Ticket #5932: 5932.7.diff

src/wp-includes/wp-db.php

@@ -158 +158 @@
         var $queries;
 
         /**
+         * 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;
+
+        /**
          * WordPress table prefix
          *
          * You can set this to have multiple WordPress installations
@@ -1130 +1140 @@
          * Connect to and select database
          *
          * @since 3.0.0
+         *
+         * @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 on successful connection, false on unsuccessful connection
          */
-        function db_connect() {
+        function db_connect( $allow_bail = true ) {
 
                 $this->is_mysql = true;
 
@@ -1152 +1166 @@
                         $this->dbh = @mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags );
                 }
 
-                if ( !$this->dbh ) {
+                if ( ! $this->dbh && $allow_bail ) {
                         wp_load_translations_early();
 
                         // Load custom DB error template, if present.
@@ -1172 +1186 @@
 <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' );
 
-                        return;
+                        return false;
+                } else if ( $this->dbh ) {
+                        $this->set_charset( $this->dbh );
+                        $this->ready = true;
+                        $this->select( $this->dbname, $this->dbh );
+
+                        return true;
                 }
 
-                $this->set_charset( $this->dbh );
+                return false;
+        }
 
-                $this->ready = true;
+        /**
+         * 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;
+                }
 
-                $this->select( $this->dbname, $this->dbh );
+                $error_reporting = false;
+
+                // 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' );
+
+                // If the bail didn't call wp_die, it's time to die, because the DB isn't coming back.
+                dead_db();
         }
 
         /**
@@ -1214 +1284 @@
                 // Keep track of the last query for debug..
                 $this->last_query = $query;
 
-                if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES )
-                        $this->timer_start();
+                $this->_do_query( $query );
 
-                $this->result = @mysql_query( $query, $this->dbh );
-                $this->num_queries++;
+                // 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 );
+                        }
+                }
 
-                if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES )
-                        $this->queries[] = array( $query, $this->timer_stop(), $this->get_caller() );
-
                 // If there is an error then take note of it..
                 if ( $this->last_error = mysql_error( $this->dbh ) ) {
                         // Clear insert_id on a subsequent failed insert.
@@ -1260 +1330 @@
         }
 
         /**
+         * 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() );
+                }
+        }
+
+        /**
          * Insert a row into a table.
          *
          * <code>

tests/phpunit/tests/db.php

@@ -41 +41 @@
         }
 
         /**
+         * 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 );
+        }
+
+        /**
          * Test that floats formatted as "0,700" get sanitized properly by wpdb
          * @global mixed $wpdb
          *