How remote site will use internet connection if primary service will not work

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i have a question please see attached image i have three remote site 1,2,3 these are connected via MPLS cloud from DATA center 1 and DATA center 2

remote sites does not have direct internet connection they take this service from data center and DATA center 1 is primary and DATA center-2 is secondary for them.

now my question is that if DATA center internet service goes down so  remote site should automatically moved on to second DATA center to take internet service, so what i need to do using BGP protocol for make this possible and also tell other secondary way if we do not have BGP 

[Marvin Rhoads · Accepted solution]

If there is not BGP or other dynamic routing protocol, we oftern use an IP SLA monitor to track reachability of the internet from a site. When that monitor reports failure of the operation, it change the value of a tracking object which is used in a default static route. The tracking object casues the default static route administrative distance to increase such that it is less preferred than a backup static route which has a different administrative distance.

Further details of such a configuration can be seen in many articles, including the following:

https://supportforums.cisco.com/document/30296/using-ipsla-change-routing

http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/813-cisco-router-ipsla-basic.html

http://www.ciscozine.com/using-ip-sla-to-change-routing/

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and how we will do it using BGP 

[Marvin Rhoads]

If you have BGP then the data centers routes with direct Internet access would be getting a default route (or even full routing table) from the ISP routers via your external BGP (eBGP) routing process. That route should re redistributed into either your internal BGP (iBGP) or any interior gateway protocol you are using (e.g. OSPF, EIGRP etc.) where it it learned by each site router.