val reuseCallConnection = planReuseCallConnection()
    if (reuseCallConnection != null) return reuseCallConnection

    // Attempt to get a connection from the pool.
    val pooled1 = planReusePooledConnection()
    if (pooled1 != null) return pooled1

    // Attempt a deferred plan before new routes.
    if (deferredPlans.isNotEmpty()) return deferredPlans.removeFirst()

    // If we raced another call connecting to this host, coalesce the connections. This makes for
    // 3 different lookups in the connection pool!
    val pooled3 = routePlanner.planReusePooledConnection(this, routes)
    if (pooled3 != null) return pooled3.connection

    connection.withLock {
      connectionPool.put(connection)
      user.acquireConnectionNoEvents(connection)
    }