Hi Mark, You can create your own conversion specifier. Here is how: https://logback.qos.ch/manual/layouts.html#customConversionSpecifier Best regards, -- Ceki Gülcü Sponsoring SLF4J/logback/reload4j at https://github.com/sponsors/qos-ch On 6/24/2022 10:07 PM, Mark Raynsford wrote:

Hello!

I have an application where parts of the application set a "domain" MDC value where appropriate, and unset it later when it's no longer applicable.

I'd like to use something like the following when "domain" is set:

<appender name="STDERR" class="ch.qos.logback.core.ConsoleAppender"> <encoder> <pattern>%level %logger [%X{domain}] %msg%n</pattern> </encoder> </appender>

... and something like the following when "domain" _isn't_ set:

<appender name="STDERR" class="ch.qos.logback.core.ConsoleAppender"> <encoder> <pattern>%level %logger %msg%n</pattern> </encoder> </appender>

Is this possible? I'm not seeing anything in the manual that would suggest it is.