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How the Monitoring Works

Published on March 25, 2025 • By UptimeSense Team

All you need to know to about UptimeSense

This guide explains the technical details of how UptimeSense monitors your websites and services, without getting into code-level implementation details.

Monitoring Technology

UptimeSense uses two primary monitoring methods:

HTTP Monitoring

What it is: HTTP monitoring checks whether your website or web service is accessible via HTTP or HTTPS protocols.

How it works:

  1. Request Process: When a check is executed, UptimeSense sends an HTTP HEAD request to your specified URL. HEAD requests only fetch headers, which is more efficient than downloading the entire page content. You can use other HTTP methods if needed.

  2. Timeout Handling: The system enforces the timeout you’ve specified (default 30 seconds). If the server doesn’t respond within this time, the monitor marks the service as down.

  3. Redirect Handling: UptimeSense follows HTTP redirects automatically, so you can monitor URLs that redirect to other locations.

  4. Status Code Verification: The system compares the received HTTP status code with your expected code (default 200 OK). If they don’t match, the service is considered down even if the server responded.

  5. Response Time Measurement: UptimeSense calculates the time taken between sending the request and receiving the response, giving you an accurate measure of your website’s response speed in milliseconds.

  6. Failure Types: HTTP monitoring can detect various failure modes:

    • DNS resolution errors
    • Connection timeouts
    • SSL/TLS certificate issues
    • HTTP errors (4xx, 5xx status codes)
    • Content mismatches (when expected status code doesn’t match)

PING Monitoring

What it is: PING monitoring uses ICMP (Internet Control Message Protocol) to check if a server is reachable at the network level.

How it works:

  1. Echo Requests: UptimeSense sends multiple ICMP “echo request” packets to the target host.

  2. Packet Sequence: Each check sends 4 packets with a short interval between them. This provides more reliable results than a single ping attempt.

  3. Round-Trip Time: The system measures how long it takes for each packet to travel to the server and back (round-trip time or RTT).

  4. Availability Determination: If the server responds to any of the packets, it’s considered up. If all packets time out, it’s marked as down.

  5. Failure Detection: PING monitoring can detect:

    • Server offline status
    • Network routing issues
    • Firewall blocks (some networks block ICMP packets)
    • Network congestion

Scheduling System

UptimeSense employs an advanced scheduling system to ensure reliable monitoring:

  1. Distributed Queue: Monitors operate on a distributed task queue that ensures checks are processed even during high system load.

  2. Precise Intervals: You can configure check intervals from as short as 1 minute to as long as 24 hours. The system maintains precise timing between checks.

  3. Immediate Execution: When you click “Check Now” on a monitor, the system immediately queues a check, bypassing the normal schedule.

  4. Failure Recovery: If a scheduled check fails to execute (due to system issues), the scheduling system will recover and resume normal operation automatically.

Data Storage and Analysis

The monitoring data is processed and stored efficiently:

  1. Time-Series Data: All check results are stored as time-series data, allowing for detailed historical analysis.

  2. Uptime Calculation:

    • 24-hour uptime: (successful checks ÷ total checks) × 100% for the past 24 hours
    • 7-day uptime: (successful checks ÷ total checks) × 100% for the past 7 days
    • 30-day uptime: (successful checks ÷ total checks) × 100% for the past 30 days

  3. Response Time Aggregation: The system calculates average, minimum, and maximum response times over different periods, helping you identify performance trends.

  4. Status Change Detection: UptimeSense specifically tracks transitions between up and down states to identify incidents and calculate downtime duration.

Notification System

The alert system uses a sophisticated process to ensure you’re notified of issues promptly:

  1. Status Change Detection: When a monitor transitions from up to down, the notification system is triggered.

  2. Mail Delivery: Alerts are sent via a reliable email delivery service that ensures high deliverability rates.

  3. Down Status: The down notification includes:

    • Monitor name and URL
    • Timestamp of the incident
    • Specific error message
    • Response time when the error occurred
    • Direct link to the monitor details

  4. Recovery Detection: When a service recovers (transitions from down to up), a recovery notification is sent.

  5. Recovery Information: The recovery notification includes:

    • Monitor name and URL
    • Timestamp of recovery
    • Precise downtime duration
    • Direct link to view monitor details

Security Enhancements

The monitoring system includes several security features:

  1. Two-Factor Authentication: Email-based verification codes protect your monitoring dashboard from unauthorized access.

  2. Secure Monitoring: HTTP checks support HTTPS and validate SSL certificates.

  3. Rate Limiting: Multiple protective layers prevent abuse of the service.

  4. Timeout Protection: All checks have enforced timeouts to prevent resource exhaustion.

Best Practices for Effective Monitoring

To get the most accurate results from UptimeSense:

  1. Choose the Right Monitor Type:

    • Use HTTP for web services, APIs, and websites
    • Use PING for basic server availability checks or when HTTP isn’t available

  2. Set Appropriate Intervals:

    • Critical services: 1-5 minute intervals
    • Important services: 5-15 minute intervals
    • Non-critical services: 30-60 minute intervals

  3. Configure Realistic Timeouts:

    • Standard web services: 10-30 seconds
    • Slow or resource-intensive endpoints: 30-60 seconds
    • Never set timeouts longer than 120 seconds

  4. HTTP Status Codes:

    • Normal websites: 200 (OK)
    • Redirecting pages: 301 or 302
    • API endpoints: May use 200, 201, 204, etc.
    • Authentication-required endpoints: May return 401 or 403 (set expected status accordingly)

  5. Monitoring Private Services:

    • Ensure firewall rules allow access from UptimeSense IP ranges (coming soon)
    • For internal services, use PING to check server availability even if the service itself isn’t publicly accessible

By understanding these technical aspects of UptimeSense, you can configure your monitors for optimal effectiveness and interpret the results with greater insight.

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