From 58043aa9dc3120291d59407ea33c0dd6b63c7cdf Mon Sep 17 00:00:00 2001
From: Rinat Khaziev <rinat.khaziev@gmail.com>
Date: Thu, 1 Aug 2024 18:37:47 -0500
Subject: [PATCH 1/2] Prototype 50x response interceptor

---
 5xx-interceptor.php | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 5xx-interceptor.php

diff --git a/5xx-interceptor.php b/5xx-interceptor.php
new file mode 100644
index 0000000000..a0d4bd9354
--- /dev/null
+++ b/5xx-interceptor.php
@@ -0,0 +1,40 @@
+<?php 
+/**
+ * This plugin intercepts the 50x status code and changes it to 58x
+ * 
+ * The status code will be rewritten at the edge.
+ * 
+ * This is a WPVIP-specific plugin and will only work on WPVIP infrastructure.
+ */
+namespace Automattic\VIP;
+
+use Automattic\VIP\Utils\Context;
+if ( ! ( Context::is_web_request() || Context::is_ajax() ) ) {
+	return;
+}
+
+// We hook on parse_request to side-step the handle_404 logic.
+// Strictly speaking send_headers would be but at that point WP()->handle_404() has already been called, potentially overriding any user 503 to 200. 
+add_action( 'parse_request', '\Automattic\VIP\rewrite_50x_headers', PHP_INT_MIN );
+function rewrite_50x_headers() {
+	$current_response_code = http_response_code();
+	$override_codes        = [
+		503 => [
+			'code'        => 583,
+			'description' => 'Service Unavailable',
+		],
+		502 => [
+			'code'        => 582,
+			'description' => 'Bad Gateway',
+		],
+	];
+
+	// Technically headers_sent() should never be true at this moment.
+	if ( ! headers_sent() && isset( $override_codes[ $current_response_code ] ) ) {
+		// 404 handler may override a 404 with a 200, so we need to ensure that the 404 handler is not triggered.
+		add_filter( 'pre_handle_404', '__return_true' );
+		// The description is important for the core logic, otherwise the non-standard codes get discarded and replaced by 200.
+		// @see wp-includes/functions.php:status_header()
+		status_header( $override_codes[ $current_response_code ]['code'], $override_codes[ $current_response_code ]['description'] );
+	}
+}

From 8144f28f3369183671c9e8d2996f7fd64af61b25 Mon Sep 17 00:00:00 2001
From: Rinat K <rinat@automattic.com>
Date: Fri, 11 Apr 2025 11:07:06 -0500
Subject: [PATCH 2/2] Update 5xx-interceptor.php, remove 502 to limit the scope

---
 5xx-interceptor.php | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/5xx-interceptor.php b/5xx-interceptor.php
index a0d4bd9354..107690aacf 100644
--- a/5xx-interceptor.php
+++ b/5xx-interceptor.php
@@ -23,10 +23,6 @@ function rewrite_50x_headers() {
 			'code'        => 583,
 			'description' => 'Service Unavailable',
 		],
-		502 => [
-			'code'        => 582,
-			'description' => 'Bad Gateway',
-		],
 	];
 
 	// Technically headers_sent() should never be true at this moment.