Trait Observer 

pub trait Observer:
    Send
    + Sync
    + 'static {
    // Provided method
    fn transaction_begun(&self, waited: Duration) { ... }
}

What a host wants to be told about. Every method has a default that ignores the measurement, so an observer names only what it records, and a measurement added here later breaks no host’s build.

Provided Methods

fn transaction_begun(&self, waited: Duration)

How long a request waited for a transaction to begin: a connection from the pool, and the BEGIN sent on it. Mostly the pool – BEGIN is one round trip – so a wait that grows is a pool that is too small for the load, or a database that is slow to hand connections back.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors