compose/context/store/storedefault.go

package store

import (
	"bytes"
	"encoding/json"
	"os/exec"

	"github.com/pkg/errors"
)

const defaultContextType = "docker"

// Represents a context as created by the docker cli
type defaultContext struct {
	Metadata  ContextMetadata
	Endpoints endpoints
}

// Normally (in docker/cli code), the endpoints are mapped as map[string]interface{}
// but docker cli contexts always have a "docker" and "kubernetes" key so we
// create real types for those to no have to juggle around with interfaces.
type endpoints struct {
	Docker     endpoint `json:"docker,omitempty"`
	Kubernetes endpoint `json:"kubernetes,omitempty"`
}

// Both "docker" and "kubernetes" endpoints in the docker cli created contexts
// have a "Host", only kubernetes has the "DefaultNamespace", we put both of
// those here for easier manipulation and to not have to create two distinct
// structs
type endpoint struct {
	Host             string
	DefaultNamespace string
}

func dockerDefaultContext() (*DockerContext, error) {
	// ensure we run this using default context, in current context has been damaged / removed in store
	cmd := exec.Command("docker-classic", "--context", "default", "context", "inspect", "default")
	var stdout bytes.Buffer
	cmd.Stdout = &stdout
	err := cmd.Run()
	if err != nil {
		return nil, err
	}

	var ctx []defaultContext
	err = json.Unmarshal(stdout.Bytes(), &ctx)
	if err != nil {
		return nil, err
	}

	if len(ctx) != 1 {
		return nil, errors.New("found more than one default context")
	}

	defaultCtx := ctx[0]

	meta := DockerContext{
		Name: "default",
		Endpoints: map[string]interface{}{
			"docker": Endpoint{
				Host: defaultCtx.Endpoints.Docker.Host,
			},
			"kubernetes": Endpoint{
				Host:             defaultCtx.Endpoints.Kubernetes.Host,
				DefaultNamespace: defaultCtx.Endpoints.Kubernetes.DefaultNamespace,
			},
		},
		Metadata: ContextMetadata{
			Type:              defaultContextType,
			Description:       "Current DOCKER_HOST based configuration",
			StackOrchestrator: defaultCtx.Metadata.StackOrchestrator,
		},
	}

	return &meta, nil
}