Method create_vmclock

clock-bound/src/daemon/io.rs:207–255

Initializes the IO task for sampling the VMClock shared memory file. A VMClock object will not be created if the daemon is running on a unsupported instance type, the shared memory file is not found or if IMDS fails to provide instance metadata. # Panics - When the vmclock device can not be constructed using the provided shared memory path.

(&mut self, vmclock_shm_path: &str)

    /// # Panics
    /// - When the vmclock device can not be constructed using the provided shared memory path.
    pub async fn create_vmclock(&mut self, vmclock_shm_path: &str) {
        info!("Creating link local source.");

        info!(?self.vmclock, "Current source entry status.");
        if self.vmclock.is_none() {
            self.vmclock = {
                let (ctrl_sender, ctrl_receiver) = mpsc::channel::<ControlRequest>(1);
                // Not all instance types are able to use vmclock. Before attempting to create the
                // vmclock object the instance is first determined to be viable.

                // NOTE: There are scenarios when the vmclock should be created, but
                // is not -- IMDS timeouts, droplet live updates and IMDS queries too close instance
                // launch will result in no vmclock runner, even when the user might expect
                // it to.
                //
                // Future work is required to disambiguate and handle these failure modes as well as identify
                // and handle vmclock runner creation on non EC2 instances.
                let instance_type = match InstanceType::get_from_imds().await {
                    Ok(it) => it,
                    Err(e) => {
                        warn!(?e, "EC2 instance type not determined. VMClock not enabled.");
                        return;
                    }
                };

                // Metal instances do not benefit from the vmclock and the vmclock will not be
                // enabled on this instance types.
                if instance_type.is_metal() {
                    info!("EC2 metal instance type determined. Not enabling VMClock");
                    return;
                }

                info!("EC2 non-metal instance type determined. Enabling VMClock.");
                let vmclock = VMClock::construct(
                    vmclock_shm_path,
                    ctrl_receiver,
                    self.clock_disruption_channels.sender.clone(),
                )
                .await
                .unwrap_or_else(|_| panic!("vmclock device not found {vmclock_shm_path}"));

                let source = Source {
                    state: SourceState::Initialized(vmclock),
                    ctrl_sender,
                };
                Some(source)
            };
        }
    }

    /// Returns `VMCLock` if it has been initialized
    pub fn vmclock(&self) -> Option<&VMClock> {