1. Troubleshooting using HTTP Headers
Steve Miller-Jones Director of Product Management Velocity Barcelona, November 18th 2014

2. WHAT DO YOU NEED DELIVERED TODAY?
When you’re delivering content to your end users with a CDN, you want to check what’s happening with specific objects or spot check what’s is happening with a new feature you’ve introduced or a new file version you’ve just published.
How does your CDN help?

3. What is troubleshooting with headers?
Request debug information about an object from the CDN edge
Debugging request / response flow
Provides detail to monitoring tools

4. What is troubleshooting with headers?
Request debug information about an object from the CDN edge
Debugging request / response flow
Provides detail to monitoring tools
Access to headers is secure for each customer

5. What is troubleshooting with headers?
Request debug information about an object from the CDN edge
Debugging request / response flow
Provides detail to monitoring tools
Access to headers is secure for each customer
Individual requests define what is returned

6. What can you find out? Is this response cachable?
Was the request a cache hit, refresh hit, cache miss, refresh miss etc
Freshness lifetime remaining
Freshness Lifetitme total
Freshness lifetime “reason”
Describes if requested object is cacheable
Use Case:
To determine what EdgePrisim thinks about the cacheability of the object.
Possible Values:
Yes No
Negative

7. What can you find out? Is this response cachable?
Describes the hit type for requested object.
Use Case:
To determine if EdgePrism had a cache hit or miss on an object, what type of hit or miss it was.
Possible Values:
Is this response cachable?
Was the request a cache hit, refresh hit, cache miss, refresh miss etc.
Freshness lifetime remaining
Freshness Lifetitme total
Freshness lifetime “reason”
HIT
IMS_HIT
MISS
NEGATIVE_HIT
REFRESH_HIT
DENIED
REF_FAIL_HIT
OFFLINE_HIT
REFRESH_MISS
REDIRECT
CLIENT_REFRESH_MISS

8. What can you find out?
Describes the number of seconds left before this object expires from the cache.
It is the TTL of the object.
Use Case:
Determine how much time EdgePrism believes this object has left before it expires.
Is this response cachable?
Was the request a cache hit, refresh hit, cache miss, refresh miss etc.
Freshness lifetime remaining
Freshness Lifetitme total
Freshness lifetime “reason”

9. What can you find out? Is this response cachable?
Returns the total number of seconds for the objects' whole life.
This is the total life of the object from the time it entered the cache until it expires (age+ttl).
Use Case:
Determine how much time EdgePrism plans to hold this object since it entered cache.
Use to see if the expire time is being set correctly on an object.
Is this response cachable?
Was the request a cache hit, refresh hit, cache miss, refresh miss etc.
Freshness lifetime remaining
Freshness Lifetime total
Freshness lifetime “reason”

10. What can you find out? Is this response cachable?
Describes how Freshness Lifetime total was derived
Use Case:
Gather more data about how the expiry time was determined.
Possible values:
unknown - data used to calculate not available
headers - Header data used to derive life span
options - Service configuration derived life span
default - EdgePrism’s default global settings
nocache - object not cachable
cdnrule - Rules at the Edge applied
Is this response cachable?
Was the request a cache hit, refresh hit, cache miss, refresh miss etc.
Freshness lifetime remaining
Freshness Lifetime total
Freshness lifetime “reason”

11. How do you do it?
HTTP Request: > GET / HTTP/1.1 > Host: > Accept: */* > Accept-Encoding:gzip,deflate > User-Agent:Mozilla/4.0 (compatible; MSIE 8.0; smj) > X-LLNW-Dbg-Secret:YYYYYYY > X-LLNW-Dbg-Hdrs:cache-hit-type,ttl,is-cacheable

12. How do you do it? Not supposed to be cachable Is not cached
HTTP Response: < HTTP/ OK < Date: Fri, 14 Nov :09:45 GMT < Cache-Control: no-cache, max-age=0, must-revalidate, no-store < Content-Type: text/html;charset=UTF-8 < Content-Language: en < Vary: Accept-Encoding < Content-Encoding: gzip … < X-LLNW-Dbg-Is-Cacheable: No < X-LLNW-Dbg-Cache-Hit-Type: MISS < X-LLNW-Dbg-TTL: 0 seconds
Not supposed to be cachable
Is not cached
Still not cached

13. How do you do it?
HTTP Request: > GET /images/background/imagename.jpg HTTP/1.1 > Host: > Accept: */* > Accept-Encoding:gzip,deflate > User-Agent:Mozilla/4.0 (compatible; MSIE 8.0; smj) > X-LLNW-Dbg-Secret:YYYYYYY > X-LLNW-Dbg-Hdrs:cache-hit-type,ttl,is-cacheable

14. How do you do it? Should be cacheable Is in cache
HTTP Response: < HTTP/ OK < Server: Apache < Accept-Ranges: bytes < Cache-Control: max-age=600 < Content-Type: image/jpeg < Date: Fri, 14 Nov :27:28 GMT < Last-Modified: Fri, 31 Oct :34:15 GMT < Expires: Fri, 14 Nov :37:28 GMT < Content-Length: < Connection: keep-alive < X-LLNW-Dbg-Is-Cacheable: Yes < X-LLNW-Dbg-Cache-Hit-Type: HIT < X-LLNW-Dbg-TTL: 382 seconds
Should be cacheable
Is in cache
382 seconds before refresh check

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