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AWS re:Invent 2016: Amazon CloudFront Flash Talks: Best Practices on Configuring, Securing and Monitoring your Distribution (CTD301)

  1. © 2016, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Best Practices for Configuring, Securing, and Monitoring Your Amazon CloudFront Distribution Alec Peterson General Manager, Amazon CloudFront Anton Radlein Software Development Manager, Amazon CloudFront Cherie Wong Sr. Software Development Manager, Amazon CloudFront Efrain Fuentes Enterprise Solutions Architect CTD301
  2. What to Expect from the Session • How Amazon CloudFront delivers content • Configuring your cache on CloudFront • Measure application performance with real user monitoring (RUM) • Stop malicious viewers with CloudFront and AWS WAF
  3. How CloudFront delivers content
  4. Definitions • Viewer • An end-user requesting content from CloudFront • On a mobile device, desktop or other internet-connected device • CloudFront POP • Point Of Presence, also referred to as an Edge Location • Located in datacenters in major metropolitan areas, directly connected to multiple ISPs • Several racks of servers and network equipment, terminating viewer connections
  5. CloudFront delivering content • Multiple identical (more or less) locations • Location selection is critical • Viewer perspective • Latency • Throughput • CloudFront perspective • Availability • Capacity • Location
  6. What does ‘routing’ actually mean? • Packet routing • Purely destination- based • Limited ability to route around congestion
  7. What does ‘routing’ actually mean? • Request routing • Latency • Throughput • Capacity • Geography • Done at the DNS layer (or higher)
  8. How does CloudFront perform routing? CloudFront edge location ISP NS authoritative NS viewer (recursive lookup) (IP address of optimal CloudFront Edge location) Primarily at the DNS layer • Recursive resolver IP routing
  9. What’s wrong with this picture?
  10. What happened? • A divergent resolver • Resolvers that serve a wide set of users across many networks/geographies • VPN users • Distributed corporate networks • What can be done? • Use a local resolver • Use a resolver that supports EDNS0 ECS
  11. What is EDNS0 client-subnet (ECS)? • IETF open internet-draft • Informational RFC 7871 • DNS query includes information about the network that originated the query: • First three octets of a IPv4 address commonly used ( • No client-side resolver modifications necessary • Some common open resolvers (such as Google’s anycast resolver) support it
  12. EDNS0 ECS-enabled DNS resolution
  13. Key takeaways • Where you are routed depends on many factors • Network • Geographic Location • Individual POP status • DNS is an imperfect request routing mechanism • But it is also ubiquitous • If your customers use ECS-enabled resolvers, their experience will improve
  14. Configuring your cache on CloudFront
  15. Why cache? Two Laws: 1. Better performance for your viewers. 2. Less load on your origin.
  16. What to expect • What we do with a viewer request? • How do we cache? • Generating cache keys • Managing your cache • Setting Cache-Control headers • Configuring your distribution and cache behaviors • Additional Best Practices • Versioning your assets • Forwarding only required values • Monitor your logs
  17. Origin IAD Edge Cache IAD12 ATL50 JFK1 JAX1 NRT Edge Cache NRT12 NRT53 NRT52 NRT20 Caching tiers
  18. What happens with each request? Is it in cache? Is it expired? Revalidate with Origin Origin responds with 304 (Not Modified) Origin responds with 200 (OK) and latest version of object Forward request to origin Y Y NN Viewer Request Hit / Refresh Hit Miss Cache it
  19. How do we generate a cache key? Use the host header to create an internal canonical URL. E.g.,, Then… - Remove query strings - Remove the protocol - Add accept-encoding (i.e., gzip, identity)
  20. Managing your cache from your origin
  21. Expires headers from origin Expires reflects when the cache must go back to the origin server to see if the object has changed. It is a fixed point in time and accuracy relies on clock synchronization. < Expires: Fri, 1 Dec 2017 12:34:50 GMT
  22. Cache-Control headers from origin These directives give you fine-grained control over what is cached and for how long (in seconds): < Cache-Control: max-age=300 < Cache-Control: max-age=30, s-maxage=3600 Example: max-age=0, s-maxage=86400 for display ads Browser Shared Edge Cache
  23. Cache-Control headers (examples) Static Assets Login Landing Pages Live Streaming Manifests Media Fragments *.css, *.js, images, software downloads index.html /*.m3u8 /*.ts Cache- Control: public; max- age=31536000 Cache- Control: no- cache=Set- Cookie; max- age=30 Cache- Control: public; max- age=2 Cache- Control: public; max- age=31536000
  24. Dynamic content? Cache it. Use Cache-Control directives to minimize load on your origin: - no-cache: cache & ask origin - max-age=0: cache & ask origin Other options: - no-store: never cached at the edge nor by the browser - private: never cached at the edge, but might be cached by the browser
  25. Managing your cache from CloudFront
  26. Cache behaviors on CloudFront Specify caching configurations based on URL path matching (i.e., for different content). Whatever you forward affects your cache key. Use Trusted Advisor checks! Be wary of: • Forwarded headers • Query string forwarding • Cookie forwarding
  27. Set Min, Max, and Default TTLs for CloudFront Min TTL Max TTLmax-age / Expires Browser Edge Cache max-age / s-maxage / Expires Max TTLmax-age / Expires max-age / s-maxage / Expires Min TTL Max TTL max-age / s-maxage / Expires Min TTLmax-age / Expires
  28. A couple tips…
  29. Errors? Cache them too! Cache and return a custom error page and response code for each HTTP error code. Give your origin just the right amount of time to recover.
  30. Enable faster iteration of new styles without issuing invalidations. Protect against browsers that don’t honor your Cache-Control headers. <link href="//“ rel="stylesheet"> <link href="//“ rel="stylesheet"> <link href="// narrow.css?<md5sum>“ rel="stylesheet"> Version your assets
  31. Minimize forwarded values All forwarded headers are used as part of the cache key, which means it dramatically reduces your cacheability.
  32. When in doubt, check the logs! #Version: 1.0 #Fields: date time x-edge-location sc-bytes c-ip cs-method cs(Host) cs-uri-stem sc-status cs(Referer) cs(User-Agent) cs-uri-query cs(Cookie) x-edge-result-type x-edge-request-id x-host-header cs-protocol cs-bytes time- taken x-forwarded-for ssl-protocol ssl-cipher x-edge-response-result-type cs-protocol-version 2014-05-23 01:13:11 FRA2 182 GET /view/my/file.html 200 Mozilla/4.0%20(compatible;%20MSIE%205.0b1;%20Mac_PowerPC) - zip=98101 RefreshHit MRVMF7KydIvxMWfJIglgwHQwZsbG2IhRJ07sn9AkKUFSHS9EXAMPLE== http - 0.001 - - - RefreshHit HTTP/1.1 2014-05-23 01:13:12 LAX1 2390282 GET /soundtrack/happy.mp3 304 Mozilla/4.0%20(compatible;%20MSIE%207.0;%20Windows%20NT%205.1) a=b&c=d zip=50158 Hit xGN7KWpVEmB9Dp7ctcVFQC4E-nrcOcEKS3QyAez--06dV7TEXAMPLE== http - 0.002 - - - Hit HTTP/1.1
  33. Log CloudFront request IDs Nginx: log_format main '$remote_addr - $remote_user [$time_local] "$request" ‘ '$status $body_bytes_sent "$http_referer" ‘ '"$http_user_agent" http_x_forwarded_for" "$http_x_amz_cf_id"'; Apache: LogFormat "%h %l %u %t "%r" %>s %b "%{Referer}i" "%{User-Agent}i" "%{X-Amz-Cf- Id}i"" combined
  34. Key takeaways • Set Cache-Control headers appropriately for your content • Cache dynamic content • Create multiple cache behaviors and adapt configurations for your content type, including errors • Forward only required values • Version your assets • Log your request IDs!
  35. Measure application performance with RUM
  36. Measure application performance with RUM Synthetic monitoring vs. real user monitoring (RUM): • Synthetic monitoring overview • RUM overview • When to use one over the other (baselining vs. gaining situational insight)
  37. What is synthetic monitoring? Pros: • Consistent signal of service health • Easy to setup (kind of) • Baseline performance synthetic monitoring configuration synthetic monitoring portal web application simulated users
  38. What is synthetic monitoring? Pros: • Consistent signal of service health • Easy to setup (kind of) • Baseline performance synthetic monitoring configuration web application simulated users
  39. Where synthetic measurements go wrong Cons: • Network path to your application might not be representative • Special cases and snowflakes synthetic monitoring configuration web application simulated usersreal user
  40. Where synthetic measurements go wrong Cons: • Network path to your application might not be representative • Special cases and snowflakes synthetic monitoring configuration web application simulated usersreal user
  41. How do you feel about RUM? web application real users script injected in web page HTTP response RUM provider portal • Script injected in web page • Script beacons data back from the user’s browser session to the RUM provider • RUM provider portal aggregates the data for analysis
  42. What can RUM tell you? • What should my next optimization be? • What is the cause of a loss of availability? *Reference:
  43. Network optimizations: connections Connection definitions: • Queueing – Time spent waiting to begin processing • Stalled/Blocking – Total time spent in queue or proxying • DNS lookup – Time taken to receive DNS records (like A or AAAA) • Initial connection – Inclusive of TCP handshake and negotiating SSL
  44. Network optimizations: requests Request definitions: • Request sent – HTTP request sent time • TTFB - Time To first byte • Content download – Time to last byte
  45. Network optimizations: head of line blocking Serialized requests could be your bottleneck due to head of line blocking in HTTP 1.1 if you’re serving from the same origin!
  46. Network optimizations: Key takeaways Insights from this example: • Evaluate your user-base • Know your data • Look at the right data Optimizations: • Use CloudFront! • Origin as close to your end-users as possible (multi-region) • HTTP/2
  47. Best practices for configuring RUM on CloudFront • Availability: Test your critical resources • Index pages • Video manifests • Critical resources required for page load • Performance: Capture Total Load time • First-Byte latency is not always important. Know your content and optimize on the appropriate dimension!
  48. Stop malicious viewers with CloudFront and AWS WAF
  49. Securing your CloudFront distribution • Leverage AWS WAF with preconfigured protections • Configure CloudFront to serve private content • Automate security response by using services like AWS Lambda • Leverage AWS Certificate Manager for SSL
  50. AWS WAF
  51. AWS WAF preconfigured protections
  52. AWS WAF preconfigured protections Access Handler
  53. AWS WAF preconfigured protections Log Parser
  54. AWS WAF preconfigured protections IP List Parser
  55. AWS WAF preconfigured protections
  56. Private content – restrict origin access Amazon S3 Origin Access Identify (OAI) • Prevents direct access to your Amazon S3 bucket • Ensures performance benefits to all customers Custom origin Block by IP address • Whitelist only the Amazon CloudFront IP range • Protects origin from overload • Ensures performance benefits to all customers
  57. Signed URLs • Add signature to the Querystring in URL • Your URL changes • Use to restrict access to individual files Signed Cookies • Add signature to a cookie • Your URL does not change • Use to restrict access to multiple files Private content – signed URLs and cookies
  58. Automate security response • Subscribe to Amazon SNS notifications for changes to IP ranges • Automatically update security groups AWS Lambda Amazon CloudFront Amazon SNS Security group Web app server Web app serverAWS IP ranges Update IP range SNS message
  59. Leverage AWS Certificate Manager for SSL
  60. Key takeaways • Leverage AWS WAF • Secure your origin and content • Automate security response
  61. Thank you!
  62. Remember to complete your evaluations!