Sentry vs Vigilmon: Error Monitoring vs Uptime Monitoring - When to Use Each

Sentry and Vigilmon both monitor your applications, but they answer fundamentally different questions. Understanding the distinction helps you build the right observability stack - and avoid paying for features you already have covered elsewhere.

What Each Tool Does

Sentry is an error monitoring and performance tracking tool:

• Captures exceptions, stack traces, and error context
• Groups related errors into issues
• Tracks error frequency, affected users, and releases
• Shows performance breakdowns (slow DB queries, N+1 problems)
• Monitors JavaScript errors in user browsers

Vigilmon is an uptime and availability monitoring tool:

• Checks if your website/API is reachable from the internet
• Measures HTTP response times and status codes
• Monitors SSL certificate expiry
• Provides public status pages for users
• Sends alerts when your service goes down

The Core Difference: Timing of Detection

When Sentry Wins

Use Sentry when you need to know what broke and why:

• Diagnosing production bugs with full stack traces
• Tracking error rates across releases (did this deploy make things worse?)
• Understanding which users are affected by a bug
• Catching JavaScript errors in browsers
• Performance profiling slow endpoints

When Vigilmon Wins

Use Vigilmon when you need to know if your service is reachable:

• Getting paged immediately when your server is completely down
• Knowing before customers that your site is returning errors
• Monitoring SSL certificate expiry
• Providing a public status page (Sentry doesn't offer this)
• Monitoring third-party APIs and services you depend on
• Checking if a non-coded service (static site, third-party SaaS) is up

The Blind Spots Each Tool Has

Sentry's Blind Spots

• Complete outages: If your server is unreachable, Sentry receives no data (the SDK can't send)
• Non-exception failures: A 503 that bypasses your application code won't generate a Sentry event
• Infrastructure failures: Nginx crash, Docker container exit, server reboot - invisible to Sentry
• External dependencies: Third-party services going down won't appear in Sentry

Vigilmon's Blind Spots

• Application errors: A 200 response with error JSON won't trigger Vigilmon
• User-specific errors: An error affecting 10% of users looks fine if the health endpoint returns 200
• Code-level root cause: Vigilmon tells you the app is down, not why
• Error rates and trends: No grouping or frequency analysis

The Right Stack: Sentry AND Vigilmon Together

The two tools are complementary, not competitive:


User reports issue
|
v
Check Vigilmon: Is the app reachable at all?
|
+--> No (downtime) -> Incident response, check infrastructure
|
+--> Yes (app is up) -> Check Sentry: What errors are occurring?
|
v
Debug with stack traces, fix, deploy


Monthly cost reality:

• Vigilmon free tier: \ (covers most use cases)
• Sentry developer plan: \ (for individuals)
• Together: full observability stack at zero cost for small apps

Migration and Overlap

Some teams use Sentry's "Crons" feature for basic uptime monitoring. This works but has limitations:

• No external uptime checking (Sentry Crons check that a cron job ran, not that a URL is up)
• No SSL monitoring
• No public status pages
• No response time trending

Vigilmon's uptime monitoring is purpose-built and more feature-rich for availability use cases.

Summary

Use Sentry for: error visibility, stack traces, performance profiling, release tracking.

Use Vigilmon for: availability monitoring, SSL expiry, status pages, infrastructure-level outage detection.

Most production applications should have both. The good news: both have generous free tiers.

Start external uptime monitoring with Vigilmon - free tier, no credit card required.