Blog Analytics (SAM)

Generates daily visitor and top pages charts from CloudFront JSON logs.
Outputs JSON files to your static site S3 bucket, rendered by Chart.js on your about page.

Architecture

EventBridge (daily 06:00 UTC)
  └─ Lambda (Node.js 22)
       ├─ Reads last 30 days of CloudFront .gz logs from S3
       ├─ Filters bots, probes, assets
       ├─ Writes visitors.json + pages.json to website S3
       └─ Invalidates CloudFront cache

Prerequisites

• AWS CLI configured (aws configure)
• SAM CLI installed (pip install aws-sam-cli)

Deploy

sam build
sam deploy --guided

On first deploy, SAM will prompt for:

Parameter	Value
LogsBucket	Your CloudFront logs bucket name
LogsPrefix	Key prefix for logs (empty if at root)
WebsiteBucket	Your website S3 bucket name
DistributionId	Your CloudFront distribution ID

SAM saves your answers in samconfig.toml for subsequent deploys (sam deploy without --guided).

Test locally

sam build
sam local invoke AnalyticsFunction

Test in AWS (manual trigger)

aws lambda invoke \
  --region eu-west-3 \
  --cli-read-timeout 0 \
  --function-name $(sam list stack-outputs --stack-name daily-statistics --region eu-west-3 --output json | jq -r '.[] | select(.OutputKey=="FunctionName") | .OutputValue') \
  /dev/stdout

Jekyll integration

Copy the contents of chart-snippet.html into your about.md (or about.html) page.

Chart.js is loaded from cdnjs — no cookies, no tracking, consistent with your privacy policy.

Monthly cost

Resource	Cost
Lambda (1 run/day, ~30s, 512MB)	~$0.00
S3 reads (log files)	~$0.01
CF invalidation (1/day)	$0.00
Total	~$0

Bot filtering

The Lambda excludes:

• Known bots (Googlebot, GPTBot, SEMrush, Ahrefs, etc.)
• Empty / missing user agents
• HEAD requests
• PHP/WordPress probes (wp-login, xmlrpc, .env, etc.)
• Static assets (CSS, JS, images, fonts, XML, JSON)

Only GET requests returning 2xx/3xx for HTML pages are counted.
Unique visitors = unique IPs per day.