remote: adding helpers for remote state storage

remote/remote.go

@@ -0,0 +1,199 @@
+package remote
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/url"
+	"os"
+	"path/filepath"
+
+	"github.com/hashicorp/terraform/terraform"
+)
+
+const (
+	// LocalDirectory is the directory created in the working
+	// dir to hold the remote state file.
+	LocalDirectory = ".terraform"
+
+	// HiddenStateFile is the name of the state file in the
+	// LocalDirectory
+	HiddenStateFile = "terraform.tfstate"
+
+	// BackupHiddenStateFile is the path we backup the state
+	// file to before modifications are made
+	BackupHiddenStateFile = "terraform.tfstate.backup"
+
+	// DefaultServer is used when no server is provided. We use
+	// the hosted cloud URL.
+	DefaultServer = "http://www.hashicorp.com/"
+)
+
+// EnsureDirectory is used to make sure the local storage
+// directory exists
+func EnsureDirectory() error {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return fmt.Errorf("Failed to get current directory: %v", err)
+	}
+	path := filepath.Join(cwd, LocalDirectory)
+	if err := os.Mkdir(path, 0770); err != nil {
+		return fmt.Errorf("Failed to make directory '%s': %v", path, err)
+	}
+	return nil
+}
+
+// HiddenStatePath is used to return the path to the hidden state file,
+// should there be one.
+func HiddenStatePath() (string, error) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return "", fmt.Errorf("Failed to get current directory: %v", err)
+	}
+	path := filepath.Join(cwd, LocalDirectory, HiddenStateFile)
+	return path, nil
+}
+
+// validConfig does a purely logical validation of the remote config
+func validConfig(conf *terraform.RemoteState) error {
+	// Verify the remote server configuration is sane
+	if (conf.Server != "" || conf.AuthToken != "") && conf.Name == "" {
+		return fmt.Errorf("Name must be provided for remote state storage")
+	}
+	if conf.Server != "" {
+		if _, err := url.Parse(conf.Server); err != nil {
+			return fmt.Errorf("Remote Server URL invalid: %v", err)
+		}
+	} else {
+		// Fill in the default server
+		conf.Server = DefaultServer
+	}
+	return nil
+}
+
+// ValidateConfig is used to take a remote state configuration,
+// ensure the local directory exists and that the remote state
+// does not conflict with an existing state file.
+func ValidateConfig(conf *terraform.RemoteState) error {
+	// Logical validation first
+	if err := validConfig(conf); err != nil {
+		return err
+	}
+
+	// Ensure the hidden directory
+	if err := EnsureDirectory(); err != nil {
+		return fmt.Errorf(
+			"Remote state setup failed: %s", err)
+	}
+
+	// Get the path to the state file
+	path, err := HiddenStatePath()
+	if err != nil {
+		return err
+	}
+
+	// Open the existing file
+	f, err := os.Open(path)
+	if err != nil {
+		if !os.IsNotExist(err) {
+			return fmt.Errorf("Failed to open state file '%s': %s", path, err)
+		}
+		return nil
+	}
+	defer f.Close()
+
+	// Decode the state
+	state, err := terraform.ReadState(f)
+	if err != nil {
+		return fmt.Errorf("Failed to read state file '%s': %v", path, err)
+	}
+
+	// If the hidden state file has no remote info, something
+	// is definitely wrong...
+	if state.Remote == nil {
+		return fmt.Errorf(`State file '%s' missing remote storage information.
+This is likely a bug, please report it.`)
+	}
+
+	// Check if there is a conflict
+	if !state.Remote.Equals(conf) {
+		return fmt.Errorf(
+			"Conflicting definitions for remote storage in existing state file '%s'", path)
+	}
+	return nil
+}
+
+// ReadState is used to read the remote state given
+// the configuration for the remote endpoint. We return
+// a boolean indicating if the remote state exists, along
+// with the state, and possible error.
+func ReadState(conf *terraform.RemoteState) (io.Reader, error) {
+	// TODO: Read actually from a server
+
+	// Return the blank state, which is done if the server
+	// returns a "not found" or equivalent
+	return blankState(conf)
+}
+
+// blankState is used to return a serialized form of a blank state
+// with only the remote info.
+func blankState(conf *terraform.RemoteState) (io.Reader, error) {
+	blank := terraform.NewState()
+	blank.Remote = conf
+	buf := bytes.NewBuffer(nil)
+	err := terraform.WriteState(blank, buf)
+	return buf, err
+}
+
+// Persist is used to write out the state given by a reader (likely
+// being streamed from a remote server) to the local storage.
+func Persist(r io.Reader) error {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return fmt.Errorf("Failed to get current directory: %v", err)
+	}
+	statePath := filepath.Join(cwd, LocalDirectory, HiddenStateFile)
+	backupPath := filepath.Join(cwd, LocalDirectory, BackupHiddenStateFile)
+
+	// Backup the old file if it exists
+	if err := copyFile(statePath, backupPath); err != nil {
+		return fmt.Errorf("Failed to backup state file '%s' to '%s': %v", statePath, backupPath, err)
+	}
+
+	// Open the state path
+	fh, err := os.Create(statePath)
+	if err != nil {
+		return fmt.Errorf("Failed to open state file '%s': %v", statePath, err)
+	}
+
+	// Copy the new state
+	_, err = io.Copy(fh, r)
+	fh.Close()
+	if err != nil {
+		os.Remove(statePath)
+		return fmt.Errorf("Failed to persist state file: %v", err)
+	}
+	return nil
+}
+
+// copyFile is used to copy from a source file if it exists to a destination.
+// This is used to create a backup of the state file.
+func copyFile(src, dst string) error {
+	srcFH, err := os.Open(src)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+	defer srcFH.Close()
+
+	dstFH, err := os.Create(dst)
+	if err != nil {
+		return err
+	}
+	defer dstFH.Close()
+
+	_, err = io.Copy(dstFH, srcFH)
+	return err
+}