550655 - Excess DNS 'A' record duplicate responses

Status: RESOLVED WONTFIX

(mozilla.org Graveyard :: Server Operations, task)

Description

[Reed Loden [:reed]]

$ host www.mozilla.org
www.mozilla.org is an alias for www-mozilla-org.geo.mozilla.com.
www-mozilla-org.geo.mozilla.com is an alias for www-mozilla-org.glb.mozilla.net.
www-mozilla-org.glb.mozilla.net has address 63.245.217.21
www-mozilla-org.glb.mozilla.net has address 63.245.217.21
www-mozilla-org.glb.mozilla.net has address 63.245.217.21
www-mozilla-org.glb.mozilla.net has address 63.245.217.21
www-mozilla-org.glb.mozilla.net has address 63.245.217.21

$ host www.mozilla.com
www.mozilla.com is an alias for www-mozilla-com.glb.mozilla.net.
www-mozilla-com.glb.mozilla.net has address 63.245.209.106
www-mozilla-com.glb.mozilla.net has address 63.245.209.106

What's with all the duplicate 'A' record responses?

Comment 1

[matthew zeier [:mrz]]

I agree that looks squirrely but that's how the GLB software works.  There are multiple different A RRs. When the masking happens you get the same quantity but only the IP that is "best" for you. 

Are you seeing actual problems?

Comment 2

[Reed Loden [:reed]]

(In reply to comment #1)
> I agree that looks squirrely but that's how the GLB software works.  There are
> multiple different A RRs. When the masking happens you get the same quantity
> but only the IP that is "best" for you.

I have to say that's probably the dumbest method of handling GLB I've ever seen... You might want to contact the vendor about getting that fixed.

> Are you seeing actual problems?

No, but it could cause minor performance issues due to the increased number of bytes in the DNS query response... I haven't measured it, so not sure how much of a hit it really is, but it is something to consider.

Comment 3

[matthew zeier [:mrz]]

It is what it is.  I'll make a note with Zeus.

This is a CANTFIX - we'll pick up an update when they rev the software (or get around to combining it into TM).

Comment 4

[matthew zeier [:mrz]]

> No, but it could cause minor performance issues due to the increased number of
> bytes in the DNS query response... I haven't measured it, so not sure how much
> of a hit it really is, but it is something to consider.

Minor performance vs. page loading from a closer origin - the latter probably wins.  And Minor performance vs. automatic failover, latter again.  

:)