# mmtaghostname: message modification module

Module Name: | mmtaghostname
Authors: | Jean-Philippe Hilaire <jean-philippe.hilaire@pmu.fr> & Philippe Duveau <philippe.duveau@free.fr>

## Purpose

As a message modification, it can be used in a different step of the message processing without interfering in the parsers’ chain process and can be applied before or after parsing process using rulesets.

The purposes are :

- to add a tag on message produce by input module which does not provide a tag like imudp or imtcp. Useful when the tag is used for routing the message.

- to force message hostname to the rsyslog value. AWS Use case : applications in auto-scaling systems provides logs to rsyslog through udp/tcp. As a result of auto-scaling, the name of the host is based on an ephemeral IPs (short term meaning). In this situation rsyslog local hostname is generally closed to business rule. So replacing hostname received by the rsyslog local Hostname provide values to the logs collected.

## Compile

To successfully compile mmtaghostname module.

    ./configure --enable-mmtaghostname ...

## Configuration Parameters

### Input Parameters

Note

Parameter names are case-insensitive. The camelCase convention is recommended.

Parameter | Summary
--- | ---
tag | Assigns a tag to messages. This is useful for inputs like `imudp` or `imtcp` that do not provide a tag.
forceLocalHostname | Forces the message `HOSTNAME` to the rsyslog `localHostName` value.

## Sample

In this sample, the message received is parsed by RFC5424 parser and then the HOSTNAME is overwritten and a tag is set.

    module(load='mmtaghostname')
    module(load='imudp')
    global(localhostname="sales-front")

    ruleset(name="TagUDP" parser=[ "rsyslog.rfc5424" ]) {
        action(type="mmtaghostname" tag="front" forceLocalHostname="on")
        call ...
    }
    input(type="imudp" port="514" ruleset="TagUDP")

Support: rsyslog Assistant | GitHub Discussions | GitHub Issues: rsyslog source project

Contributing: Source & docs: rsyslog source project

© 2008–2025 Rainer Gerhards and others. Licensed under the Apache License 2.0.