Make spare connections more explicit

qgis · Aug 8, 2018 · 58da975 · 58da975
1 parent e0cc66c
commit 58da975
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Showing 4 changed files with 13 additions and 4 deletions.
diff --git a/python/core/auto_generated/qgsapplication.sip.in b/python/core/auto_generated/qgsapplication.sip.in
@@ -801,7 +801,12 @@ Set a single custom expression variable.
 
     int maxConcurrentConnectionsPerPool() const;
 %Docstring
-The maximum number of concurrent connections per connections pool
+The maximum number of concurrent connections per connections pool.
+
+.. note::
+
+   QGIS may in some situations allocate more than this amount
+   of connections to avoid deadlocks.
 
 .. versionadded:: 3.4
 %End

diff --git a/src/core/qgsapplication.cpp b/src/core/qgsapplication.cpp
@@ -85,7 +85,7 @@
 #include <cpl_conv.h> // for setting gdal options
 #include <sqlite3.h>
 
-#define CONN_POOL_MAX_CONCURRENT_CONNS      6
+#define CONN_POOL_MAX_CONCURRENT_CONNS      4
 
 QObject *ABISYM( QgsApplication::mFileOpenEventReceiver );
 QStringList ABISYM( QgsApplication::mFileOpenEventList );

diff --git a/src/core/qgsapplication.h b/src/core/qgsapplication.h
@@ -733,7 +733,10 @@ class CORE_EXPORT QgsApplication : public QApplication
     static void setCustomVariable( const QString &name, const QVariant &value );
 
     /**
-     * The maximum number of concurrent connections per connections pool
+     * The maximum number of concurrent connections per connections pool.
+     *
+     * \note QGIS may in some situations allocate more than this amount
+     *       of connections to avoid deadlocks.
      *
      * \since QGIS 3.4
      */

diff --git a/src/core/qgsconnectionpool.h b/src/core/qgsconnectionpool.h
@@ -31,6 +31,7 @@
 
 
 #define CONN_POOL_EXPIRATION_TIME           60    // in seconds
+#define CONN_POOL_SPARE_CONNECTIONS          2    // number of spare connections in case all the base connections are used but we have a nested request with the risk of a deadlock
 
 
 /**
@@ -67,7 +68,7 @@ class QgsConnectionPoolGroup
 
     QgsConnectionPoolGroup( const QString &ci )
       : connInfo( ci )
-      , sem( QgsApplication::instance()->maxConcurrentConnectionsPerPool() )
+      , sem( QgsApplication::instance()->maxConcurrentConnectionsPerPool() + CONN_POOL_SPARE_CONNECTIONS )
     {
     }