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Overview

The Error Handler module provides centralized exception management, comprehensive logging, and user-friendly error display functionality. It implements NIST SP 800-53 Rev. 5 security controls for audit logging and error handling.

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NIST SP 800-53 Rev. 5 Controls

  • AU-3: Content of Audit Records - Comprehensive logging with timestamps and context
  • AU-4: Audit Storage Capacity - Log file management and storage
  • AU-6: Audit Review, Analysis, and Reporting - Error analysis and reporting
  • AU-8: Time Stamps - Timestamp generation for all logged events
  • SI-11: Error Handling - Systematic error handling and user notification

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handle_exception

Centralized function to handle exceptions. Logs the error to both file and console, and displays a message to the user. 
handle_exception(exception: Exception, user_message: str = "An unexpected error occurred.") -> None

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Parameters

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exception
Exception
required
The exception that was caught and needs to be handled
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user_message
str
default:"An unexpected error occurred."
A user-friendly message to display in the Streamlit UI. Should not contain sensitive information.

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Returns

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return
None
This function does not return a value. It logs the error and displays a message to the user.

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NIST Controls Implemented

  • SI-11: Error Handling - Centralized exception management
  • AU-3: Content of Audit Records - Complete exception context capture
  • AU-6: Audit Review - Error logging for analysis

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Example Usage

from error_handler import handle_exception

try:
    # Your code that might raise an exception
    result = risky_operation()
except Exception as e:
    handle_exception(
        e,
        "Failed to complete the operation. Please try again."
    )

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log_error

Logs the error details to both file and console with timestamp and traceback. 
log_error(error_message: str, additional_info: str | None = None) -> None

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Parameters

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error_message
str
required
The main error message to log
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additional_info
str | None
default:"None"
Any additional context or information about the error

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Returns

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return
None
This function does not return a value. It writes to log files and console.

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NIST Controls Implemented

  • AU-3: Content of Audit Records - Complete error context and metadata
  • AU-8: Time Stamps - Precise timestamp for each error event
  • AU-6: Audit Review - Structured format for analysis
  • SI-11: Error Handling - Comprehensive error capture and logging

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Example Usage

from error_handler import log_error

log_error(
    "Database connection failed",
    additional_info="Connection timeout after 30 seconds"
)

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display_error_to_user

Displays an error message to the user in the Streamlit UI. 
display_error_to_user(user_message: str) -> None

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Parameters

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user_message
str
required
The error message to display to the user. Should be user-friendly and not contain sensitive details.

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Returns

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return
None
This function does not return a value. It displays the error in the Streamlit interface.

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NIST Controls Implemented

  • SI-11: Error Handling - User-friendly error messages without sensitive details
  • AU-6: Audit Review - User notification as part of error handling process

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Example Usage

from error_handler import display_error_to_user

display_error_to_user(
    "Unable to load threat model. Please check your input and try again."
)

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setup_logging

Set up logging configuration and create log directory if it doesn’t exist. 
setup_logging() -> None

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Returns

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return
None
This function does not return a value. It configures the logging system.

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NIST Controls Implemented

  • AU-3: Content of Audit Records - Structured logging format
  • AU-4: Audit Storage Capacity - Log directory creation and management
  • AU-8: Time Stamps - Timestamp format configuration

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Example Usage

from error_handler import setup_logging

# Called automatically when the module is imported
# Can be called manually if needed
setup_logging()

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Error Handling Patterns

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Pattern 1: Simple Exception Handling

Use handle_exception() for straightforward error handling with user feedback: 
try:
    process_threat_model(data)
except Exception as e:
    handle_exception(e, "Failed to process threat model")

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Pattern 2: Detailed Error Logging

Use log_error() when you need to log errors with additional context: 
try:
    api_response = call_external_api()
except ConnectionError as e:
    log_error(
        f"API connection failed: {str(e)}",
        additional_info=f"Endpoint: {api_endpoint}, Retry: {retry_count}"
    )
    display_error_to_user("Unable to connect to external service")

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Pattern 3: User-Only Error Display

Use display_error_to_user() for validation errors that don’t need full logging: 
if not user_input:
    display_error_to_user("Please provide input before submitting")
    return

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Configuration

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Log Directory

LOG_DIR = Path("logs")
LOG_FILE = LOG_DIR / "error.log"
Logs are stored in the logs/ directory with the filename error.log. The directory is created automatically if it doesn’t exist.

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Log Format

%(asctime)s - %(name)s - %(levelname)s - %(message)s
Example log entry: 
2026-03-11 14:30:45 - error_handler - ERROR - [2026-03-11 14:30:45] ERROR: API call failed | Info: Connection timeout

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