n2vc/juju_watcher.py

# Copyright 2020 Canonical Ltd.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
#     Unless required by applicable law or agreed to in writing, software
#     distributed under the License is distributed on an "AS IS" BASIS,
#     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#     See the License for the specific language governing permissions and
#     limitations under the License.

import asyncio
import time
from juju.client import client
from n2vc.exceptions import EntityInvalidException
from n2vc.n2vc_conn import N2VCConnector
from juju.model import ModelEntity, Model
from juju.client.overrides import Delta
from juju.status import derive_status
from juju.application import Application
from websockets.exceptions import ConnectionClosed
import logging

logger = logging.getLogger("__main__")


def status(application: Application) -> str:
    unit_status = []
    for unit in application.units:
        unit_status.append(unit.workload_status)
    return derive_status(unit_status)


def entity_ready(entity: ModelEntity) -> bool:
    entity_type = entity.entity_type
    if entity_type == "machine":
        return entity.agent_status in ["started"]
    elif entity_type == "action":
        return entity.status in ["completed", "failed", "cancelled"]
    elif entity_type == "application":
        # Workaround for bug: https://github.com/juju/python-libjuju/issues/441
        return status(entity) in ["active", "blocked"]
    else:
        raise EntityInvalidException("Unknown entity type: {}".format(entity_type))


class JujuModelWatcher:
    @staticmethod
    async def wait_for(
        model,
        entity: ModelEntity,
        progress_timeout: float = 3600,
        total_timeout: float = 3600,
        db_dict: dict = None,
        n2vc: N2VCConnector = None,
    ):
        """
        Wait for entity to reach its final state.

        :param: model:              Model to observe
        :param: entity:             Entity object
        :param: progress_timeout:   Maximum time between two updates in the model
        :param: total_timeout:      Timeout for the entity to be active
        :param: db_dict:            Dictionary with data of the DB to write the updates
        :param: n2vc:               N2VC Connector objector

        :raises: asyncio.TimeoutError when timeout reaches
        """

        if progress_timeout is None:
            progress_timeout = 3600.0
        if total_timeout is None:
            total_timeout = 3600.0

        entity_type = entity.entity_type
        if entity_type not in ["application", "action", "machine"]:
            raise EntityInvalidException("Unknown entity type: {}".format(entity_type))

        # Coroutine to wait until the entity reaches the final state
        wait_for_entity = asyncio.ensure_future(
            asyncio.wait_for(
                model.block_until(lambda: entity_ready(entity)), timeout=total_timeout,
            )
        )

        # Coroutine to watch the model for changes (and write them to DB)
        watcher = asyncio.ensure_future(
            JujuModelWatcher.model_watcher(
                model,
                entity_id=entity.entity_id,
                entity_type=entity_type,
                timeout=progress_timeout,
                db_dict=db_dict,
                n2vc=n2vc,
            )
        )

        tasks = [wait_for_entity, watcher]
        try:
            # Execute tasks, and stop when the first is finished
            # The watcher task won't never finish (unless it timeouts)
            await asyncio.wait(tasks, return_when=asyncio.FIRST_COMPLETED)
        except Exception as e:
            raise e
        finally:
            # Cancel tasks
            for task in tasks:
                task.cancel()

    @staticmethod
    async def model_watcher(
        model: Model,
        entity_id: str,
        entity_type: str,
        timeout: float,
        db_dict: dict = None,
        n2vc: N2VCConnector = None,
    ):
        """
        Observes the changes related to an specific entity in a model

        :param: model:          Model to observe
        :param: entity_id:      ID of the entity to be observed
        :param: entity_type:    Entity Type (p.e. "application", "machine, and "action")
        :param: timeout:        Maximum time between two updates in the model
        :param: db_dict:        Dictionary with data of the DB to write the updates
        :param: n2vc:           N2VC Connector objector

        :raises: asyncio.TimeoutError when timeout reaches
        """

        allwatcher = client.AllWatcherFacade.from_connection(model.connection())

        # Genenerate array with entity types to listen
        entity_types = (
            [entity_type, "unit"]
            if entity_type == "application"  # TODO: Add "action" too
            else [entity_type]
        )

        # Get time when it should timeout
        timeout_end = time.time() + timeout

        try:
            while True:
                change = await allwatcher.Next()
                for delta in change.deltas:
                    write = False
                    delta_entity = None

                    # Get delta EntityType
                    delta_entity = delta.entity

                    if delta_entity in entity_types:
                        # Get entity id
                        if entity_type == "application":
                            id = (
                                delta.data["application"]
                                if delta_entity == "unit"
                                else delta.data["name"]
                            )
                        else:
                            id = delta.data["id"]

                        # Write if the entity id match
                        write = True if id == entity_id else False

                        # Update timeout
                        timeout_end = time.time() + timeout
                        (
                            status,
                            status_message,
                            vca_status,
                        ) = JujuModelWatcher.get_status(delta)

                        if write and n2vc is not None and db_dict:
                            # Write status to DB
                            status = n2vc.osm_status(delta_entity, status)
                            await n2vc.write_app_status_to_db(
                                db_dict=db_dict,
                                status=status,
                                detailed_status=status_message,
                                vca_status=vca_status,
                                entity_type=delta_entity,
                            )
                # Check if timeout
                if time.time() > timeout_end:
                    raise asyncio.TimeoutError()
        except ConnectionClosed:
            pass
            # This is expected to happen when the
            # entity reaches its final state, because
            # the model connection is closed afterwards

    @staticmethod
    def get_status(delta: Delta) -> (str, str, str):
        """
        Get status from delta

        :param: delta:          Delta generated by the allwatcher
        :param: entity_type:    Entity Type (p.e. "application", "machine, and "action")

        :return (status, message, vca_status)
        """
        if delta.entity == "machine":
            return (
                delta.data["agent-status"]["current"],
                delta.data["instance-status"]["message"],
                delta.data["instance-status"]["current"],
            )
        elif delta.entity == "action":
            return (
                delta.data["status"],
                delta.data["status"],
                delta.data["status"],
            )
        elif delta.entity == "application":
            return (
                delta.data["status"]["current"],
                delta.data["status"]["message"],
                delta.data["status"]["current"],
            )
        elif delta.entity == "unit":
            return (
                delta.data["workload-status"]["current"],
                delta.data["workload-status"]["message"],
                delta.data["workload-status"]["current"],
            )