# HG changeset patch
# User Sebastien Jodogne <s.jodogne@gmail.com>
# Date 1610027616 -3600
# Node ID 2397b0e12bc82c96c144cb24cbf2b2cdff7e7bd8
# Parent  404aca6160f0e041fa330c74b53a97a61b33a672
solution to avoid deadlock in Python OnChange()

diff -r 404aca6160f0 -r 2397b0e12bc8 Sphinx/source/plugins/python.rst
--- a/Sphinx/source/plugins/python.rst	Thu Jan 07 09:03:34 2021 +0100
+++ b/Sphinx/source/plugins/python.rst	Thu Jan 07 14:53:36 2021 +0100
@@ -289,6 +289,24 @@
    thread, passing the pending events to be processed through a
    message queue.
 
+Here is the template of a possible solution to avoid such deadlocks by
+relying on the multithreading primitives of Python::
+
+  import orthanc
+  import threading
+
+  def OnChange(changeType, level, resource):
+      # One can safely invoke the "orthanc" module in this function
+      orthanc.LogWarning("Hello world")
+  
+  def _OnChange(changeType, level, resource):
+      # Invoke the actual "OnChange()" function in a separate thread
+      t = threading.Timer(0, function = OnChange, args = (changeType, level, resource))
+      t.start()
+
+  orthanc.RegisterOnChangeCallback(_OnChange)
+
+   
 
 Accessing the content of a new instance
 .......................................