create clistate.Locker interface

Simplify the use of clistate.Lock by creating a clistate.Locker
instance, which stores the context of locking a state, to allow unlock
to be called without knowledge of how the state was locked.

This alows the backend code to bring the needed UI methods to the point
where the state is locked, and still unlock the state from an outer
scope.

backend/local/backend_apply.go

@@ -59,18 +59,13 @@ func (b *Local) opApply(
 		lockCtx, cancel := context.WithTimeout(stopCtx, op.StateLockTimeout)
 		defer cancel()
 
-		lockInfo := state.NewLockInfo()
+		unlock, err := clistate.Lock(lockCtx, opState, op.Type.String(), "", b.CLI, b.Colorize())
-		lockInfo.Operation = op.Type.String()
-		lockID, err := clistate.Lock(lockCtx, opState, lockInfo, b.CLI, b.Colorize())
 		if err != nil {
 			runningOp.Err = errwrap.Wrapf("Error locking state: {{err}}", err)
 			return
 		}
-
 		defer func() {
-			if err := clistate.Unlock(opState, lockID, b.CLI, b.Colorize()); err != nil {
+			runningOp.Err = unlock(runningOp.Err)
-				runningOp.Err = multierror.Append(runningOp.Err, err)
-			}
 		}()
 	}
 

backend/local/backend_plan.go

@@ -9,12 +9,10 @@ import (
 	"strings"
 
 	"github.com/hashicorp/errwrap"
-	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/backend"
 	"github.com/hashicorp/terraform/command/clistate"
 	"github.com/hashicorp/terraform/command/format"
 	"github.com/hashicorp/terraform/config/module"
-	"github.com/hashicorp/terraform/state"
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -66,18 +64,13 @@ func (b *Local) opPlan(
 		lockCtx, cancel := context.WithTimeout(stopCtx, op.StateLockTimeout)
 		defer cancel()
 
-		lockInfo := state.NewLockInfo()
+		unlock, err := clistate.Lock(lockCtx, opState, op.Type.String(), "", b.CLI, b.Colorize())
-		lockInfo.Operation = op.Type.String()
-		lockID, err := clistate.Lock(lockCtx, opState, lockInfo, b.CLI, b.Colorize())
 		if err != nil {
 			runningOp.Err = errwrap.Wrapf("Error locking state: {{err}}", err)
 			return
 		}
-
 		defer func() {
-			if err := clistate.Unlock(opState, lockID, b.CLI, b.Colorize()); err != nil {
+			runningOp.Err = unlock(runningOp.Err)
-				runningOp.Err = multierror.Append(runningOp.Err, err)
-			}
 		}()
 	}
 

backend/local/backend_refresh.go

@@ -8,11 +8,9 @@ import (
 	"strings"
 
 	"github.com/hashicorp/errwrap"
-	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/backend"
 	"github.com/hashicorp/terraform/command/clistate"
 	"github.com/hashicorp/terraform/config/module"
-	"github.com/hashicorp/terraform/state"
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -57,18 +55,13 @@ func (b *Local) opRefresh(
 		lockCtx, cancel := context.WithTimeout(stopCtx, op.StateLockTimeout)
 		defer cancel()
 
-		lockInfo := state.NewLockInfo()
+		unlock, err := clistate.Lock(lockCtx, opState, op.Type.String(), "", b.CLI, b.Colorize())
-		lockInfo.Operation = op.Type.String()
-		lockID, err := clistate.Lock(lockCtx, opState, lockInfo, b.CLI, b.Colorize())
 		if err != nil {
 			runningOp.Err = errwrap.Wrapf("Error locking state: {{err}}", err)
 			return
 		}
-
 		defer func() {
-			if err := clistate.Unlock(opState, lockID, b.CLI, b.Colorize()); err != nil {
+			runningOp.Err = unlock(runningOp.Err)
-				runningOp.Err = multierror.Append(runningOp.Err, err)
-			}
 		}()
 	}
 

backend/remote-state/consul/client.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"runtime/debug"
 	"sync"
 	"time"
 
@@ -81,6 +82,9 @@ func (c *RemoteClient) Get() (*remote.Payload, error) {
 
 	c.modifyIndex = pair.ModifyIndex
 
+	log.Println("[XXXX] GOT STATE WITH INDEX:", c.modifyIndex)
+	log.Println(string(debug.Stack()))
+
 	payload := pair.Value
 	// If the payload starts with 0x1f, it's gzip, not json
 	if len(pair.Value) >= 1 && pair.Value[0] == '\x1f' {
@@ -280,6 +284,7 @@ func (c *RemoteClient) lock() (string, error) {
 		return "", lockErr
 	}
 
+	defer log.Println("[XXXX] OBTAINED CONSUL LOCK")
 	c.lockCh = lockCh
 
 	err = c.putLockInfo(c.info)

command/clistate/state.go

@@ -8,9 +8,11 @@ import (
 	"context"
 	"fmt"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/hashicorp/errwrap"
+	multierror "github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/helper/slowmessage"
 	"github.com/hashicorp/terraform/state"
 	"github.com/mitchellh/cli"
@@ -48,47 +50,119 @@ that no one else is holding a lock.
 `
 )
 
-// Lock locks the given state and outputs to the user if locking
+// Locker allows for more convenient locking, by creating the timeout context
-// is taking longer than the threshold.  The lock is retried until the context
+// and LockInfo for the caller, while storing any related data required for
-// is cancelled.
+// Unlock.
-func Lock(ctx context.Context, s state.State, info *state.LockInfo, ui cli.Ui, color *colorstring.Colorize) (string, error) {
+type Locker interface {
-	var lockID string
+	// Lock the provided state, storing the reason string in the LockInfo.
+	Lock(s state.State, reason string) error
+	// Unlock the previously locked state.
+	// An optional error can be passed in, and will be combined with any error
+	// from the Unlock operation.
+	Unlock(error) error
+}
+
+type locker struct {
+	mu      sync.Mutex
+	ctx     context.Context
+	timeout time.Duration
+	state   state.State
+	ui      cli.Ui
+	color   *colorstring.Colorize
+	lockID  string
+}
+
+// Create a new Locker.
+// The provided context will be used for lock cancellation, and combined with
+// the timeout duration. Lock progress will be be reported to the user through
+// the provided UI.
+func NewLocker(
+	ctx context.Context,
+	timeout time.Duration,
+	ui cli.Ui,
+	color *colorstring.Colorize) Locker {
+
+	l := &locker{
+		ctx:     ctx,
+		timeout: timeout,
+		ui:      ui,
+		color:   color,
+	}
+	return l
+}
+
+// Locker locks the given state and outputs to the user if locking is taking
+// longer than the threshold. The lock is retried until the context is
+// cancelled.
+func (l *locker) Lock(s state.State, reason string) error {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	l.state = s
+
+	ctx, cancel := context.WithTimeout(l.ctx, l.timeout)
+	defer cancel()
+
+	lockInfo := state.NewLockInfo()
+	lockInfo.Operation = reason
 
 	err := slowmessage.Do(LockThreshold, func() error {
-		id, err := state.LockWithContext(ctx, s, info)
+		id, err := state.LockWithContext(ctx, s, lockInfo)
-		lockID = id
+		l.lockID = id
 		return err
 	}, func() {
-		if ui != nil {
+		if l.ui != nil {
-			ui.Output(color.Color(LockMessage))
+			l.ui.Output(l.color.Color(LockMessage))
 		}
 	})
 
 	if err != nil {
-		err = errwrap.Wrapf(strings.TrimSpace(LockErrorMessage), err)
+		return errwrap.Wrapf(strings.TrimSpace(LockErrorMessage), err)
 	}
 
-	return lockID, err
+	return nil
+}
+
+func (l *locker) Unlock(parentErr error) error {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	if l.lockID == "" {
+		return parentErr
 	}
 
-// Unlock unlocks the given state and outputs to the user if the
-// unlock fails what can be done.
-func Unlock(s state.State, id string, ui cli.Ui, color *colorstring.Colorize) error {
 	err := slowmessage.Do(LockThreshold, func() error {
-		return s.Unlock(id)
+		return l.state.Unlock(l.lockID)
 	}, func() {
-		if ui != nil {
+		if l.ui != nil {
-			ui.Output(color.Color(UnlockMessage))
+			l.ui.Output(l.color.Color(UnlockMessage))
 		}
 	})
 
 	if err != nil {
-		ui.Output(color.Color(fmt.Sprintf(
+		l.ui.Output(l.color.Color(fmt.Sprintf(
 			"\n"+strings.TrimSpace(UnlockErrorMessage)+"\n", err)))
 
-		err = fmt.Errorf(
+		if parentErr != nil {
-			"Error releasing the state lock. Please see the longer error message above.")
+			parentErr = multierror.Append(parentErr, err)
+		}
 	}
 
+	return parentErr
+
+}
+
+type noopLocker struct{}
+
+// NewNoopLocker returns a valid Locker that does nothing.
+func NewNoopLocker() Locker {
+	return noopLocker{}
+}
+
+func (l noopLocker) Lock(state.State, string) error {
+	return nil
+}
+
+func (l noopLocker) Unlock(err error) error {
 	return err
 }

command/meta_backend.go

@@ -586,15 +586,11 @@ func (m *Meta) backendFromPlan(opts *BackendOpts) (backend.Backend, error) {
 		lockCtx, cancel := context.WithTimeout(context.Background(), m.stateLockTimeout)
 		defer cancel()
 
-		// Lock the state if we can
+		unlock, err := clistate.Lock(lockCtx, realMgr, "backend from plan", "", m.Ui, m.Colorize())
-		lockInfo := state.NewLockInfo()
-		lockInfo.Operation = "backend from plan"
-
-		lockID, err := clistate.Lock(lockCtx, realMgr, lockInfo, m.Ui, m.Colorize())
 		if err != nil {
 			return nil, fmt.Errorf("Error locking state: %s", err)
 		}
-		defer clistate.Unlock(realMgr, lockID, m.Ui, m.Colorize())
+		defer unlock(nil)
 	}
 
 	if err := realMgr.RefreshState(); err != nil {
@@ -967,15 +963,11 @@ func (m *Meta) backend_C_r_s(
 		lockCtx, cancel := context.WithTimeout(context.Background(), m.stateLockTimeout)
 		defer cancel()
 
-		// Lock the state if we can
+		unlock, err := clistate.Lock(lockCtx, sMgr, "backend from config", "", m.Ui, m.Colorize())
-		lockInfo := state.NewLockInfo()
-		lockInfo.Operation = "backend from config"
-
-		lockID, err := clistate.Lock(lockCtx, sMgr, lockInfo, m.Ui, m.Colorize())
 		if err != nil {
 			return nil, fmt.Errorf("Error locking state: %s", err)
 		}
-		defer clistate.Unlock(sMgr, lockID, m.Ui, m.Colorize())
+		defer unlock(nil)
 	}
 
 	// Store the metadata in our saved state location
@@ -1050,15 +1042,11 @@ func (m *Meta) backend_C_r_S_changed(
 		lockCtx, cancel := context.WithTimeout(context.Background(), m.stateLockTimeout)
 		defer cancel()
 
-		// Lock the state if we can
+		unlock, err := clistate.Lock(lockCtx, sMgr, "backend from config", "", m.Ui, m.Colorize())
-		lockInfo := state.NewLockInfo()
-		lockInfo.Operation = "backend from config"
-
-		lockID, err := clistate.Lock(lockCtx, sMgr, lockInfo, m.Ui, m.Colorize())
 		if err != nil {
 			return nil, fmt.Errorf("Error locking state: %s", err)
 		}
-		defer clistate.Unlock(sMgr, lockID, m.Ui, m.Colorize())
+		defer unlock(nil)
 	}
 
 	// Update the backend state
@@ -1193,15 +1181,11 @@ func (m *Meta) backend_C_R_S_unchanged(
 		lockCtx, cancel := context.WithTimeout(context.Background(), m.stateLockTimeout)
 		defer cancel()
 
-		// Lock the state if we can
+		unlock, err := clistate.Lock(lockCtx, sMgr, "backend from config", "", m.Ui, m.Colorize())
-		lockInfo := state.NewLockInfo()
-		lockInfo.Operation = "backend from config"
-
-		lockID, err := clistate.Lock(lockCtx, sMgr, lockInfo, m.Ui, m.Colorize())
 		if err != nil {
 			return nil, fmt.Errorf("Error locking state: %s", err)
 		}
-		defer clistate.Unlock(sMgr, lockID, m.Ui, m.Colorize())
+		defer unlock(nil)
 	}
 
 	// Unset the remote state

command/meta_backend_migrate.go

@@ -236,25 +236,17 @@ func (m *Meta) backendMigrateState_s_s(opts *backendMigrateOpts) error {
 		lockCtx, cancel := context.WithTimeout(context.Background(), m.stateLockTimeout)
 		defer cancel()
 
-		lockInfoOne := state.NewLockInfo()
+		unlockOne, err := clistate.Lock(lockCtx, stateOne, "migration", "source state", m.Ui, m.Colorize())
-		lockInfoOne.Operation = "migration"
-		lockInfoOne.Info = "source state"
-
-		lockIDOne, err := clistate.Lock(lockCtx, stateOne, lockInfoOne, m.Ui, m.Colorize())
 		if err != nil {
 			return fmt.Errorf("Error locking source state: %s", err)
 		}
-		defer clistate.Unlock(stateOne, lockIDOne, m.Ui, m.Colorize())
+		defer unlockOne(nil)
 
-		lockInfoTwo := state.NewLockInfo()
+		unlockTwo, err := clistate.Lock(lockCtx, stateTwo, "migration", "destination state", m.Ui, m.Colorize())
-		lockInfoTwo.Operation = "migration"
-		lockInfoTwo.Info = "destination state"
-
-		lockIDTwo, err := clistate.Lock(lockCtx, stateTwo, lockInfoTwo, m.Ui, m.Colorize())
 		if err != nil {
 			return fmt.Errorf("Error locking destination state: %s", err)
 		}
-		defer clistate.Unlock(stateTwo, lockIDTwo, m.Ui, m.Colorize())
+		defer unlockTwo(nil)
 
 		// We now own a lock, so double check that we have the version
 		// corresponding to the lock.

command/taint.go

@@ -7,7 +7,6 @@ import (
 	"strings"
 
 	"github.com/hashicorp/terraform/command/clistate"
-	"github.com/hashicorp/terraform/state"
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -87,15 +86,13 @@ func (c *TaintCommand) Run(args []string) int {
 		lockCtx, cancel := context.WithTimeout(context.Background(), c.stateLockTimeout)
 		defer cancel()
 
-		lockInfo := state.NewLockInfo()
+		unlock, err := clistate.Lock(lockCtx, st, "taint", "", c.Ui, c.Colorize())
-		lockInfo.Operation = "taint"
-		lockID, err := clistate.Lock(lockCtx, st, lockInfo, c.Ui, c.Colorize())
 		if err != nil {
 			c.Ui.Error(fmt.Sprintf("Error locking state: %s", err))
 			return 1
 		}
 
-		defer clistate.Unlock(st, lockID, c.Ui, c.Colorize())
+		defer unlock(nil)
 	}
 
 	// Get the actual state structure

command/untaint.go

@@ -7,7 +7,6 @@ import (
 	"strings"
 
 	"github.com/hashicorp/terraform/command/clistate"
-	"github.com/hashicorp/terraform/state"
 )
 
 // UntaintCommand is a cli.Command implementation that manually untaints
@@ -75,15 +74,12 @@ func (c *UntaintCommand) Run(args []string) int {
 		lockCtx, cancel := context.WithTimeout(context.Background(), c.stateLockTimeout)
 		defer cancel()
 
-		lockInfo := state.NewLockInfo()
+		unlock, err := clistate.Lock(lockCtx, st, "untaint", "", c.Ui, c.Colorize())
-		lockInfo.Operation = "untaint"
-		lockID, err := clistate.Lock(lockCtx, st, lockInfo, c.Ui, c.Colorize())
 		if err != nil {
 			c.Ui.Error(fmt.Sprintf("Error locking state: %s", err))
 			return 1
 		}
-
+		defer unlock(nil)
-		defer clistate.Unlock(st, lockID, c.Ui, c.Colorize())
 	}
 
 	// Get the actual state structure

command/workspace_delete.go

@@ -6,7 +6,6 @@ import (
 	"strings"
 
 	"github.com/hashicorp/terraform/command/clistate"
-	"github.com/hashicorp/terraform/state"
 	"github.com/mitchellh/cli"
 	"github.com/posener/complete"
 )
@@ -114,10 +113,7 @@ func (c *WorkspaceDeleteCommand) Run(args []string) int {
 		lockCtx, cancel := context.WithTimeout(context.Background(), c.stateLockTimeout)
 		defer cancel()
 
-		// Lock the state if we can
+		unlock, err := clistate.Lock(lockCtx, sMgr, "workspace delete", "", c.Ui, c.Colorize())
-		lockInfo := state.NewLockInfo()
-		lockInfo.Operation = "workspace delete"
-		lockID, err := clistate.Lock(lockCtx, sMgr, lockInfo, c.Ui, c.Colorize())
 		if err != nil {
 			c.Ui.Error(fmt.Sprintf("Error locking state: %s", err))
 			return 1
@@ -132,7 +128,7 @@ func (c *WorkspaceDeleteCommand) Run(args []string) int {
 		// state deletion, i.e. in a CI environment. Adding Delete() as a
 		// required method of States would allow the removal of the resource to
 		// be delegated from the Backend to the State itself.
-		clistate.Unlock(sMgr, lockID, c.Ui, c.Colorize())
+		unlock(nil)
 	}
 
 	err = b.DeleteState(delEnv)

command/workspace_new.go

@@ -7,7 +7,6 @@ import (
 	"strings"
 
 	"github.com/hashicorp/terraform/command/clistate"
-	"github.com/hashicorp/terraform/state"
 	"github.com/hashicorp/terraform/terraform"
 	"github.com/mitchellh/cli"
 	"github.com/posener/complete"
@@ -118,15 +117,12 @@ func (c *WorkspaceNewCommand) Run(args []string) int {
 		lockCtx, cancel := context.WithTimeout(context.Background(), c.stateLockTimeout)
 		defer cancel()
 
-		// Lock the state if we can
+		unlock, err := clistate.Lock(lockCtx, sMgr, "workspace_new", "", c.Ui, c.Colorize())
-		lockInfo := state.NewLockInfo()
-		lockInfo.Operation = "workspace new"
-		lockID, err := clistate.Lock(lockCtx, sMgr, lockInfo, c.Ui, c.Colorize())
 		if err != nil {
 			c.Ui.Error(fmt.Sprintf("Error locking state: %s", err))
 			return 1
 		}
-		defer clistate.Unlock(sMgr, lockID, c.Ui, c.Colorize())
+		defer unlock(nil)
 	}
 
 	// read the existing state file