info_tfgrid/collections/developers/internals/zos/internals/container

Container Module

Table of Contents

• ZBus
• Home Directory
• Introduction
  • zinit unit
• Interface

---

ZBus

Storage module is available on zbus over the following channel

module	object	version
container	container	0.0.1

Home Directory

contd keeps some data in the following locations

directory	path
root	/var/cache/modules/containerd

Introduction

The container module, is a proxy to containerd. The proxy provides integration with zbus.

The implementation is the moment is straight forward, which includes preparing the OCI spec for the container, the tenant containerd namespace, setting up proper capabilities, and finally creating the container instance on containerd.

The module is fully stateless, all container information is queried during runtime from containerd.

zinit unit

contd must run after containerd is running, and the node boot process is complete. Since it doesn't keep state, no dependency on stroaged is needed

exec: contd -broker unix:///var/run/redis.sock -root /var/cache/modules/containerd
after:
  - containerd
  - boot

Interface

package pkg

// ContainerID type
type ContainerID string

// NetworkInfo defines a network configuration for a container
type NetworkInfo struct {
    // Currently a container can only join one (and only one)
    // network namespace that has to be pre defined on the node
    // for the container tenant

    // Containers don't need to know about anything about bridges,
    // IPs, wireguards since this is all is only known by the network
    // resource which is out of the scope of this module
    Namespace string
}

// MountInfo defines a mount point
type MountInfo struct {
    Source  string   // source of the mount point on the host
    Target  string   // target of mount inside the container
    Type    string   // mount type
    Options []string // mount options
}

//Container creation info
type Container struct {
    // Name of container
    Name string
    // path to the rootfs of the container
    RootFS string
    // Env env variables to container in format {'KEY=VALUE', 'KEY2=VALUE2'}
    Env []string
    // Network network info for container
    Network NetworkInfo
    // Mounts extra mounts for container
    Mounts []MountInfo
    // Entrypoint the process to start inside the container
    Entrypoint string
    // Interactivity enable Core X as PID 1 on the container
    Interactive bool
}

// ContainerModule defines rpc interface to containerd
type ContainerModule interface {
    // Run creates and starts a container on the node. It also auto
    // starts command defined by `entrypoint` inside the container
    // ns: tenant namespace
    // data: Container info
    Run(ns string, data Container) (ContainerID, error)

    // Inspect, return information about the container, given its container id
    Inspect(ns string, id ContainerID) (Container, error)
    Delete(ns string, id ContainerID) error
}