Macro warn 

macro_rules! warn {
    ($module:expr, $($arg:tt)+) => { ... };
}

Emits a warning log entry through the global logging service.

Use this level for abnormal but non-fatal events: authentication failures, request conflicts, resource-not-found responses, or any condition that is unexpected but does not indicate a server malfunction.

This macro is a complete no-op if the logger has not been initialized. See info! for parameter documentation and general behaviour.

Usage

warn!(Module::Api, "unauthorized access attempt for blob {}", hash);