How to use multiple key values ​in discriminator in logback

Question

I am currently trying to generate a log path using the discriminator supported by logback.

When creating a log path, I am using org.slf4j.MDC to create the log path by putting the value in the key I specified in the log path.

Below is the source code that I actually save as MDC.

LogServeice.java

MDC.put("key1", "test1";
MDC.put("key2", "test2");
MDC.clear();

Below this is the file source code actually set in logback-spring.xml.

logback-spring.xml

<appender name="ApiRollingFile" class="ch.qos.logback.classic.sift.SiftingAppender">
    <discriminator>
        <key>key1</key>
        <defaultValue>unknown</defaultValue>
    </discriminator>
    <discriminator>
        <key>key2</key>
        <defaultValue>unknown</defaultValue>
    </discriminator>
    <sift>
        <appender name="LOG_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
            <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
                <fileNamePattern>%d{yyyyMMddHH}/${key1}/${key2}/${API_FILENAME}.log
                </fileNamePattern>
            </rollingPolicy>
            <encoder class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
                <layout class="ch.qos.logback.classic.PatternLayout">
                    <pattern>%m%n</pattern>
                </layout>
            </encoder>
        </appender>
    </sift>
</appender>

I used it like this

The value of key1 is not recognized.

key1_IS_UNDEFINED A folder is created like this.

However, the folder for key2 is created fine.

Can I find out why this is the case?

Isn't it possible to use multiple key values ​​in MDC?

Is there a way to use multiple of them?

Below is the source code that I actually save as MDC.