qorb 0.4.1

Connection Pooling
Documentation 
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//! Connections which are borrowed from the connection pool.

use crate::backend::Connection;
use crate::slot::BorrowedConnection;
use tokio::sync::mpsc::OwnedPermit;

/// A [Connection] which is returned to the pool when dropped.
///
/// Note that this method implements [std::ops::Deref] for the
/// generic `Conn` type, and generally, clients should transparently
/// use a handle as a connection.
pub struct Handle<Conn: Connection> {
    inner: Option<BorrowedConnection<Conn>>,
    permit: Option<OwnedPermit<BorrowedConnection<Conn>>>,
}

impl<Conn: Connection> Handle<Conn> {
    pub(crate) fn new(
        conn: BorrowedConnection<Conn>,
        permit: OwnedPermit<BorrowedConnection<Conn>>,
    ) -> Self {
        Self {
            inner: Some(conn),
            permit: Some(permit),
        }
    }

    #[cfg(feature = "probes")]
    pub(crate) fn slot_id(&self) -> crate::slot::SlotId {
        self.inner.as_ref().map(|inner| inner.id()).unwrap()
    }
}

impl<Conn> std::ops::Deref for Handle<Conn>
where
    Conn: Send + 'static,
{
    type Target = Conn;
    fn deref(&self) -> &Self::Target {
        self.inner.as_ref().map(|inner| &inner.conn).unwrap()
    }
}

impl<Conn> std::ops::DerefMut for Handle<Conn>
where
    Conn: Send + 'static,
{
    fn deref_mut(&mut self) -> &mut Self::Target {
        self.inner.as_mut().map(|inner| &mut inner.conn).unwrap()
    }
}

impl<Conn: Connection> Drop for Handle<Conn> {
    fn drop(&mut self) {
        let conn = self.inner.take().unwrap();
        let permit = self.permit.take().unwrap();

        permit.send(conn);
    }
}