Bug Fix

Compaction Batch Filename Collision — Critical Data Loss

When a partition accumulated more than 30 files, the compaction system split them into sequential batches of 30. Each batch generated its output filename using second-precision timestamps (YYYYMMDD_HHMMSS), causing all batches completing within the same second to produce identical filenames. Each batch overwrote the previous batch's compacted file, destroying up to 84% of ingested data.

Impact: Any measurement with more than 30 files per hour partition was affected. This is common with max_buffer_age_ms below 1000ms or high-frequency ingestion pipelines. Telegraf default configurations with multiple field groups were particularly susceptible.

Fix: Added nanosecond precision to compacted output filenames, guaranteeing uniqueness across sequential batches. Updated extractNewestFileTime to parse both old and new filename formats.

Upgrade: Drop-in replacement for v26.03.1. No configuration changes required.