rewrite_tag loses records when emitter buffer limit is reached, even with filesystem buffering #12667

Fluent Bit version: 5.1.3

Describe the bug

When emitter_mem_buf_limit is reached, rewrite_tag stops re-emitting records, even when emitter_storage.type filesystem is enabled.

Issue #12026 was addressed by PR #12029, which preserves the original record when re-emission fails. However, the record keeps its original tag, effectively skipping the intended rewrite_tag processing.

If downstream outputs only match the rewritten tag, those records are never delivered.

Observed behavior

In our tests:

230 records sent through the OpenTelemetry input.

Only 49 records reached S3.

Increasing emitter_mem_buf_limit resulted in all 230 records being delivered.

Filesystem buffering was enabled on the input and all rewrite_tag emitters.

Debug log:

[input:emitter:datacontenttype_emitter] emitter memory buffer limit reached. Not accepting record.

Expected behavior

Reaching the emitter memory limit should not cause records to skip the required rewrite_tag processing.

With filesystem buffering enabled, Fluent Bit should queue records on disk and retry re-emission, or propagate backpressure upstream until the records can be processed.

Preserving the original record without retrying the failed rewrite is not sufficient to prevent end-to-end data loss.

Related: #12026, #12029.