On 4/26/12 4:16 PM, Michael Turner wrote:
Hi all,
Leif, we spoke yesterday in IRC about this but I wanted to follow up. You
mentioned faking the host headers (which we can do with curl) to load the cache
with the vip address on both the independent real traffic servers.
Doing this, I could only get 404 results, and it never seemed to actually fetch
from the origin.
$ curl -H "Host:<real_ats_server> -o /dev/null http://<ats server
vip>/path_to_cache
If I removed the "Host:<real ats server>" component, it works.
Am I missing something? :)
Hmmm, I do this all the time. Lets make sure I understand, and I'll make a
fictitious setup:
a. The SLB has a VIP of 192.168.201.69.
b. The REALs behind the SLB are 192.168.202.2 and 192.168.202.3
c. The SLB VIP has a DNS record: ats.example.com. IN A 192.168.201.69
Normally, a user would fetch e.g. http://ats.example.com/file.jpg. For that
to work , your ATS boxes would have a remap.config like
map http://ats.example.com http://origin.example.com
To fetch file.jpg from each host behind the SLB, you would do e.g.
for i in 192.168.202.2 192.168.202.3; do
curl -s -o /dev/null -D - -H "Host: ats.example.com" http://$i/file.jpg
done
This is where it can get sketchy, your REALs must obviously have a way to
route directly here, at yahoo we did tricks with iptables and route tables
and what not, since the VIPs for the CDN were in-line and not DSR.
Now, for your specific error, I'm guessing, but not sure, that your
remap.config is not matching what the Host: header is that you set via -H?
Typically, a 404 means that the server can't figure out how to map the
request to an origin (or, the origin is generating a 404, but that's easy to
figure out).
Another thing to look at is if your "pristine" host header setting in
records.config is on or off. What should it be? Well, it depends on what
your origin server expects to see! If the origin expects to see Host:
ats.example.com, then pristine host headers should be set to "1", it the
origin (in this example) expects to see Host: origin.example.com, then
pristine host headers should be set to "0".
I hope that helps.
Cheers,
-- Leif
