no changes if new netconf timestamp is same

inventory_provider/juniper.py

@@ -399,3 +399,18 @@ def snmp_community_string(netconf_config):
                 if me in allowed_network:
                     return community.xpath('./name/text()')[0]
     return None
+
+
+def netconf_changed_timestamp(netconf_config):
+    '''
+    <configuration changed-seconds="1549049195" changed-localtime="2019-02-01 19:26:35 UTC">
+    return the last change timestamp published by the config document
+    :param netconf_config: netconf lxml etree document
+    :return: an epoch timestamp (integer number of seconds) or None
+    '''
+    for ts in netconf_config.xpath('/configuration/@changed-seconds'):
+        if re.match(r'^\d+$', ts):
+            return int(ts)
+    logger = logging.getLogger(__name__)
+    logger.warning('no valid timestamp found in netconf configuration')
+    return None

inventory_provider/tasks/worker.py

@@ -311,39 +311,63 @@ def reload_router_config(self, hostname):
             'message': 'loading router netconf data'
         })
 
+    # get the timestamp for the current netconf data
+    current_netconf_timestamp = None
+    netconf_doc = load_netconf_data(hostname)
+    if netconf_doc:
+        current_netconf_timestamp \
+            = juniper.netconf_changed_timestamp(netconf_doc)
+        logger.debug(
+            'current netconf timestamp: %r' % current_netconf_timestamp)
+
+    # load new netconf data
     netconf_refresh_config.apply(args=[hostname])
 
     netconf_doc = load_netconf_data(hostname)
     if netconf_doc is None:
         raise InventoryTaskError(
-            'no netconf data available for %r' % hostname)
+            'failure loading netconf data for %r' % hostname)
+
+    # return if new timestamp is the same as the original timestamp
+    new_netconf_timestamp = juniper.netconf_changed_timestamp(netconf_doc)
+    assert new_netconf_timestamp, \
+        'no timestamp available for new netconf data'
+    if new_netconf_timestamp == current_netconf_timestamp:
+        logger.debug('no netconf change timestamp change, aborting')
+        logger.debug('<<< reload_router_config')
+        return {
+            'task': 'reload_router_config',
+            'hostname': hostname,
+            'message': 'OK (no change)'
+        }
+
+    # clear cached classifier responses for this router, and
+    # refresh peering data
+    self.update_state(
+        state=states.STARTED,
+        meta={
+            'task': 'reload_router_config',
+            'hostname': hostname,
+            'message': 'refreshing peers & clearing cache'
+        })
+    refresh_ix_public_peers(hostname, netconf_doc)
+    refresh_vpn_rr_peers(hostname, netconf_doc)
+    clear_cached_classifier_responses(hostname)
+
+    # load snmp indexes
+    community = juniper.snmp_community_string(netconf_doc)
+    if not community:
+        raise InventoryTaskError(
+            'error extracting community string for %r' % hostname)
     else:
         self.update_state(
             state=states.STARTED,
             meta={
                 'task': 'reload_router_config',
                 'hostname': hostname,
-                'message': 'refreshing peers'
+                'message': 'refreshing snmp interface indexes'
             })
-        refresh_ix_public_peers(hostname, netconf_doc)
-        refresh_vpn_rr_peers(hostname, netconf_doc)
-
-        community = juniper.snmp_community_string(netconf_doc)
-        if not community:
-            raise InventoryTaskError(
-                'error extracting community string for %r' % hostname)
-        else:
-            self.update_state(
-                state=states.STARTED,
-                meta={
-                    'task': 'reload_router_config',
-                    'hostname': hostname,
-                    'message': 'refreshing snmp interface indexes'
-                })
-            snmp_refresh_interfaces.apply(args=[hostname, community])
-
-            # TODO: move this out of else? (i.e. clear even if netconf fails?)
-            clear_cached_classifier_responses(hostname)
+        snmp_refresh_interfaces.apply(args=[hostname, community])
 
     logger.debug('<<< reload_router_config')