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Altostratus

Oct 08, 2020

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iRule HSL logging question with user specified text

I wish to log via HSL a mesage that contains some repeatable text as well as some user generated text. so one of two ways to get text generated I can see. But I some issues with each method. #1: Use a loggin profile template, but when you do how to you add some text to the end (or access via a variable text you feed it? i.e the vIP has a template assignmed, iRule has an HSL::open call, then the iRule later calls say HSL::send $hsl "and does this then get appended to the end?". And all you get is what is specified in the template. How can I pass my string body (value or reference) into the template.

#2 Use all text generation in the iRule, but then how do I get at dynamic values that I want but that are only available when you log via the profile/template. For example: $DATE_MON $DATE_DD $TIME_HMS $BIGIP_HOSTNAME and so on.

Hello Martin.

With a request-logging profile you can set any kind of format in the template field.

An example of CEF format:

CEF:0|F5|MyEnv|1|sip=$CLIENT_IP sprt=$CLIENT_PORT snatip=$SNAT_IP snatprt=$SNAT_PORT dstip=$SERVER_IP dstprt=$SERVER_PORT dhost=$BIGIP_HOSTNAME apm=$X_APM

Where 'X_APM can be configured injecting an HTTP header:

when HTTP_REQUEST {
	HTTP::header replace X_APM [ACCESS::session data get session.custom.name]
}
when HTTP_REQUEST_RELEASE {
	HTTP::header remove X_APM
}

---

In case you still want to use an iRule, you can get those parameters with:

1) Hostname

$static::tcl_platform(machine)

2) Time

set curtime [clock seconds]
set formattedtime [clock format $curtime]
log "$curtime seconds since epoch, $formattedtime"

Output: 1129552706 seconds since epoch, Mon Oct 17 07:38:26 CDT 2005

Regards,

Dario.

6 Replies

Dario_Garrido
Noctilucent
Oct 19, 2020
Hello Martin.

It's better to use a request logging profile.
https://support.f5.com/csp/article/K00847516

You can add extra variables injecting HTTP headers into the HTTP_REQUEST and referencing them with the same name of the header:
$BIGIP_HOSTNAME $Host ${X-Forwarded-For} ...

If you want to avoid sending those headers to the backend server, you can remove them again using this event:
https://clouddocs.f5.com/api/irules/HTTP-REQUEST-RELEASE.html

Regards,
Dario.
- martyn
  Altostratus
  Oct 19, 2020
  Thanks, Not sure that would work in this case. What I need to simulate is the CEF logging format and that is not available from a native profile format choice, plus the data I need to pass in (some arbitrary data). If in effect I am manually writing the CEF formatted message out by a number of profile objects/variables and as well a HTTP header variable(s) or two as data place holders I pretty much may as well just manually create the whole thing via HSL as I am currently. However some (most) of the data that I want is matched from data available in a logging profile, This I am currently getting it from TCL calls, Should they have too great a performance hit I may well see if your proposal would alleviate that. I also didn't know of (think of) using HTTP_REQUEST like that. Interesting and devious I will file that one away, thank you. Martyn Roberts Vodafone/IBM Venture Swindon ISC 07881846887
  - Dario_Garrido
    Noctilucent
    Oct 20, 2020
    Hello Martin.
    With a request-logging profile you can set any kind of format in the template field.
    An example of CEF format:
    CEF:0|F5|MyEnv|1|sip=$CLIENT_IP sprt=$CLIENT_PORT snatip=$SNAT_IP snatprt=$SNAT_PORT dstip=$SERVER_IP dstprt=$SERVER_PORT dhost=$BIGIP_HOSTNAME apm=$X_APM
    Where 'X_APM can be configured injecting an HTTP header:
    when HTTP_REQUEST { HTTP::header replace X_APM [ACCESS::session data get session.custom.name] } when HTTP_REQUEST_RELEASE { HTTP::header remove X_APM }
    ---
    In case you still want to use an iRule, you can get those parameters with:
    1) Hostname
    $static::tcl_platform(machine)
    2) Time
    set curtime [clock seconds] set formattedtime [clock format $curtime] log "$curtime seconds since epoch, $formattedtime"
    Output: 1129552706 seconds since epoch, Mon Oct 17 07:38:26 CDT 2005
    Regards,
    Dario.