Error and Warning Trapping System (EWTS)

The EWTS is a multi-language logging framework for hydrologic modules that run within ngen or as standalone applications. It provides consistent log levels, module identities, and environment-driven configuration across C, C++, Fortran, and Python.

What EWTS provides

  • centralized logging behavior when running under ngen
  • consistent log formatting across supported language-specific Runtime Libraries
  • stable module identifiers generated from a shared registry
  • standalone runtime logging outside the ngen environment
  • per-rank log files for MPI execution
  • unified or split-by-module log output under ngen

Reliability and Design Improvements

EWTS has been redesigned to address limitations observed in earlier logging implementations, particularly in multi-language and parallel environments.

Key improvements include:

  • environment-driven configuration
  • safe, non-global logging state
  • MPI-aware logging with per-rank files
  • consistent behavior across all supported languages
  • centralized, reusable logging implementation

For more details, see: - Design Improvements

Choose the right documentation

This documentation site is user-facing. It focuses on behavior, configuration, and runtime usage.

For implementation details and repository-local development guidance, use the README.md files located in the corresponding runtime, integration, or tooling subdirectory.

Terminology: Integrations vs Runtime Libraries

EWTS separates its functionality into two distinct layers to support both modules and the systems that run or prepare them.

Runtime Libraries

Runtime Libraries are language-specific libraries used directly by module implementations. As development continues, these libraries are intended for broader reuse across workflow components to minimize duplication and ensure consistent behavior. Initial development has focused on hydrologic modules used by ngen.

These are the components that:

  • are linked or imported into module code (Fortran, C, C++, Python)
  • provide logging APIs such as write_log(...)
  • manage module identity and log levels
  • operate in both standalone and integrated environments

Examples:

  • Fortran modules using use logger
  • C/C++ code calling EWTS logging APIs
  • Python packages importing EWTS logging utilities

Integrations

Integrations provide the bridge between EWTS and higher-level systems that run, coordinate, or prepare module executions.

These components:

  • connect EWTS logging to a system’s execution module
  • route log messages into system-specific outputs
  • configure behavior based on the runtime environment
  • coordinate logging across multiple modules and MPI ranks (when applicable)
  • ensure consistent logging across the entire workflow

Examples include:

  • Integration with ngen for executing hydrologic modules
  • Future integration of workflow components such as:
    • Model Setup Workflow Manager
    • Calibration Manager
    • Evaluation Manager

These workflow systems prepare inputs, manage runs, or analyze results without being part of ngen itself, but still use EWTS to ensure consistent logging behavior.

Why This Separation Exists

This separation allows EWTS to:

  • support multiple programming languages consistently
  • run both inside ngen and standalone
  • support end-to-end workflows beyond just module execution
  • avoid coupling module code to any specific framework
  • provide a single, consistent logging interface across all components

Summary

Layer Used By Purpose
Runtime Libraries modules Provide logging APIs and behavior
Integrations Systems and workflow components Connect EWTS to execution and workflow environments

Documentation map

Getting started

Architecture

Integrations

Libraries and Package

Tools