Realtional URI rewrites

Question

I am completely new to irules and I would like some validation, or perhaps a better way to do what I want.
I am deploying a new website that uses a completely new set of URIs.  All of the previous URIs do not exist on the new site, but the data is still there using a completely different uri.   There are numerous links to these pages out on the web and we would like to preserve their funcitonality.
So, I have a table of begin values and end values.
eg:
OLD                   NEW
abc                   xyz
bcd                   wxy
and i would like them to perform as such:
www.site.com/abc  &gt;   www.site.com/xyz
www.site.com/bcd  &gt;   www.site.com/wxy
I have read that you can not use relational data in classes creating irules, so I am guessing that I need an irule looking like this:
when HTTP_REQUEST 
{ if { [HTTP::uri] contains "/abc" } { HTTP::respond 301 Location "http://www.mydomain.com/xyz" }
{ if { [HTTP::uri] contains "/bcd" } { HTTP::respond 301 Location "http://www.mydomain.com/wxy" }
}
Let's just say I have 1000 such URLs that I need to redirect like this and I am not sure of the performance impact of such a large irule, not to mention the managability of it.
Thank you for your help!
Shawn

jrahm · Answer

I couldn't quite infer whether those mappings are static or dynamically generated, but if they are static, you can easily create a class for that:
class myURImappings {
 "abc xyz"
 "bcd wxy"
 "cde vwx"
 "def uvw"
}
Then your rule is quite simple:
when HTTP_REQUEST {
  if { [matchclass [string tolower [HTTP::uri]] starts_with $::myURImappings] } {
    HTTP::respond 301 Location "http://www.mydomain.com/[findclass [string tolower[HTTP::uri] $::myURImappings " "]"
  }
}

shawno_84086 · Answer

Thank you.   &nbsp;
&nbsp;Yes the mappings are static.   &nbsp;
&nbsp;Can you foresee any problems related to the number of mappings?   &nbsp;
&nbsp;If I had 10,000 mappings would I realize any impact on non-redirected URLs? &nbsp;
&nbsp;Shawn

jrahm · Answer

There certainly will be an impact, but to what degree depends on several factors, including device hardware, traffic patterns, where the match occurs in the class, etc.  I haven’t tested anything to this scale, so I’d recommend doing that so you know where your performance thresholds are.

joe_pruitt · Answer

Posted By citizen_elah  on  05/31/2007 6:23 AM&nbsp;
&nbsp;I couldn't quite infer whether those mappings are static or dynamically generated, but if they are static, you can easily create a class for that:&nbsp;&nbsp;
class myURImappings {
 "abc xyz"
 "bcd wxy"
 "cde vwx"
 "def uvw"
}&nbsp;
&nbsp;Then your rule is quite simple:&nbsp;&nbsp;
when HTTP_REQUEST {
  if { [matchclass [string tolower [HTTP::uri]] starts_with $::myURImappings] } {
    HTTP::respond 301 Location "http://www.mydomain.com/[findclass [string tolower[HTTP::uri] $::myURImappings " "]"
  }
} &nbsp;&nbsp;
&nbsp;That won't quite work because the value of HTTP::uri will always start with a slash.  Also, your findclass call is assuming that the URI equals the value in the class, but the originally supplied code used the contains operator.  &nbsp;
&nbsp;We don't have measurements for class lists of 10000+ entries, but you'll have to expect that it will have a performance impact (you can't get 10000 string comparisons for free).&nbsp;
&nbsp;If you can supply some real examples of what you are trying to map from/to there might be a way to use some tricks to limit the number of mappings needed.  For instance, if you need to map:&nbsp;&nbsp;/aaa/foo -&gt; /ZZZ/foo
&nbsp;/aaa/bar -&gt; /ZZZ/bar
&nbsp;...&nbsp;&nbsp;
&nbsp;Then you can do some string splitting and just extract the first element of the URI and look that up, then dynamically build the redirect/respond retaining the original trailing section of the URI.  But without examples/requirements I don't know if that will work for you.&nbsp;
&nbsp;-Joe

wil_schultz_101 · Answer

Rumor has it that switches are faster, I don't know this for a fact, however I do use switches wherever possible and have not run into any problems yet 😄
when HTTP_REQUEST {
 switch -glob [string tolower [HTTP::uri]] {
  "/abc*" { HTTP::respond 301 Location "http://www.mydomain.com/xyz" }
  "/bcd*" { HTTP::respond 301 Location "http://www.mydomain.com/wxy" }
  "/cde*" { HTTP::respond 301 Location "http://www.mydomain.com/vwx" }
  "/def*" { HTTP::respond 301 Location "http://www.mydomain.com/uvw" }
 }
}

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