When you build a daemon, it is crucial to anticipate and handle failures gracefully. Common failure modes for daemons include unexpected crashes due to programming errors, resource exhaustion (like running out of memory or file descriptors), unhandled exceptions, or external factors such as missing files or lost network connectivity. If a daemon process simply exits on error, it can leave critical services unavailable or data in an inconsistent state. For this reason, robust daemons often incorporate self-recovery mechanisms. These mechanisms automatically restart the daemon after a crash, clean up resources, and attempt to restore normal operation. By doing so, you reduce downtime and improve reliability, which is especially important for background services that users and other systems depend on.

Both the C and Python examples above implement a basic watchdog mechanism. The parent process acts as a monitor: it forks a child process to run the daemon code, waits for the child to exit, and checks the exit status. If the child exits normally (with status 0), the watchdog also exits, assuming the work is done. If the child crashes or exits with an error, the watchdog restarts it, ensuring the daemon remains running. This pattern is especially useful for critical background services that must be resilient to unexpected failures. Watchdog logic is best used when you require high availability and cannot risk the daemon remaining down after a crash. However, it is important to avoid endless restart loops in the case of persistent errors, so you may want to add limits or backoff strategies in production systems.