Standard exit code when shutdown via signal

[mprimi]

State:
🟧 Code: POC for early feedback
🟥 Tests: missing

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When receiving , exit with code 128+.

Pros:

• Implement de-facto convention
• Easier integration for any tool/script that expects this convention
• Easier investigationof "why did server shutdown?" mystery scenarios

Cons:

• May break some existing integration/tools/script (Hyrum's Law)

Sources:

• https://tldp.org/LDP/abs/html/exitcodes.html
• https://en.wikipedia.org/wiki/Exit_status#Shell_and_scripts
• https://www.baeldung.com/linux/status-codes#fatal-error-signal

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Behavior without this change:

• Exit 1 in case of error
• Exit 0 in case of signal

Target behavior:

• Exit 1 in case of error
• Exit 128+signal in case of signal and no shutdown errors
• Exit 1 in error during shutdown as a result of signal

Signed-off-by: Marco Primi marco@nats.io

[mprimi]

Closing after receiving feedback.

Current behavior is fine as-is. Exit with zero as a result of signal is an appropriate behavior for a long-running service.
Carrying a bit more info into the exit code does not justify the risk of breakage and churn the change would create.
For example service-managers like systemd or K8s controllers may restart due to "restart on error" policies.