AWS CloudFront Deep Skill

Advanced CloudFront management including Lambda@Edge, origin groups, cache policies, and real-time monitoring.

Core Helper Functions

#!/bin/bash
export AWS_PAGER=""

# Get distribution config
cf_config() {
    local dist_id="$1"
    aws cloudfront get-distribution-config --id "$dist_id" --output json
}

# Get CloudFront metrics
cf_metric() {
    local dist_id="$1" metric="$2" stat="${3:-Average}" days="${4:-7}"
    local end_time start_time
    end_time=$(date -u +"%Y-%m-%dT%H:%M:%S")
    start_time=$(date -u -d "$days days ago" +"%Y-%m-%dT%H:%M:%S" 2>/dev/null || date -u -v-${days}d +"%Y-%m-%dT%H:%M:%S")
    aws cloudwatch get-metric-statistics \
        --namespace AWS/CloudFront --metric-name "$metric" \
        --dimensions Name=DistributionId,Value="$dist_id" Name=Region,Value=Global \
        --start-time "$start_time" --end-time "$end_time" \
        --period $((days * 86400)) --statistics "$stat" \
        --output text --query 'Datapoints[0].'$stat
}

MANDATORY: Discovery-First Pattern

Phase 1: Discovery

#!/bin/bash
export AWS_PAGER=""

echo "=== Distribution Inventory ==="
aws cloudfront list-distributions --output json | jq -r '
    .DistributionList.Items[] | "\(.Id)\t\(.DomainName)\t\(.Status)\t\(.Enabled)\t\(.PriceClass)\t\(.Origins.Quantity) origins"
' | column -t | head -20

echo ""
echo "=== Cache Policies ==="
aws cloudfront list-cache-policies --output json | jq -r '
    .CachePolicyList.Items[] | "\(.CachePolicy.Id[:12])\t\(.CachePolicy.CachePolicyConfig.Name)\t\(.CachePolicy.CachePolicyConfig.DefaultTTL)s TTL"
' | column -t | head -10

echo ""
echo "=== Origin Request Policies ==="
aws cloudfront list-origin-request-policies --output json | jq -r '
    .OriginRequestPolicyList.Items[] | "\(.OriginRequestPolicy.Id[:12])\t\(.OriginRequestPolicy.OriginRequestPolicyConfig.Name)"
' | column -t | head -10

echo ""
echo "=== Functions ==="
aws cloudfront list-functions --output json 2>/dev/null | jq -r '
    .FunctionList.Items[]? | "\(.Name)\t\(.FunctionConfig.Runtime)\t\(.Status)\t\(.FunctionMetadata.Stage)"
' | column -t | head -10

Phase 2: Analysis

#!/bin/bash
export AWS_PAGER=""
DIST_ID="${1:?Distribution ID required}"

echo "=== Performance Metrics (7d) ==="
for metric in CacheHitRate Requests 4xxErrorRate 5xxErrorRate BytesDownloaded; do
    val=$(cf_metric "$DIST_ID" "$metric")
    printf "%s: %s\n" "$metric" "${val:-N/A}"
done

echo ""
echo "=== Behavior Configuration ==="
cf_config "$DIST_ID" | jq '
    .DistributionConfig.CacheBehaviors.Items[]? | {
        PathPattern, ViewerProtocolPolicy, AllowedMethods: .AllowedMethods.Items,
        CachePolicyId: .CachePolicyId[:12], Compress
    }' | head -30

echo ""
echo "=== Origin Groups (Failover) ==="
cf_config "$DIST_ID" | jq '
    .DistributionConfig.OriginGroups.Items[]? | {
        Id, Members: [.Members.Items[].OriginId],
        FailoverCodes: .FailoverCriteria.StatusCodes.Items
    }'

echo ""
echo "=== Lambda@Edge Associations ==="
cf_config "$DIST_ID" | jq '
    [.DistributionConfig | .DefaultCacheBehavior, .CacheBehaviors.Items[]?] |
    .[] | select(.LambdaFunctionAssociations.Quantity > 0) |
    .LambdaFunctionAssociations.Items[] | {EventType, LambdaFunctionARN: .LambdaFunctionARN[-40:]}
' | head -20

Output Rules

• TOKEN EFFICIENCY: Target <=50 lines per output
• Use parallel execution with & and wait for multi-distribution queries
• CloudFront API calls must go through us-east-1

Safety Rules

• Read-only by default: Use list/get/describe for inspection
• Distribution updates take 15-20 min to deploy globally
• Never delete distributions without disabling first and confirming
• Lambda@Edge changes propagate to all edge locations -- test thoroughly

Output Format

Present results as a structured report:

Managing Aws Cloudfront Deep Report
═══════════════════════════════════
Resources discovered: [count]

Resource       Status    Key Metric    Issues
──────────────────────────────────────────────
[name]         [ok/warn] [value]       [findings]

Summary: [total] resources | [ok] healthy | [warn] warnings | [crit] critical
Action Items: [list of prioritized findings]

Target ≤50 lines of output. Use tables for multi-resource comparisons.

Anti-Hallucination Rules

1. NEVER assume resource names — always discover via CLI/API in Phase 1 before referencing in Phase 2.
2. NEVER fabricate metric names or dimensions — verify against the service documentation or --help output.
3. NEVER mix CLI commands between service versions — confirm which version/API you are targeting.
4. ALWAYS use the discovery → verify → analyze chain — every resource referenced must have been discovered first.
5. ALWAYS handle empty results gracefully — an empty response is valid data, not an error to retry.

Counter-Rationalizations

Shortcut	Counter	Why
"I'll skip discovery and check known resources"	Always run Phase 1 discovery first	Resource names change, new resources appear — assumed names cause errors
"The user only asked for a quick check"	Follow the full discovery → analysis flow	Quick checks miss critical issues; structured analysis catches silent failures
"Default configuration is probably fine"	Audit configuration explicitly	Defaults often leave logging, security, and optimization features disabled
"Metrics aren't needed for this"	Always check relevant metrics when available	API/CLI responses show current state; metrics reveal trends and intermittent issues
"I don't have access to that"	Try the command and report the actual error	Assumed permission failures prevent useful investigation; actual errors are informative

Common Pitfalls

• All API calls route to us-east-1 regardless of configured region
• CacheHitRate is 0-100 not 0-1; do not multiply by 100
• Invalidation costs: First 1000 paths/month free, then $0.005/path
• Origin groups require two origins and specific failover status codes
• Cache policy vs legacy settings: New distributions should use managed cache policies