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
  """
  import asyncio
  from abc import abstractmethod
  
  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, point: "MonitoringPoint", logger) -> None:
          """
          All plugins must realize this method.
  
          This function call after end of request
  
          Args:
              point: point for monitoring
              logger: logger
          """
  
      async def handleEvent(self, points: list["MonitoringPoint"], logger):
          await asyncio.gather(*[self.flushPointToMonitoring(point, logger) for point in points])
  
  
  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: ClientSession | None = 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, point: "MonitoringPoint", logger) -> None:
          """
          Callback for sending a request monitoring data.
  
          Args:
              point: point for monitoring
              logger: logger
          """
          logger.debug(f"Plugin 'flushPointToMonitoring' get point, series: {point.series}, 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 luna_plugins.base.plugins_meta.base_plugins import BaseBackgroundHandler, BaseBackgroundPlugin, pluginHTTPResponse
  
  
  class HandlerExample(BaseBackgroundHandler):
      """
      Handler example
      """
  
      async def get(self, request):  # pylint: disable=unused-argument
          """
          Method get example.
  
          Returns:
              response
          """
          return self.response(body="I am teapot", headers={"Content-Type": "text/plain"}, statusCode=418)
  
  
  def anotherHandlerExample(request):  # pylint: disable=unused-argument
      """Standalone handler example"""
      return pluginHTTPResponse(statusCode=200, body="T800", headers={"Content-Type": "text/plain"})
  
  
  class BackgroundPluginExample(BaseBackgroundPlugin):
      """
      Background plugin example.
  
      Create background task and add a route.
      """
  
      def __init__(self, app: "LunaApplication"):
          super().__init__(app)
          self.task: Task | None = None
          self.temperature = 0
  
      async def initialize(self):
          """
          Initialize plugin
          """
          self.addRoute("/teapot", HandlerExample)
          self.addRoute("/teapot/version", anotherHandlerExample, methods={"get"})
  
      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_backport4/plugins directory of the service. The plugin filename should be added to the LUNA_BACKPORT4_ACTIVE_PLUGINS configuration setting.