matching. For example: `"foo,bar,x-fc-*"` | - |
 
 **Notes:**
 - Command line arguments take precedence over environment variables.

httpbin/cmd/cmd.go

@@ -27,10 +27,10 @@ const (
 	defaultLogFormat  = "text"
 	defaultEnvPrefix  = "HTTPBIN_ENV_"
 
-	// Reasonable defaults for our http server
-	srvReadTimeout       = 5 * time.Second
-	srvReadHeaderTimeout = 1 * time.Second
-	srvMaxHeaderBytes    = 16 * 1024 // 16kb
+	// Reasonable defaults for the underlying http.Server
+	defaultSrvReadTimeout       = 5 * time.Second
+	defaultSrvReadHeaderTimeout = 1 * time.Second
+	defaultSrvMaxHeaderBytes    = 16 * 1024 // 16kb
 )
 
 // Main is the main entrypoint for the go-httpbin binary. See loadConfig() for
@@ -96,9 +96,9 @@ func mainImpl(args []string, getEnvVal func(string) string, getEnviron func() []
 	srv := &http.Server{
 		Addr:              net.JoinHostPort(cfg.ListenHost, strconv.Itoa(cfg.ListenPort)),
 		Handler:           app.Handler(),
-		MaxHeaderBytes:    srvMaxHeaderBytes,
-		ReadHeaderTimeout: srvReadHeaderTimeout,
-		ReadTimeout:       srvReadTimeout,
+		MaxHeaderBytes:    cfg.SrvMaxHeaderBytes,
+		ReadHeaderTimeout: cfg.SrvReadHeaderTimeout,
+		ReadTimeout:       cfg.SrvReadTimeout,
 	}
 
 	if err := listenAndServeGracefully(srv, cfg, logger); err != nil {
@@ -124,6 +124,9 @@ type config struct {
 	TLSCertFile            string
 	TLSKeyFile             string
 	LogFormat              string
+	SrvMaxHeaderBytes      int
+	SrvReadHeaderTimeout   time.Duration
+	SrvReadTimeout         time.Duration
 
 	// temporary placeholders for arguments that need extra processing
 	rawAllowedRedirectDomains string
@@ -162,6 +165,9 @@ func loadConfig(args []string, getEnvVal func(string) string, getEnviron func()
 	fs.StringVar(&cfg.TLSKeyFile, "https-key-file", "", "HTTPS Server private key file")
 	fs.StringVar(&cfg.ExcludeHeaders, "exclude-headers", "", "Drop platform-specific headers. Comma-separated list of headers key to drop, supporting wildcard matching.")
 	fs.StringVar(&cfg.LogFormat, "log-format", defaultLogFormat, "Log format (text or json)")
+	fs.IntVar(&cfg.SrvMaxHeaderBytes, "srv-max-header-bytes", defaultSrvMaxHeaderBytes, "Value to use for the http.Server's MaxHeaderBytes option")
+	fs.DurationVar(&cfg.SrvReadHeaderTimeout, "srv-read-header-timeout", defaultSrvReadHeaderTimeout, "Value to use for the http.Server's ReadHeaderTimeout option")
+	fs.DurationVar(&cfg.SrvReadTimeout, "srv-read-timeout", defaultSrvReadTimeout, "Value to use for the http.Server's ReadTimeout option")
 
 	// in order to fully control error output whether CLI arguments or env vars
 	// are used to configure the app, we need to take control away from the
@@ -275,6 +281,26 @@ func loadConfig(args []string, getEnvVal func(string) string, getEnviron func()
 		}
 	}
 
+	// set the http.Server options
+	if cfg.SrvMaxHeaderBytes == defaultSrvMaxHeaderBytes && getEnvVal("SRV_MAX_HEADER_BYTES") != "" {
+		cfg.SrvMaxHeaderBytes, err = strconv.Atoi(getEnvVal("SRV_MAX_HEADER_BYTES"))
+		if err != nil {
+			return nil, configErr("invalid value %#v for env var SRV_MAX_HEADER_BYTES: parse error", getEnvVal("SRV_MAX_HEADER_BYTES"))
+		}
+	}
+	if cfg.SrvReadHeaderTimeout == defaultSrvReadHeaderTimeout && getEnvVal("SRV_READ_HEADER_TIMEOUT") != "" {
+		cfg.SrvReadHeaderTimeout, err = time.ParseDuration(getEnvVal("SRV_READ_HEADER_TIMEOUT"))
+		if err != nil {
+			return nil, configErr("invalid value %#v for env var SRV_READ_HEADER_TIMEOUT: parse error", getEnvVal("SRV_READ_HEADER_TIMEOUT"))
+		}
+	}
+	if cfg.SrvReadTimeout == defaultSrvReadTimeout && getEnvVal("SRV_READ_TIMEOUT") != "" {
+		cfg.SrvReadTimeout, err = time.ParseDuration(getEnvVal("SRV_READ_TIMEOUT"))
+		if err != nil {
+			return nil, configErr("invalid value %#v for env var SRV_READ_TIMEOUT: parse error", getEnvVal("SRV_READ_TIMEOUT"))
+		}
+	}
+
 	// reset temporary fields to their zero values
 	cfg.rawAllowedRedirectDomains = ""
 	cfg.rawUseRealHostname = false