command: Adding backup of state file

command/apply.go

@@ -3,6 +3,7 @@ package command
 import (
 	"bytes"
 	"fmt"
+	"log"
 	"os"
 	"sort"
 	"strings"
@@ -20,7 +21,7 @@ type ApplyCommand struct {
 
 func (c *ApplyCommand) Run(args []string) int {
 	var refresh bool
-	var statePath, stateOutPath string
+	var statePath, stateOutPath, backupPath string
 
 	args = c.Meta.process(args)
 
@@ -28,6 +29,7 @@ func (c *ApplyCommand) Run(args []string) int {
 	cmdFlags.BoolVar(&refresh, "refresh", true, "refresh")
 	cmdFlags.StringVar(&statePath, "state", DefaultStateFilename, "path")
 	cmdFlags.StringVar(&stateOutPath, "state-out", "", "path")
+	cmdFlags.StringVar(&backupPath, "backup", "", "path")
 	cmdFlags.Usage = func() { c.Ui.Error(c.Help()) }
 	if err := cmdFlags.Parse(args); err != nil {
 		return 1
@@ -59,6 +61,12 @@ func (c *ApplyCommand) Run(args []string) int {
 		stateOutPath = statePath
 	}
 
+	// If we don't specify a backup path, default to state out with
+	// the extention
+	if backupPath == "" {
+		backupPath = stateOutPath + DefaultBackupExtention
+	}
+
 	// Build the context based on the arguments given
 	ctx, planned, err := c.Context(configPath, statePath)
 	if err != nil {
@@ -69,6 +77,20 @@ func (c *ApplyCommand) Run(args []string) int {
 		return 1
 	}
 
+	// Create a backup of the state before updating
+	if backupPath != "-" {
+		log.Printf("[INFO] Writing backup state to: %s", backupPath)
+		f, err := os.Create(backupPath)
+		if err == nil {
+			defer f.Close()
+			err = terraform.WriteState(c.State, f)
+		}
+		if err != nil {
+			c.Ui.Error(fmt.Sprintf("Error writing backup state file: %s", err))
+			return 1
+		}
+	}
+
 	// Plan if we haven't already
 	if !planned {
 		if refresh {
@@ -201,6 +223,10 @@ Usage: terraform apply [options] [dir]
 
 Options:
 
+  -backup=path           Path to backup the existing state file before
+                         modifying. Defaults to the "-state-out" path with
+                         ".backup" extention. Set to "-" to disable backup.
+
   -no-color              If specified, output won't contain any color.
 
   -refresh=true          Update state prior to checking for differences. This

command/command.go

@@ -10,6 +10,9 @@ import (
 // DefaultStateFilename is the default filename used for the state file.
 const DefaultStateFilename = "terraform.tfstate"
 
+// DefaultBackupExtention is added to the state file to form the path
+const DefaultBackupExtention = ".backup"
+
 func validateContext(ctx *terraform.Context, ui cli.Ui) bool {
 	if ws, es := ctx.Validate(); len(ws) > 0 || len(es) > 0 {
 		ui.Output(

command/meta.go

@@ -16,6 +16,7 @@ type Meta struct {
 	Color       bool
 	ContextOpts *terraform.ContextOpts
 	Ui          cli.Ui
+	State       *terraform.State
 
 	// This can be set by the command itself to provide extra hooks.
 	extraHooks []terraform.Hook
@@ -77,6 +78,9 @@ func (m *Meta) Context(path, statePath string) (*terraform.Context, bool, error)
 		}
 	}
 
+	// Store the loaded state
+	m.State = state
+
 	config, err := config.LoadDir(path)
 	if err != nil {
 		return nil, false, fmt.Errorf("Error loading config: %s", err)

command/plan.go

@@ -17,7 +17,7 @@ type PlanCommand struct {
 
 func (c *PlanCommand) Run(args []string) int {
 	var destroy, refresh bool
-	var outPath, statePath string
+	var outPath, statePath, backupPath string
 
 	args = c.Meta.process(args)
 
@@ -26,6 +26,7 @@ func (c *PlanCommand) Run(args []string) int {
 	cmdFlags.BoolVar(&refresh, "refresh", true, "refresh")
 	cmdFlags.StringVar(&outPath, "out", "", "path")
 	cmdFlags.StringVar(&statePath, "state", DefaultStateFilename, "path")
+	cmdFlags.StringVar(&backupPath, "backup", "", "path")
 	cmdFlags.Usage = func() { c.Ui.Error(c.Help()) }
 	if err := cmdFlags.Parse(args); err != nil {
 		return 1
@@ -58,6 +59,12 @@ func (c *PlanCommand) Run(args []string) int {
 		}
 	}
 
+	// If we don't specify a backup path, default to state out with
+	// the extention
+	if backupPath == "" {
+		backupPath = statePath + DefaultBackupExtention
+	}
+
 	ctx, _, err := c.Context(path, statePath)
 	if err != nil {
 		c.Ui.Error(err.Error())
@@ -68,6 +75,20 @@ func (c *PlanCommand) Run(args []string) int {
 	}
 
 	if refresh {
+		// Create a backup of the state before updating
+		if backupPath != "-" {
+			log.Printf("[INFO] Writing backup state to: %s", backupPath)
+			f, err := os.Create(backupPath)
+			if err == nil {
+				defer f.Close()
+				err = terraform.WriteState(c.State, f)
+			}
+			if err != nil {
+				c.Ui.Error(fmt.Sprintf("Error writing backup state file: %s", err))
+				return 1
+			}
+		}
+
 		c.Ui.Output("Refreshing Terraform state prior to plan...\n")
 		if _, err := ctx.Refresh(); err != nil {
 			c.Ui.Error(fmt.Sprintf("Error refreshing state: %s", err))
@@ -130,6 +151,10 @@ Usage: terraform plan [options] [dir]
 
 Options:
 
+  -backup=path        Path to backup the existing state file before
+                      modifying. Defaults to the "-state-out" path with
+                      ".backup" extention. Set to "-" to disable backup.
+
   -destroy            If set, a plan will be generated to destroy all resources
                       managed by the given configuration and state.
 

command/refresh.go

@@ -16,13 +16,14 @@ type RefreshCommand struct {
 }
 
 func (c *RefreshCommand) Run(args []string) int {
-	var statePath, stateOutPath string
+	var statePath, stateOutPath, backupPath string
 
 	args = c.Meta.process(args)
 
 	cmdFlags := c.Meta.flagSet("refresh")
 	cmdFlags.StringVar(&statePath, "state", DefaultStateFilename, "path")
 	cmdFlags.StringVar(&stateOutPath, "state-out", "", "path")
+	cmdFlags.StringVar(&backupPath, "backup", "", "path")
 	cmdFlags.Usage = func() { c.Ui.Error(c.Help()) }
 	if err := cmdFlags.Parse(args); err != nil {
 		return 1
@@ -50,6 +51,12 @@ func (c *RefreshCommand) Run(args []string) int {
 		stateOutPath = statePath
 	}
 
+	// If we don't specify a backup path, default to state out with
+	// the extention
+	if backupPath == "" {
+		backupPath = stateOutPath + DefaultBackupExtention
+	}
+
 	// Verify that the state path exists. The "ContextArg" function below
 	// will actually do this, but we want to provide a richer error message
 	// if possible.
@@ -86,6 +93,20 @@ func (c *RefreshCommand) Run(args []string) int {
 		return 1
 	}
 
+	// Create a backup of the state before updating
+	if backupPath != "-" {
+		log.Printf("[INFO] Writing backup state to: %s", backupPath)
+		f, err := os.Create(backupPath)
+		if err == nil {
+			defer f.Close()
+			err = terraform.WriteState(c.State, f)
+		}
+		if err != nil {
+			c.Ui.Error(fmt.Sprintf("Error writing backup state file: %s", err))
+			return 1
+		}
+	}
+
 	state, err := ctx.Refresh()
 	if err != nil {
 		c.Ui.Error(fmt.Sprintf("Error refreshing state: %s", err))
@@ -119,6 +140,10 @@ Usage: terraform refresh [options] [dir]
 
 Options:
 
+  -backup=path        Path to backup the existing state file before
+                      modifying. Defaults to the "-state-out" path with
+                      ".backup" extention. Set to "-" to disable backup.
+
   -no-color           If specified, output won't contain any color.
 
   -state=path         Path to read and save state (unless state-out