Making QGIS layer update from changed data source

This is related to the introduction of the OGR connection pool. [1]

Before QGIS 2.10, a file was reopened on every single access (e.g. repaint).

Since QGIS 2.10 the file handle is kept open and this means if a file is replaced the handle still points to the old file on Unix based systems.

QGIS 2.10: workaround

Unfortunately there is no API to nicely force QGIS to reopen the file in QGIS 2.10. As a workaround you can use an ugly hack:

layer.dataProvider().changeAttributeValues( { -1: { 0: 0 } } )
layer.triggerRepaint()

QGIS 2.12: solution

I just introduced a new method which will be available starting from QGIS 2.12:

layer.dataProvider().forceReload()
layer.triggerRepaint()

General approach

If you have the possibility to control how the file is being overwritten you can open the existing files with write permissions and change the content instead of replacing the files completely (delete/recreate) on disk.

[1] The connection pool was introduced to significantly speed up access to certain data sources.

If you pan or otherwise refresh the map it should update.

This article says that you can use the following in PyQGIS:

myLayer.triggerRepaint()

To refresh all layers following function can be used:

def refresh_layers(self):
    for layer in qgis.utils.iface.mapCanvas().layers():
         layer.triggerRepaint()