Load core faasd service definitions from compose

**What**
- Use the compose-go library to read the service definitions from an
  external compose file instead of building them in Go
- Add default compose file and copy during `faasd install`
- Add test for load and parse of compose file
- Make testing easier  by sorting the env keys
- Allow append to instantiate the slices so that we can more easily test
  for proper parsing (e.g. nil is still nil etc)
- Add the arch suffix to the compose file and set this as part of the
  env when we parse the compose file. This allows faasd to dynamically
  set the arch suffix used for the basic auth and the gateway images.

Signed-off-by: Lucas Roesler <roesler.lucas@gmail.com>

pkg/supervisor.go

@@ -7,7 +7,11 @@ import (
 	"log"
 	"os"
 	"path"
+	"sort"
 
+	"github.com/alexellis/k3sup/pkg/env"
+	"github.com/compose-spec/compose-go/loader"
+	compose "github.com/compose-spec/compose-go/types"
 	"github.com/containerd/containerd"
 	"github.com/containerd/containerd/cio"
 	"github.com/containerd/containerd/containers"
@@ -15,6 +19,7 @@ import (
 	gocni "github.com/containerd/go-cni"
 	"github.com/openfaas/faasd/pkg/cninetwork"
 	"github.com/openfaas/faasd/pkg/service"
+	"github.com/pkg/errors"
 
 	"github.com/containerd/containerd/namespaces"
 	"github.com/opencontainers/runtime-spec/specs-go"
@@ -234,3 +239,108 @@ func withOCIArgs(args []string) oci.SpecOpts {
 		return nil
 	}
 }
+
+// ParseCompose converts a docker-compose Config into a service list that we can
+// pass to the supervisor client Start.
+//
+// The only anticipated error is a failure if the value mounts are not of type 	`bind`.
+func ParseCompose(config *compose.Config) ([]Service, error) {
+	services := make([]Service, len(config.Services))
+	for idx, s := range config.Services {
+		// environment is a map[string]*string
+		// but we want a []string
+
+		var env []string
+
+		envKeys := sortedEnvKeys(s.Environment)
+		for _, name := range envKeys {
+			value := s.Environment[name]
+			if value == nil {
+				env = append(env, fmt.Sprintf(`%s=""`, name))
+			} else {
+				env = append(env, fmt.Sprintf(`%s=%s`, name, *value))
+			}
+		}
+
+		var mounts []Mount
+		for _, v := range s.Volumes {
+			if v.Type != "bind" {
+				return nil, errors.Errorf("unsupported volume mount type '%s' when parsing service '%s'", v.Type, s.Name)
+			}
+			mounts = append(mounts, Mount{
+				Src:  v.Source,
+				Dest: v.Target,
+			})
+		}
+
+		services[idx] = Service{
+			Name:  s.Name,
+			Image: s.Image,
+			// ShellCommand is just an alias of string slice
+			Args:   []string(s.Command),
+			Caps:   s.CapAdd,
+			Env:    env,
+			Mounts: mounts,
+		}
+	}
+
+	return services, nil
+}
+
+// LoadComposeFile is a helper method for loading a docker-compose file
+func LoadComposeFile(wd string, file string) (*compose.Config, error) {
+	file = path.Join(wd, file)
+	b, err := ioutil.ReadFile(file)
+	if err != nil {
+		return nil, err
+	}
+	config, err := loader.ParseYAML(b)
+	if err != nil {
+		return nil, err
+	}
+
+	archSuffix, err := GetArchSuffix(env.GetClientArch)
+	if err != nil {
+		return nil, err
+	}
+
+	var files []compose.ConfigFile
+	files = append(files, compose.ConfigFile{Filename: file, Config: config})
+	return loader.Load(compose.ConfigDetails{
+		WorkingDir:  wd,
+		ConfigFiles: files,
+		Environment: map[string]string{
+			"ARCH_SUFFIX": archSuffix,
+		},
+	})
+}
+
+func sortedEnvKeys(env map[string]*string) (keys []string) {
+	for k := range env {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	return keys
+}
+
+type ArchGetter func() (string, string)
+
+func GetArchSuffix(getClientArch ArchGetter) (suffix string, err error) {
+	clientArch, clientOS := getClientArch()
+
+	if clientOS != "Linux" {
+		return "", fmt.Errorf("You can only use faasd on Linux")
+	}
+	switch clientArch {
+	case "x86_64":
+		// no suffix needed
+		return "", nil
+	case "armhf", "armv7l":
+		return "-armhf", nil
+	case "arm64", "aarch64":
+		return "-arm64", nil
+	default:
+		// unknown, so use the default without suffix for now
+		return "", nil
+	}
+}