How to send a Slack notification when there's a recording to watch

Paul D'Ambra

Oct 25, 2024

session replay

Sometimes it's important to watch recordings as soon as they are available. You can take advantage of a little custom code and our new Hog powered functions to receive a Slack notification every time there's a new recording.

Prerequisites

You'll need:

PostHog Cloud or a self-hosted PostHog instance
A little custom code when you start posthog-js
A destination sending to Slack

Data pipeline realtime destinations

We'll be using PostHog's data pipelines to react to events in realtime, sending messages to destinations like Slack, Airtable, and many more.

This enables us to send an event to PostHog from a user's browser when we detect a recording that we want to act on and have that converted to a message to a Slack channel.

A little custom code

When you start posthog-js, we can add code once the library is loaded to watch for the condition that for your app means the recording is ready to watch.

Here we'll wait until a recording has been idle for 5 minutes, but you might wait for some time after starting or use the onCapture hook to send a Slack message when a user experiences a $exception event.

JavaScript

posthog.init('<ph_project_api_key>', {
    api_host: 'https://us.i.posthog.com',
    defaults: '2025-05-24',
    loaded: (ph) => {
      let checkInterval

      // this will be called every time a new sesson starts
      ph.onSessionId((sessionId) => {
        clearInterval(checkInterval)

        // setup a check for the condition that means the recording is interesting enough to be watched
        checkInterval = setInterval(() => {
          // we want to read the session data, but not change it, so we pass `true`
          const { 
            lastActivityTimestamp, 
            // or maybe sessionStartTimestamp, 
            sessionId 
           } = ph.sessionManager.checkAndGetSessionAndWindowId(true)
            
            const sinceLastActivity = Math.abs(new Date().getTime() - lastActivityTimestamp)
            const fiveMinutesInMillis = 5 * 60 * 1000
            if (sinceLastActivity > fiveMinutesInMillis) {
                // capture an event that will be used to trigger the posthog destination
              ph.capture('session_idle_for_five_minutes', {
                sessionURL: ph.get_session_replay_url({ withTimestamp: true }),
                idleSessionId: sessionId,
              })

              // clear the interval so we only send the event once
              clearInterval(checkInterval)
            }
          
        }, 5000)
      })
    }
  })

Now, for every session this instance of PostHog starts, whenever it first sees 5 minutes of inactivity, it sends an event with the session ID and URL for the recording.

A CDP destination

You can see how to setup a Slack destination in our docs here

In this case, we want to set the event trigger to the event emitted above:

Set the event trigger to the event session_idle_for_five_minutes.
If you use our replay ingestion controls, not all sessions are recorded. You can add a filter for session_recording_start_reason is set to only react to sessions where recording is running.

Finally, you can change the templated message we send to Slack. Here we add a button to jump to the person or straight to the recording:

Hog

[
  {
    "text": {
      "text": "*{person.name}* has a recording available to watch",
      "type": "mrkdwn"
    },
    "type": "section"
  },
  {
    "type": "actions",
    "elements": [
      {
        "url": "{person.url}",
        "text": {
          "text": "View Person in PostHog",
          "type": "plain_text"
        },
        "type": "button"
      },
      {
        "url": "{event.properties.sessionURL}",
        "text": {
          "text": "Replay URL",
          "type": "plain_text"
        },
        "type": "button"
      }
    ]
  }
]

How to send a Slack notification when there's a recording to watch

Contents

Prerequisites

Data pipeline realtime destinations

A little custom code

A CDP destination

Product for Engineers

Community questions