Can't see Sleuth spanId or traceId in custom logback

logback configuration is down below

    <appender name="ELK-CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder class="net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder">
            <providers>
                <pattern>
                    <pattern>
                    {
                        "timestamp": "@timestamp",
                        "severity": "%level",
                        "service": "${springAppName:-}",
                        "trace": "%X{traceId:-}",
                        "span": "%X{spanId:-}",
                        "pid": "${PID:-}",
                        "thread": "%thread",
                        "class": "%logger{40}",
                        "rest": "%message"
                        }
                    </pattern>
                </pattern>
            </providers>
        </encoder>
    </appender>

But span or trace is always null ,

{
    "timestamp":"@timestamp",
    "severity":"INFO",
    "service":"springAppName_IS_UNDEFINED",
    "trace":"",
    "span":"",
    "pid":"21524",
    "thread":"reactor-http-nio-3",
    "class":"elk-logger",
    "rest":"test log content"
}

Not sure is there is any configuraiton that i'm missing, Thanks for any advice

I tried %X{X-B3-TraceId:-} ,But still doesn't work

"trace": "%X{X-B3-TraceId:-}",
"span": "%X{X-B3-SpanId:-}",

Solution

There are some possible reasons why you can't see Sleuth spanId or traceId in your custom logback configuration.

One reason is that you need to include the Sleuth pattern in your log pattern, which is %X{traceId:-} %X{spanId:-} %X{parentId:-}.
Another reason is that you need to include the base.xml file from Spring Boot, which contains the default configuration for Sleuth logging.
A third reason is that you need to set the logging.level.org.springframework.cloud.sleuth property to DEBUG or higher

I hope this helps you solve your problem. If you want to learn more about Sleuth and Logback, you can check out these resources: • Get Current Trace ID in Spring Cloud Sleuth: A tutorial on how to get the current trace ID and span ID using the Tracer object.