Adding "\n" while using multiline.parser with Tail

[duj4]

Bug Report

Describe the bug “\n” will be added when using multiline.parser.

To Reproduce The simplest one is the official one: before:

single line...
Dec 14 06:41:08 Exception in thread "main" java.lang.RuntimeException: Something has gone wrong, aborting!
    at com.myproject.module.MyProject.badMethod(MyProject.java:22)
    at com.myproject.module.MyProject.oneMoreMethod(MyProject.java:18)
    at com.myproject.module.MyProject.anotherMethod(MyProject.java:14)
    at com.myproject.module.MyProject.someMethod(MyProject.java:10)
    at com.myproject.module.MyProject.main(MyProject.java:6)
another line...

after:

[0] tail.0: [0.000000000, {"log"=>"single line...
"}]
[1] tail.0: [1626634867.472226330, {"log"=>"Dec 14 06:41:08 Exception in thread "main" java.lang.RuntimeException: Something has gone wrong, aborting!
    at com.myproject.module.MyProject.badMethod(MyProject.java:22)
    at com.myproject.module.MyProject.oneMoreMethod(MyProject.java:18)
    at com.myproject.module.MyProject.anotherMethod(MyProject.java:14)
    at com.myproject.module.MyProject.someMethod(MyProject.java:10)
    at com.myproject.module.MyProject.main(MyProject.java:6)
"}]
[2] tail.0: [1626634867.472226330, {"log"=>"another line...
"}]

Expected behavior Both single line and multi-line logs should be as still, no "\n" is added:

[0] tail.0: [0.000000000, {"log"=>"single line..."}]
[1] tail.0: [1626634867.472226330, {"log"=>"Dec 14 06:41:08 Exception in thread "main" java.lang.RuntimeException: Something has gone wrong, aborting!
    at com.myproject.module.MyProject.badMethod(MyProject.java:22)
    at com.myproject.module.MyProject.oneMoreMethod(MyProject.java:18)
    at com.myproject.module.MyProject.anotherMethod(MyProject.java:14)
    at com.myproject.module.MyProject.someMethod(MyProject.java:10)
    at com.myproject.module.MyProject.main(MyProject.java:6)"}]
[2] tail.0: [1626634867.472226330, {"log"=>"another line..."}]

Screenshots Another example in my own case:

multiline-parser:

parser:

before:

after:

Your Environment

• Version used: v3.0.6
• Configuration: as screenshot above
• Environment name and version (e.g. Kubernetes? What version?): VM
• Server type and version: Linux
• Operating System and version: RHEL8

[duj4]

Same issue had been opened in https://github.com/fluent/fluent-bit/issues/4227 but without any further update.

[duj4]

Thanks @patrick-stephens 's suggestion, Lua can remove the last "\n" but it will twist the record order:

Any further suggestion would be appreciated.

[duj4]

Another workaround is add a "\n" to the end of parser to match the newly added newline, so the new parser will be:

However, it would be better to fix the "adding newline" issue natively. @lecaros

[lecaros]

hi there. What's the impact of this issue other than the visualization in stdout?

[duj4]

hi @lecaros , thanks for the reply.

The impact I could see for now is the visualization in either output or Grafana, but that's not a big deal, you may close this one for now.