Plugins¶

The service supports the system of plugins. Plugins must be written in the Python programming language.

Plugin types¶

There are two sorts of plugins:

On event plugin. The plugin is triggered when an event occurs. The plugin should implement a callback function. This function is called on each event of the corresponding type. The set of event types is defined by the service developers.

event type

description

monitoring_event

Event contains monitoring points for sending to a custom monitoring system

sending_event

Event contains handler-generated event data for sending to the third-party source

event type	description
monitoring_event	Event contains monitoring points for sending to a custom monitoring system
sending_event	Event contains handler-generated event data for sending to the third-party source

Monitoring plugin example:

"""
Module request monitoring plugin example
"""
from abc import abstractmethod
from typing import List, Optional

from aiohttp import ClientSession

from crutches_on_wheels.monitoring.points import BaseRequestMonitoringPoint
from crutches_on_wheels.plugins.plugins_meta.base_plugins import BaseEventPlugin
from crutches_on_wheels.utils.log import Logger
from crutches_on_wheels.web.application import LunaApplication


class BaseRequestMonitoringPlugin(BaseEventPlugin):
    """
    Base class for requests monitoring.
    """

    # event name for triggering callback
    eventName = "monitoring_event"

    @abstractmethod
    async def flushPointToMonitoring(self, points: List[BaseRequestMonitoringPoint], logger: Logger) -> None:
        """
        All plugins must realize this method.

        This function call after end of request

        Args:
            points: points for monitoring which corresponding the request
            logger: logger
        """

    async def handleEvent(  # pylint: disable-msg=C0204,W0221
        self, points: List[BaseRequestMonitoringPoint], logger: Logger
    ):
        await self.flushPointToMonitoring(points=points, logger=logger)


class RequestMonitoringPlugin(BaseRequestMonitoringPlugin):
    """
    Example plugin sends a request data for monitoring to third-party source.
    Only one instance of this class exist during the program execution.
    """

    def __init__(self, app: LunaApplication):
        super().__init__(app)
        self.url = "http://127.0.0.1:5020/1/buckets"
        self.session: Optional[ClientSession] = None
        self.bucket = "plugin_test_bucket"

    async def close(self):
        """
        Stop plugin.

        Close all open connections and ect
        """
        if self.session:
            await self.session.close()

    async def initialize(self):
        """
        Initialize plugin.

        Close all open connections and ect
        """
        self.session = ClientSession()
        async with self.session.post(f"{self.url}?bucket={self.bucket}") as resp:
            if resp.status not in (201, 409):
                response = await resp.json()
                raise RuntimeError(f"failed create bucket, {self.bucket}, response: {response}")

    async def flushPointToMonitoring(self, points: List[BaseRequestMonitoringPoint], logger: Logger) -> None:
        """
        Callback for sending a request monitoring data.

        Args:
            points: point for monitoring which corresponding the request
            logger: logger
        """
        if not points:
            return
        point = points[0]
        logger.debug(
            f"Plugin 'flushPointToMonitoring' get point, request_id: {point.requestId}, "
            f"start time: {point.eventTime}"
        )
        msg = {"tags": point.tags, "fields": point.fields}
        async with self.session.post(f"{self.url}/{self.bucket}/objects", json=msg) as resp:
            logger.info(resp.status)
            logger.info(await resp.text())

This plugin demonstrates the sending of a request monitoring data to another service. All monitoring plugins must implement the BaseRequestMonitoringPlugin abstract class.

Event sending plugin example:

from abc import abstractmethod
from typing import List, Optional, Union

from aiohttp import ClientSession

from classes.event import Event
from classes.schemas.event_raw import RawEvent
from crutches_on_wheels.plugins.plugins_meta.base_plugins import BaseEventPlugin
from crutches_on_wheels.utils.log import Logger
from crutches_on_wheels.web.application import LunaApplication


class BaseEventSendingPlugin(BaseEventPlugin):
    """Base class for event sending."""

    # event name for triggering callback
    eventName = "sending_event"

    @abstractmethod
    async def sendEvents(
        self,
        events: Union[List[Event], List[RawEvent]],
        handlerId: str,
        accountId: str,
        requestId: str,
        createEventTime: str,
        endEventTime: str,
        logger: Logger,
    ) -> None:
        """
        Callback that is triggered on every success request to handlers.

        Args:
            events: event list
            handlerId: handler id
            accountId: account id
            requestId: request id
            createEventTime: event creation time
            endEventTime: event end time
            logger: logger

        """

    async def handleEvent(
        self,
        events: Union[List[Event], List[RawEvent]],
        handlerId: str,
        accountId: str,
        requestId: str,
        createEventTime: str,
        endEventTime: str,
        logger: Logger,
    ):
        """
        Handle events.
        Args:
            events: event list
            handlerId: handler id
            accountId: account id
            requestId: request id
            createEventTime: event creation time
            endEventTime: event end time
            logger: logger

        """
        await self.sendEvents(events, handlerId, accountId, requestId, createEventTime, endEventTime, logger)


class EventSendingPlugin(BaseEventSendingPlugin):
    """Sends events to the third-party source. Only one instance of this class exist during the program execution."""

    def __init__(self, app: LunaApplication):
        super().__init__(app)
        self.url = "http://127.0.0.1:5020/1/buckets"
        self.session: Optional[ClientSession] = None
        self.bucket = "plugin_test_bucket"

    async def close(self):
        """Stop plugin. Close all open connections and etc."""
        if self.session:
            await self.session.close()

    async def initialize(self):
        """Initialize plugin."""
        self.session = ClientSession()
        async with self.session.post(f"{self.url}?bucket={self.bucket}") as resp:
            if resp.status not in (201, 409):
                response = await resp.json()
                raise RuntimeError(f"failed create bucket, {self.bucket}, response: {response}")

    async def sendEvents(
        self,
        events: Union[List[Event], List[RawEvent]],
        handlerId: str,
        accountId: str,
        requestId: str,
        createEventTime: str,
        endEventTime: str,
        logger: Logger,
    ) -> None:

        logger.debug(
            f"Plugin 'EventsOnFinishExampleClass' get events, request_id: {requestId}, "
            f"event_create_time: {createEventTime}, event_end_time: {endEventTime}"
        )
        prepareEvents = []
        for event in events:
            if isinstance(event, Event):
                serializationEvent = event.asDict()
            else:
                serializationEvent = event.asHandlerEventDict()
            prepareEvents.append(serializationEvent)
        msg = {
            "handler_id": handlerId,
            "account_id": accountId,
            "Luna-Request-Id": requestId,
            "events": prepareEvents,
            "event_create_time": createEventTime,
            "event_end_time": endEventTime,
        }
        async with ClientSession() as session:
            async with session.post(f"{self.url}/{self.bucket}/objects", json=msg) as resp:
                logger.debug(resp.status)
                logger.debug(await resp.text())

This plugin demonstrates the sending of a handler generates event data to the third-party source. All event sending plugins must implement the BaseEventSendingPlugin abstract class.

Background plugin. This sort of plugin is intended for background work.

The background plugin can implement:

custom route
background monitoring of service resources
collaboration of an event plugin and a background plugin (batching monitoring points)
connection to other data sources (Redis, RabbitMQ) and their data processing

Plugin example:

"""
Module realizes background plugin example
"""
import asyncio
from asyncio import Task
from typing import Optional

from sanic.response import HTTPResponse

from crutches_on_wheels.plugins.plugins_meta.base_plugins import BaseBackgroundPlugin
from crutches_on_wheels.web.application import LunaApplication
from crutches_on_wheels.web.handlers import BaseHandler


class HandlerExample(BaseHandler):
    """
    Handler example
    """

    async def get(self) -> HTTPResponse:
        """
        Method get example.

        Returns:
            response
        """
        return self.success(body="I am teapot", contentType="text/plain", statusCode=418)

    @property
    def app(self):
        """
        Get app
        Abstract method of `BaseHandler`
        Returns:
            app
        """
        return self.request.app

    @property
    def config(self):
        """
        Get app config
        Abstract method of `BaseHandler`
        Returns:
            app config
        """
        return self.request.app.ctx.serviceConfig


class BackgroundPluginExample(BaseBackgroundPlugin):
    """
    Background plugin example.

    Create background task and add a route.
    """

    def __init__(self, app: LunaApplication):
        super().__init__(app)
        app.addRoutes([("/teapot", HandlerExample)])
        self.task: Optional[Task] = None
        self.temperature = 0

    async def initialize(self):
        """
        Initialize plugin
        """

    async def close(self):
        """
        Stop background process
        Returns:

        """
        if self.task:
            self.task.cancel()

    async def usefulJob(self):
        """
        Some useful  async work
        """
        while True:
            await asyncio.sleep(1)
            self.temperature = min(100, self.temperature + 1)
            if self.temperature < 100:
                self.app.ctx.logger.info(f"I boil water, temperature: {self.temperature}")
            else:
                self.app.ctx.logger.info("boiling water is ready, would you care for a cup of tea?")

    async def start(self):
        """
        Run background process

        .. warning::
            The function suppose that the process is handle in this coroutine. The coroutine must start
            the process only without awaiting a end of the process
        """
        self.task = asyncio.create_task(self.usefulJob())

This plugin demonstrates background work and implements a route. All background plugins must implement the BaseRequestMonitoringPlugin abstract class.

Enable plugin¶

If the user implements a plugin, the file with the plugin should be added to the luna_handlers/plugins directory of the service. The plugin filename should be added to the LUNA_HANDLERS_ACTIVE_PLUGINS configuration setting.

LUNA_HANDLERS_ACTIVE_PLUGINS = [event_sending_plugin_example]

List should contains filenames without extension (.py).