Problem Description

In distributed training scenarios using torchrun with custom coverage plugins, we encounter empty other_data during coverage combine. Specifically, when the tracer, arc, and line_bits tables in the coverage database contain zero records, this leads to a critical error:

Conflicting file tracer name for 'xxx': '' vs 'coverage_plugin'

Configuration Context

[run]
parallel = True
plugins =
    coverage_plugin
...

Root Cause

• Distributed Process Behavior: Multiple processes in torchrun may generate coverage data with different plugin configurations
• Empty Coverage Data: Some processes produce coverage databases with no actual measurements (all three key tables empty)

Solution

Added a pre-check in CoverageData.update() to skip empty coverage data by querying record counts from tracer, arc, and line_bits tables, and skipping update operations when all three tables contain zero records.