CDN Log Analysis and Monitoring: Real-time Insights into CDN Operations

CDN logs are the window into website acceleration effectiveness. Through log analysis, you can discover cache optimization opportunities, identify abnormal traffic, and track user access patterns.

1. Information Contained in CDN Logs

Different CDN providers offer slightly different log formats, but they typically include:

Field Description Example
Request Time Time of request arrival 2026-07-15T10:30:00Z
Client IP User IP address 203.0.113.1
Request Method GET/POST etc. GET
Request URI Request path /images/logo.png
Status Code HTTP status code 200, 304, 404
Response Size Response bytes 10240
Cache Status HIT/MISS/EXPIRED HIT
User-Agent Client identifier Mozilla/5.0...
Referer Referrer URL https://google.com
Response Time CDN processing time 15ms

2. Log Collection Solutions

2.1 CDN Log Export Methods

CDN Provider Log Export Method Frequency
Cloudflare Logpush → R2/S3/Splunk Per minute
AWS CloudFront Standard logs → S3 Per hour
Alibaba Cloud CDN Offline logs → OSS Per hour
Tencent Cloud CDN Real-time logs → CLS Real-time
Fastly Real-time log stream Real-time

2.2 Log Analysis Architecture

CDN Logs → S3/OSS → ETL → Analytics Engine → Visualization
                                       ├── Cache Hit Ratio Dashboard
                                       ├── Traffic Trend Chart
                                       ├── Anomaly Alerts
                                       └── Cost Analysis

2.3 Recommended Tool Stack

  • Collection: Logstash / Fluentd / Vector
  • Storage: Elasticsearch / ClickHouse / S3 + Athena
  • Analysis: Spark / Presto / Trino
  • Visualization: Grafana / Kibana / Tableau

3. Key Monitoring Metrics

3.1 Cache Hit Ratio

Cache hit ratio is the core metric of CDN efficiency.

Metric Description Healthy Value
Byte Hit Ratio Proportion of traffic served directly by CDN > 85%
Request Hit Ratio Proportion of requests handled directly by CDN > 90%
Static Resource Hit Ratio Image/CSS/JS hit ratio > 95%

3.2 Performance Metrics

  • P50/P95/P99 Response Time: Observe latency distribution
  • Time to First Byte (TTFB): CDN response speed
  • Download Speed: Large file transfer speed

3.3 Errors and Anomalies

  • 4xx/5xx Status Codes: Anomalous request monitoring
  • Origin Pull Ratio: Too many origin requests indicate cache strategy needs optimization
  • Bandwidth: Real-time bandwidth usage and trends

4. Grafana Dashboard Example

A complete CDN monitoring dashboard should include:

  1. Real-time bandwidth and request count
  2. Cache hit ratio trends
  3. Popular URI rankings
  4. Status code distribution
  5. Geographic distribution
  6. Response time heatmap

5. Alert Rules

Trigger Condition Severity Response
Cache hit ratio < 70% Warning Check cache configuration
Error rate > 1% Warning Check origin and CDN
Origin bandwidth spike 5x Critical Check for attacks
Widespread CDN node failure Critical Enable backup CDN