RFR: 8271186: Add UL option to replace newline char

[Mikhailo Seledtsov]

On Fri, 23 Jul 2021 04:09:29 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

> Most of UL entries would print log in one line, however some categories (e.g. `exceptions`) have multiline entries as following:
> 
> 
> [0.157s][info][exceptions] Exception <a 'java/lang/NullPointerException'{0x000000008b918f70}: test>
>  thrown in interpreter method <{method} {0x00007f8335000248} 'main' '([Ljava/lang/String;)V' in 'Test'>
>  at bci 9 for thread 0x00007f8330017160 (main)
> 
> 
> It is ease to parse with log shipper (Fluent Bit, Logstash, and more) if UL can print all logs in one line.
> Famous log shippers support multiline logs of course, but its configuration tends to be complex, and also some input plugins (e.g. TCP on Fluent Bit) do not support multiline logs.
> 
> So I want to introduce new UL option newline to replace `\n` to other chars. For example, the user specifies `newline=\\n` to UL output, newline char (`\n`) will replace `\\n`.
> 
> After this patch, we can get following logs with `newline=\\n`:
> 
> 
> [0.166s][info][exceptions] Exception <a 'java/lang/NullPointerException'{0x000000008b918f70}: test>\n thrown in interpreter method <{method} {0x00007fbc81000248} 'main' '([Ljava/lang/String;)V' in 'Test'>\n at bci 9 for thread 0x00007fbc9c0171a0 (main)
> 
> 
> I've also filed [CSR](https://bugs.openjdk.java.net/browse/JDK-8271188) for this issue, please review it.

Could you, please, consider adding a test for this issue? Or updating an existing test?

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PR: https://git.openjdk.java.net/jdk/pull/4885