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My fairly ignorant opinion is this is some kind of DNS problem although I've made no DNS changes for weeks. Maybe S3 is having a problem but no one seems to be reporting and S3 issues.

Sometime last night files in one of our S3 buckets became only occasionally reachable through the URL we typically use. The file is reliably reachable if I use a native amazon URL. Here's an example:

Not reliably reachable: http://guiders.iguiders.com/Guider-1309959830.js

Reachable https://s3.amazonaws.com/guiders.iguiders.com/Guider-1309959830.js http://guiders.iguiders.com.s3.amazonaws.com/Guider-1309959830.js

guiders.iguiders.com is CNAME'd to guiders.iguiders.com.s3.amazonaws.com however tracerout to the 2 names returns different IP addresses - I don't know if that's significant or not.

guiders.iguiders.com is reachable in a browser but I get the "It Works" ubuntu default www page which suggests it's actually pointing to one of our EC2 instances even though the DNS is set to point to amazon S3.

I don't know how it could be an S3 problem but it seems even less likely that DNS is just suddenly not working for this one URL.

Also, I know it's not a local problem (like it's not that I had the DNS changer virus) becuase I use pingdom to check the ability to reach a file in that bucket and every few minutes it tells me the server is down, then it's up, then it's down.

Any ideas for something I should try to discover what the issue is?

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I think the problem may be correcting itself because, although I still cannot reach the file, pingdom has stopped telling me the file is down and I found that I CAN reach the file if I go through a proxy. –  Dave L Jul 27 '12 at 16:39
    
Yes, the problem has somehow corrected itself. –  Dave L Jul 27 '12 at 17:14
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1 Answer

iguiders.com has two nameservers configured: ns2.zoneedit.com and ns18.zoneedit.com

When I run

dig guiders.iguiders.com @ns18.zoneedit.com

I get

guiders.iguiders.com.   7200    IN      CNAME   guiders.iguiders.com.s3.amazonaws.com.

But if I do

 guiders.iguiders.com @ns2.zoneedit.com

I get

 guiders.iguiders.com.   7200    IN      CNAME   x.guiders.iguiders.com.s3.amazonaws.com.

which exists, but has a different IP address. This is the cause of the discrepancy in IP addresses. I'm not sure why your primary and secondary nameservers have different values for the CNAME, that's something to take up with zoneedit.com

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I can possibly explain that. I first suspected that the DNS entry was somehow changed or corrupted. The zoneedit tool would not let me just republish the current definition. So I changed it to x.guiders.iguiders.com.s3.amazonaws.com, published, and then seconds later changed it back. Maybe the change back didn't make it to the second nameserver yet. In any case, the problem did not change in any way when I broke the DNS record or when I set it back. But your post did teach me a new tool, "dig" –  Dave L Jul 27 '12 at 16:08
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