CODEWITHSUNDEEP
httpvarnish
Erick Vitor Barros
Erick Vitor Barros

Reputation: 11

Varnish: Hiding internal backend requests

That is my scenario:

1) Varnish (172.16.217.131:80), receives a request from a client, i.e: http://172.16.217.131:80/a.png

2) Request is forwarded to the Default Backend (127.0.0.1:8000)

3) Default backend receive the request and process it

4) That processing results in a new URL, i.e: http://172.16.217.132:80/a.png (**As you can see the IP has changed)

5) 172.16.217.132:80 is another backend in Varnish's config file

6) The new URL points to a resource that should be provided by Varnish (that resource generally is an image)

My problem is: The client needs to execute 2 GETs to obtain the image.

My question: How can I configure varnish to internally receive the response from the first backend(127.0.0.1:8000), and fetch data from the second backend (172.16.217.132:80), and after that, send the data to the client?

Thanks.

Upvotes: 1

Views: 1291

Answers (1)

ivy
ivy

Reputation: 5559

By step 4;

4) That processing results in a new URL, i.e: http://172.16.217.132:80/a.png (**As you can see the IP has changed)

do you mean that it results in a HTTP Redirect? Then you could check the backend response status code in vcl_fetch (check for 301, 302 etc), use the Location header as your new url and do a restart. I found a great example of this in the Varnish Book

sub vcl_fetch {
        if (req.restarts == 0 &&
                 req.request == "GET" &&
                 beresp.status == 301) {
                set beresp.http.location = regsub(beresp.http.location,"^http://","");
                set req.http.host = regsub(beresp.http.location,"/.*$","");
                set req.url = regsub(beresp.http.location,"[^/]*","");
                return (restart);
        }
}

Upvotes: 2

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