buildkit: add ability to pass a flag to connect to an existing buildk…

…it: --buildkit_addr (#1297)

internal/build/buildkit/client.go

@@ -42,6 +42,7 @@ var (
 var (
 	BuildOnNamespaceCloud           = knobs.Bool("build_in_nscloud", "If set to true, builds are triggered remotely.", false)
 	BuildOnNamespaceCloudUnlessHost = knobs.Bool("build_in_nscloud_unless_host", "If set to true, builds that match the host platform run locally. All other builds are triggered remotely.", false)
+	BuildOnExistingBuildkit         = knobs.String("buildkit_addr", "The address of an existing buildkitd to use.", "")
 )
 
 const SSHAgentProviderID = "default"
@@ -118,6 +119,17 @@ func (c *clientInstance) Inputs() *compute.In {
 }
 
 func (c *clientInstance) Compute(ctx context.Context, _ compute.Resolved) (*GatewayClient, error) {
+	if addr := BuildOnExistingBuildkit.Get(c.conf); addr != "" {
+		fmt.Fprintf(console.Debug(ctx), "buildkit: using existing buildkit: %q\n", addr)
+
+		cli, err := client.New(ctx, addr)
+		if err != nil {
+			return nil, err
+		}
+
+		return newClient(ctx, cli, false)
+	}
+
 	if c.overrides.BuildkitAddr != "" {
 		cli, err := client.New(ctx, c.overrides.BuildkitAddr)
 		if err != nil {

std/cfg/knobs/knobs.go

@@ -30,6 +30,10 @@ func Bool(name, description string, value bool) Knob[bool] {
 	return Define[bool](name, description, BoolValue(value))
 }
 
+func String(name, description string, value string) Knob[string] {
+	return Define[string](name, description, StringValue(value))
+}
+
 func Define[V any](name, description string, value Value) Knob[V] {
 	knob := Knob[V]{name, description, value}
 	knobs = append(knobs, knob)
@@ -59,7 +63,7 @@ func (knob Knob[V]) Get(src cfg.Configuration) V {
 func (knob Knob[V]) setupFlags(flags *pflag.FlagSet) {
 	var v V
 	switch reflect.TypeOf(v).Kind() {
-	case reflect.Bool:
+	case reflect.Bool, reflect.String:
 		knob.value.setupFlags(flags, knob.name, knob.description)
 
 	default:

std/cfg/knobs/types.go

@@ -39,3 +39,27 @@ func (b *boolv) decode(any *anypb.Any) (any, error) {
 func (b *boolv) setupFlags(flags *pflag.FlagSet, name, description string) {
 	flags.BoolVar(&b.value, name, b.value, description)
 }
+
+func StringValue[V string](defaultValue string) Value {
+	return &stringv{value: defaultValue}
+}
+
+type stringv struct {
+	value string
+}
+
+func (b *stringv) get() any {
+	return b.value
+}
+
+func (b *stringv) decode(any *anypb.Any) (any, error) {
+	bv := &wrapperspb.StringValue{}
+	if err := any.UnmarshalTo(bv); err != nil {
+		return nil, err
+	}
+	return bv.Value, nil
+}
+
+func (b *stringv) setupFlags(flags *pflag.FlagSet, name, description string) {
+	flags.StringVar(&b.value, name, b.value, description)
+}