proxy: Support slave removal

Additionally timestamp is updated on each slave removal.

slapos/proxy/views.py

@@ -758,6 +758,14 @@ def requestSlave(software_release, software_type, partition_reference, partition
   # Add slave to partition slave_list if not present else replace information
   slave_updated_or_added = False
   slave_instance_list = partition['slave_instance_list']
+  if requested_state == 'destroyed':
+    if slave_instance_list:
+      slave_instance_list = loads(slave_instance_list.encode('utf-8'))
+    before_count = len(slave_instance_list)
+    slave_instance_list = [x for x in slave_instance_list if x['slave_reference'] != slave_reference]
+    if before_count != len(slave_instance_list):
+      slave_updated_or_added = True
+  else:
     if slave_instance_list:
       slave_instance_list = loads(slave_instance_list.encode('utf-8'))
       for i, x in enumerate(slave_instance_list):

slapos/tests/test_slapproxy.py

@@ -916,6 +916,29 @@ class TestSlaveRequest(MasterMixin):
     self.assertEqual(len(after._parameter_dict['slave_instance_list']), 2)
     self.assertEqual(before_timestamp, after_timestamp, 'No-op change of the slave shall not change the timestamp')
 
+  def test_slave_request_destroyed(self):
+    self.format_for_number_of_partitions(1)
+    # Provide partition
+    master_partition = self.request('http://sr//', None, 'MyMasterInstance', 'slappart4')
+    def getPartition():
+      return self.getFullComputerInformation()._computer_partition_list[0]
+    def getTimestamp(partition):
+      return float(partition._parameter_dict['timestamp'])
+
+    self.request('http://sr//', None, 'MyFirstSlave', shared=True)
+    self.request('http://sr//', None, 'MySecondSlave', shared=True)
+    after = getPartition()
+    self.assertEqual(len(after._parameter_dict['slave_instance_list']), 2)
+    before_timestamp = getTimestamp(after)
+
+    time.sleep(.1)
+    self.request('http://sr//', None, 'MyFirstSlave', shared=True, state='destroyed')
+    after = getPartition()
+    after_timestamp = getTimestamp(after)
+    self.assertEqual(len(after._parameter_dict['slave_instance_list']), 1)
+    self.assertLess(before_timestamp, after_timestamp, 'Slave destroy shall result with timestamp update')
+    self.assertEqual(after._parameter_dict['slave_instance_list'][0]['slave_reference'], '_MySecondSlave')
+
 
   def test_slave_request_set_parameters_are_updated(self):
     """