Support machine configuration directly in fly.toml (#4045)

* Support machine configuration directly in fly.toml

* Move it to experimental and simplify as a single string option

* fly m run --machine-config

Author: dangra

internal/appconfig/config.go

@@ -162,6 +162,7 @@ type Experimental struct {
 	EnableEtcd     bool     `toml:"enable_etcd,omitempty" json:"enable_etcd,omitempty"`
 	LazyLoadImages bool     `toml:"lazy_load_images,omitempty" json:"lazy_load_images,omitempty"`
 	Attached       Attached `toml:"attached,omitempty" json:"attached,omitempty"`
+	MachineConfig  string   `toml:"machine_config,omitempty" json:"machine_config,omitempty"`
 }
 
 type Attached struct {

internal/appconfig/machines.go

@@ -1,7 +1,11 @@
 package appconfig
 
 import (
+	"encoding/json"
 	"fmt"
+	"io"
+	"os"
+	"strings"
 
 	"github.com/docker/go-units"
 	"github.com/google/shlex"
@@ -146,7 +150,9 @@ func (c *Config) ToTestMachineConfig(svc *ServiceMachineCheck, origMachine *fly.
 	}
 
 	if c.Experimental != nil {
-		mConfig.Init.Entrypoint = c.Experimental.Entrypoint
+		if v := c.Experimental.Entrypoint; v != nil {
+			mConfig.Init.Entrypoint = v
+		}
 	}
 
 	mConfig.Env["FLY_TEST_COMMAND"] = "1"
@@ -235,6 +241,30 @@ func (c *Config) updateMachineConfig(src *fly.MachineConfig) (*fly.MachineConfig
 		mConfig = helpers.Clone(src)
 	}
 
+	if c.Experimental != nil && len(c.Experimental.MachineConfig) > 0 {
+		emc := c.Experimental.MachineConfig
+		var buf []byte
+		switch {
+		case strings.HasPrefix(emc, "{"):
+			buf = []byte(emc)
+		case strings.HasSuffix(emc, ".json"):
+			fo, err := os.Open(emc)
+			if err != nil {
+				return nil, err
+			}
+			buf, err = io.ReadAll(fo)
+			if err != nil {
+				return nil, err
+			}
+		default:
+			return nil, fmt.Errorf("invalid machine config source: %q", emc)
+		}
+
+		if err := json.Unmarshal(buf, mConfig); err != nil {
+			return nil, fmt.Errorf("invalid machine config %q: %w", emc, err)
+		}
+	}
+
 	// Metrics
 	mConfig.Metrics = nil
 	if len(c.Metrics) > 0 {

internal/appconfig/machines_test.go

@@ -53,6 +53,7 @@ func TestToMachineConfig(t *testing.T) {
 		Restart: &fly.MachineRestart{
 			Policy: fly.MachineRestartPolicyAlways,
 		},
+		DNS: &fly.DNSConfig{Nameservers: []string{"1.2.3.4"}},
 	}
 
 	got, err := cfg.ToMachineConfig("", nil)
@@ -79,7 +80,7 @@ func TestToMachineConfig(t *testing.T) {
 	assert.Equal(t, "24/7", got.Schedule)
 	assert.Equal(t, true, got.AutoDestroy)
 	assert.Equal(t, &fly.MachineRestart{Policy: "always"}, got.Restart)
-	assert.Equal(t, &fly.DNSConfig{SkipRegistration: true}, got.DNS)
+	assert.Equal(t, &fly.DNSConfig{SkipRegistration: true, Nameservers: []string{"1.2.3.4"}}, got.DNS)
 	assert.Equal(t, "propagated", got.Metadata["retain"])
 	assert.Empty(t, got.Init.Cmd)
 }
@@ -460,7 +461,7 @@ func TestToTestMachineConfigWTestMachine(t *testing.T) {
 	}
 	got, err := cfg.ToTestMachineConfig(check, machine)
 	assert.NoError(t, err)
-	assert.Equal(t, got, want)
+	assert.Equal(t, want, got)
 }
 
 func TestToConsoleMachineConfig(t *testing.T) {

internal/appconfig/processgroups.go

@@ -162,6 +162,7 @@ func (c *Config) Flatten(groupName string) (*Config, error) {
 		dst.Metrics[i].Processes = []string{groupName}
 	}
 
+	// [[restart]]
 	dst.Restart = lo.Filter(dst.Restart, func(x Restart, _ int) bool {
 		return matchesGroups(x.Processes)
 	})

internal/appconfig/testdata/tomachine.toml

@@ -46,3 +46,6 @@ guest_path = "/guest/path"
 url_prefix = "/url/prefix"
 tigris_bucket = "example-bucket"
 index_document = "index.html"
+
+[experimental]
+machine_config = '{"dns": {"nameservers": ["1.2.3.4"]}}'

internal/command/machine/run.go

@@ -2,8 +2,11 @@ package machine
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
+	"io"
 	"math/rand"
+	"os"
 	"strconv"
 	"strings"
 	"time"
@@ -91,6 +94,10 @@ var sharedFlags = flag.Set{
 		Description: "Do not use the cache when building the image",
 		Hidden:      true,
 	},
+	flag.String{
+		Name:        "machine-config",
+		Description: "Read machine config from json file or string",
+	},
 	flag.StringArray{
 		Name:        "kernel-arg",
 		Description: "A list of kernel arguments to provide to the init. Can be specified multiple times.",
@@ -636,6 +643,29 @@ func determineMachineConfig(
 ) (*fly.MachineConfig, error) {
 	machineConf := mach.CloneConfig(&input.initialMachineConf)
 
+	if emc := flag.GetString(ctx, "machine-config"); emc != "" {
+		var buf []byte
+		switch {
+		case strings.HasPrefix(emc, "{"):
+			buf = []byte(emc)
+		case strings.HasSuffix(emc, ".json"):
+			fo, err := os.Open(emc)
+			if err != nil {
+				return nil, err
+			}
+			buf, err = io.ReadAll(fo)
+			if err != nil {
+				return nil, err
+			}
+		default:
+			return nil, fmt.Errorf("invalid machine config source: %q", emc)
+		}
+
+		if err := json.Unmarshal(buf, machineConf); err != nil {
+			return nil, fmt.Errorf("invalid machine config %q: %w", emc, err)
+		}
+	}
+
 	var err error
 	machineConf.Guest, err = flag.GetMachineGuest(ctx, machineConf.Guest)
 	if err != nil {