From a9213ccb4c77b134c8693a7e1765050f7663a20c Mon Sep 17 00:00:00 2001
From: Gilles Dubuc <gilles@wikimedia.org>
Date: Mon, 20 Nov 2017 07:57:29 +0100
Subject: [PATCH] Add ability to proxy thumbnail requests to a service

Bug: T169144
Change-Id: I4af09a8b75e7158d6ff15f97e8f067b66ac33d5c
---
 includes/filerepo/FileRepo.php | 27 ++++++++++++++++++-
 thumb.php                      | 48 +++++++++++++++++++++++++++++++++-
 2 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/includes/filerepo/FileRepo.php b/includes/filerepo/FileRepo.php
index b4df68a4c9..6b32953449 100644
--- a/includes/filerepo/FileRepo.php
+++ b/includes/filerepo/FileRepo.php
@@ -132,6 +132,13 @@ class FileRepo {
 	/** @var array callable|bool Override these in the base class */
 	protected $oldFileFactoryKey = false;
 
+	/** @var string URL of where to proxy thumb.php requests to.
+	 *    Example: http://127.0.0.1:8888/wiki/dev/thumb/
+	 */
+	protected $thumbProxyUrl;
+	/** @var string Secret key to pass as an X-Swift-Secret header to the proxied thumb service */
+	protected $thumbProxySecret;
+
 	/**
 	 * @param array|null $info
 	 * @throws MWException
@@ -159,7 +166,7 @@ class FileRepo {
 		$optionalSettings = [
 			'descBaseUrl', 'scriptDirUrl', 'articleUrl', 'fetchDescription',
 			'thumbScriptUrl', 'pathDisclosureProtection', 'descriptionCacheExpiry',
-			'scriptExtension', 'favicon'
+			'scriptExtension', 'favicon', 'thumbProxyUrl', 'thumbProxySecret'
 		];
 		foreach ( $optionalSettings as $var ) {
 			if ( isset( $info[$var] ) ) {
@@ -611,6 +618,24 @@ class FileRepo {
 		return $this->thumbScriptUrl;
 	}
 
+	/**
+	 * Get the URL thumb.php requests are being proxied to
+	 *
+	 * @return string
+	 */
+	public function getThumbProxyUrl() {
+		return $this->thumbProxyUrl;
+	}
+
+	/**
+	 * Get the secret key for the proxied thumb service
+	 *
+	 * @return string
+	 */
+	public function getThumbProxySecret() {
+		return $this->thumbProxySecret;
+	}
+
 	/**
 	 * Returns true if the repository can transform files via a 404 handler
 	 *
diff --git a/thumb.php b/thumb.php
index 02ac0b024d..c4b40dc76f 100644
--- a/thumb.php
+++ b/thumb.php
@@ -337,7 +337,16 @@ function wfStreamThumb( array $params ) {
 		return;
 	}
 
-	list( $thumb, $errorMsg ) = wfGenerateThumbnail( $img, $params, $thumbName, $thumbPath );
+	$thumbProxyUrl = $img->getRepo()->getThumbProxyUrl();
+
+	if ( strlen( $thumbProxyUrl ) ) {
+		wfProxyThumbnailRequest( $img, $thumbName );
+		// No local fallback when in proxy mode
+		return;
+	} else {
+		// Generate the thumbnail locally
+		list( $thumb, $errorMsg ) = wfGenerateThumbnail( $img, $params, $thumbName, $thumbPath );
+	}
 
 	/** @var MediaTransformOutput|MediaTransformError|bool $thumb */
 
@@ -377,6 +386,43 @@ function wfStreamThumb( array $params ) {
 	}
 }
 
+/**
+ * Proxies thumbnail request to a service that handles thumbnailing
+ *
+ * @param File $img
+ * @param string $thumbName
+ */
+function wfProxyThumbnailRequest( $img, $thumbName ) {
+	$thumbProxyUrl = $img->getRepo()->getThumbProxyUrl();
+
+	// Instead of generating the thumbnail ourselves, we proxy the request to another service
+	$thumbProxiedUrl = $thumbProxyUrl . $img->getThumbRel( $thumbName );
+
+	$req = MWHttpRequest::factory( $thumbProxiedUrl );
+	$secret = $img->getRepo()->getThumbProxySecret();
+
+	// Pass a secret key shared with the proxied service if any
+	if ( strlen( $secret ) ) {
+		$req->setHeader( 'X-Swift-Secret', $secret );
+	}
+
+	// Send request to proxied service
+	$status = $req->execute();
+
+	// Simply serve the response from the proxied service as-is
+	header( 'HTTP/1.1 ' . $req->getStatus() );
+
+	$headers = $req->getResponseHeaders();
+
+	foreach ( $headers as $key => $values ) {
+		foreach ( $values as $value ) {
+			header( $key . ': ' . $value, false );
+		}
+	}
+
+	echo $req->getContent();
+}
+
 /**
  * Actually try to generate a new thumbnail
  *
-- 
2.20.1