cache: Add in-process caching to MessageBlobStore

This allows us to continue to use MessageBlobStore::get() as a way
to pre-fetch messages in batches for multiple modules while also
allowing individual modules to retrieve  their messages in a convenient
way.

This is in preparation for implementing ResourceLoaderModule::buildContents
and using it in ResourceLoaderModule::getVersionHash.

ResourceLoader::respond() already fetches message blobs in batches for the
actual response, but it also needs getVersionHash(), which would otherwise
fetch the same messages a second time.

Change-Id: I7e4c8b65765b54807123e85cfbb7eb2e5b2f39bd

diff --git a/includes/cache/MessageBlobStore.php b/includes/cache/MessageBlobStore.php
index 011cae6..19349b2 100644 (file)
--- a/includes/cache/MessageBlobStore.php
+++ b/includes/cache/MessageBlobStore.php
@@ -32,6 +32,15 @@
  * constituent messages or the resource itself is changed.
  */
 class MessageBlobStore {
+       /**
+        * In-process cache for message blobs.
+        *
+        * Keyed by language code, then module name.
+        *
+        * @var array
+        */
+       protected $blobCache = array();
+
        /**
         * Get the singleton instance
         *
@@ -56,18 +65,40 @@ class MessageBlobStore {
                if ( !count( $modules ) ) {
                        return array();
                }
-               // Try getting from the DB first
-               $blobs = $this->getFromDB( $resourceLoader, array_keys( $modules ), $lang );
 
-               // Generate blobs for any missing modules and store them in the DB
-               $missing = array_diff( array_keys( $modules ), array_keys( $blobs ) );
-               foreach ( $missing as $name ) {
+               $blobs = array();
+
+               // Try in-process cache
+               $missingFromCache = array();
+               foreach ( $modules as $name => $module ) {
+                       if ( isset( $this->blobCache[$lang][$name] ) ) {
+                               $blobs[$name] = $this->blobCache[$lang][$name];
+                       } else {
+                               $missingFromCache[] = $name;
+                       }
+               }
+
+               // Try DB cache
+               if ( $missingFromCache ) {
+                       $blobs += $this->getFromDB( $resourceLoader, $missingFromCache, $lang );
+               }
+
+               // Generate new blobs for any remaining modules and store in DB
+               $missingFromDb = array_diff( array_keys( $modules ), array_keys( $blobs ) );
+               foreach ( $missingFromDb as $name ) {
                        $blob = $this->insertMessageBlob( $name, $modules[$name], $lang );
                        if ( $blob ) {
                                $blobs[$name] = $blob;
                        }
                }
 
+               // Update in-process cache
+               if ( isset( $this->blobCache[$lang] ) ) {
+                       $this->blobCache[$lang] += $blobs;
+               } else {
+                       $this->blobCache[$lang] = $blobs;
+               }
+
                return $blobs;
        }
 
@@ -339,6 +370,10 @@ class MessageBlobStore {
         * @return array Array mapping module names to blobs
         */
        private function getFromDB( ResourceLoader $resourceLoader, $modules, $lang ) {
+               if ( !count( $modules ) ) {
+                       return array();
+               }
+
                $config = $resourceLoader->getConfig();
                $retval = array();
                $dbr = wfGetDB( DB_SLAVE );