Logging Model¶

EWTS supports two logging modes:

• logging routed through the ngen integration layer
• standalone runtime logging outside ngen

ngen-integrated logging¶

When ngen is active, the integration layer becomes the owner of logging implementation and policy. It is responsible for:

• reading ngen_logging.json
• resolving effective log levels
• formatting output consistently
• exporting module-specific configuration where needed
• writing output files under NGEN_RESULTS_DIR/logs/

In this mode, language-specific Runtime Libraries forward log messages through the shared bridge code rather than deciding their own output policy.

Lazy initialization in the integration layer¶

The ngen logger is initialized lazily on the first logging call. That first call performs configuration loading, rank detection, and file setup.

This avoids requiring a separate logger initialization step in ngen itself.

MPI behavior¶

EWTS writes one file per MPI rank. It does not merge all ranks into one shared output file.

Examples:

logs/ngen_mpi_process_0.log
logs/ngen_mpi_process_1.log

Unified and split-by-module layouts¶

Under ngen, EWTS supports two file layout modes.

Unified layout¶

Each rank writes to one log file:

logs/ngen_mpi_process_0.log

Split-by-module layout¶

Each rank writes separate files by module:

logs/cfe_mpi_process_0.log
logs/ngen_mpi_process_0.log
logs/noahowp_mpi_process_0.log
logs/smp_mpi_process_0.log

This keeps module output separated while preserving the one-file-per-rank rule.

Standalone runtime logging¶

When a runtime is used outside ngen, the language-specific logger is responsible for formatting, log-level resolution, and output selection.

Typical standalone output directory priority is:

1. EWTS_LOG_DIR
2. $HOME/run_logs
3. ./run_logs