Introduce 'FetchChangesList' hook; see docs/hooks.txt for more information

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

diff --git a/includes/LoadBalancer.php b/includes/LoadBalancer.php
index eb1aa59..f985a7b 100644 (file)
--- a/includes/LoadBalancer.php
+++ b/includes/LoadBalancer.php
@@ -95,17 +95,13 @@ class LoadBalancer {
                        return false;
                }
 
-               $sum = 0;
-               foreach ( $weights as $w ) {
-                       $sum += $w;
-               }
-
+               $sum = array_sum( $weights );
                if ( $sum == 0 ) {
                        # No loads on any of them
-                       # Just pick one at random
-                       foreach ( $weights as $i => $w ) {
-                               $weights[$i] = 1;
-                       }
+                       # In previous versions, this triggered an unweighted random selection,
+                       # but this feature has been removed as of April 2006 to allow for strict 
+                       # separation of query groups. 
+                       return false;
                }
                $max = mt_getrandmax();
                $rand = mt_rand(0, $max) / $max * $sum;
@@ -129,7 +125,6 @@ class LoadBalancer {
                        }
                }
 
-
                # Find out if all the slaves with non-zero load are lagged
                $sum = 0;
                foreach ( $loads as $load ) {
@@ -140,7 +135,7 @@ class LoadBalancer {
                        # Do NOT use the master
                        # Instead, this function will return false, triggering read-only mode,
                        # and a lagged slave will be used instead.
-                       unset ( $loads[0] );
+                       return false;
                }
 
                if ( count( $loads ) == 0 ) {
@@ -191,11 +186,11 @@ class LoadBalancer {
                                        }
                                        $serverIndex = $i;
                                        if ( $i !== false ) {
-                                               wfDebugLog( 'connect', "Using reader #$i: {$this->mServers[$i]['host']}...\n" );
+                                               wfDebugLog( 'connect', "$fname: Using reader #$i: {$this->mServers[$i]['host']}...\n" );
                                                $this->openConnection( $i );
 
                                                if ( !$this->isOpen( $i ) ) {
-                                                       wfDebug( "Failed\n" );
+                                                       wfDebug( "$fname: Failed\n" );
                                                        unset( $loads[$i] );
                                                        $sleepTime = 0;
                                                } else {
@@ -203,7 +198,9 @@ class LoadBalancer {
                                                        if ( isset( $this->mServers[$i]['max threads'] ) &&
                                                          $status['Threads_running'] > $this->mServers[$i]['max threads'] )
                                                        {
-                                                               # Slave is lagged, wait for a while
+                                                               # Too much load, back off and wait for a while.
+                                                               # The sleep time is scaled by the number of threads connected,
+                                                               # to produce a roughly constant global poll rate.
                                                                $sleepTime = AVG_STATUS_POLL * $status['Threads_connected'];
 
                                                                # If we reach the timeout and exit the loop, don't use it
@@ -337,21 +334,33 @@ class LoadBalancer {
         */
        function &getConnection( $i, $fail = true, $groups = array() )
        {
+               global $wgDBtype;
                $fname = 'LoadBalancer::getConnection';
                wfProfileIn( $fname );
 
+
                # Query groups
-               $groupIndex = false;
-               foreach ( $groups as $group ) {
-                       $groupIndex = $this->getGroupIndex( $group );
+               if ( !is_array( $groups ) ) {
+                       $groupIndex = $this->getGroupIndex( $groups, $i );
                        if ( $groupIndex !== false ) {
                                $i = $groupIndex;
-                               break;
+                       }
+               } else {
+                       foreach ( $groups as $group ) {
+                               $groupIndex = $this->getGroupIndex( $group, $i );
+                               if ( $groupIndex !== false ) {
+                                       $i = $groupIndex;
+                                       break;
+                               }
                        }
                }
 
+               # For now, only go through all this for mysql databases
+               if ($wgDBtype != 'mysql') {
+                       $i = $this->getWriterIndex();
+               }
                # Operation-based index
-               if ( $i == DB_SLAVE ) {
+               elseif ( $i == DB_SLAVE ) {
                        $i = $this->getReaderIndex();
                } elseif ( $i == DB_MASTER ) {
                        $i = $this->getWriterIndex();
@@ -427,7 +436,7 @@ class LoadBalancer {
         */
        function reallyOpenConnection( &$server ) {
                if( !is_array( $server ) ) {
-                       wfDebugDieBacktrace( 'You must update your load-balancing configuration. See DefaultSettings.php entry for $wgDBservers.' );
+                       throw new MWException( 'You must update your load-balancing configuration. See DefaultSettings.php entry for $wgDBservers.' );
                }
 
                extract( $server );
@@ -460,7 +469,7 @@ class LoadBalancer {
                                        $conn->reportConnectionError( $this->mLastError );
                                } else {
                                        // If all servers were busy, mLastError will contain something sensible
-                                       wfEmergencyAbort( $conn, $this->mLastError );
+                                       throw new DBConnectionError( $conn, $this->mLastError );
                                }
                        } else {
                                if ( $this->mFailFunction ) {
@@ -468,28 +477,42 @@ class LoadBalancer {
                                } else {
                                        $conn->failFunction( false );
                                }
-                               $conn->reportConnectionError( "{$this->mLastError} ({$conn->mServer})" );
+                               $server = $conn->getProperty( 'mServer' );
+                               $conn->reportConnectionError( "{$this->mLastError} ({$server})" );
                        }
                        $reporting = false;
                }
                wfProfileOut( $fname );
        }
 
-       function getWriterIndex()
-       {
+       function getWriterIndex() {
                return 0;
        }
 
-       function force( $i )
-       {
+       /**
+        * Force subsequent calls to getConnection(DB_SLAVE) to return the 
+        * given index. Set to -1 to restore the original load balancing
+        * behaviour. I thought this was a good idea when I originally 
+        * wrote this class, but it has never been used.
+        */
+       function force( $i ) {
                $this->mForce = $i;
        }
 
-       function haveIndex( $i )
-       {
+       /**
+        * Returns true if the specified index is a valid server index
+        */
+       function haveIndex( $i ) {
                return array_key_exists( $i, $this->mServers );
        }
 
+       /**
+        * Returns true if the specified index is valid and has non-zero load
+        */
+       function isNonZeroLoad( $i ) {
+               return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
+       }
+
        /**
         * Get the number of defined servers (not the number of open connections)
         */