Tools: Solved: Monitor SSL Certificate Expiry With Python And Slack API

Posted on Jan 18

• Originally published at wp.me

TL;DR: SSL certificate expiry is a critical issue causing service outages and reputational damage, often due to manual monitoring inefficiencies. This guide presents an automated, cost-effective solution using Python and the Slack API to proactively monitor domain certificates, calculate their validity, and send timely alerts, ensuring no expiry deadlines are missed.

As a Senior DevOps Engineer, I know the drill: the constant dread of an expiring SSL certificate bringing down a critical service. It is a nightmare scenario that far too many organizations experience, leading to lost revenue, reputational damage, and frantic all-hands-on-deck efforts to restore services. Manual monitoring is tedious, error-prone, and unsustainable, especially as your infrastructure scales. While commercial SaaS solutions exist, they often come with a hefty price tag and might not always integrate seamlessly with your existing workflows.

At TechResolve, we believe in empowering teams with robust, open-source, and cost-effective solutions. This tutorial will walk you through building your own automated SSL certificate expiry monitor using Python and the Slack API. You will learn how to proactively check your domain certificates, calculate their remaining validity, and send timely alerts directly to your Slack channels, ensuring you never miss an expiry deadline again. This DIY approach not only saves costs but also gives you complete control over your monitoring logic and integration points.

Before we dive into the code, ensure you have the following:

The Slack Incoming Webhook URL is the endpoint our Python script will use to send messages to your chosen Slack channel. Follow these steps to generate one:

Our Python script will leverage a couple of external libraries for network requests and SSL certificate parsing. Open your terminal or command prompt and install them using pip:

Now, let’s write the Python code that connects to your domains, fetches their SSL certificates, and determines their expiry status. Create a new Python file, for example, ssl_monitor.py, and add the following code:

Now, let’s enhance our script to send notifications to Slack when a certificate is nearing its expiry. We will define a threshold (e.g., 30 days) and send an alert if a certificate expires within that period.

Modify your ssl_monitor.py file by adding the send_slack_message function and integrating it into the

Source: Dev.to