rdbms: make LoadBalancer::getConnection() ignore CONN_TRX_AUTO when unusable

[lhc/web/wiklou.git] / includes / libs / rdbms / loadbalancer / LoadBalancer.php

diff --git a/includes/libs/rdbms/loadbalancer/LoadBalancer.php b/includes/libs/rdbms/loadbalancer/LoadBalancer.php
index 569ea0e..99a24c2 100644 (file)
--- a/includes/libs/rdbms/loadbalancer/LoadBalancer.php
+++ b/includes/libs/rdbms/loadbalancer/LoadBalancer.php
@@ -680,6 +680,22 @@ class LoadBalancer implements ILoadBalancer {
                        $domain = false; // local connection requested
                }
 
+               if ( ( $flags & self::CONN_TRX_AUTO ) === self::CONN_TRX_AUTO ) {
+                       // Assuming all servers are of the same type (or similar), which is overwhelmingly
+                       // the case, use the master server information to get the attributes. The information
+                       // for $i cannot be used since it might be DB_REPLICA, which might require connection
+                       // attempts in order to be resolved into a real server index.
+                       $attributes = $this->getServerAttributes( $this->getWriterIndex() );
+                       if ( $attributes[Database::ATTR_DB_LEVEL_LOCKING] ) {
+                               // Callers sometimes want to (a) escape REPEATABLE-READ stateness without locking
+                               // rows (e.g. FOR UPDATE) or (b) make small commits during a larger transactions
+                               // to reduce lock contention. None of these apply for sqlite and using separate
+                               // connections just causes self-deadlocks.
+                               $flags &= ~self::CONN_TRX_AUTO;
+                               $this->connLogger->info( __METHOD__ . ': ignoring CONN_TRX_AUTO to avoid deadlocks.' );
+                       }
+               }
+
                $groups = ( $groups === false || $groups === [] )
                        ? [ false ] // check one "group": the generic pool
                        : (array)$groups;
@@ -981,6 +997,13 @@ class LoadBalancer implements ILoadBalancer {
                return $conn;
        }
 
+       public function getServerAttributes( $i ) {
+               return Database::attributesFromType(
+                       $this->getServerType( $i ),
+                       isset( $this->servers[$i]['driver'] ) ? $this->servers[$i]['driver'] : null
+               );
+       }
+
        /**
         * Test if the specified index represents an open connection
         *