Get notified when a Colab cell finishes, crashes or disconnects

Colab's built-in browser notification

Colab can show a browser notification when a cell finishes while you are looking at another tab. You turn it on in Colab's settings, and it applies to all cells rather than one.

For the popup to appear, notifications must be allowed in two places:

• Your browser's site settings for colab.research.google.com
• Your operating system's settings for the browser itself

In Colab's issue tracker in August 2023, a user had Chrome set up correctly and still saw nothing; macOS was blocking notifications from Chrome. This alert only fires while the Colab tab stays open on your computer, and it never reaches your phone.

Play a sound when the cell ends

If you stay within earshot, end the cell with a beep. IPython's Audio object with autoplay=True plays a generated tone in the notebook output. Chrome only allows autoplay with sound after you have interacted with the site, so run a short test cell before the long job.

import numpy as np
from IPython.display import Audio, display


def beep(seconds=0.5, freq=880, rate=22050):
    t = np.linspace(0, seconds, int(rate * seconds), endpoint=False)
    display(Audio(np.sin(2 * np.pi * freq * t), rate=rate, autoplay=True))


train()
beep()

Send a phone alert from the last line

To get an alert on your phone, post to a Discord webhook or a Telegram bot at the end of the cell. Wrap the work in try/except so a crash sends a message too.

• Keep the webhook URL or bot token in Colab's Secrets panel and read it with google.colab.userdata.get(). Secrets are only available when the notebook runs from the Colab UI.
• A Discord webhook takes JSON with content up to 2,000 characters.
• Telegram's sendMessage takes text from 1 to 4,096 characters.

import requests
from google.colab import userdata

DISCORD_WEBHOOK_URL = userdata.get("DISCORD_WEBHOOK_URL")


def send(text):
    try:
        requests.post(DISCORD_WEBHOOK_URL, json={"content": text[:2000]}, timeout=10)
    except requests.RequestException as exc:
        print(f"notification failed: {exc!r}")


try:
    train()
except Exception as exc:
    send(f"Colab cell crashed: {exc!r}")
    raise
else:
    send("Colab cell finished")

When the runtime disconnects, nothing runs

Free Colab notebooks run for at most 12 hours, depending on availability and usage patterns, and idle runtimes time out sooner. Colab doesn't publish the idle timeout. Colab Pro+ supports continuous execution for up to 24 hours if you have enough compute units, and idle timeouts only apply once code execution ends.

When a runtime disconnects or is reclaimed, the rest of the cell never runs, so a notification on the last line never fires. To hear about a dead runtime, something outside the notebook has to notice the silence.

A notebook kernel keeps running after the cell ends and IPython handles cell exceptions itself, so the two end_run() calls report the result. Use the drop-in import in notebooks, since the tqdm.notebook widget bar is not streamed.

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