On Tue, 22 Oct 2013, Erik Steffl wrote:
On 10/22/2013 01:10 AM, Rainer Gerhards wrote:
Hi all,
I wonder what are the actual use cases behind the desire to have global
variables in rsyslog. There are two that I know (I describe them very
briefly as they were expressed at length in the past couple of days):
1. counting messages for some reason
2. load-balancing output actions
Number 2 is - I think - a weak one, as this should better go into a
specific facility inside the engine (read: nothing that the admin should
need to emulate in the conf file).
Are there any other *real-world* use cases?
I am asking because I would like to think if future development directions
of the rsyslog engine should consider the re-addition of global variable
support (which requires a major rewrite).
not sure what are global variables, searched a bit found nothing (found
something in google cache for http://www.rsyslog.com/doc/rainerscript.html,
are those the variables that start with $/?). We are using variables to set
the information we want to include in CEE messages, e.g.
set $!clusterName = "name";
using $!var since this was before $.var was added. Not sure what the
lifetime of $!var or $.var are, $!var seems to be surviving during lifetime
of rsyslog.
Later on we use $!clusterName in template. This is pretty bad solution
because it can pollute json. It would be really helpful to have a separate
(global) namespace (or ability to parse json into subtree under $! which you
mentioned is a possibility).
From what I understand $.var are local variables and only live during
lifetime of a given message so are n ot suitable for the usage as above.
$! and $. variables only exist for the lifetime of a given message.
$! are the variables that have traditionally been part of the all-json group. $.
variables were added so that you could use variables without polluting the $!
tree
global variables existed in 7.5.4 and 7.5.5 but have now been removed, they were
$/ variables and would continue to exist after a message is finished.
The problem they had was that the way that statements are executed results in
less than obvious results when you update them for each message (like a
counter)
right now, we are trying to gather examples of what people would want to do with
global variables so that a new mechanism can be implemented.
David Lang
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