fix(sdk): count logs dropped by the recursion guard

[RichardoMrMu]

Description

SimpleLogRecordProcessor.on_emit discards a record when it detects a recursive emit loop
and logs that it is doing so, but does not record the drop on
otel.sdk.processor.log.processed. The already-shutdown early return nine lines below it
does record its drop, with error.type=already_shutdown:

if cnt > 3:
    _propagate_false_logger.warning(
        "SimpleLogRecordProcessor.on_emit has entered a recursive loop. Dropping log ..."
    )
    return                                    # <- dropped, not counted
token = attach(...)
try:
    if self._shutdown:
        _logger.warning("Processor is already shutdown, ignoring call")
        self._metrics.drop_items(1, "already_shutdown")   # <- dropped, counted
        return

Two discard paths in the same method, with the same self._metrics in hand, disagree about
whether a dropped record is worth counting.

Measured on main, driving a real recursion with an exporter that logs while exporting:

discard path	records dropped	recorded on the counter
recursion guard	1	0 — counter reads {'<none>': 4}
already shutdown	1	1 — counter reads {'already_shutdown': 1}

A consumer summing otel.sdk.processor.log.processed therefore cannot tell that a record
was lost, even though the SDK knew it was dropping one and already has the vocabulary to
say so.

Why this touches _processor_metrics.py too

drop_items selects between prebuilt attribute dicts rather than building them from its
argument:

def drop_items(self, count: int, error_type: str = "queue_full") -> None:
    if error_type == "already_shutdown":
        self._processed.add(count, self._already_shutdown_attrs)
    else:
        self._processed.add(count, self._dropped_attrs)

So adding the call alone would silently attribute a recursion drop to
error.type=queue_full, which would be worse than not counting it. The change adds one
prebuilt dict and one branch, mirroring the existing already_shutdown shape; there is no
signature or public API change, and NoOpProcessorMetrics is unaffected.

History

The recursion guard came from #4799 (merged 2025-12) and the processor accounting from
#5472 (merged 2026-08). #5472's diff on this file begins after the try: — it moved
finish_items and reworked error handling — so the guard above it was never in scope for
that work. This fills that gap rather than revisiting a decision.

Tests

test_metrics_recursive_loop in opentelemetry-sdk/tests/logs/test_export.py, placed
beside test_simple_log_record_processor_doesnt_enter_recursive_loop whose gap it fills.
It is the intersection of two tests this suite already has: the recursion trigger from that
test, and the counter assertions from test_metrics_already_shutdown.

• On main it fails with 0 != 1 : the log dropped by the recursion guard was not counted.
• With this change it passes.
• The whole of test_export.py passes: 25 passed.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Does This PR Require a Core Repo Change?

• Yes.
• No.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: RichardoMrMu / name: RichardoMu (f4f222f)

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[herin049]

Reminder to run pre-commit to fix the failing formatting checks in CI.

[herin049]

Please include the package name (i.e. opentelemetry-sdk) in the changelog fragment.

[RichardoMrMu]

Added the package name -- the fragment now reads `opentelemetry-sdk`: count logs dropped by ..., matching the house style (e.g. #5660/#5680). Updated in the latest commit.