[#4878] Allow custom CKAN callback URL for the DataPusher

The DataPusher pings back CKAN when performing or finishing
a job (calling the datapusher_hook action), and it does so
via an HTTP request to the host defined in ckan.site_url.

There are a number of scenarios where this does not work, eg:

* CKAN and DataPusher sitting behind a Firewall that doesn't
  allow external requests
* Standard Docker compose setup for development where the
  ckan.site_url is http://localhost:5000 or similar

This change adds a new config option that allows to define an
alternative internal URL that DataPusher can reach.

ckanext/datapusher/logic/action.py

@@ -62,7 +62,14 @@ def datapusher_submit(context, data_dict):
     datapusher_url = config.get('ckan.datapusher.url')
 
     site_url = h.url_for('/', qualified=True)
-    callback_url = h.url_for('/api/3/action/datapusher_hook', qualified=True)
+
+    callback_url_base = config.get('ckan.datapusher.callback_url_base')
+    if callback_url_base:
+        callback_url = urlparse.urljoin(
+            callback_url_base.rstrip('/'), '/api/3/action/datapusher_hook')
+    else:
+        callback_url = h.url_for(
+            '/api/3/action/datapusher_hook', qualified=True)
 
     user = p.toolkit.get_action('user_show')(context, {'id': context['user']})
 

doc/maintaining/configuration.rst

@@ -1490,6 +1490,22 @@ running on port 8800. If you want to manually install the DataPusher, follow
 the installation `instructions <http://docs.ckan.org/projects/datapusher>`_.
 
 
+.. _ckan.datapusher.callback_url_base:
+
+ckan.datapusher.url
+^^^^^^^^^^^^^^^^^^^
+
+Example::
+
+  ckan.datapusher.callback_url_base = http://ckan:5000/
+
+Default value: Value of ``ckan.site_url``
+
+Alternative callback URL for DataPusher when performing a request to CKAN. This is
+useful on scenarios where the host where DataPusher is running can not access the
+public CKAN site URL.
+
+
 .. _ckan.datapusher.assume_task_stale_after:
 
 ckan.datapusher.assume_task_stale_after