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<title>[27075] trunk: When the MySQL server has "gone away," attempt to reconnect and retry the query.</title>
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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://core.trac.wordpress.org/changeset/27075">27075</a></dd>
<dt>Author</dt> <dd>nacin</dd>
<dt>Date</dt> <dd>2014-02-02 22:06:42 +0000 (Sun, 02 Feb 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>When the MySQL server has "gone away," attempt to reconnect and retry the query.
props pento.
see <a href="http://core.trac.wordpress.org/ticket/5932">#5932</a>.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpincludeswpdbphp">trunk/src/wp-includes/wp-db.php</a></li>
<li><a href="#trunktestsphpunittestsdbphp">trunk/tests/phpunit/tests/db.php</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunksrcwpincludeswpdbphp"></a>
<div class="modfile"><h4>Modified: trunk/src/wp-includes/wp-db.php (27074 => 27075)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/src/wp-includes/wp-db.php 2014-02-02 21:47:58 UTC (rev 27074)
+++ trunk/src/wp-includes/wp-db.php 2014-02-02 22:06:42 UTC (rev 27075)
</span><span class="lines">@@ -158,6 +158,16 @@
</span><span class="cx"> var $queries;
</span><span class="cx">
</span><span class="cx"> /**
</span><ins>+ * The number of times to retry reconnecting before dying.
+ *
+ * @since 3.9.0
+ * @access protected
+ * @see wpdb::check_connection()
+ * @var int
+ */
+ protected $reconnect_retries = 5;
+
+ /**
</ins><span class="cx"> * WordPress table prefix
</span><span class="cx"> *
</span><span class="cx"> * You can set this to have multiple WordPress installations
</span><span class="lines">@@ -1192,11 +1202,17 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> /**
</span><del>- * Connect to and select database
</del><ins>+ * Connect to and select database.
</ins><span class="cx"> *
</span><span class="cx"> * @since 3.0.0
</span><ins>+ *
+ * @param bool $allow_bail Optional. Allows the function to bail, default true. If this is set
+ * to false, you will need to handle the lack of database connection
+ * manually. Available since 3.9.0.
+ *
+ * @return bool True with a successful connection, false on failure.
</ins><span class="cx"> */
</span><del>- function db_connect() {
</del><ins>+ function db_connect( $allow_bail = true ) {
</ins><span class="cx">
</span><span class="cx"> $this->is_mysql = true;
</span><span class="cx">
</span><span class="lines">@@ -1217,7 +1233,7 @@
</span><span class="cx"> $this->dbh = @mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags );
</span><span class="cx"> }
</span><span class="cx">
</span><del>- if ( !$this->dbh ) {
</del><ins>+ if ( ! $this->dbh && $allow_bail ) {
</ins><span class="cx"> wp_load_translations_early();
</span><span class="cx">
</span><span class="cx"> // Load custom DB error template, if present.
</span><span class="lines">@@ -1237,16 +1253,72 @@
</span><span class="cx"> <p>If you're unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href='http://wordpress.org/support/'>WordPress Support Forums</a>.</p>
</span><span class="cx"> " ), htmlspecialchars( $this->dbhost, ENT_QUOTES ) ), 'db_connect_fail' );
</span><span class="cx">
</span><del>- return;
</del><ins>+ return false;
+ } else if ( $this->dbh ) {
+ $this->set_charset( $this->dbh );
+ $this->set_sql_mode();
+ $this->ready = true;
+ $this->select( $this->dbname, $this->dbh );
+
+ return true;
</ins><span class="cx"> }
</span><span class="cx">
</span><del>- $this->set_charset( $this->dbh );
</del><ins>+ return false;
+ }
</ins><span class="cx">
</span><del>- $this->set_sql_mode();
</del><ins>+ /**
+ * Check that the connection to the database is still up. If not, try to reconnect.
+ *
+ * If this function is unable to reconnect, it will forcibly die.
+ *
+ * @since 3.9.0
+ *
+ * @return bool True if the connection is up.
+ */
+ function check_connection() {
+ if ( @mysql_ping( $this->dbh ) ) {
+ return true;
+ }
</ins><span class="cx">
</span><del>- $this->ready = true;
</del><ins>+ $error_reporting = false;
</ins><span class="cx">
</span><del>- $this->select( $this->dbname, $this->dbh );
</del><ins>+ // Disable warnings, as we don't want to see a multitude of "unable to connect" messages
+ if ( WP_DEBUG ) {
+ $error_reporting = error_reporting();
+ error_reporting( $error_reporting & ~E_WARNING );
+ }
+
+ for ( $tries = 1; $tries <= $this->reconnect_retries; $tries++ ) {
+ // On the last try, re-enable warnings. We want to see a single instance of the
+ // "unable to connect" message on the bail() screen, if it appears.
+ if ( $this->reconnect_retries === $tries && WP_DEBUG ) {
+ error_reporting( $error_reporting );
+ }
+
+ if ( $this->db_connect( false ) ) {
+ if ( $error_reporting ) {
+ error_reporting( $error_reporting );
+ }
+
+ return true;
+ }
+
+ sleep( 1 );
+ }
+
+ // We weren't able to reconnect, so we better bail.
+ $this->bail( sprintf( ( "
+<h1>Error reconnecting to the database</h1>
+<p>This means that we lost contact with the database server at <code>%s</code>. This could mean your host's database server is down.</p>
+<ul>
+ <li>Are you sure that the database server is running?</li>
+ <li>Are you sure that the database server is not under particularly heavy load?</li>
+</ul>
+<p>If you're unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href='http://wordpress.org/support/'>WordPress Support Forums</a>.</p>
+" ), htmlspecialchars( $this->dbhost, ENT_QUOTES ) ), 'db_connect_fail' );
+
+ // Call dead_db() if bail didn't die, because this database is no more. It has ceased to be (at least temporarily).
+ dead_db();
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> /**
</span><span class="lines">@@ -1262,6 +1334,7 @@
</span><span class="cx"> function query( $query ) {
</span><span class="cx"> if ( ! $this->ready )
</span><span class="cx"> return false;
</span><ins>+
</ins><span class="cx"> /**
</span><span class="cx"> * Filter the database query.
</span><span class="cx"> *
</span><span class="lines">@@ -1281,15 +1354,15 @@
</span><span class="cx"> // Keep track of the last query for debug..
</span><span class="cx"> $this->last_query = $query;
</span><span class="cx">
</span><del>- if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES )
- $this->timer_start();
</del><ins>+ $this->_do_query( $query );
</ins><span class="cx">
</span><del>- $this->result = @mysql_query( $query, $this->dbh );
- $this->num_queries++;
</del><ins>+ // MySQL server has gone away, try to reconnect
+ if ( empty( $this->dbh ) || 2006 == mysql_errno( $this->dbh ) ) {
+ if ( $this->check_connection() ) {
+ $this->_do_query( $query );
+ }
+ }
</ins><span class="cx">
</span><del>- if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES )
- $this->queries[] = array( $query, $this->timer_stop(), $this->get_caller() );
-
</del><span class="cx"> // If there is an error then take note of it..
</span><span class="cx"> if ( $this->last_error = mysql_error( $this->dbh ) ) {
</span><span class="cx"> // Clear insert_id on a subsequent failed insert.
</span><span class="lines">@@ -1327,6 +1400,29 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> /**
</span><ins>+ * Internal function to perform the mysql_query call
+ *
+ * @since 3.9.0
+ *
+ * @access private
+ * @see wpdb::query()
+ *
+ * @param string $query The query to run
+ */
+ private function _do_query( $query ) {
+ if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES ) {
+ $this->timer_start();
+ }
+
+ $this->result = @mysql_query( $query, $this->dbh );
+ $this->num_queries++;
+
+ if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES ) {
+ $this->queries[] = array( $query, $this->timer_stop(), $this->get_caller() );
+ }
+ }
+
+ /**
</ins><span class="cx"> * Insert a row into a table.
</span><span class="cx"> *
</span><span class="cx"> * <code>
</span></span></pre></div>
<a id="trunktestsphpunittestsdbphp"></a>
<div class="modfile"><h4>Modified: trunk/tests/phpunit/tests/db.php (27074 => 27075)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/tests/phpunit/tests/db.php 2014-02-02 21:47:58 UTC (rev 27074)
+++ trunk/tests/phpunit/tests/db.php 2014-02-02 22:06:42 UTC (rev 27075)
</span><span class="lines">@@ -41,6 +41,23 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> /**
</span><ins>+ * Test that WPDB will reconnect when the DB link dies
+ * @ticket 5932
+ */
+ public function test_db_reconnect() {
+ global $wpdb;
+
+ $var = $wpdb->get_var( "SELECT ID FROM $wpdb->users LIMIT 1" );
+ $this->assertGreaterThan( 0, $var );
+
+ mysql_close( $wpdb->dbh );
+ unset( $wpdb->dbh );
+
+ $var = $wpdb->get_var( "SELECT ID FROM $wpdb->users LIMIT 1" );
+ $this->assertGreaterThan( 0, $var );
+ }
+
+ /**
</ins><span class="cx"> * Test that floats formatted as "0,700" get sanitized properly by wpdb
</span><span class="cx"> * @global mixed $wpdb
</span><span class="cx"> *
</span></span></pre>
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