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 logging import Logger
  from typing import List, Optional
  
  from aiohttp import ClientSession
  from luna_plugins.base.plugins_meta.base_plugins import BaseEventPlugin
  
  
  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 luna_plugins.base.plugins_meta.base_plugins import BaseBackgroundPlugin
  from sanic.response import HTTPResponse
  
  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.router.reset()
          app.addRoutes([("/teapot", HandlerExample)])
          app.finalize()
          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.