NimbostratusI am trying to do something similar in 10.x that Sideband of 11.x allows. Is there anyway I can grab a web page in my iRule when the client connects or upon init for processing? I know all of the I/O commands have been stripped out of iRules, so that's out. Changing the URI when a client comes in merely directs them to the page I want to grab to look for the address that is in the X-Forwarded-For.
Thanks,
Mitch
Employee
Here's what it would generally look like:
when CLIENT_ACCEPTED {
set initial lookup status - do lookup
set lookup 1
}
when HTTP_REQUEST {
if { [info exists lookup] and $lookup == 1 } {
Unset the lookup flag
unset lookup
Save the client's original request
set request [HTTP::request]
Save the original pool
set default_pool [LB::server pool]
Set to a new “sideband” IP and port
node 10.70.0.1 80
Set new URI for sideband request
at this point ingress flow is diverted to the new resource (with a new URI).
HTTP::uri "/http-retry-test.php"
}
}
when HTTP_RESPONSE {
The sideband response will return just like a regular response,
so you need a way of determining which is which. If you can
craft the web server's response so that it returns a unique
non-standard value, you can capture that here. Otherwise
you can set a temporary variable at the end of the
HTTP_REQUEST event and perform an "if { [info exists variable] }"
conditional in the HTTP_RESPONSE (make sure to unset the
variable right away).
if { [HTTP::status] eq "600" } {
collect the payload from the sideband response
HTTP::collect [HTTP::header value Content-Length]
}
}
when HTTP_RESPONSE_DATA {
Capture payload data - this will be the sideband response data
set payload [HTTP::payload]
Reset to the original pool
pool $default_pool
Example: modify original (potentially modified) request with data from sideband call
set new_request [string map "\"GET / \" \"GET /?sideband=[URI::encode $payload] \"" $request]
Reset the original (potentially modified) request to the default pool
HTTP::retry $new_request
}
The primary difference between this method and v11 sideband calls, aside from more intuitive coding, is that v11 sideband calls are blocking. When you issue a sideband call, the response is returned to the sideband object before anything else happens. With HTTP::request and HTTP::retry you have to capture the sideband response in a normal HTTP response event, so you have to be crafty about how you distinguish between regular and sideband responses. You can kind of think of the old method like a pendulum. You have to keep the momentum of the "ball" as it travels between the client and server, but the sideband call allows you to quickly tilt the table so that the ball will take a different path.
NimbostratusHoly smokes...glad I asked. I would never have figured that one out.
Cirrostratus
if { [info exists lookup] and $lookup == 1 } {
[info exists ] is a "set" command, like set and append, which all write to a variable. So what you're really saying is, "is this variable set?" (which has nothing to do with what may already be inside the variable).
Cirrostratus