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My organisation currently has 2 data centres from which it hosts its corporate website, with Akamai providing load-balancing, and other CDN services. Now, I'm told that if our server stack in 1 data centre stops responding, Akamai will automatically route the incoming traffic to the alternate data centre.

Q: Now my question is, what is the trigger that causes Akamai to initiate this routing?

ie. Does Apache Http server literally have to stop listening/responding on port 80, or would returning non-2XX/3XX/4XX codes do it? (ie. have the application server return HTTP 500's)

If so, can it be configured to work on a context-by-context basis, so that if goes down (app server returns HTTP 500), traffic to /search is routed elsewhere, but all other traffic still hits both stacks?

Q: Also, how long after restoration of service would traffic start being routed back?

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You should ask Akamai about all this stuff. – gekkz Apr 19 '12 at 16:04
up vote 3 down vote accepted

(1) This is one the fail-over, typically called Fail-over to Alternate Data Center "Mirror Fail-over"·

Fail-over can be directed to use the backup site in case the primary is unavailable. You may choose to have the backup site be different from the origin site - for example, it may contain reduced functionality or content. Upon receiving a request for content that resides on the primary site and determining that the primary site is unavailable, the Akami edge server will obtain the request content[ or its defined substitute] from the mirror site "Alternative DC" in a manner invisible to the end user.·

(2) The restoration depends on your thresholds. What is your frequency of your check and how long your response need to be validated. When I was using Akamai. I add some extra checks to ensure the DC

  • Edge bandwidth usage drops or bursts
  • Does Origin server within a data center fails.·
  • Is there a Origin connection failure "Associating to DC load balancer"·
  • Origin DNS failure·
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Thanks for your answer. Let me see what options I have access to now that I can contact Akamai. – Crollster Apr 25 '12 at 8:35

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