logback.xml

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

    <property scope="context" name="sys" value="${SYS:-UNKNOWN}" />
    <property scope="context" name="app" value="${APP:-UNKNOWN}" />
    <property scope="context" name="binary" value="${ARTIFACT_ID:-UNKNOWN}" />
    <property scope="context" name="group" value="${GROUP_ID:-UNKNOWN}" />
    <property scope="context" name="version" value="${VERSION:-UNKNOWN}" />

    <property scope="local" name="log.level" value="${LOG_LEVEL:-INFO}" />
    <property scope="local" name="appender" value="${LOG_FORMAT:-JSON}" />

    <!-- Cf. https://github.com/logstash/logstash-logback-encoder -->
    <appender name="JSON" class="ch.qos.logback.core.ConsoleAppender">
        <encoder class="net.logstash.logback.encoder.LogstashEncoder">
            <timeZone>UTC</timeZone>
            <fieldNames>
                <!-- cf. #customizing-standard-field-names -->
                <logger>category</logger>
                <thread>thread</thread>
                <level>level</level>
                <stackTrace>trace</stackTrace>
            </fieldNames>
        </encoder>
    </appender>

    <!-- Copy of the standard SpringBoot log format -->

    <appender name="TEXT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>

    <root level="${log.level}">
        <appender-ref ref="${appender}" />
    </root>

</configuration>