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Vigilmon vs Prometheus + Grafana: External Uptime vs Internal Observability

#prometheus #grafana #devops #monitoring

Prometheus is the industry standard for metrics collection. Paired with Grafana for dashboards, it gives you deep visibility into your application internals — CPU, memory, request rates, error rates, and any custom metric you can instrument.

But Prometheus does not tell you what your users experience.

This guide explains the difference between Prometheus + Grafana and Vigilmon, and how to use both together effectively.

What Prometheus + Grafana Does

Prometheus scrapes metrics from your application at regular intervals. Your app exposes a /metrics endpoint, Prometheus collects it, and Grafana renders it on dashboards.

Prometheus is excellent for:

  • Internal metrics (memory usage, request counts, queue depths)
  • Custom business metrics (orders per minute, active users)
  • Historical trend analysis
  • Alert rules based on metric thresholds
  • Infrastructure-wide visibility

Prometheus sees inside your application and infrastructure.

What Vigilmon Does

Vigilmon makes external HTTP requests to your endpoints from multiple geographic regions and tells you whether they are reachable and returning correct responses.

Vigilmon is excellent for:

  • External uptime verification (is the site reachable from the internet?)
  • SSL certificate expiry alerts
  • Geographic availability (is it down in APAC but up in US?)
  • Status pages for your users
  • Simple setup for teams without Prometheus expertise

Vigilmon sees what your users see.

A Real Scenario: The Routing Failure

Your app is healthy. Prometheus shows normal request rates, CPU is fine, memory is fine. But your load balancer has a misconfigured routing rule — 30% of requests to /api/checkout are going to a decommissioned service and returning 503.

Prometheus does not see this if the decommissioned service is not in your scrape targets. Vigilmon pings /api/checkout from 5 regions, gets 503s, and fires an alert in 60 seconds.

Another Scenario: The Regional Outage

Your Prometheus metrics look healthy. But your CDN is routing all APAC traffic to a misconfigured edge node. Vigilmon checks from Singapore and Tokyo show failures. US and EU checks are green.

You now know it is a regional routing issue — your Prometheus dashboards cannot tell you that because they only have visibility from inside your infrastructure.

Feature Comparison

Feature Prometheus + Grafana Vigilmon
External uptime checks No Yes
Multi-region monitoring No Yes
Custom application metrics Yes No
Infrastructure metrics Yes No
Status pages Via plugin Built-in
Setup complexity High Minimal
Self-hosted Yes SaaS
On-call alerting Via Alertmanager Built-in
SSL expiry alerts No Yes
Cost Free + infra Free tier available

When to Choose Each

Use Prometheus + Grafana when:

  • You need deep application metrics (latency percentiles, error rates by endpoint)
  • You want historical dashboards for capacity planning
  • You have the infrastructure and expertise to run it
  • You need complex alert rules based on metric combinations

Use Vigilmon when:

  • You need external confirmation that the app is reachable
  • You want multi-region monitoring with zero setup
  • You need a public status page
  • Your team does not have time to maintain Prometheus infrastructure
  • You want simple uptime alerts without configuring Alertmanager

Using Both Together

The most effective production monitoring stack combines both:

  1. Prometheus + Grafana for internal observability — you know your app is working correctly
  2. Vigilmon for external verification — you know your users can reach it

When Vigilmon fires an alert (external failure), you open your Grafana dashboards to correlate with internal metrics. Was there a spike in error rate? Did request latency jump? Did the database connection pool exhaust?

The two systems feed each other. Vigilmon tells you that something went wrong. Prometheus + Grafana tell you what went wrong internally.

Practical Setup

Step 1: Expose a Health Endpoint

Your app already exposes /metrics for Prometheus. Add a /health endpoint for Vigilmon:

// Go example
http.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(http.StatusOK)
    json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
})
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Step 2: Add to Vigilmon

  1. Sign up at vigilmon.online — free for 50 monitors
  2. Add https://yourapp.com/health
  3. Set check interval to 1 minute
  4. Connect your Slack channel for alerts

Step 3: Add a Prometheus Alert for Correlation

In Prometheus Alertmanager, add an alert that fires when error rate spikes:

groups:
  - name: app_alerts
    rules:
      - alert: HighErrorRate
        expr: rate(http_requests_total{status=~"5.."}[5m]) > 0.05
        for: 2m
        labels:
          severity: critical
        annotations:
          summary: "High error rate detected"
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When both alerts fire together, you have strong signal of a real incident. When only Vigilmon fires (but Prometheus metrics look normal), suspect your networking or load balancer.

Summary

Prometheus + Grafana and Vigilmon are complementary tools, not competing ones. Prometheus gives you deep internal visibility. Vigilmon gives you external user-perspective monitoring.

For a complete production setup, use both. Start with Vigilmon (5-minute setup) and add Prometheus as your team grows.

Start monitoring externally at vigilmon.online — free tier, no credit card required.

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