How to create iRule to deliver an alternate page response other than 'page unavailable'

You may find useful the following docs:

Automatic maintenance page sorry page with images

( Contributed by: thepacketmaster )

LTM Maintenance Page

( Contributed by: spark, based off several other contributors including citizen_elah )

Note: your example shows that you are trying to run the iRule on a disabled vip. That wont work because disabled vips does not receive new conns.

Richard,

Might a Fallback Host entry set as "http://internalsite.co.uk/slp/maintenance.html" in a HTTP Profile on the VIP work for you? Also, do you disable the VIP itself or the pool member(s) within?

Hope this helps, N

Here's what we use on our public web sites. Stored the HTML and images in iFiles for use elsewhere.

when HTTP_REQUEST {
   if {[active_members [LB::server pool]] < 1} {
      switch [HTTP::uri] {
         "/guardian_header.jpg" { HTTP::respond 200 content [ifile get "guardian_header_jpg"] }
         "/guardian_logo.jpg" { HTTP::respond 200 content [ifile get "guardian_logo_jpg"] }
         default { HTTP::respond 200 content [ifile get "maint_index_html"] }
      }
   }
}

The problem is that you're disabling the virtual server. A disabled VIP isn't going to respond to any requests or evaluate any iRule events. A simple alternative would be to disable the pool members and use an active_member check in the CLIENT_ACCEPTED event.

When you disable the virtual server the F5 no longer responds on that IP/port, so no iRules will be triggered. I think that you want to disable the servers in the pools instead of the F5 virtual server instead. If all of the pool member servers are disabled, either manually or due to failing health monitors and an HTTP request comes in, a LB_FAILED event will be triggered and you can craft your response. I recommend something simpler, this is the basics of what we use, where your can add your own html, you could also do a HTTP::redirect instead. Remember that the virtual server will need to have an HTTP profile.

when LB_FAILED { log local0.info "LoadBalanceFailureHost [HTTP::host]" HTTP::respond 500 content { Put your HTML here. } }

Thanks all , very much for your ideas and help. This is such a good forum, I was not expecting anything back for a while, so really pleased. Looks like I can work this out now, but I'll post back if I need any more help. Thanks again

See: https://devcentral.f5.com/wiki/iRules.active_members.ashx

when HTTP_REQUEST {
   if { [active_members http_pool] < 1 } {
      HTTP::respond 200 content "html maintenance page..."
   }
}

One big problem I see with the various options above is that they use the Status Code 200, which signifies "OK". Since the situation is not OK the proper code should be issued, for instance:

HTTP::respond 404 content "html maintenance page..."

See section 10 of RFC 2616 for a list of proper Status Codes.

Dont want to be tricky, but RFC actually states the Oposite. 404 is given when "The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent."

"..10.4.5 404 Not Found

The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent. The 410 (Gone) status code SHOULD be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address. This status code is commonly used when the server does not wish to reveal exactly why the request has been refused, or when no other response is applicable."

For what it's worth we use a 503 (Service Unavailable) from LB_FAILED;-

when LB_FAILED {
    HTTP::respond 503 Content [b64decode [class lookup $sorry dg_content]] noserver Content-Type "text/html" Retry-After "600" Content-Encoding "gzip" Connection "close"
    return
}

We have the HTML gzipped, b64-encoded, and stored in a data group (dg_content). The Retry-After header is for SEO.