ErrorHandler

ErrorHandler is a software component responsible for managing errors that occur during program execution. By centralizing error processing, it helps maintain separation of concerns between business logic and error handling. Core tasks include detecting errors, categorizing their severity, recording contextual information to logs, and determining an appropriate response such as propagating the error, retrying, applying a fallback, or terminating the operation.

In many systems, an error handler also coordinates user notifications, metrics, and alerting, and may escalate issues to monitoring systems. Centralized handlers can improve consistency of messages and reduce duplication, while localized handlers enable specialized behavior for particular modules.

Implementation approaches vary by language and paradigm. In synchronous languages, error handling may rely on exceptions (try and catch blocks) or on explicit error codes. In asynchronous environments, error handlers must manage promise rejections, callbacks, or event-driven faults. Frameworks often provide error-handling middleware that catches unhandled errors and formats responses for clients.

Design patterns include centralized versus distributed handling, usage of error codes and enums, structured logging, and mechanisms for recovery such as retries, fallbacks, or circuit breakers. A good error handler preserves useful context, avoids exposing sensitive information, and minimizes performance impact. It should also balance robustness with clarity, ensuring failures are detected promptly and diagnosed effectively without overwhelming users or operators.

Related concepts include exception handling, logging, fault tolerance, and middleware.