Enhancement: conditional set-tag()

[faxm0dem]

It would be nice to have this in our toolbox, together with conditional set().

Cheers

[mehul-m-prajapati]

Hi @faxm0dem,

I can see KW_SET_TAG is already there in lib/rewrite/rewrite-expr-grammar.ym.
Can you give me a brief idea about what enhancement is required for set-tag() ?

[furiel]

Some rewrite rules already accept a condition option. Though set-tag does not accept it yet. In the meantime, grammar level if statement was introduced, that can cover this use case as well.

Still, I think set-tag("tag" condition(filter-expression)); is a neat syntax, and I would happy to see it implemented.
With a little code reorganization and a well placed rewrite_condition_opt in the grammar, this can work.

@version: 3.26

log {
  source { example-msg-generator(num(1) template("test message")); };
  rewrite { set-tag("matching-tag" condition(match("test" value("MSG")))); };
  rewrite { set-tag("non-matching-tag" condition(match("donotmatch" value("MSG")))); };
  destination { file("/dev/stdout" template("${TAGS}\n")); };
};

outputting:

[2020-03-17T09:36:01.797268] syslog-ng starting up; version='3.26.1.43.g0b84be1.dirty'
matching-tag,.source.#anon-source0