how to set the case of skywalking java agent+ logstash-logback in async mode

[jevonsnotes]

I have tried various asynchronous configurations, but all failed without exception, resulting in the loss of tid. Only the synchronous method below can properly push tid. If switching to asynchronous, how should it be configured, and are there any reference cases available?

<?xml version="1.0"?>
<!-- Logback configuration. See http://logback.qos.ch/manual/index.html -->
<configuration scan="true" scanPeriod="10 seconds">

	<springProperty scope="context" name="springAppName" source="spring.application.name" defaultValue="xxx"/>
	<springProperty scope="context" name="springAppEnv" source="spring.application.env" defaultValue="unknown"/>
	<springProperty scope="context" name="port" source="server.port" defaultValue="0"/>

    <property name="LOG_HOME" value="${LOG_ROOT:-logs}/${springAppName}" />
    <property name="LOG_PREFIX" value="${springAppName}" />

	
	<appender name="LOGSTASH" class="net.logstash.logback.appender.LogstashTcpSocketAppender">
		<destination>xxxx</destination>
		<queueSize>1048576</queueSize>
		<encoder charset="UTF-8" class="net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder">

			<providers>

				<!-- ✅ SkyWalking TraceId Provider -->
				<provider class="org.apache.skywalking.apm.toolkit.log.logback.v1.x.logstash.TraceIdJsonProvider">
					<fieldName>trace.id</fieldName>
				</provider>

				<!-- ✅ SkyWalking Context Provider -->
				<provider class="org.apache.skywalking.apm.toolkit.log.logback.v1.x.logstash.SkyWalkingContextJsonProvider">
					<fieldName>skywalking.ctx</fieldName>
				</provider>
				<timestamp>
					<timeZone>UTC</timeZone>
				</timestamp>
				<pattern>

					<pattern>
						{
						"server_date":"%date{yyyy-MM-dd HH:mm:ss.SSS}",
						"server": "%ip:${port}",
						"app_name":"${springAppName}",
						"service_name": "xxx",
						"file_line":"%file:%line",
						"port":"${port}",
						"level": "%level",
						"thread": "%thread",
						"class": "%logger{40}",
						"message": "%message",
						"stack_trace": "%exception",
						}
					</pattern>
				</pattern>
			</providers>
		</encoder>
	</appender>

	<appender name="ASYNC_LOGSTASH" class="ch.qos.logback.classic.AsyncAppender">
		<queueSize>512</queueSize>
		<includeCallerData>true</includeCallerData>
		<includeMdcKeys>true</includeMdcKeys>
		<appender-ref ref="LOGSTASH"/>
	</appender>

	

	<root level="INFO">
		
<!--		<appender-ref ref="ASYNC_LOGSTASH"/>-->
		<appender-ref ref="LOGSTASH"/>
	</root>

	<jmxConfigurator />
</configuration>

[wu-sheng]

Use the AI we provided on the website. Here is the clear answer from it.

This is a known issue with SkyWalking and async appenders. The core problem is that when using ch.qos.logback.classic.AsyncAppender wrapping a SkyWalking-aware appender, the trace context is lost because logging happens on a different thread.

The Recommended Solution

Don't use AsyncAppender with SkyWalking's log appenders. SkyWalking's GRPCLogClientAppender and similar appenders already have an internal async mechanism, so wrapping them in an AsyncAppender is unnecessary and breaks trace ID propagation. [[AsyncAppender missing tid](https://github.com//discussions/12220)]

For your specific case with LogstashTcpSocketAppender, the working solution is to use it synchronously (which you've already confirmed works), or configure it with the TraceIdJsonProvider directly — without an outer AsyncAppender. [[logstash logback plugin](https://github.com//issues/5746)]

A confirmed working configuration from the community is:

<appender name="logstash" class="net.logstash.logback.appender.LogstashTcpSocketAppender">
    <destination>${logging.logstash}</destination>
    <encoder charset="UTF-8" class="net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder">
        <providers>
            <provider class="org.apache.skywalking.apm.toolkit.log.logback.v1.x.logstash.TraceIdJsonProvider"/>
            <timestamp>
                <timeZone>UTC</timeZone>
            </timestamp>
            <pattern>
                <pattern>
                    {
                    "level": "%level",
                    "pid": "${PID:-}",
                    "thread": "%thread",
                    "class": "%logger{1.}:%L",
                    "message": "%message",
                    "stackTrace": "%exception{10}"
                    }
                </pattern>
            </pattern>
        </providers>
    </encoder>
</appender>

<root level="INFO">
    <appender-ref ref="logstash"/>
</root>

Note that LogstashTcpSocketAppender itself has a built-in queueSize parameter (which you're already using), so it handles async buffering internally — you don't need an additional AsyncAppender wrapper on top of it. [[logstash logback plugin](https://github.com//issues/5746)]

If You Must Use AsyncAppender (for console/file appenders)

For standard console or file appenders, SkyWalking does support AsyncAppender when using the MDC-based layout (TraceIdMDCPatternLogbackLayout with %X{tid}): [[Print trace ID in logs](https://skywalking.apache.org/docs/skywalking-java/latest/en/setup/service-agent/java-agent/application-toolkit-logback-1.x/#print-trace-id-in-your-logs)]

<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <encoder class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
        <layout class="org.apache.skywalking.apm.toolkit.log.logback.v1.x.mdc.TraceIdMDCPatternLogbackLayout">
            <Pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%X{tid}] [%thread] %-5level %logger{36} -%msg%n</Pattern>
        </layout>
    </encoder>
</appender>

<appender name="ASYNC" class="ch.qos.logback.classic.AsyncAppender">
    <discardingThreshold>0</discardingThreshold>
    <queueSize>1024</queueSize>
    <neverBlock>true</neverBlock>
    <appender-ref ref="STDOUT"/>
</appender>

However, this MDC approach is not directly applicable to your LogstashTcpSocketAppender + TraceIdJsonProvider setup. The bottom line for your case: keep the sync configuration you have, since LogstashTcpSocketAppender already buffers internally via its queueSize.