irule stream::exporession and data group list

Hi Yves,

 

 

You can set multiple find/replace strings in a stream expression using the format from the STREAM::expression wiki page:

 

 

STREAM::expression {@IE@Apache@ @Windows@Linux@}

 

 

So you could get the contents of the class and create a stream expression, but just referencing the datagroups by name won't work.

 

 

Which LTM version are you running? The way to reference datagroups has changed from v9 to v10.

 

 

Aaron

Hi Aaron,

 

 

I just read about the change in V 10.1.

 

I am running 10.1.

 

I have tried changing the irule to

 

 

when HTTP_RESPONSE {

 

STREAM::expression "@[class get test_in]@[class get test_out]@"

 

STREAM::enable

 

}

 

 

but that does not yet do the trick.

 

Would it be an option to loop through the list crteated by the get class list_in ?

 

If so, could someone get me started on a loop through a list?

 

 

thanks,

 

yves

 

 

Hi yves,

 

You can use a for loop

 

 

I.E

 

 

foreach { select_test_in } [class get test_in] {

 

scan $select_test_in { parse } variable1 Variable 2 etc..

 

}

 

 

 

Here is a blurb on for and for each loops

 

 

http://devcentral.f5.com/Tutorials/TechTips/tabid/63/articleType/ArticleView/articleId/118/iRules-Optimization-101--03--for-vs-foreach.aspx

 

 

 

I hope this helps

 

 

Bhattman

For the moment, I have this:

 

 

when HTTP_REQUEST {

 

Don't allow data to be chunked

 

if { [HTTP::version] eq "1.1" } {

 

if { [HTTP::header is_keepalive] } {

 

HTTP::header replace "Connection" "Keep-Alive"

 

}

 

HTTP::version "1.0"

 

}

 

}

 

 

when HTTP_RESPONSE {

 

foreach stukje1 [class get test_in] stukje2 [class get test_out])

 

{

 

log local0. "stukje1: $stukje1"

 

STREAM::expression "@$stukje1@$stukje2@"

 

STREAM::enable

 

}

 

}

 

 

and my logging looks lik ethis:

 

 

TCL error: response_rewrite - list element in braces followed by ")" instead of space while executing "foreach stukje1 [class get test_in] stukje2 [class get test_out]) { log local0. "stukje1: $stukje1" STREAM::expression "@$stukje1@$stukje2@" ..."

 

 

so it looks like my "class get" is not even working.

 

 

Another option would be to store the expressions each as a single entry in the string data group

class stream_expressions {
   {
      "@five@six@"
      "@nine@ten@"
      "@one@two@"
      "@seven@eight@"
      "@three@four@"
   }
}

Then you could do something like this to pull each one out and append it to a string and use that for the expression

set expressions [class get stream_expressions]
  set se ""
  foreach {re} $expressions {
    append se [lindex $re 0]
  }
  if { [llength se] > 0 } {
    STREAM::expression $se;
  } else {
    STREAM::disable;
  }
}

Of course, you could just store the entire concatenated string as a single entry as well and that would save on some string allocations. The class would look something like this

class stream_expressions {
   "@one@two@@three@four@@five@six@@seven@eight@@nine@ten@"
}

And the iRule could be like

  set se [lindex [class element 0 stream_expressions] 0];
  if { [llength se] > 0 } {
    STREAM::expression $se;
  } else {
    STREAM::disable;
  }
}

Hope this helps...

-Joe

Joe,

 

 

since there are "s (double quotes) in my list entries, a data group list seems to be the only decent option to describe the list.

 

 

 

You should be able to escape the double quotes with backslashes, or just use curly braces to force literal interpretation of the double quotes:

 

 

STREAM::expression "@\"find1\"@\"replace1\"@@\"find2\"@\"replace2\"@"

 

 

or maybe something like this:

 

 

STREAM::expression {@"find1"@"replace1"@@"find2"@"replace2"@}

 

 

Aaron

Hello all,

thanks for all the input. What I finally put together:

I created 2 data group lists testin and testout

I linked the default stream profile to my virtual server, as well as the below irule.

when HTTP_RESPONSE {
set listlengte [llength [class get testin]]
set streamexpression ""
foreach {stringin} [class get testin] {stringout} [class get testout]
    {
        set streamexpression [concat $streamexpression "@[lindex $stringin 1]@[lindex $stringout 1]@"]
    }
set streamexpression [string map {"@ @" "@@"} $streamexpression]
STREAM::expression $streamexpression
STREAM::enable
} 

All I need to do is to add the part that disabls chunking:

when HTTP_REQUEST {
   Don't allow data to be chunked
  if { 
[HTTP::version] eq "1.1" } {
    if { [HTTP::header is_keepalive] } {
       
 HTTP::header replace "Connection" "Keep-Alive"
    }
    
HTTP::version "1.0"
  }
}

Is there anyone that can estimate the impact (performance wise) of an iRule like this? I used the foreach instead of the 'heavier' for loop, and I used string map instead of string replace, so I would expect it to be 'as light as possible'. If anyone can think of ways to make it even lighter, please let me know.

Yves

The most efficient option would be to hard code the stream expression in the iRule. Are you expecting to need to change the search/replace strings often enough to justify the overhead in creating it on every TCP connection or HTTP request/response?

 

 

Aaron