refactor: extract shared hypervisor BaseConfig and CloneSetup

CH and FC config had 12 identical methods (dir layout, timeouts,
EnsureDirs) differing only in the backend name string. Extract
hypervisor.BaseConfig with a backendName field; both backends
embed it and keep only their unique methods (BinaryName, PIDFileName,
backend-specific paths).

cloneSetup was also character-for-character identical in both backends
(validate CPU, backfill image, reserve record, create dirs, build
cleanup func). Promote to Backend.CloneSetup so both Clone and
DirectClone in each backend call the shared implementation.

Net: ~70 lines removed, zero behavior change.

Author: CMGS

hypervisor/backend.go

@@ -194,6 +194,37 @@ func (b *Backend) ReserveVM(ctx context.Context, id string, vmCfg *types.VMConfi
 	})
 }
 
+// CloneSetup handles the shared pre-clone sequence used by both
+// backends' Clone and DirectClone entry points: validate CPU, backfill
+// image ref from snapshot, reserve a placeholder record, create dirs,
+// and return a cleanup function.
+func (b *Backend) CloneSetup(ctx context.Context, vmID string, vmCfg *types.VMConfig, snapshotConfig *types.SnapshotConfig) (runDir, logDir string, now time.Time, cleanup func(), err error) {
+	if err = ValidateHostCPU(vmCfg.CPU); err != nil {
+		return "", "", time.Time{}, nil, err
+	}
+	if vmCfg.Image == "" && snapshotConfig.Image != "" {
+		vmCfg.Image = snapshotConfig.Image
+	}
+
+	now = time.Now()
+	runDir = b.Conf.VMRunDir(vmID)
+	logDir = b.Conf.VMLogDir(vmID)
+
+	cleanup = func() {
+		_ = RemoveVMDirs(runDir, logDir)
+		b.RollbackCreate(ctx, vmID, vmCfg.Name)
+	}
+
+	if err = b.ReserveVM(ctx, vmID, vmCfg, snapshotConfig.ImageBlobIDs, runDir, logDir); err != nil {
+		return "", "", time.Time{}, nil, fmt.Errorf("reserve VM record: %w", err)
+	}
+	if err = utils.EnsureDirs(runDir, logDir); err != nil {
+		cleanup()
+		return "", "", time.Time{}, nil, fmt.Errorf("ensure dirs: %w", err)
+	}
+	return runDir, logDir, now, cleanup, nil
+}
+
 // RollbackCreate removes a placeholder VM record from the DB.
 func (b *Backend) RollbackCreate(ctx context.Context, id, name string) {
 	if err := b.DB.Update(ctx, func(idx *VMIndex) error {

hypervisor/baseconfig.go

@@ -0,0 +1,69 @@
+package hypervisor
+
+import (
+	"path/filepath"
+	"time"
+
+	"github.com/cocoonstack/cocoon/config"
+	"github.com/cocoonstack/cocoon/utils"
+)
+
+const (
+	defaultSocketWaitTimeout    = 5 * time.Second
+	defaultTerminateGracePeriod = 5 * time.Second
+)
+
+// BaseConfig holds the directory layout and timeout defaults shared by
+// all hypervisor backends. Each backend embeds BaseConfig and adds
+// backend-specific methods (BinaryName, PIDFileName, etc.).
+type BaseConfig struct {
+	*config.Config
+	backendName string
+}
+
+// NewBaseConfig creates a BaseConfig for the named backend.
+func NewBaseConfig(conf *config.Config, name string) BaseConfig {
+	return BaseConfig{Config: conf, backendName: name}
+}
+
+func (c *BaseConfig) dir() string   { return filepath.Join(c.RootDir, c.backendName) }
+func (c *BaseConfig) dbDir() string { return filepath.Join(c.dir(), "db") }
+
+// RunDir returns the top-level runtime directory for this backend.
+func (c *BaseConfig) RunDir() string { return filepath.Join(c.Config.RunDir, c.backendName) }
+
+// LogDir returns the top-level log directory for this backend.
+func (c *BaseConfig) LogDir() string { return filepath.Join(c.Config.LogDir, c.backendName) }
+
+// IndexFile returns the VM index store path.
+func (c *BaseConfig) IndexFile() string { return filepath.Join(c.dbDir(), "vms.json") }
+
+// IndexLock returns the VM index lock path.
+func (c *BaseConfig) IndexLock() string { return filepath.Join(c.dbDir(), "vms.lock") }
+
+// VMRunDir returns the per-VM runtime directory.
+func (c *BaseConfig) VMRunDir(vmID string) string { return filepath.Join(c.RunDir(), vmID) }
+
+// VMLogDir returns the per-VM log directory.
+func (c *BaseConfig) VMLogDir(vmID string) string { return filepath.Join(c.LogDir(), vmID) }
+
+// EnsureDirs creates all static directories required by the backend.
+func (c *BaseConfig) EnsureDirs() error {
+	return utils.EnsureDirs(c.dbDir(), c.RunDir(), c.LogDir())
+}
+
+// SocketWaitTimeout returns the configured socket wait timeout or the default (5s).
+func (c *BaseConfig) SocketWaitTimeout() time.Duration {
+	if c.SocketWaitTimeoutSeconds > 0 {
+		return time.Duration(c.SocketWaitTimeoutSeconds) * time.Second
+	}
+	return defaultSocketWaitTimeout
+}
+
+// TerminateGracePeriod returns the configured SIGTERM→SIGKILL grace period or the default (5s).
+func (c *BaseConfig) TerminateGracePeriod() time.Duration {
+	if c.TerminateGracePeriodSeconds > 0 {
+		return time.Duration(c.TerminateGracePeriodSeconds) * time.Second
+	}
+	return defaultTerminateGracePeriod
+}

hypervisor/cloudhypervisor/clone.go

@@ -21,7 +21,7 @@ import (
 
 // Clone creates a new VM from a snapshot tar stream.
 func (ch *CloudHypervisor) Clone(ctx context.Context, vmID string, vmCfg *types.VMConfig, networkConfigs []*types.NetworkConfig, snapshotConfig *types.SnapshotConfig, snapshot io.Reader) (_ *types.VM, err error) {
-	runDir, logDir, now, cleanup, err := ch.cloneSetup(ctx, vmID, vmCfg, snapshotConfig)
+	runDir, logDir, now, cleanup, err := ch.CloneSetup(ctx, vmID, vmCfg, snapshotConfig)
 	if err != nil {
 		return nil, err
 	}
@@ -38,35 +38,6 @@ func (ch *CloudHypervisor) Clone(ctx context.Context, vmID string, vmCfg *types.
 	return ch.cloneAfterExtract(ctx, vmID, vmCfg, networkConfigs, runDir, logDir, now)
 }
 
-func (ch *CloudHypervisor) cloneSetup(ctx context.Context, vmID string, vmCfg *types.VMConfig, snapshotConfig *types.SnapshotConfig) (runDir, logDir string, now time.Time, cleanup func(), err error) {
-	// Shared validation for stream and direct clone.
-	if err = hypervisor.ValidateHostCPU(vmCfg.CPU); err != nil {
-		return "", "", time.Time{}, nil, err
-	}
-
-	if vmCfg.Image == "" && snapshotConfig.Image != "" {
-		vmCfg.Image = snapshotConfig.Image
-	}
-
-	now = time.Now()
-	runDir = ch.conf.VMRunDir(vmID)
-	logDir = ch.conf.VMLogDir(vmID)
-
-	cleanup = func() {
-		_ = hypervisor.RemoveVMDirs(runDir, logDir)
-		ch.RollbackCreate(ctx, vmID, vmCfg.Name)
-	}
-
-	if err = ch.ReserveVM(ctx, vmID, vmCfg, snapshotConfig.ImageBlobIDs, runDir, logDir); err != nil {
-		return "", "", time.Time{}, nil, fmt.Errorf("reserve VM record: %w", err)
-	}
-	if err = utils.EnsureDirs(runDir, logDir); err != nil {
-		cleanup()
-		return "", "", time.Time{}, nil, fmt.Errorf("ensure dirs: %w", err)
-	}
-	return runDir, logDir, now, cleanup, nil
-}
-
 // cloneAfterExtract resumes from snapshot data already placed in runDir.
 func (ch *CloudHypervisor) cloneAfterExtract(ctx context.Context, vmID string, vmCfg *types.VMConfig, networkConfigs []*types.NetworkConfig, runDir, logDir string, now time.Time) (*types.VM, error) {
 	logger := log.WithFunc("cloudhypervisor.Clone")

hypervisor/cloudhypervisor/cloudhypervisor.go

@@ -31,7 +31,7 @@ func New(conf *config.Config) (*CloudHypervisor, error) {
 	if conf == nil {
 		return nil, fmt.Errorf("config is nil")
 	}
-	cfg := &Config{Config: conf}
+	cfg := NewConfig(conf)
 	if err := cfg.EnsureDirs(); err != nil {
 		return nil, fmt.Errorf("ensure dirs: %w", err)
 	}

hypervisor/cloudhypervisor/config.go

@@ -2,54 +2,26 @@ package cloudhypervisor
 
 import (
 	"path/filepath"
-	"time"
 
 	"github.com/cocoonstack/cocoon/config"
-	"github.com/cocoonstack/cocoon/utils"
+	"github.com/cocoonstack/cocoon/hypervisor"
 )
 
-// BinaryName returns the base name of the Cloud Hypervisor binary.
-func (c *Config) BinaryName() string { return filepath.Base(c.CHBinary) }
-
-// PIDFileName returns the PID file name for the Cloud Hypervisor backend.
-func (c *Config) PIDFileName() string { return "ch.pid" }
-
-const (
-	defaultSocketWaitTimeout    = 5 * time.Second
-	defaultTerminateGracePeriod = 5 * time.Second
-)
-
-// Config holds Cloud Hypervisor specific configuration, embedding the global config.
+// Config holds Cloud Hypervisor specific configuration.
 type Config struct {
-	*config.Config
+	hypervisor.BaseConfig
 }
 
-// EnsureDirs creates all static directories required by the Cloud Hypervisor backend.
-func (c *Config) EnsureDirs() error {
-	return utils.EnsureDirs(
-		c.dbDir(),
-		c.RunDir(),
-		c.LogDir(),
-	)
+// NewConfig creates a Config from a global config.
+func NewConfig(conf *config.Config) *Config {
+	return &Config{BaseConfig: hypervisor.NewBaseConfig(conf, "cloudhypervisor")}
 }
 
-// RunDir returns the top-level CH runtime directory.
-func (c *Config) RunDir() string { return filepath.Join(c.Config.RunDir, "cloudhypervisor") }
-
-// LogDir returns the top-level CH log directory.
-func (c *Config) LogDir() string { return filepath.Join(c.Config.LogDir, "cloudhypervisor") }
-
-// IndexFile returns the VM index store path.
-func (c *Config) IndexFile() string { return filepath.Join(c.dbDir(), "vms.json") }
-
-// IndexLock returns the VM index lock path.
-func (c *Config) IndexLock() string { return filepath.Join(c.dbDir(), "vms.lock") }
-
-// VMRunDir returns the per-VM runtime directory.
-func (c *Config) VMRunDir(vmID string) string { return filepath.Join(c.RunDir(), vmID) }
+// BinaryName returns the base name of the Cloud Hypervisor binary.
+func (c *Config) BinaryName() string { return filepath.Base(c.CHBinary) }
 
-// VMLogDir returns the per-VM log directory.
-func (c *Config) VMLogDir(vmID string) string { return filepath.Join(c.LogDir(), vmID) }
+// PIDFileName returns the PID file name for the Cloud Hypervisor backend.
+func (c *Config) PIDFileName() string { return "ch.pid" }
 
 // COWRawPath returns the path for the OCI COW raw disk.
 func (c *Config) COWRawPath(vmID string) string {
@@ -63,24 +35,5 @@ func (c *Config) OverlayPath(vmID string) string {
 
 // CidataPath returns the path for the cloud-init NoCloud cidata disk.
 func (c *Config) CidataPath(vmID string) string {
-	return filepath.Join(c.VMRunDir(vmID), "cidata.img")
+	return filepath.Join(c.VMRunDir(vmID), cidataFile)
 }
-
-// SocketWaitTimeout returns the configured socket wait timeout or the default.
-func (c *Config) SocketWaitTimeout() time.Duration {
-	if c.SocketWaitTimeoutSeconds > 0 {
-		return time.Duration(c.SocketWaitTimeoutSeconds) * time.Second
-	}
-	return defaultSocketWaitTimeout
-}
-
-// TerminateGracePeriod returns the configured SIGTERM→SIGKILL grace period or the default.
-func (c *Config) TerminateGracePeriod() time.Duration {
-	if c.TerminateGracePeriodSeconds > 0 {
-		return time.Duration(c.TerminateGracePeriodSeconds) * time.Second
-	}
-	return defaultTerminateGracePeriod
-}
-
-func (c *Config) dir() string   { return filepath.Join(c.RootDir, "cloudhypervisor") }
-func (c *Config) dbDir() string { return filepath.Join(c.dir(), "db") }

hypervisor/cloudhypervisor/direct.go

@@ -16,7 +16,7 @@ import (
 // Files are handled per-type: hardlink for memory-range-*, reflink/copy for
 // the COW disk, plain copy for small metadata, and cidata is regenerated.
 func (ch *CloudHypervisor) DirectClone(ctx context.Context, vmID string, vmCfg *types.VMConfig, networkConfigs []*types.NetworkConfig, snapshotConfig *types.SnapshotConfig, srcDir string) (_ *types.VM, err error) {
-	runDir, logDir, now, cleanup, err := ch.cloneSetup(ctx, vmID, vmCfg, snapshotConfig)
+	runDir, logDir, now, cleanup, err := ch.CloneSetup(ctx, vmID, vmCfg, snapshotConfig)
 	if err != nil {
 		return nil, err
 	}

hypervisor/firecracker/clone.go

@@ -17,7 +17,7 @@ import (
 
 // Clone creates a new VM from a snapshot tar stream via FC snapshot/load.
 func (fc *Firecracker) Clone(ctx context.Context, vmID string, vmCfg *types.VMConfig, networkConfigs []*types.NetworkConfig, snapshotConfig *types.SnapshotConfig, snapshot io.Reader) (_ *types.VM, err error) {
-	runDir, logDir, now, cleanup, err := fc.cloneSetup(ctx, vmID, vmCfg, snapshotConfig)
+	runDir, logDir, now, cleanup, err := fc.CloneSetup(ctx, vmID, vmCfg, snapshotConfig)
 	if err != nil {
 		return nil, err
 	}
@@ -34,36 +34,6 @@ func (fc *Firecracker) Clone(ctx context.Context, vmID string, vmCfg *types.VMCo
 	return fc.cloneAfterExtract(ctx, vmID, vmCfg, networkConfigs, runDir, logDir, now)
 }
 
-func (fc *Firecracker) cloneSetup(ctx context.Context, vmID string, vmCfg *types.VMConfig, snapshotConfig *types.SnapshotConfig) (runDir, logDir string, now time.Time, cleanup func(), err error) {
-	// Shared validation point for Clone (stream) and DirectClone
-	// (local dir) — both enter here via cloneSetup.
-	if err = hypervisor.ValidateHostCPU(vmCfg.CPU); err != nil {
-		return "", "", time.Time{}, nil, err
-	}
-
-	if vmCfg.Image == "" && snapshotConfig.Image != "" {
-		vmCfg.Image = snapshotConfig.Image
-	}
-
-	now = time.Now()
-	runDir = fc.conf.VMRunDir(vmID)
-	logDir = fc.conf.VMLogDir(vmID)
-
-	cleanup = func() {
-		_ = hypervisor.RemoveVMDirs(runDir, logDir)
-		fc.RollbackCreate(ctx, vmID, vmCfg.Name)
-	}
-
-	if err = fc.ReserveVM(ctx, vmID, vmCfg, snapshotConfig.ImageBlobIDs, runDir, logDir); err != nil {
-		return "", "", time.Time{}, nil, fmt.Errorf("reserve VM record: %w", err)
-	}
-	if err = utils.EnsureDirs(runDir, logDir); err != nil {
-		cleanup()
-		return "", "", time.Time{}, nil, fmt.Errorf("ensure dirs: %w", err)
-	}
-	return runDir, logDir, now, cleanup, nil
-}
-
 // cloneAfterExtract contains all clone logic after snapshot data is in runDir.
 // FC snapshots require the same directory layout — paths are absolute.
 func (fc *Firecracker) cloneAfterExtract(ctx context.Context, vmID string, vmCfg *types.VMConfig, networkConfigs []*types.NetworkConfig, runDir, logDir string, now time.Time) (*types.VM, error) {

hypervisor/firecracker/config.go

@@ -2,68 +2,19 @@ package firecracker
 
 import (
 	"path/filepath"
-	"time"
 
 	"github.com/cocoonstack/cocoon/config"
-	"github.com/cocoonstack/cocoon/utils"
+	"github.com/cocoonstack/cocoon/hypervisor"
 )
 
-const (
-	defaultSocketWaitTimeout    = 5 * time.Second
-	defaultTerminateGracePeriod = 5 * time.Second
-)
-
-// Config holds Firecracker specific configuration, embedding the global config.
+// Config holds Firecracker specific configuration.
 type Config struct {
-	*config.Config
+	hypervisor.BaseConfig
 }
 
-// EnsureDirs creates all static directories required by the Firecracker backend.
-func (c *Config) EnsureDirs() error {
-	return utils.EnsureDirs(
-		c.dbDir(),
-		c.RunDir(),
-		c.LogDir(),
-	)
-}
-
-// RunDir returns the top-level FC runtime directory.
-func (c *Config) RunDir() string { return filepath.Join(c.Config.RunDir, "firecracker") }
-
-// LogDir returns the top-level FC log directory.
-func (c *Config) LogDir() string { return filepath.Join(c.Config.LogDir, "firecracker") }
-
-// IndexFile returns the VM index store path.
-func (c *Config) IndexFile() string { return filepath.Join(c.dbDir(), "vms.json") }
-
-// IndexLock returns the VM index lock path.
-func (c *Config) IndexLock() string { return filepath.Join(c.dbDir(), "vms.lock") }
-
-// VMRunDir returns the per-VM runtime directory.
-func (c *Config) VMRunDir(vmID string) string { return filepath.Join(c.RunDir(), vmID) }
-
-// VMLogDir returns the per-VM log directory.
-func (c *Config) VMLogDir(vmID string) string { return filepath.Join(c.LogDir(), vmID) }
-
-// COWRawPath returns the path for the OCI COW raw disk.
-func (c *Config) COWRawPath(vmID string) string {
-	return filepath.Join(c.VMRunDir(vmID), cowFileName)
-}
-
-// SocketWaitTimeout returns the configured socket wait timeout or the default.
-func (c *Config) SocketWaitTimeout() time.Duration {
-	if c.SocketWaitTimeoutSeconds > 0 {
-		return time.Duration(c.SocketWaitTimeoutSeconds) * time.Second
-	}
-	return defaultSocketWaitTimeout
-}
-
-// TerminateGracePeriod returns the configured SIGTERM→SIGKILL grace period or the default.
-func (c *Config) TerminateGracePeriod() time.Duration {
-	if c.TerminateGracePeriodSeconds > 0 {
-		return time.Duration(c.TerminateGracePeriodSeconds) * time.Second
-	}
-	return defaultTerminateGracePeriod
+// NewConfig creates a Config from a global config.
+func NewConfig(conf *config.Config) *Config {
+	return &Config{BaseConfig: hypervisor.NewBaseConfig(conf, "firecracker")}
 }
 
 // BinaryName returns the base name of the Firecracker binary.
@@ -72,5 +23,7 @@ func (c *Config) BinaryName() string { return filepath.Base(c.FCBinary) }
 // PIDFileName returns the PID file name for the Firecracker backend.
 func (c *Config) PIDFileName() string { return pidFileName }
 
-func (c *Config) dir() string   { return filepath.Join(c.RootDir, "firecracker") }
-func (c *Config) dbDir() string { return filepath.Join(c.dir(), "db") }
+// COWRawPath returns the path for the OCI COW raw disk.
+func (c *Config) COWRawPath(vmID string) string {
+	return filepath.Join(c.VMRunDir(vmID), cowFileName)
+}