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<title>[8901] sites/trunk/wordpress.org/public_html/wp-content/plugins/plugin-directory/libs/site-search/jetpack-search.php: Plugin Directory: Search: Tweak the 'search stampede' code to allow two concurrent search requests.</title>
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<dt style="float: left; width: 6em; font-weight: bold">Revision</dt> <dd><a style="font-weight: bold" href="http://meta.trac.wordpress.org/changeset/8901">8901</a><script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","description":"Review this Commit","action":{"@type":"ViewAction","url":"http://meta.trac.wordpress.org/changeset/8901","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>dd32</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2019-05-31 06:33:07 +0000 (Fri, 31 May 2019)</dd>
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<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>Plugin Directory: Search: Tweak the 'search stampede' code to allow two concurrent search requests.
Currently the locked-with-no-stale-response warning is triggered far too often, this relaxes it a bit while hopefully not overloading things.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#sitestrunkwordpressorgpublic_htmlwpcontentpluginsplugindirectorylibssitesearchjetpacksearchphp">sites/trunk/wordpress.org/public_html/wp-content/plugins/plugin-directory/libs/site-search/jetpack-search.php</a></li>
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<h3>Diff</h3>
<a id="sitestrunkwordpressorgpublic_htmlwpcontentpluginsplugindirectorylibssitesearchjetpacksearchphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: sites/trunk/wordpress.org/public_html/wp-content/plugins/plugin-directory/libs/site-search/jetpack-search.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- sites/trunk/wordpress.org/public_html/wp-content/plugins/plugin-directory/libs/site-search/jetpack-search.php 2019-05-31 00:09:32 UTC (rev 8900)
+++ sites/trunk/wordpress.org/public_html/wp-content/plugins/plugin-directory/libs/site-search/jetpack-search.php 2019-05-31 06:33:07 UTC (rev 8901)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -229,9 +229,19 @@
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> $response = wp_cache_get( $cache_key, self::CACHE_GROUP );
</span><span class="cx" style="display: block; padding: 0 10px">
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- // Use a temporary lock to prevent cache stampedes. This ensures only one process (per search term per memcache instance) will run the remote post.
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+
+ // Use a temporary lock to prevent cache stampedes.
+ // This will ensure that a maximum of two processes are performing the search, or one when the stale value is still known.
</ins><span class="cx" style="display: block; padding: 0 10px"> // Other processes will use the stale cached value if it's present, even for a while after the expiration time if a fresh value is still being fetched.
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ $do_fresh_request = false;
</ins><span class="cx" style="display: block; padding: 0 10px"> if ( wp_cache_add( $lock_key, 1, self::CACHE_GROUP, 15 ) ) {
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ $do_fresh_request = true;
+ } elseif ( ! $response && 2 === wp_cache_incr( $lock_key, 1, self::CACHE_GROUP ) ) {
+ // If we don't have cached data, this is the second request and, error volume is low, still perform the request.
+ $do_fresh_request = $this->error_volume_is_low();
+ }
+
+ if ( $do_fresh_request ) {
</ins><span class="cx" style="display: block; padding: 0 10px"> // Keep track of the number of concurrent requests for this key
</span><span class="cx" style="display: block; padding: 0 10px"> wp_cache_set( $count_key, 1, self::CACHE_GROUP, 60 );
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -256,7 +266,7 @@
</span><span class="cx" style="display: block; padding: 0 10px"> if ( is_wp_error( $request ) || 200 != wp_remote_retrieve_response_code( $request ) ) {
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> // Lock further requests for the same search for 3-7 seconds. We probably don't need anything more complex like exponential backoff here because this is per search.
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- wp_cache_set( $lock_key, 1, self::CACHE_GROUP, mt_rand( 3, 7 ) );
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ wp_cache_set( $lock_key, 2, self::CACHE_GROUP, mt_rand( 3, 7 ) );
</ins><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> if ( is_wp_error( $request ) ) {
</span><span class="cx" style="display: block; padding: 0 10px"> $this->search_error( 'http error ' . $request->get_error_message(), E_USER_WARNING );
</span></span></pre>
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