Implement SLF4Jm JUL, and Log4J2 providers for Java SDK

[uranusjr]

Additional mechanism is added Logger in sdk.execution to support sending arbitrary log messages to LogSender. Once that's in place, we can implement various adapters to support common Java logging providers with a bit boilerplate code for each.

Those providers are implemented in separate artifacts since nobody needs all of them at once. The user can choose what they want. Documentation is added to describe how to do it.

I changed examples to prefer the Java Platform Logging interface instead of SLF4J too. This is built-in since Java 9. All the logging tools are more or less the same, so users should adapt pretty easily.

[uranusjr]

Don’t know if it makes sense… since Airflow uses structlog, and the log forwarder actually works best with structured arguments, trying out intentionally NOT rendering the message but put the arguments in the dict instead

Is this too weird?

[phanikumv]

Suggested change

	s.split(Regex("""[\s,]+""")).forEach {
	val parts = it.split(Regex("""\s*=\s*"""), 2)
	val level = parse(parts[1])
	if (level != null) put(parts[0], level)
	s.split(Regex("""[\s,]+""")).forEach {
	if (it.isEmpty()) return@forEach
	val parts = it.split(Regex("""\s*=\s*"""), 2)
	if (parts.size != 2) return@forEach // <- guards parts[1]
	val level = parse(parts[1])
	if (level != null) put(parts[0], level)
	}

[phanikumv]

The happy path works fine, however,

Say a deployment sets:

AIRFLOW__LOGGING__NAMESPACE_LEVELS="botocore=debug,"

A trailing comma — extremely common when people build up a comma list. Now trace it:

Step 1 — split "botocore=debug," on [\s,]+:

["botocore=debug", ""]

The trailing comma produces an empty-string token at the end.

Step 2 — the loop reaches the "" token and splits it on =:

"".split(Regex("""\s*=\s*"""), 2) -> [""] // size 1, no "=" to split on

Step 3 — parse(parts[1]) reads index 1 of a 1-element list:

java.lang.IndexOutOfBoundsException: Index 1 out of bounds for length 1

The same thing happens for "botocore" (a bare name, no =), " botocore=debug" (leading space), ",botocore=debug" (leading comma), or the env var set to "".

The example value in config.yml for this exact option is:

example: "sqlalchemy=INFO sqlalchemy.engine=DEBUG, botocor"

That last token, botocor, has no =level — so a user who copies the documented example verbatim hits the crash

The Python parser (structlog.py) has the same parsing gap, but it fails loudly with a ValueError at config time naming the bad value

[ashb]

That example is broken and got truncated in my PR that I added. It should fail with an error, but a nice one.

[uranusjr]

I’ll add some nicer errors.

The Python implementation currently also just use regex without error handling. Should we improve it too?

airflow/shared/logging/src/airflow_shared/logging/structlog.py

Lines 560 to 564 in d74fbff

	if isinstance(namespace_log_levels, str):
	log_from_level = partial(re.compile(r"\s*=\s*").split, maxsplit=2)
	namespace_log_levels = {
	log: level for log, level in map(log_from_level, re.split(r"[\s,]+", namespace_log_levels))
	}

[phanikumv]

yes we should, but may be in a separate PR