Redirect to other url

gundam · September 2018

Can we redirect to external url when all real servers failed health check.

diederik · September 2018

Yes this is possible using aFlex.

You can use something like this:

when HTTP_REQUEST {
   if {[LB::status pool Server_HTTP] == "down" } {
      HTTP::respond 302 Location "https://[HTTP::host][HTTP::uri]"
   }
}

Use the HTTP response code that suits your requirements best.

Google & Github are your friend

https://github.com/a10networks/aflex-collection
https://www.a10networks.com/resources/articles/aflex-examples

gundam · September 2018

Hi diederik

Thank you for the info and so I can put like this?

when HTTP_REQUEST {
if {[LB::status pool Server_HTTP] == "down" } {
HTTP::respond 302 Location "https://backup.example.com"
}
}

Thank you

diederik · September 2018

Yes that should work. Make sufre the " " are the correct ones though.
See the difference in your post and mine.

gundam · September 2018

Thank you diederik

How about this case, can I setup redirect for each web site?

1 VIP 205.222.120.38
2 real servers web001.com 10.1.1.1 web002.com 10.1.1.2

hosting multiple web sites on same service-group (server-http)

https://www.abc.com -> redirect to maintenance.abc.com
https://www.def.com -> redirect to maintenance.def.com
https://www.ghi.com -> redirect to maintenance.ghi.com

Is it possible?

Thank you

diederik · September 2018

Of course, you could do it something like this:

when HTTP_REQUEST {
   if {[LB::status pool Server_HTTP] == "down" } {
      set HOST [HTTP::host]
      switch [HTTP::host] {
         www.abc.com  { HTTP::respond 302 Location "maintenance.abc.com" }
         www.def.com  { HTTP::respond 302 Location "maintenance.def.com" }
         www.ghi.com  { HTTP::respond 302 Location "maintenance.ghi.com" }
         default {   log "Unknown HTTP::host $HOST cannot redirect, rejecting connection."
                     reject }
      }
   }
}

Or like this:

when HTTP_REQUEST {
   if {[LB::status pool Server_HTTP] == "down" } {
      set HOST [HTTP::host]
      set REDIRECTHOST ""
      switch [HTTP::host] {
         www.abc.com  { set REDIRECTHOST "maintenance.abc.com" }
         www.def.com  { set REDIRECTHOST "maintenance.def.com" }
         www.ghi.com  { set REDIRECTHOST "maintenance.ghi.com" }
         default {   log "Unknown HTTP::host $HOST cannot redirect, rejecting connection."
                     reject }
      }
      HTTP::respond 302 Location "$REDIRECTHOST"
   }
}

Or you could have the A10 generate the maintenance page for you?

HTTP::respond 503 content "<html><head><title>Apology
Page</title></head><body>We are sorry, but the site you are looking
for is temporarily out of service<br>If you feel you have reached this
page in error, please try again.<p></body></html>"

If you always remove the www and put "maintenance" in front of the hostname you could also look at using regsub to replace "www." in the host with "maintenance.".

gundam · September 2018

Thank you diederik

When I applied this aflex,

when HTTP_REQUEST {

if
{[LB::status pool dlteam-group108_port443] == “down” }

{ HTTP::redirect “http://maintenance.example.com/maintenance.html” }

}

This error massage showed up

Warning: aFleX syntax error: line 3: "wrong # args: no expression after "if" argument"

dlteam-group108_port443 is service-group name

Thank you

diederik · September 2018

That is most likely because you quotation marks are wrong.
Note the difference between:

if {[LB::status pool Server_HTTP] == "down" } {

and you version:

if
{[LB::status pool dlteam-group108_port443] == “down” }

You need to use ""
And you are missing a {

ericn · September 2018

An easier, and generally more efficient way, to do redirect to URL when the service-group is down (usually because all the servers in that group are down) is to use an HTTP template.

slb template http MY_HTTP
   . . .
   failover-url http://sorry.example.com
   . . .

slb virtual-server VIP <some.ip.addr>
   port 80 http
      . . .
      template http MY_HTTP
      . . .

The . . . stuff is a stand-in for other needed or desired configuration. In the case of the template http, maybe the only feature you want to use is failover-url, which is fine.

I have seen the failover-url used in two basic ways (although I am sure there are more)

1. Lots of vPorts redirect to the same "fail-whale" page somewhere else
2. There are 2 data-centers, perhaps we're using GSLB, and each location redirects to a specific URL that resolves to another data-center, something like east.www.example.com and west.www.example.com. Of course, there is a bunch more DNS related config to make such a design work.

gundam · September 2018

I put "" and got new error.

when HTTP_REQUEST {

     if {[LB::status pool “dlteam-group108_port443”] == “down” } {

          HTTP::redirect “http://maintenance.example.com/maintenance.html”

     }

}

Warning: aFleX syntax error: line 3: "syntax error in expression "[LB::status pool “dlteam-group108_port443”]...""

Thank you

diederik · September 2018

I'm afraid you are still using the wrong quotation marks, and you do not need to put quotation marks around the pool name.

Do not use word/wordpad or any other word processing tool that wants to intelligently look at your text. You need a plain-text editor or a code-writing tool that does not adjust the quotations to an open and close version.

The neutral (vertical) quotation mark is used in coding.

Your code needs to look like this:

when HTTP_REQUEST {
     if {[LB::status pool dlteam-group108_port443] == "down" } {
          HTTP::redirect "http://maintenance.example.com/maintenance.html"
     }
}

Redirect to other url

Comments