Function log_mdc::extend_scoped

pub fn extend_scoped<K, V, I>(entries: I) -> ExtendGuard where
    K: Into<String>,
    V: Into<String>,
    I: IntoIterator<Item = (K, V)>, 

Extends the MDC with new entries in a scoped fashion.

When the returned guard falls out of scope, it will restore the old values corresponding to the keys.

Examples

log_mdc::insert("foo", "a");

let entries = [
    ("foo", "b"),
    ("fizz", "buzz"),
];

let guard = log_mdc::extend_scoped(entries.iter().cloned());
log_mdc::get("foo", |v| assert_eq!(Some("b"), v));
log_mdc::get("fizz", |v| assert_eq!(Some("buzz"), v));

drop(guard);
log_mdc::get("foo", |v| assert_eq!(Some("a"), v));
log_mdc::get("fizz", |v| assert_eq!(None, v));