Hooks! Hoooooks!

[lhc/web/wiklou.git] / includes / LoadBalancer.php

diff --git a/includes/LoadBalancer.php b/includes/LoadBalancer.php
index 287ca8b..40b4613 100644 (file)
--- a/includes/LoadBalancer.php
+++ b/includes/LoadBalancer.php
@@ -19,6 +19,12 @@ define( 'DB_LAST', -3 );     # Whatever database was used last
 define( 'DB_READ', -1 );
 define( 'DB_WRITE', -2 );
 
+
+# Scale polling time so that under overload conditions, the database server
+# receives a SHOW STATUS query at an average interval of this many microseconds
+define( 'AVG_STATUS_POLL', 2000 );
+
+
 /**
  * Database load balancing object
  *
@@ -30,7 +36,7 @@ class LoadBalancer {
        /* private */ var $mFailFunction, $mErrorConnection;
        /* private */ var $mForce, $mReadIndex, $mLastIndex;
        /* private */ var $mWaitForFile, $mWaitForPos, $mWaitTimeout;
-       /* private */ var $mLaggedSlaveMode;
+       /* private */ var $mLaggedSlaveMode, $mLastError = 'Unknown error';
 
        function LoadBalancer()
        {
@@ -153,9 +159,8 @@ class LoadBalancer {
         *
         * Side effect: opens connections to databases
         */
-       function getReaderIndex()
-       {
-               global $wgMaxLag, $wgReadOnly, $wgDBClusterTimeout;
+       function getReaderIndex() {
+               global $wgReadOnly, $wgDBClusterTimeout;
 
                $fname = 'LoadBalancer::getReaderIndex';
                wfProfileIn( $fname );
@@ -198,7 +203,7 @@ class LoadBalancer {
                                                          $status['Threads_running'] > $this->mServers[$i]['max threads'] )
                                                        {
                                                                # Slave is lagged, wait for a while
-                                                               $sleepTime = 5000 * $status['Threads_connected'];
+                                                               $sleepTime = AVG_STATUS_POLL * $status['Threads_connected'];
 
                                                                # If we reach the timeout and exit the loop, don't use it
                                                                $i = false;
@@ -219,6 +224,11 @@ class LoadBalancer {
                                        }
                                } while ( count( $loads ) && !$done && $totalElapsed / 1e6 < $wgDBClusterTimeout );
 
+                               if ( $totalElapsed / 1e6 >= $wgDBClusterTimeout ) {
+                                       $this->mErrorConnection = false;
+                                       $this->mLastError = 'All servers busy';
+                               }
+                               
                                if ( $i !== false && $this->isOpen( $i ) ) {
                                        # Wait for the session master pos for a short time
                                        if ( $this->mWaitForFile ) {
@@ -427,7 +437,9 @@ class LoadBalancer {
                }
 
                # Create object
-               return new $class( $host, $user, $password, $dbname, 1, $flags );
+               $db = new $class( $host, $user, $password, $dbname, 1, $flags );
+               $db->setLBInfo( $server );
+               return $db;
        }
 
        function reportConnectionError( &$conn )
@@ -440,14 +452,23 @@ class LoadBalancer {
                if ( !$reporting ) {
                        $reporting = true;
                        if ( !is_object( $conn ) ) {
+                               // No last connection, probably due to all servers being too busy
                                $conn = new Database;
-                       }
-                       if ( $this->mFailFunction ) {
-                               $conn->failFunction( $this->mFailFunction );
+                               if ( $this->mFailFunction ) {
+                                       $conn->failFunction( $this->mFailFunction );
+                                       $conn->reportConnectionError( $this->mLastError );
+                               } else {
+                                       // If all servers were busy, mLastError will contain something sensible
+                                       wfEmergencyAbort( $conn, $this->mLastError );
+                               }
                        } else {
-                               $conn->failFunction( false );
+                               if ( $this->mFailFunction ) {
+                                       $conn->failFunction( $this->mFailFunction );
+                               } else {
+                                       $conn->failFunction( false );
+                               }
+                               $conn->reportConnectionError( "{$this->mLastError} ({$conn->mServer})" );
                        }
-                       $conn->reportConnectionError();
                        $reporting = false;
                }
                wfProfileOut( $fname );
@@ -573,11 +594,13 @@ class LoadBalancer {
         * Results are cached for a short time in memcached
         */
        function getLagTimes() {
+               global $wgDBname;
+               
                $expiry = 5;
                $requestRate = 10;
 
                global $wgMemc;
-               $times = $wgMemc->get( 'lag_times' );
+               $times = $wgMemc->get( "$wgDBname:lag_times" );
                if ( $times ) {
                        # Randomly recache with probability rising over $expiry
                        $elapsed = time() - $times['timestamp'];
@@ -599,7 +622,7 @@ class LoadBalancer {
 
                # Add a timestamp key so we know when it was cached
                $times['timestamp'] = time();
-               $wgMemc->set( 'lag_times', $times, $expiry );
+               $wgMemc->set( "$wgDBname:lag_times", $times, $expiry );
 
                # But don't give the timestamp to the caller
                unset($times['timestamp']);