n2vc/juju_watcher.py

   1 # Copyright 2020 Canonical Ltd.
   2 #
   3 # Licensed under the Apache License, Version 2.0 (the "License");
   4 # you may not use this file except in compliance with the License.
   5 # You may obtain a copy of the License at
   6 #
   7 #     http://www.apache.org/licenses/LICENSE-2.0
   8 #
   9 #     Unless required by applicable law or agreed to in writing, software
  10 #     distributed under the License is distributed on an "AS IS" BASIS,
  11 #     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 #     See the License for the specific language governing permissions and
  13 #     limitations under the License.
  14
  15 import asyncio
  16 import time
  17 from juju.client import client
  18 from n2vc.exceptions import EntityInvalidException
  19 from n2vc.n2vc_conn import N2VCConnector
  20 from juju.model import ModelEntity, Model
  21 from juju.client.overrides import Delta
  22 from juju.status import derive_status
  23 from juju.application import Application
  24 from websockets.exceptions import ConnectionClosed
  25 import logging
  26
  27 logger = logging.getLogger("__main__")
  28
  29
  30 def status(application: Application) -> str:
  31     unit_status = []
  32     for unit in application.units:
  33         unit_status.append(unit.workload_status)
  34     return derive_status(unit_status)
  35
  36
  37 def entity_ready(entity: ModelEntity) -> bool:
  38     entity_type = entity.entity_type
  39     if entity_type == "machine":
  40         return entity.agent_status in ["started"]
  41     elif entity_type == "action":
  42         return entity.status in ["completed", "failed", "cancelled"]
  43     elif entity_type == "application":
  44         # Workaround for bug: https://github.com/juju/python-libjuju/issues/441
  45         return status(entity) in ["active", "blocked"]
  46     else:
  47         raise EntityInvalidException("Unknown entity type: {}".format(entity_type))
  48
  49
  50 class JujuModelWatcher:
  51     @staticmethod
  52     async def wait_for(
  53         model,
  54         entity: ModelEntity,
  55         progress_timeout: float = 3600,
  56         total_timeout: float = 3600,
  57         db_dict: dict = None,
  58         n2vc: N2VCConnector = None,
  59     ):
  60         """
  61         Wait for entity to reach its final state.
  62
  63         :param: model:              Model to observe
  64         :param: entity:             Entity object
  65         :param: progress_timeout:   Maximum time between two updates in the model
  66         :param: total_timeout:      Timeout for the entity to be active
  67         :param: db_dict:            Dictionary with data of the DB to write the updates
  68         :param: n2vc:               N2VC Connector objector
  69
  70         :raises: asyncio.TimeoutError when timeout reaches
  71         """
  72
  73         if progress_timeout is None:
  74             progress_timeout = 3600.0
  75         if total_timeout is None:
  76             total_timeout = 3600.0
  77
  78         entity_type = entity.entity_type
  79         if entity_type not in ["application", "action", "machine"]:
  80             raise EntityInvalidException("Unknown entity type: {}".format(entity_type))
  81
  82         # Coroutine to wait until the entity reaches the final state
  83         wait_for_entity = asyncio.ensure_future(
  84             asyncio.wait_for(
  85                 model.block_until(lambda: entity_ready(entity)), timeout=total_timeout,
  86             )
  87         )
  88
  89         # Coroutine to watch the model for changes (and write them to DB)
  90         watcher = asyncio.ensure_future(
  91             JujuModelWatcher.model_watcher(
  92                 model,
  93                 entity_id=entity.entity_id,
  94                 entity_type=entity_type,
  95                 timeout=progress_timeout,
  96                 db_dict=db_dict,
  97                 n2vc=n2vc,
  98             )
  99         )
 100
 101         tasks = [wait_for_entity, watcher]
 102         try:
 103             # Execute tasks, and stop when the first is finished
 104             # The watcher task won't never finish (unless it timeouts)
 105             await asyncio.wait(tasks, return_when=asyncio.FIRST_COMPLETED)
 106         except Exception as e:
 107             raise e
 108         finally:
 109             # Cancel tasks
 110             for task in tasks:
 111                 task.cancel()
 112
 113     @staticmethod
 114     async def model_watcher(
 115         model: Model,
 116         entity_id: str,
 117         entity_type: str,
 118         timeout: float,
 119         db_dict: dict = None,
 120         n2vc: N2VCConnector = None,
 121     ):
 122         """
 123         Observes the changes related to an specific entity in a model
 124
 125         :param: model:          Model to observe
 126         :param: entity_id:      ID of the entity to be observed
 127         :param: entity_type:    Entity Type (p.e. "application", "machine, and "action")
 128         :param: timeout:        Maximum time between two updates in the model
 129         :param: db_dict:        Dictionary with data of the DB to write the updates
 130         :param: n2vc:           N2VC Connector objector
 131
 132         :raises: asyncio.TimeoutError when timeout reaches
 133         """
 134
 135         allwatcher = client.AllWatcherFacade.from_connection(model.connection())
 136
 137         # Genenerate array with entity types to listen
 138         entity_types = (
 139             [entity_type, "unit"]
 140             if entity_type == "application"  # TODO: Add "action" too
 141             else [entity_type]
 142         )
 143
 144         # Get time when it should timeout
 145         timeout_end = time.time() + timeout
 146
 147         try:
 148             while True:
 149                 change = await allwatcher.Next()
 150                 for delta in change.deltas:
 151                     write = False
 152                     delta_entity = None
 153
 154                     # Get delta EntityType
 155                     delta_entity = delta.entity
 156
 157                     if delta_entity in entity_types:
 158                         # Get entity id
 159                         if entity_type == "application":
 160                             id = (
 161                                 delta.data["application"]
 162                                 if delta_entity == "unit"
 163                                 else delta.data["name"]
 164                             )
 165                         else:
 166                             id = delta.data["id"]
 167
 168                         # Write if the entity id match
 169                         write = True if id == entity_id else False
 170
 171                         # Update timeout
 172                         timeout_end = time.time() + timeout
 173                         (
 174                             status,
 175                             status_message,
 176                             vca_status,
 177                         ) = JujuModelWatcher.get_status(delta)
 178
 179                         if write and n2vc is not None and db_dict:
 180                             # Write status to DB
 181                             status = n2vc.osm_status(delta_entity, status)
 182                             await n2vc.write_app_status_to_db(
 183                                 db_dict=db_dict,
 184                                 status=status,
 185                                 detailed_status=status_message,
 186                                 vca_status=vca_status,
 187                                 entity_type=delta_entity,
 188                             )
 189                 # Check if timeout
 190                 if time.time() > timeout_end:
 191                     raise asyncio.TimeoutError()
 192         except ConnectionClosed:
 193             pass
 194             # This is expected to happen when the
 195             # entity reaches its final state, because
 196             # the model connection is closed afterwards
 197
 198     @staticmethod
 199     def get_status(delta: Delta) -> (str, str, str):
 200         """
 201         Get status from delta
 202
 203         :param: delta:          Delta generated by the allwatcher
 204         :param: entity_type:    Entity Type (p.e. "application", "machine, and "action")
 205
 206         :return (status, message, vca_status)
 207         """
 208         if delta.entity == "machine":
 209             return (
 210                 delta.data["agent-status"]["current"],
 211                 delta.data["instance-status"]["message"],
 212                 delta.data["instance-status"]["current"],
 213             )
 214         elif delta.entity == "action":
 215             return (
 216                 delta.data["status"],
 217                 delta.data["status"],
 218                 delta.data["status"],
 219             )
 220         elif delta.entity == "application":
 221             return (
 222                 delta.data["status"]["current"],
 223                 delta.data["status"]["message"],
 224                 delta.data["status"]["current"],
 225             )
 226         elif delta.entity == "unit":
 227             return (
 228                 delta.data["workload-status"]["current"],
 229                 delta.data["workload-status"]["message"],
 230                 delta.data["workload-status"]["current"],
 231             )