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.

    Supported event types:

    event type

    description

    monitoring_event

    Event contains monitoring points for sending to a custom monitoring system

    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.

  • 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_api/plugins directory of the service. The plugin filename should be added to the LUNA_API_ACTIVE_PLUGINS configuration setting.