dd-trace/packages/dd-trace/src/plugins/plugin.js

Datadog APM tracing client for JavaScript

'use strict'

const dc = require('diagnostics_channel')
const { storage } = require('../../../datadog-core')

class Subscription {
  constructor (event, handler) {
    this._channel = dc.channel(event)
    this._handler = (message, name) => {
      const store = storage.getStore()

      if (!store || !store.noop) {
        handler(message, name)
      }
    }
  }

  enable () {
    this._channel.subscribe(this._handler)
  }

  disable () {
    this._channel.unsubscribe(this._handler)
  }
}

module.exports = class Plugin {
  constructor (tracer) {
    this._subscriptions = []
    this._enabled = false
    this._storeStack = []
    this._tracer = tracer
  }

  get tracer () {
    return this._tracer._tracer
  }

  enter (span, store) {
    store = store || storage.getStore()
    this._storeStack.push(store)
    storage.enterWith({ ...store, span })
  }

  exit () {
    storage.enterWith(this._storeStack.pop())
  }

  addSub (channelName, handler) {
    this._subscriptions.push(new Subscription(channelName, handler))
  }

  configure (config) {
    this.config = config
    if (config.enabled && !this._enabled) {
      this._enabled = true
      this._subscriptions.forEach(sub => sub.enable())
    } else if (!config.enabled && this._enabled) {
      this._enabled = false
      this._subscriptions.forEach(sub => sub.disable())
    }
  }
}