From: Catrope <roan.kattouw@gmail.com>
Date: Tue, 15 Jan 2013 23:32:10 +0000 (-0800)
Subject: (bug 31044) Make ResourceLoader behave in read-only mode
X-Git-Tag: 1.31.0-rc.0~21026
X-Git-Url: http://git.cyclocoop.org/%22.%24image2.%22?a=commitdiff_plain;h=e2e8461fd23d81aa3c89a56245053c6d3f06da84;p=lhc%2Fweb%2Fwiklou.git

(bug 31044) Make ResourceLoader behave in read-only mode

When the database is in read-only mode or writes fail for some other
reason, ResourceLoader should make every attempt to still serve JS and
CSS correctly.

* Surround a bunch of DB write code in MessageBlobStore.php in try-catch
  blocks.
* Surround the DB write in ResourceLoaderFileModule.php in a try-catch
  block rather than checking wfReadOnly(), because the DB may fail for
  other reasons.
* In ResourceLoader::respond() and helpers, set a short cache timeout on
  responses that include commented-out error messages.

Change-Id: Idc83a0fe042806263f9337c40ade8c38c56aa3cd
---

diff --git a/includes/MessageBlobStore.php b/includes/MessageBlobStore.php
index 09561bd78a..6322be7565 100644
--- a/includes/MessageBlobStore.php
+++ b/includes/MessageBlobStore.php
@@ -80,42 +80,45 @@ class MessageBlobStore {
 			return false;
 		}
 
-		$dbw = wfGetDB( DB_MASTER );
-		$success = $dbw->insert( 'msg_resource', array(
-				'mr_lang' => $lang,
-				'mr_resource' => $name,
-				'mr_blob' => $blob,
-				'mr_timestamp' => $dbw->timestamp()
-			),
-			__METHOD__,
-			array( 'IGNORE' )
-		);
-
-		if ( $success ) {
-			if ( $dbw->affectedRows() == 0 ) {
-				// Blob was already present, fetch it
-				$blob = $dbw->selectField( 'msg_resource', 'mr_blob', array(
-						'mr_resource' => $name,
-						'mr_lang' => $lang,
-					),
-					__METHOD__
-				);
-			} else {
-				// Update msg_resource_links
-				$rows = array();
+		try {
+			$dbw = wfGetDB( DB_MASTER );
+			$success = $dbw->insert( 'msg_resource', array(
+					'mr_lang' => $lang,
+					'mr_resource' => $name,
+					'mr_blob' => $blob,
+					'mr_timestamp' => $dbw->timestamp()
+				),
+				__METHOD__,
+				array( 'IGNORE' )
+			);
 
-				foreach ( $module->getMessages() as $key ) {
-					$rows[] = array(
-						'mrl_resource' => $name,
-						'mrl_message' => $key
+			if ( $success ) {
+				if ( $dbw->affectedRows() == 0 ) {
+					// Blob was already present, fetch it
+					$blob = $dbw->selectField( 'msg_resource', 'mr_blob', array(
+							'mr_resource' => $name,
+							'mr_lang' => $lang,
+						),
+						__METHOD__
+					);
+				} else {
+					// Update msg_resource_links
+					$rows = array();
+
+					foreach ( $module->getMessages() as $key ) {
+						$rows[] = array(
+							'mrl_resource' => $name,
+							'mrl_message' => $key
+						);
+					}
+					$dbw->insert( 'msg_resource_links', $rows,
+						__METHOD__, array( 'IGNORE' )
 					);
 				}
-				$dbw->insert( 'msg_resource_links', $rows,
-					__METHOD__, array( 'IGNORE' )
-				);
 			}
+		} catch ( Exception $e ) {
+			wfDebug( __METHOD__ . " failed to update DB: $e\n" );
 		}
-
 		return $blob;
 	}
 
@@ -141,48 +144,51 @@ class MessageBlobStore {
 		$oldBlob = $row->mr_blob;
 		$newBlob = self::generateMessageBlob( $module, $lang );
 
-		$newRow = array(
-			'mr_resource' => $name,
-			'mr_lang' => $lang,
-			'mr_blob' => $newBlob,
-			'mr_timestamp' => $dbw->timestamp()
-		);
+		try {
+			$newRow = array(
+				'mr_resource' => $name,
+				'mr_lang' => $lang,
+				'mr_blob' => $newBlob,
+				'mr_timestamp' => $dbw->timestamp()
+			);
 
-		$dbw->replace( 'msg_resource',
-			array( array( 'mr_resource', 'mr_lang' ) ),
-			$newRow, __METHOD__
-		);
+			$dbw->replace( 'msg_resource',
+				array( array( 'mr_resource', 'mr_lang' ) ),
+				$newRow, __METHOD__
+			);
 
-		// Figure out which messages were added and removed
-		$oldMessages = array_keys( FormatJson::decode( $oldBlob, true ) );
-		$newMessages = array_keys( FormatJson::decode( $newBlob, true ) );
-		$added = array_diff( $newMessages, $oldMessages );
-		$removed = array_diff( $oldMessages, $newMessages );
+			// Figure out which messages were added and removed
+			$oldMessages = array_keys( FormatJson::decode( $oldBlob, true ) );
+			$newMessages = array_keys( FormatJson::decode( $newBlob, true ) );
+			$added = array_diff( $newMessages, $oldMessages );
+			$removed = array_diff( $oldMessages, $newMessages );
 
-		// Delete removed messages, insert added ones
-		if ( $removed ) {
-			$dbw->delete( 'msg_resource_links', array(
-					'mrl_resource' => $name,
-					'mrl_message' => $removed
-				), __METHOD__
-			);
-		}
+			// Delete removed messages, insert added ones
+			if ( $removed ) {
+				$dbw->delete( 'msg_resource_links', array(
+						'mrl_resource' => $name,
+						'mrl_message' => $removed
+					), __METHOD__
+				);
+			}
 
-		$newLinksRows = array();
+			$newLinksRows = array();
 
-		foreach ( $added as $message ) {
-			$newLinksRows[] = array(
-				'mrl_resource' => $name,
-				'mrl_message' => $message
-			);
-		}
+			foreach ( $added as $message ) {
+				$newLinksRows[] = array(
+					'mrl_resource' => $name,
+					'mrl_message' => $message
+				);
+			}
 
-		if ( $newLinksRows ) {
-			$dbw->insert( 'msg_resource_links', $newLinksRows, __METHOD__,
-				 array( 'IGNORE' ) // just in case
-			);
+			if ( $newLinksRows ) {
+				$dbw->insert( 'msg_resource_links', $newLinksRows, __METHOD__,
+					array( 'IGNORE' ) // just in case
+				);
+			}
+		} catch ( Exception $e ) {
+			wfDebug( __METHOD__ . " failed to update DB: $e\n" );
 		}
-
 		return $newBlob;
 	}
 
@@ -192,50 +198,58 @@ class MessageBlobStore {
 	 * @param $key String: message key
 	 */
 	public static function updateMessage( $key ) {
-		$dbw = wfGetDB( DB_MASTER );
-
-		// Keep running until the updates queue is empty.
-		// Due to update conflicts, the queue might not be emptied
-		// in one iteration.
-		$updates = null;
-		do {
-			$updates = self::getUpdatesForMessage( $key, $updates );
-
-			foreach ( $updates as $k => $update ) {
-				// Update the row on the condition that it
-				// didn't change since we fetched it by putting
-				// the timestamp in the WHERE clause.
-				$success = $dbw->update( 'msg_resource',
-					array(
-						'mr_blob' => $update['newBlob'],
-						'mr_timestamp' => $dbw->timestamp() ),
-					array(
-						'mr_resource' => $update['resource'],
-						'mr_lang' => $update['lang'],
-						'mr_timestamp' => $update['timestamp'] ),
-					__METHOD__
-				);
+		try {
+			$dbw = wfGetDB( DB_MASTER );
+
+			// Keep running until the updates queue is empty.
+			// Due to update conflicts, the queue might not be emptied
+			// in one iteration.
+			$updates = null;
+			do {
+				$updates = self::getUpdatesForMessage( $key, $updates );
+
+				foreach ( $updates as $k => $update ) {
+					// Update the row on the condition that it
+					// didn't change since we fetched it by putting
+					// the timestamp in the WHERE clause.
+					$success = $dbw->update( 'msg_resource',
+						array(
+							'mr_blob' => $update['newBlob'],
+							'mr_timestamp' => $dbw->timestamp() ),
+						array(
+							'mr_resource' => $update['resource'],
+							'mr_lang' => $update['lang'],
+							'mr_timestamp' => $update['timestamp'] ),
+						__METHOD__
+					);
 
-				// Only requeue conflicted updates.
-				// If update() returned false, don't retry, for
-				// fear of getting into an infinite loop
-				if ( !( $success && $dbw->affectedRows() == 0 ) ) {
-					// Not conflicted
-					unset( $updates[$k] );
+					// Only requeue conflicted updates.
+					// If update() returned false, don't retry, for
+					// fear of getting into an infinite loop
+					if ( !( $success && $dbw->affectedRows() == 0 ) ) {
+						// Not conflicted
+						unset( $updates[$k] );
+					}
 				}
-			}
-		} while ( count( $updates ) );
+			} while ( count( $updates ) );
 
-		// No need to update msg_resource_links because we didn't add
-		// or remove any messages, we just changed their contents.
+			// No need to update msg_resource_links because we didn't add
+			// or remove any messages, we just changed their contents.
+		} catch ( Exception $e ) {
+			wfDebug( __METHOD__ . " failed to update DB: $e\n" );
+		}
 	}
 
 	public static function clear() {
 		// TODO: Give this some more thought
 		// TODO: Is TRUNCATE better?
-		$dbw = wfGetDB( DB_MASTER );
-		$dbw->delete( 'msg_resource', '*', __METHOD__ );
-		$dbw->delete( 'msg_resource_links', '*', __METHOD__ );
+		try {
+			$dbw = wfGetDB( DB_MASTER );
+			$dbw->delete( 'msg_resource', '*', __METHOD__ );
+			$dbw->delete( 'msg_resource_links', '*', __METHOD__ );
+		} catch ( Exception $e ) {
+			wfDebug( __METHOD__ . " failed to update DB: $e\n" );
+		}
 	}
 
 	/**
diff --git a/includes/resourceloader/ResourceLoader.php b/includes/resourceloader/ResourceLoader.php
index b4bd98cd8e..5abe2260f4 100644
--- a/includes/resourceloader/ResourceLoader.php
+++ b/includes/resourceloader/ResourceLoader.php
@@ -176,6 +176,7 @@ class ResourceLoader {
 		} catch ( Exception $exception ) {
 			// Return exception as a comment
 			$result = $this->makeComment( $exception->__toString() );
+			$this->hasErrors = true;
 		}
 
 		wfProfileOut( __METHOD__ );
@@ -435,6 +436,7 @@ class ResourceLoader {
 
 		wfProfileIn( __METHOD__ );
 		$errors = '';
+		$this->hasErrors = false;
 
 		// Split requested modules into two groups, modules and missing
 		$modules = array();
@@ -446,6 +448,7 @@ class ResourceLoader {
 				// This is a security issue, see bug 34907.
 				if ( $module->getGroup() === 'private' ) {
 					$errors .= $this->makeComment( "Cannot show private module \"$name\"" );
+					$this->hasErrors = true;
 					continue;
 				}
 				$modules[$name] = $this->getModule( $name );
@@ -460,6 +463,7 @@ class ResourceLoader {
 		} catch( Exception $e ) {
 			// Add exception to the output as a comment
 			$errors .= $this->makeComment( $e->__toString() );
+			$this->hasErrors = true;
 		}
 
 		wfProfileIn( __METHOD__.'-getModifiedTime' );
@@ -477,14 +481,12 @@ class ResourceLoader {
 			} catch ( Exception $e ) {
 				// Add exception to the output as a comment
 				$errors .= $this->makeComment( $e->__toString() );
+				$this->hasErrors = true;
 			}
 		}
 
 		wfProfileOut( __METHOD__.'-getModifiedTime' );
 
-		// Send content type and cache related headers
-		$this->sendResponseHeaders( $context, $mtime );
-
 		// If there's an If-Modified-Since header, respond with a 304 appropriately
 		if ( $this->tryRespondLastModified( $context, $mtime ) ) {
 			wfProfileOut( __METHOD__ );
@@ -501,6 +503,7 @@ class ResourceLoader {
 		// response in a comment if we're in debug mode.
 		if ( $context->getDebug() && strlen( $warnings = ob_get_contents() ) ) {
 			$response = $this->makeComment( $warnings ) . $response;
+			$this->hasErrors = true;
 		}
 
 		// Save response to file cache unless there are errors
@@ -515,6 +518,9 @@ class ResourceLoader {
 			}
 		}
 
+		// Send content type and cache related headers
+		$this->sendResponseHeaders( $context, $mtime, $this->hasErrors );
+
 		// Remove the output buffer and output the response
 		ob_end_clean();
 		echo $response;
@@ -526,13 +532,15 @@ class ResourceLoader {
 	 * Send content type and last modified headers to the client.
 	 * @param $context ResourceLoaderContext
 	 * @param $mtime string TS_MW timestamp to use for last-modified
+	 * @param $error bool Whether there are commented-out errors in the response
 	 * @return void
 	 */
-	protected function sendResponseHeaders( ResourceLoaderContext $context, $mtime ) {
+	protected function sendResponseHeaders( ResourceLoaderContext $context, $mtime, $errors ) {
 		global $wgResourceLoaderMaxage;
 		// If a version wasn't specified we need a shorter expiry time for updates
 		// to propagate to clients quickly
-		if ( is_null( $context->getVersion() ) ) {
+		// If there were errors, we also need a shorter expiry time so we can recover quickly
+		if ( is_null( $context->getVersion() ) || $errors ) {
 			$maxage  = $wgResourceLoaderMaxage['unversioned']['client'];
 			$smaxage = $wgResourceLoaderMaxage['unversioned']['server'];
 		// If a version was specified we can use a longer expiry time since changing
@@ -680,6 +688,7 @@ class ResourceLoader {
 			} catch ( Exception $e ) {
 				// Add exception to the output as a comment
 				$exceptions .= $this->makeComment( $e->__toString() );
+				$this->hasErrors = true;
 			}
 		} else {
 			$blobs = array();
@@ -785,6 +794,7 @@ class ResourceLoader {
 			} catch ( Exception $e ) {
 				// Add exception to the output as a comment
 				$exceptions .= $this->makeComment( $e->__toString() );
+				$this->hasErrors = true;
 
 				// Register module as missing
 				$missing[] = $name;
diff --git a/includes/resourceloader/ResourceLoaderFileModule.php b/includes/resourceloader/ResourceLoaderFileModule.php
index fa84843d5b..fad00274cd 100644
--- a/includes/resourceloader/ResourceLoaderFileModule.php
+++ b/includes/resourceloader/ResourceLoaderFileModule.php
@@ -312,15 +312,19 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 		// Collect referenced files
 		$this->localFileRefs = array_unique( $this->localFileRefs );
 		// If the list has been modified since last time we cached it, update the cache
-		if ( $this->localFileRefs !== $this->getFileDependencies( $context->getSkin() ) && !wfReadOnly() ) {
-			$dbw = wfGetDB( DB_MASTER );
-			$dbw->replace( 'module_deps',
-				array( array( 'md_module', 'md_skin' ) ), array(
-					'md_module' => $this->getName(),
-					'md_skin' => $context->getSkin(),
-					'md_deps' => FormatJson::encode( $this->localFileRefs ),
-				)
-			);
+		try {
+			if ( $this->localFileRefs !== $this->getFileDependencies( $context->getSkin() ) ) {
+				$dbw = wfGetDB( DB_MASTER );
+				$dbw->replace( 'module_deps',
+					array( array( 'md_module', 'md_skin' ) ), array(
+						'md_module' => $this->getName(),
+						'md_skin' => $context->getSkin(),
+						'md_deps' => FormatJson::encode( $this->localFileRefs ),
+					)
+				);
+			}
+		} catch ( Exception $e ) {
+			wfDebug( __METHOD__ . " failed to update DB: $e\n" );
 		}
 		return $styles;
 	}