Events not firing

[hansy]

I'm not sure why, but no events are being sent via the track function.

import Mixpanel from 'mixpanel'

const mixpanel = Mixpanel.init(process.env.MIXPANEL_TOKEN)
mixpanel.track('testEvent', { distinct_id: "abc123" })

I don't even know how to debug this. I even tried adding a callback argument to look for an error, but nothing:

mixpanel.track('testEvent', { distinct_id: "abc123" }, (err) => {
  console.log(err) // no output
  console.log('Something') // no output
})

What am I doing wrong?

System info:
Mixpanel v0.13.0
Node v14.5.0
MacOS Catalina 10.15.6

[hansy]

Since I was using this in an async serverless function I needed to wait for the Mixpanel request to complete. I ended up turning track into a Promise via promisify to await the Mixpanel response.

[abierbaum]

@hansy Thanks for this tip. Saved me a ton of time. I really miss having promises in this API.

[steviec]

It's kinda ridiculous. The library just doesn't work in AWS lambda at all unless you wrap it since the callback doesn't have time to fire before the lambda ends.

[walterholohan]

If anyone wants an example of how to create a promise wrapper here is one.

/**
 * Due to the fact that the mixpanel library does not support promises
 * we have to wrap the track function in a promise. Otherwise the
 * lambda function will finish before the request has been sent.
 * @param event - The event to track
 * @param properties - The properties to track with the event
 * @param mixpanel - The mixpanel instance
 * @param userId - The user id
 * @returns A promise that resolves when the track request has been sent
 */
async function mixpanelAsyncTrack({
  event,
  properties,
  mixpanel,
  userId,
}: {
  event: string
  userId: string
  properties?: { [key: string]: string | number | boolean | undefined }
  mixpanel: Mixpanel.Mixpanel
}) {
  return new Promise((resolve, reject) => {
    mixpanel.track(event, { distinct_id: userId, properties }, (err) => {
      if (err) {
        reject(err)
      } else {
        resolve('success')
      }
    })
  })
}

[Collin0810]

@walterholohan Thanks! Have been struggling for hours to set up Mixpanel event tracking in a NextJS API route (which gets turned into a serverless lambda function when deploying to Vercel into production). This works great!