Cache Purge

Cache purging removes cached content from Sudun edge servers, forcing fresh content to be fetched from your origin. This guide covers purge methods, best practices, and automation options.

When to Purge Cache

Common scenarios requiring cache purge:

Purge Methods

Purge by URL

Remove specific URLs from cache:

https://example.com/blog/post-1
https://example.com/images/hero.jpg
https://example.com/css/styles.css

Best for: Individual content updates, targeted cache clearing

Purge by Prefix

Remove all URLs matching a path prefix:

https://example.com/blog/*
https://example.com/images/*
https://example.com/api/v1/*

Best for: Section updates, versioned asset deployments

Purge by Cache Tag

Remove content by associated tags:

Tags: product-123, category-electronics, homepage

Best for: Dynamic content relationships, CMS integrations

Purge Everything

Remove all cached content for a domain:

Domain: example.com
Action: Purge All

Warning: Purging everything causes a surge of requests to your origin. Use sparingly and preferably during low-traffic periods.

Using the Dashboard

Purge Single URL

1. Go to Domains → Select your domain
2. Navigate to Caching → Purge Cache
3. Select Purge by URL
4. Enter the full URL(s) to purge
5. Click Purge

Purge by Prefix

1. Go to Caching → Purge Cache
2. Select Purge by Prefix
3. Enter the URL prefix (e.g., https://example.com/blog/)
4. Click Purge

Purge Everything

1. Go to Caching → Purge Cache
2. Select Purge Everything
3. Confirm by typing your domain name
4. Click Purge All

Cache tags allow content-based purging without knowing exact URLs.

Setting Cache Tags

Add tags via response headers from your origin:

Cache-Tag: product-123, category-shoes, homepage

Or configure in Sudun:

{
  "cache_tags": {
    "rules": [
      {
        "match": { "path": "/products/*" },
        "tags": ["products", "catalog"]
      },
      {
        "match": { "path": "/blog/*" },
        "tags": ["blog", "content"]
      }
    ]
  }
}

Purging by Tag

# Purge all content with tag "product-123"
curl -X POST https://api.Sudun.com/v1/domains/example.com/purge \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"tags": ["product-123"]}'

Tag Best Practices

Purge Propagation

After initiating a purge:

Purge Request → Sudun API → Global PoPs
                                  │
                          ┌───────┴───────┐
                          │               │
                     ~1-5 seconds    ~30 seconds
                     (most PoPs)     (all PoPs)

Soft Purge vs Hard Purge

Hard Purge (Default)

Immediately removes content from cache:

Cache State: MISS
Origin Request: Required

Soft Purge

Marks content as stale but keeps it available:

Cache State: STALE
Origin Request: Background revalidation

Benefits of Soft Purge:

• Prevents origin overload
• Users see content immediately (stale)
• Fresh content served after revalidation

# Soft purge via API
curl -X POST https://api.Sudun.com/v1/domains/example.com/purge \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{"urls": ["https://example.com/page"], "soft": true}'

Purge Automation

Webhooks

Trigger purge from your CMS or deployment pipeline:

# WordPress example: purge on post update
curl -X POST https://api.Sudun.com/v1/domains/example.com/purge \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{"tags": ["post-${POST_ID}"]}'

CI/CD Integration

Purge after deployment:

# GitHub Actions example
- name: Purge CDN Cache
  run: |
    curl -X POST https://api.Sudun.com/v1/domains/$DOMAIN/purge \
      -H "Authorization: Bearer $YESudunPI_KEY" \
      -d '{"prefix": "https://$DOMAIN/assets/"}'

Scheduled Purge

Set up automatic purge schedules:

1. Go to Caching → Scheduled Tasks
2. Click Add Schedule
3. Configure:

- Frequency: Daily, Weekly, Custom

- Time: Choose off-peak hours

- Purge Type: Prefix or Tag

Rate Limits

Purge operations have rate limits to protect the system:

Purge History

View purge history in the dashboard:

1. Go to Caching → Purge History
2. Filter by date, type, or status
3. View details including:

- Timestamp

- Purge type

- URLs/Tags affected

- Propagation status

- Initiated by (user or API)

Troubleshooting

Content Still Cached After Purge

1. Check URL exactness: Purge URL must match cached URL exactly

```

Cached: https://example.com/page?v=1

Purge: https://example.com/page ← Won't match!

```

1. Query string variations: If caching includes query strings, purge all variations

2. Browser cache: Clear browser cache or use incognito mode

3. Propagation delay: Wait 30-60 seconds for global propagation

Purge Request Failed

Origin Overload After Purge All

If your origin struggles after a full purge:

1. Use soft purge instead of hard purge
2. Purge during low-traffic periods
3. Implement staggered purge by prefix
4. Enable origin shield for additional protection

API Reference

Purge by URL

curl -X POST https://api.Sudun.com/v1/domains/example.com/purge \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "urls": [
      "https://example.com/page1",
      "https://example.com/page2"
    ]
  }'

Purge by Prefix

curl -X POST https://api.Sudun.com/v1/domains/example.com/purge \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{"prefix": "https://example.com/blog/"}'

Purge by Tag

curl -X POST https://api.Sudun.com/v1/domains/example.com/purge \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{"tags": ["product-123", "homepage"]}'

Purge Everything

curl -X POST https://api.Sudun.com/v1/domains/example.com/purge \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{"purge_everything": true}'

Need help with cache purging? Contact support@Sudun.com