Added support for arbitrary container registry. (#24)

Added support for arbitrary container registry.

Recall that `weaver kube deploy` needs to build and upload a container
image to some registry. Before this PR, `weaver kube deploy` uploaded
images to Docker Hub. In PR #21, @giautm suggested we add support for
arbitrary container registries. This PR implements his idea.

Specifically, the user provides a `image` field inside the `"kube"`
section of the config file. For example, given the following config
file:

```toml
[serviceweaver]
binary = "./foo"

[kube]
image = "my_username/foo"
```

`weaver kube deploy` will run `docker push my_username/foo:TAG`. The
user can provide any registry that is compatible with `docker push`.
Some examples:

- Docker Hub: USERNAME/NAME
- Google Artifact Registry: LOCATION-docker.pkg.dev/PROJECT-ID/REPOSITORY/NAME
- GitHub Container Registry: ghcr.io/NAMESPACE/NAME

cmd/weaver-kube/deploy.go

@@ -40,9 +40,39 @@ var (
 	deployCmd = tool.Command{
 		Name:        "deploy",
 		Description: "Deploy a Service Weaver app",
-		Help:        "Usage:\n  weaver kube deploy <configfile>",
-		Flags:       flag.NewFlagSet("deploy", flag.ContinueOnError),
-		Fn:          deploy,
+		Help: `Usage:
+  weaver kube deploy <configfile>
+
+Flags:
+  -h, --help	Print this help message.
+
+Container Image Names:
+  "weaver kube deploy" builds and uploads a container image. You need to
+  specify the name of the container using the "image" field inside the "kube"
+  section of the config file. For example, consider the following config file:
+
+      [serviceweaver]
+      binary = "./foo"
+
+      [kube]
+      image = "docker.io/my_docker_hub_username/foo"
+
+  Using this config file, "weaver kube deploy" will build a container called
+  "docker.io/my_docker_hub_username/foo" and upload it to Docker Hub. The
+  format of the "image" field depends on the registry being used. Some
+  examples:
+
+      - Docker Hub: USERNAME/NAME or docker.io/USERNAME/NAME
+      - Google Artifact Registry: LOCATION-docker.pkg.dev/PROJECT-ID/REPOSITORY/NAME
+      - GitHub Container Registry: ghcr.io/NAMESPACE/NAME
+
+  "weaver kube deploy" will automatically append a tag to the image name, so
+  the "image" field should not contain a tag.
+
+  Note that for "weaver kube deploy" to work correctly, you must be
+  authenticated with the provided registry (e.g., by running "docker login".)`,
+		Flags: flag.NewFlagSet("deploy", flag.ContinueOnError),
+		Fn:    deploy,
 	}
 )
 
@@ -76,6 +106,9 @@ func deploy(ctx context.Context, args []string) error {
 	if err := runtime.ParseConfigSection(configKey, shortConfigKey, app.Sections, config); err != nil {
 		return fmt.Errorf("parse kube config: %w", err)
 	}
+	if config.Image == "" {
+		return fmt.Errorf("No image name provided in config file. See `weaver kube deploy --help` for details")
+	}
 	binListeners, err := bin.ReadListeners(app.Binary)
 	if err != nil {
 		return fmt.Errorf("cannot read listeners from binary %s: %w", app.Binary, err)
@@ -99,7 +132,7 @@ func deploy(ctx context.Context, args []string) error {
 	}
 
 	// Build the docker image for the deployment, and upload it to docker hub.
-	image, err := impl.BuildAndUploadDockerImage(ctx, dep)
+	image, err := impl.BuildAndUploadDockerImage(ctx, dep, config.Image)
 	if err != nil {
 		return err
 	}

internal/impl/docker.go

@@ -28,11 +28,6 @@ import (
 	"github.com/google/uuid"
 )
 
-// dockerHubIDEnvKey is the name of the env variable that contains the docker hub id.
-//
-// Note that w/o a docker hub id, we cannot push the docker image to docker hub.
-const dockerHubIDEnvKey = "SERVICEWEAVER_DOCKER_HUB_ID"
-
 // dockerfileTmpl contains the templatized content of the Dockerfile.
 var dockerfileTmpl = template.Must(template.New("Dockerfile").Parse(`
 {{if . }}
@@ -56,9 +51,9 @@ type imageSpecs struct {
 }
 
 // BuildAndUploadDockerImage builds a docker image and upload it to docker hub.
-func BuildAndUploadDockerImage(ctx context.Context, dep *protos.Deployment) (string, error) {
+func BuildAndUploadDockerImage(ctx context.Context, dep *protos.Deployment, image string) (string, error) {
 	// Create the docker image specifications.
-	specs, err := buildImageSpecs(dep)
+	specs, err := buildImageSpecs(dep, image)
 	if err != nil {
 		return "", fmt.Errorf("unable to build image specs: %w", err)
 	}
@@ -77,7 +72,7 @@ func BuildAndUploadDockerImage(ctx context.Context, dep *protos.Deployment) (str
 
 // buildImage creates a docker image with specs.
 func buildImage(ctx context.Context, specs *imageSpecs) error {
-	fmt.Fprintf(os.Stderr, greenText(), fmt.Sprintf("Building Image %s ...", specs.name))
+	fmt.Fprintf(os.Stderr, greenText(), fmt.Sprintf("Building image %s...", specs.name))
 	// Create:
 	//  workDir/
 	//    file1
@@ -129,7 +124,7 @@ func dockerBuild(ctx context.Context, buildContext, tag string) error {
 
 // uploadImage upload image appImage to docker hub.
 func uploadImage(ctx context.Context, appImage string) error {
-	fmt.Fprintf(os.Stderr, greenText(), fmt.Sprintf("\nUploading Image %s to Docker Hub ...", appImage))
+	fmt.Fprintf(os.Stderr, greenText(), fmt.Sprintf("\nUploading image %s...", appImage))
 
 	c := exec.CommandContext(ctx, "docker", "push", appImage)
 	c.Stdout = os.Stdout
@@ -138,16 +133,7 @@ func uploadImage(ctx context.Context, appImage string) error {
 }
 
 // buildImageSpecs build the docker image specs for an app deployment.
-func buildImageSpecs(dep *protos.Deployment) (*imageSpecs, error) {
-	// Get the docker hub id.
-	dockerID, ok := os.LookupEnv(dockerHubIDEnvKey)
-	if !ok {
-		return nil, fmt.Errorf("unable to get the docker hub id; env variable %q not set", dockerHubIDEnvKey)
-	}
-	if dockerID == "" {
-		return nil, fmt.Errorf("unable to get the docker hub id; empty value for env variable %q", dockerHubIDEnvKey)
-	}
-
+func buildImageSpecs(dep *protos.Deployment, image string) (*imageSpecs, error) {
 	// Copy the app binary and the tool that starts the babysitter into the image.
 	files := []string{dep.App.Binary}
 	var goInstall []string
@@ -163,7 +149,7 @@ func buildImageSpecs(dep *protos.Deployment) (*imageSpecs, error) {
 		goInstall = append(goInstall, "github.com/ServiceWeaver/weaver-kube/cmd/weaver-kube@latest")
 	}
 	return &imageSpecs{
-		name:      fmt.Sprintf("%s/weaver-%s:%s", dockerID, dep.App.Name, dep.Id[:8]),
+		name:      fmt.Sprintf("%s:%s", image, dep.Id[:8]),
 		files:     files,
 		goInstall: goInstall,
 	}, nil

internal/impl/kube.go

@@ -123,9 +123,24 @@ type ListenerOptions struct {
 	Public bool
 }
 
-// kubeConfig stores the configuration information for one execution of a
+// KubeConfig stores the configuration information for one execution of a
 // Service Weaver application deployed using the Kube deployer.
 type KubeConfig struct {
+	// Image is the name of the container image that "weaver kube deploy"
+	// builds and uploads. For example, if Image is "docker.io/alanturing/foo",
+	// then "weaver kube deploy" will build a container called
+	// "docker.io/alanturing/foo" and upload it to Docker Hub.
+	//
+	// The format of Image depends on the registry being used. For example:
+	//
+	// - Docker Hub: USERNAME/NAME or docker.io/USERNAME/NAME
+	// - Google Artifact Registry: LOCATION-docker.pkg.dev/PROJECT-ID/REPOSITORY/NAME
+	// - GitHub Container Registry: ghcr.io/NAMESPACE/NAME
+	//
+	// Note that "weaver kube deploy" will automatically append a unique tag to
+	// Image, so Image should not already contain a tag.
+	Image string
+
 	// Options for the application listeners, keyed by listener name.
 	// If a listener isn't specified in the map, default options will be used.
 	Listeners map[string]*ListenerOptions