Prometheus Metrics Guide

Overview

The Rewind capture agent now exposes Prometheus metrics at http://localhost:9090/metrics when running.

Configuration

Metrics are configured in config/config.yaml:

metrics:
  enabled: true        # Enable/disable metrics
  port: 9090          # Metrics server port
  endpoint: "/metrics" # Metrics endpoint path

Available Metrics

Counters (always increasing)

• rewind_packets_total{type="processed"} - Total packets processed
• rewind_http_messages_total{type="all"} - Total HTTP messages (requests + responses)
• rewind_http_messages_total{type="requests"} - Total HTTP requests
• rewind_http_messages_total{type="responses"} - Total HTTP responses
• rewind_sessions_total{action="created"} - Total sessions created
• rewind_sessions_total{action="closed"} - Total sessions closed
• rewind_errors_total{type="general"} - Total errors
• rewind_errors_total{type="dropped_packets"} - Total dropped packets

Gauges (current value)

• rewind_active_sessions{state="active"} - Currently active sessions

Histograms (distribution of durations)

• rewind_operation_duration_seconds{operation="capture"} - Capture operation latency
  • Buckets: 0.001s, 0.01s, 0.1s, 1.0s, 10.0s
• rewind_operation_duration_seconds{operation="session"} - Session durations
  • Buckets: 0.1s, 1.0s, 10.0s, 60.0s, 300.0s

Usage

1. Run the Capture Agent

cd C:\Users\sreek\Desktop\rewind\services\capture-agent
.\build\Release\capture-agent.exe

When metrics are enabled, you'll see:

Metrics server started on port 9090

2. Access Metrics

While the capture agent is running, open a browser or use curl:

curl http://localhost:9090/metrics

Example output:

# HELP rewind_packets_total Total number of packets processed
# TYPE rewind_packets_total counter
rewind_packets_total{type="processed"} 150

# HELP rewind_http_messages_total Total number of HTTP messages
# TYPE rewind_http_messages_total counter
rewind_http_messages_total{type="all"} 50
rewind_http_messages_total{type="requests"} 25
rewind_http_messages_total{type="responses"} 25

# HELP rewind_active_sessions Number of currently active sessions
# TYPE rewind_active_sessions gauge
rewind_active_sessions{state="active"} 5

3. Disable Metrics (Optional)

To disable metrics, edit config/config.yaml:

metrics:
  enabled: false

Integration with Prometheus

To scrape these metrics with a Prometheus server, add this to your prometheus.yml:

scrape_configs:
  - job_name: 'rewind-capture-agent'
    static_configs:
      - targets: ['localhost:9090']

Troubleshooting

Port already in use: If port 9090 is already in use, change the port in config/config.yaml:

metrics:
  port: 9091  # Use a different port

Metrics server failed to start: Check the logs for error messages. Common issues:

• Port already in use
• Firewall blocking the port
• Missing dependencies

No metrics showing up:

• Ensure metrics.enabled: true in config
• Verify the capture agent is running
• Check the correct port and endpoint
• Try accessing http://localhost:9090/metrics directly