sleuth logging pattern: pid and defaultvalues

[vy]

sleuth logging pattern: pid and defaultvalues

[vy]

Hey @mschwehl, I am glad you liked the project. Though I am a bit confused by your questions. Let me elaborate that a bit:

1. Judging by logback-spring.xml you shared, spring-cloud-samples uses Logback for logging, though, as its name implies, log4j2-logstash-layout is a Log4j 2.x layout plugin. So I am totally puzzled here. That being said, I will address your questions assuming you want to use Log4j 2.x in combination with log4j2-logstash-layout plugin in spring-cloud-examples.
2. You want to expose pid. I think what you need is to just add a pid attribute referencing to ${env:PID}. Just create a new template JSON having "pid": "${env:PID}" and you are done. (Why can't we ship it by default? Because we stick to JSONEventLayoutV1, which has a pre-defined structure.)
3. We are using the default Jackson ObjectMapper to read and write JSON. So you want to configure this mapper, say, to emit empty string on null entries. Correct?

[mschwehl]

Hello @vy,

Thank you for your quick response and sorry for the confusion here.
My office is using an infrastructure using elkstack. One huge client is sending json messages in the 'sleuth' format and i want to produce the same output for my client using your log4j-json library

All works fine so far, thank you for providing this lib, it really fills a gap.

Refering to 2:

My tester is

        MDC.put("X-B3-TraceId", "tracID");
	logger.info("Test Message");

       // pattern.json
	{
			"message": "${json:message}",
			"severity": "${json:level}",
			"trace": "${json:mdc:X-B3-TraceId}",
			"nulltest": "${json:mdc:nulltest}",
			"pid": "${env:PID}"
	}
	//output
	{"message":"Test Message","severity":"INFO","trace":"tracID","nulltest":"null","pid":"${env:PID}"}

i think the PID is not evaluated, therefore my question i asked to you

Refering to 3:

I will have a look how to achieve the translation from 'null' to "" in nulltest using jackson.

best regards
Martin.

[vy]

There was indeed a bug with resolving null MDC (context data) values. I pushed the fix. Would you mind testing it, please? If it works for you, I will make a new release.

Coming back to the PID discussion... I thought you already had an environment variable called PID passed to your Java application. My suggestion is to first retrieve the PID in Java and then call System.setProperty("PID", pid), which will make it accessible to Log4j lookups with ${env:PID} variable.

[mschwehl]

I can confirm that the null-issue is fixed, thank you

Back to PID. It was my misanderstanding, i was thinking that

https://github.com/apache/logging-log4j2/blob/master/log4j-core/src/main/java/org/apache/logging/log4j/core/LogEvent.java

is providing the pid just like the ThreadId. I was wrong, thank you for pointing me to my error.

There are several ways to put the pid in the MDC. I will choose one of them and can go on with my coding. If you don't mind i will close this issue after your next release (or you can do as well)

Bist wishes
Martin

[vy]

@mschwehl, great! Thanks for taking time to test it. I have just pushed the new release to Sonatype. v0.11 should appear in Maven Central momentarily.

[MPeli]

Is it possible to get PID without manipulating MDC? We have got an application which we cannot modify, but we have got access to log4j2.xml. Thank you.

[vy]

Using LogstashLayout, you can have the PID as follows:

1. Put the PID into an environment variable, e.g., PID.
2. Configure LogstashLayout as follows:

<LogstashLayout ...>
    <EventTemplateAdditionalFields>
        <KeyValuePair key="pid" value="${env:PID}"/>
    </EventTemplateAdditionalFields>
</LogstashLayout>

If you can use JsonTemplateLayout instead, which I strongly recommend you to do, you can solve this without introducing any environment variables:

<JsonTemplateLayout eventTemplateUri="classpath:GelfLayout.json">
  <EventTemplateAdditionalField
       key="pid"
       format="JSON"
       value='{"$resolver": "pattern", "pattern": "%pid"}'/>
</JsonTemplateLayout>