log4j2 integration doesn't work, "logging.pattern.level" syntax incorrect in TraceEnvironmentPostProcessor

[farnetto]

Description

traceId and spanId don't appear in log when using log4j2, e.g.:

2021-08-12 12:54:14.737 INFO [hello-app,,] 106004 --- [nio-8080-exec-1] c.e.d.FooController : hello

Reproduce

1. exclude org.springframework.boot:spring-boot-starter-logging
2. include org.springframework.boot:spring-boot-starter-log4j2, org.springframework.cloud:spring-cloud-starter-sleuth and io.zipkin.brave:brave-context-log4j2
3. define bean of type ScopeDecorator with ThreadContextScopeDecorator.get()

Cause

The value for logging.pattern.level in TraceEnvironmentPostProcessor uses e.g. %X{traceId:-} but the syntax for an empty default value isn't supported by log4j2. See Pattern Layout

Workaround

Override the property with e.g.:

logging.pattern.level=%5p [${spring.zipkin.service.name:${spring.application.name:}},%X{traceId},%X{spanId}]

i.e. no :-

[marcingrzejszczak]

Can you please answer all the required questions described in the issue template? For your convenience let me paste it here

Describe the bug
Please provide details of the problem, including the version of Spring Cloud that you
are using.

Sample
If possible, please provide a test case or sample application that reproduces
the problem. This makes it much easier for us to diagnose the problem and to verify that
we have fixed it.

[farnetto]

I certainly did.

[farnetto]

spring-boot-starter-parent 2.5.3 and spring-cloud.version 2020.0.3

[marcingrzejszczak]

Since manual work is required to add such support with Brave maybe it's enough to document that the pattern must be changed? WDYT?

[farnetto]

Yes, that's a good idea. Is the pattern that way for slf4j? I expected that spring-cloud-sleuth + log4j2 would work "out of the box", but there are a couple steps you have to go through on top of the issue with the pattern. I'm sure more documentation would be appreciated. Thanks.

[farnetto]

On the other hand, I think the pattern might only be an issue if you use the default log4j2 configuration in org/springframework/boot/logging/log4j2/log4j2.xml or the property LOG_LEVEL_PATTERN.

[marcingrzejszczak]

Are you willing to add such an entry to the docs?

[farnetto]

Yes, I'll give it a shot.

[spring-cloud-issues]

If you would like us to look at this issue, please provide the requested information. If the information is not provided within the next 7 days this issue will be closed.