Make spare connections more explicit

m-kuhn · m-kuhn · commit 58da97590e2b · 2018-08-08T07:18:47.000+02:00
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 )
     {
     }
 

Original file line number	Diff line number	Diff line change
`@@ -31,6 +31,7 @@`
`31`	`31`
`32`	`32`
`33`	`33`	`#define CONN_POOL_EXPIRATION_TIME 60 // in seconds`
	`34`	`+#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`
`34`	`35`
`35`	`36`
`36`	`37`	`/**`
`@@ -67,7 +68,7 @@ class QgsConnectionPoolGroup`
`67`	`68`
`68`	`69`	`QgsConnectionPoolGroup( const QString &ci )`
`69`	`70`	`: connInfo( ci )`
`70`		`- , sem( QgsApplication::instance()->maxConcurrentConnectionsPerPool() )`
	`71`	`+ , sem( QgsApplication::instance()->maxConcurrentConnectionsPerPool() + CONN_POOL_SPARE_CONNECTIONS )`
`71`	`72`	`{`
`72`	`73`	`}`
`73`	`74`