Kubernetes 中的服务发现与 Docker 容器间的环境变量传递源码探究

K8S_APP_MONITOR_TEST_PORT_3000_TCP_ADDR=10.254.56.68
K8S_APP_MONITOR_TEST_PORT=tcp://10.254.56.68:3000
K8S_APP_MONITOR_TEST_PORT_3000_TCP_PROTO=tcp
K8S_APP_MONITOR_TEST_SERVICE_PORT_HTTP=3000
K8S_APP_MONITOR_TEST_PORT_3000_TCP_PORT=3000
K8S_APP_MONITOR_TEST_PORT_3000_TCP=tcp://10.254.56.68:3000
K8S_APP_MONITOR_TEST_SERVICE_HOST=10.254.56.68
K8S_APP_MONITOR_TEST_SERVICE_PORT=3000

// Config contains the configuration data about a container.
// It should hold only portable information about the container.
// Here, "portable" means "independent from the host we are running on".
// Non-portable information *should* appear in HostConfig.
// All fields added to this struct must be marked `omitempty` to keep getting
// predictable hashes from the old `v1Compatibility` configuration.
type Config struct {
 Hostname        string                // Hostname
 Domainname      string                // Domainname
 User            string                // User that will run the command(s) inside the container
 Env             []string              // List of environment variable to set in the container
 Cmd             strslice.StrSlice     // Command to run when starting the container

// RunContainerOptions specify the options which are necessary for running containers
type RunContainerOptions struct {
 // The environment variables list.
 Envs []EnvVar
   // The mounts for the containers.
 Mounts []Mount
 // The host devices mapped into the containers.

pkg/kubelet/kuberuntime/kuberuntime_container.go

// generateContainerConfig generates container config for kubelet runtime v1.
func (m *kubeGenericRuntimeManager) generateContainerConfig(container *v1.Container, pod *v1.Pod, restartCount int, podIP, imageRef string) (*runtimeapi.ContainerConfig, error) {
    opts, _, err := m.runtimeHelper.GenerateRunContainerOptions(pod, container, podIP)
 // set environment variables
 envs := make([]*runtimeapi.KeyValue, len(opts.Envs))
 for idx := range opts.Envs {
  e := opts.Envs[idx]
  envs[idx] = &runtimeapi.KeyValue{
   Key:   e.Name,
   Value: e.Value,
 config.Envs = envs
 return config, nil

// GenerateRunContainerOptions generates the RunContainerOptions, which can be used by
// the container runtime to set parameters for launching a container.
func (kl *Kubelet) GenerateRunContainerOptions(pod *v1.Pod, container *v1.Container, podIP string) (*kubecontainer.RunContainerOptions, bool, error) {
 opts := &kubecontainer.RunContainerOptions{CgroupParent: cgroupParent}
 opts.Envs, err = kl.makeEnvironmentVariables(pod, container, podIP)
    return opts, useClusterFirstPolicy, nil

// Make the environment variables for a pod in the given namespace.
func (kl *Kubelet) makeEnvironmentVariables(pod *v1.Pod, container *v1.Container, podIP string) ([]kubecontainer.EnvVar, error) {
 var result []kubecontainer.EnvVar
 // Note:  These are added to the docker Config, but are not included in the checksum computed
 // by dockertools.BuildDockerName(...).  That way, we can still determine whether an
 // v1.Container is already running by its hash. (We don't want to restart a container just
 // because some service changed.)
 // Note that there is a race between Kubelet seeing the pod and kubelet seeing the service.
 // To avoid this users can: (1) wait between starting a service and starting; or (2) detect
 // missing service env var and exit and be restarted; or (3) use DNS instead of env vars
 // and keep trying to resolve the DNS name of the service (recommended).