Hyperstart

Hyperstart is a daemon running on the guest as an agent for managing containers and processes potentially running within those containers.

It is statically built out of a compact C code base, with a strong focus on both simplicity and memory footprint. The hyperstart execution unit is the pod. A hyperstart pod is a container sandbox defined by a set of namespaces (UTS, PID, mount and IPC). Although a pod can hold several containers, cc-oci-runtime always runs a single container per pod.

Hyperstart sends and receives specific commands over a control serial interface for controlling and managing pods and containers. For example, cc-oci-runtime will send the following hyperstart commands sequence when starting a container:

• STARTPOD creates a Pod sandbox and takes a Pod structure as its argument:

  type Pod struct {
    Hostname              string                `json:"hostname"`
    DeprecatedContainers  []Container           `json:"containers,omitempty"`
    DeprecatedInterfaces  []NetworkInf          `json:"interfaces,omitempty"`
    Dns                   []string              `json:"dns,omitempty"`
    DeprecatedRoutes      []Route               `json:"routes,omitempty"`
    ShareDir              string                `json:"shareDir"`
    PortmappingWhiteLists *PortmappingWhiteList `json:"portmappingWhiteLists,omitempty"`
  }
  

• NEWCONTAINER will create and start a container within the previously created pod. This command takes a container description as its argument:

type Container struct {
	Id            string              `json:"id"`
	Rootfs        string              `json:"rootfs"`
	Fstype        string              `json:"fstype,omitempty"`
	Image         string              `json:"image"`
	Addr          string              `json:"addr,omitempty"`
	Volumes       []*VolumeDescriptor `json:"volumes,omitempty"`
	Fsmap         []*FsmapDescriptor  `json:"fsmap,omitempty"`
	Sysctl        map[string]string   `json:"sysctl,omitempty"`
	Process       *Process            `json:"process"`
	RestartPolicy string              `json:"restartPolicy"`
	Initialize    bool                `json:"initialize"`
	Ports         []Port              `json:"ports,omitempty"` //deprecated
}

Hyperstart uses a separate serial channel for passing the container processes output streams (stdout, stderr) back to cc-proxy and receiving the input stream (stdin) for them. As all streams for all containers are going through one single serial channel, hyperstart prepends them with container specific sequence numbers. There are at most 2 sequence numbers per container process, one for stdout and stdin, and another one for stderr.