2-phase proxying


#1

Hi,

I need to configure/modify nginx to use it in a 2-phase proxy kind of
configuration in which:

  • use the hash value of one of the arguments in the original uri to
    find the index of the first backend server (defined in an upstream) that
    needs to be called,
  • generate a separate request from the original request and send it to
    the server specified in the previous stage,
  • parse the output of the first call and generate a second request and
    send it to the second backend server (possibly defined through another
    upstream),
  • return the reply from the second server back to the user

I am guessing that given the complexity, I would probably need to modify
nginx, or possibly write a new module. I am wondering if anyone has any
suggestions, maybe it is possible to do it with just modifying the
configuration(??), maybe there is something similar that is already
built in which I can use to modify, if not, what nginx module (proxy,
addition_filter, …?) I need to modify or use to write my own module.

Thanks,
-M


#2

On Mon, Jan 26, 2009 at 7:19 PM, Mohammad K.
removed_email_address@domain.invalid wrote:

Hi,

I need to configure/modify nginx to use it in a 2-phase proxy kind of
configuration in which:

  • use the hash value of one of the arguments in the original uri to find
    the index of the first backend server (defined in an upstream) that needs to
    be called,
  • generate a separate request from the original request and send it to the
    server specified in the previous stage,
  • parse the output of the first call and generate a second request and
    send it to the second backend server (possibly defined through another
    upstream),

Maybe it will be enough to use the X-Accel-Redirect feature?

Mike


#3

Is it possible to have a configuration similar to the following:

    location /x {
        proxy_pass http://www.yahoo.com;
    }

    location /y {
        add_before_body /x;
        add_after_body  http://www.google.com;
    }

which would supposedly add the content of the www.yahoo.com and
www.google.com before and after the content of the page at
/y/index.html? The addition filter module states that the texts after
add_before_body and add_after_body are URI, but the above config doesn’t
seem to be doing it!

Thanks,
-M


#4

On Wed, Jan 28, 2009 at 08:55:53PM +0100, Valery K. wrote:

Probably this should work:

location /y {
add_before_body @x;
add_after_body @x;
}

No, add_before_body does not support named locations.


#5

On Wed, Jan 28, 2009 at 11:21:35AM -0800, Mohammad K. wrote:

which would supposedly add the content of the www.yahoo.com and www.google.com before and after the content of the page at /y/index.html? The addition filter module states that the texts after add_before_body and add_after_body are URI, but the above config doesn’t seem to be doing it!

This should work, but it’s better to use 0.7.32 for this:

     location = /x {
         proxy_pass http://www.yahoo.com/;
     }

     location = /g{
         proxy_pass  http://www.google.com/;
     }

     location /y {
         add_before_body /x;
         add_after_body  /q;
     }

#6

Probably this should work:

location /y {
add_before_body @x;
add_after_body @x;
}

location @x {
proxy_pass http://www.yahoo.com;
}