wdcli: Implement backup & snapshot

This commit implements command backup and snapshot.

cmd/snapshot.go

@@ -1,9 +1,8 @@
 package cmd
 
 import (
-	"fmt"
+	"io/fs"
 	"os"
-	"path/filepath"
 
 	wisski_distillery "github.com/FAU-CDI/wisski-distillery"
 	"github.com/FAU-CDI/wisski-distillery/env"
@@ -16,7 +15,8 @@ import (
 var Snapshot wisski_distillery.Command = snapshot{}
 
 type snapshot struct {
-	Keepalive bool `short:"k" long:"keepalive" description:"Keep instance running while taking a backup. Might lead to inconsistent state"`
+	Keepalive   bool `short:"k" long:"keepalive" description:"Keep instance running while taking a backup. Might lead to inconsistent state"`
+	StagingOnly bool `short:"s" long:"staging-only" description:"Do not package into a snapshot archive, but only create a staging directory"`
 
 	Positionals struct {
 		Slug string `positional-arg-name:"SLUG" required:"1-1" description:"slug of instance to take a snapshot of"`
@@ -46,65 +46,81 @@ func (bi snapshot) Run(context wisski_distillery.Context) error {
 		return err
 	}
 
-	// TODO: Allow skipping backups of individual parts and make them concurrent!
-
-	// start the snapshot and shutdown the instance (if requested)
 	logging.LogMessage(context.IOStream, "Creating snapshot of instance %s", bi.Positionals.Slug)
 
-	// create a new temporary directory
-	logging.LogMessage(context.IOStream, "Creating new snapshot staging directory")
-	sPath, err := dis.NewSnapshotStagingDir(instance.Slug)
-	if err != nil {
-		return errSnapshotFailed.Wrap(err)
+	// determine the target path for the archive
+	var sPath string
+	if !bi.StagingOnly {
+		// regular mode: create a temporary staging directory
+		logging.LogMessage(context.IOStream, "Creating new snapshot staging directory")
+		sPath, err = dis.NewSnapshotStagingDir(instance.Slug)
+		if err != nil {
+			return errSnapshotFailed.Wrap(err)
+		}
+		defer func() {
+			logging.LogMessage(context.IOStream, "Removing snapshot staging directory")
+			os.RemoveAll(sPath)
+		}()
+	} else {
+		// staging mode: use dest as a destination
+		sPath = bi.Positionals.Dest
+		if sPath == "" {
+			sPath, err = dis.NewSnapshotStagingDir(instance.Slug)
+			if err != nil {
+				return errSnapshotFailed.Wrap(err)
+			}
+		}
+
+		// create the directory (if it doesn't already exist)
+		logging.LogMessage(context.IOStream, "Creating staging directory")
+		err = os.Mkdir(sPath, fs.ModePerm)
+		if !os.IsExist(err) && err != nil {
+			return errSnapshotFailed.WithMessageF(err)
+		}
+		err = nil
 	}
-	defer func() {
-		logging.LogMessage(context.IOStream, "Removing snapshot staging directory")
-		os.RemoveAll(sPath)
-	}()
+	context.Println(sPath)
+
+	// TODO: Allow skipping backups of individual parts and make them concurrent!
 
 	// take a snapshot into the staging area!
-	sreport := instance.Snapshot(context.IOStream, bi.Keepalive, sPath)
-
-	// write out the report!
 	logging.LogOperation(func() error {
+		sreport := instance.Snapshot(context.IOStream, env.SnapshotDescription{
+			Dest:      sPath,
+			Keepalive: bi.Keepalive,
+		})
 
-		logging.LogOperation(func() error {
-			reportPath := filepath.Join(sPath, "report.txt")
-			context.Println(reportPath)
-
-			// create the report file!
-			report, err := os.Create(reportPath)
-			if err != nil {
-				return err
-			}
-			defer report.Close()
-
-			// print the report into it!
-			_, err = fmt.Fprintf(report, "%#v\n", sreport)
-			return err
-		}, context.IOStream, "Writing snapshot report")
+		// write out the report, ignoring any errors!
+		sreport.WriteReport(context.IOStream)
 
 		return nil
-	}, context.IOStream, "Creating snapshot")
+	}, context.IOStream, "Generating Snapshot")
 
-	// copy everything into the final archive
-
-	finalPath := bi.Positionals.Dest
-	if finalPath == "" {
-		finalPath = dis.NewSnapshotArchivePath(instance.Slug)
+	// if we requested to only have a staging area, then we are done
+	if bi.StagingOnly {
+		context.Printf("Wrote %s\n", sPath)
+		return nil
 	}
 
-	if err := logging.LogOperation(func() error {
-		context.IOStream.Println(finalPath)
+	// create the archive path
+	archivePath := bi.Positionals.Dest
+	if archivePath == "" {
+		archivePath = dis.NewSnapshotArchivePath(instance.Slug)
+	}
 
-		targz.Package(finalPath, sPath, func(src string) {
-			context.Println(src)
+	// and write everything into it!
+	// TODO: Should we move the open call to here?
+	var count int64
+	if err := logging.LogOperation(func() error {
+		context.IOStream.Println(archivePath)
+
+		count, err = targz.Package(archivePath, sPath, func(dst, src string) {
+			context.Println(dst)
 		})
 		return err
-	}, context.IOStream, "Writing final backup"); err != nil {
+	}, context.IOStream, "Writing snapshot archive"); err != nil {
 		return errSnapshotFailed.Wrap(err)
 	}
-	context.Printf("Wrote %s\n", finalPath)
-
+	context.Printf("Wrote %d byte(s) to %s\n", count, archivePath)
 	return nil
 }