Support creating machines in "stopped" state (#32)

cmd/fly-autoscaler/main.go

@@ -9,6 +9,7 @@ import (
 	"log/slog"
 	"os"
 	"os/signal"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -75,7 +76,7 @@ func run(ctx context.Context, args []string) error {
 			printUsage()
 			return flag.ErrHelp
 		}
-		return fmt.Errorf("litefs %s: unknown command", cmd)
+		return fmt.Errorf("fly-autoscaler %s: unknown command", cmd)
 	}
 }
 
@@ -120,6 +121,7 @@ type Config struct {
 	CreatedMachineN        string        `yaml:"created-machine-count"`
 	MinCreatedMachineN     string        `yaml:"min-created-machine-count"`
 	MaxCreatedMachineN     string        `yaml:"max-created-machine-count"`
+	InitialMachineState    string        `yaml:"initial-machine-state"`
 	StartedMachineN        string        `yaml:"started-machine-count"`
 	MinStartedMachineN     string        `yaml:"min-started-machine-count"`
 	MaxStartedMachineN     string        `yaml:"max-started-machine-count"`
@@ -149,6 +151,7 @@ func NewConfigFromEnv() (_ *Config, err error) {
 	c.CreatedMachineN = os.Getenv("FAS_CREATED_MACHINE_COUNT")
 	c.MinCreatedMachineN = os.Getenv("FAS_MIN_CREATED_MACHINE_COUNT")
 	c.MaxCreatedMachineN = os.Getenv("FAS_MAX_CREATED_MACHINE_COUNT")
+	c.InitialMachineState = os.Getenv("FAS_INITIAL_MACHINE_STATE")
 	c.StartedMachineN = os.Getenv("FAS_STARTED_MACHINE_COUNT")
 	c.MinStartedMachineN = os.Getenv("FAS_MIN_STARTED_MACHINE_COUNT")
 	c.MaxStartedMachineN = os.Getenv("FAS_MAX_STARTED_MACHINE_COUNT")
@@ -158,6 +161,10 @@ func NewConfigFromEnv() (_ *Config, err error) {
 		c.Regions = strings.Split(s, ",")
 	}
 
+	if c.InitialMachineState == "" {
+		c.InitialMachineState = fly.MachineStateStarted
+	}
+
 	if s := os.Getenv("FAS_CONCURRENCY"); s != "" {
 		if c.Concurrency, err = strconv.Atoi(s); err != nil {
 			return nil, fmt.Errorf("cannot parse FAS_CONCURRENCY as integer: %q", s)
@@ -266,6 +273,10 @@ func (c *Config) Validate() error {
 		return err
 	}
 
+	if !slices.Contains([]string{fly.MachineStateStarted, fly.MachineStateStopped}, c.InitialMachineState) {
+		return fmt.Errorf("initial machine state must be either 'started' or 'stopped'")
+	}
+
 	for i, collectorConfig := range c.MetricCollectors {
 		if err := collectorConfig.Validate(); err != nil {
 			return fmt.Errorf("metric-collectors[%d]: %w", i, err)

cmd/fly-autoscaler/serve.go

@@ -75,6 +75,7 @@ func (c *ServeCommand) Run(ctx context.Context, args []string) (err error) {
 		r.MaxCreatedMachineN = maxCreatedMachineN
 		r.MinStartedMachineN = minStartedMachineN
 		r.MaxStartedMachineN = maxStartedMachineN
+		r.InitialMachineState = c.Config.InitialMachineState
 		r.Regions = c.Config.Regions
 		r.Collectors = collectors
 		return r

reconciler.go

@@ -40,6 +40,9 @@ type Reconciler struct {
 	MinStartedMachineN string
 	MaxStartedMachineN string
 
+	// Initial machine state (started or stopped)
+	InitialMachineState string
+
 	// List of collectors to fetch metric values from.
 	Collectors []MetricCollector
 
@@ -335,8 +338,9 @@ func (r *Reconciler) listMachines(ctx context.Context) ([]*fly.Machine, error) {
 
 func (r *Reconciler) createMachine(ctx context.Context, config *fly.MachineConfig, region string) (*fly.Machine, error) {
 	machine, err := r.Client.Launch(ctx, fly.LaunchMachineInput{
-		Config: config,
-		Region: region,
+		Config:     config,
+		Region:     region,
+		SkipLaunch: r.InitialMachineState == fly.MachineStateStopped,
 	})
 	if err != nil {
 		r.Stats.MachineCreateFailed.Add(1)