Modify backup process to utilize contexts and exponential backoffs

If a request to upload a file part to S3 fails for any 5xx reason it will begin using an exponential backoff to keep re-trying the upload until we've reached a minute of trying to access the endpoint.

This should resolve temporary resolution issues with URLs and certain S3 compatiable systems such as B2 that sometimes return a 5xx error and just need a retry to be successful.

Also supports using the server context to ensure backups are terminated when a server is deleted, and removes the http call without a timeout, replacing it with a 2 hour timeout to account for connections as slow as 10Mbps on a huge file upload.

go.mod

@@ -14,6 +14,7 @@ require (
 	github.com/asaskevich/govalidator v0.0.0-20200907205600-7a23bdc65eef
 	github.com/beevik/etree v1.1.0
 	github.com/buger/jsonparser v1.1.0
+	github.com/cenkalti/backoff/v4 v4.1.0
 	github.com/cobaugh/osrelease v0.0.0-20181218015638-a93a0a55a249
 	github.com/containerd/containerd v1.4.3 // indirect
 	github.com/containerd/fifo v0.0.0-20201026212402-0724c46b320c // indirect

go.sum

@@ -73,7 +73,10 @@ github.com/bketelsen/crypt v0.0.3-0.20200106085610-5cbc8cc4026c/go.mod h1:MKsuJm
 github.com/buger/jsonparser v1.1.0 h1:EPAGdKZgZCON4ZcMD+h4l/NN4ndr6ijSpj4INh8PbUY=
 github.com/buger/jsonparser v1.1.0/go.mod h1:6RYKKt7H4d4+iWqouImQ9R2FZql3VbhNgx27UK13J/0=
 github.com/casbin/casbin/v2 v2.1.2/go.mod h1:YcPU1XXisHhLzuxH9coDNf2FbKpjGlbCg3n9yuLkIJQ=
+github.com/cenkalti/backoff v2.2.1+incompatible h1:tNowT99t7UNflLxfYYSlKYsBpXdEet03Pg2g16Swow4=
 github.com/cenkalti/backoff v2.2.1+incompatible/go.mod h1:90ReRw6GdpyfrHakVjL/QHaoyV4aDUVVkXQJJJ3NXXM=
+github.com/cenkalti/backoff/v4 v4.1.0 h1:c8LkOFQTzuO0WBM/ae5HdGQuZPfPxp7lqBRwQRm4fSc=
+github.com/cenkalti/backoff/v4 v4.1.0/go.mod h1:scbssz8iZGpm3xbr14ovlUdkxfGXNInqkPWOWmG2CLw=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
 github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=

server/backup.go

@@ -66,7 +66,7 @@ func (s *Server) Backup(b backup.BackupInterface) error {
 		}
 	}
 
-	ad, err := b.Generate(s.Filesystem().Path(), ignored)
+	ad, err := b.Generate(s.Context(), s.Filesystem().Path(), ignored)
 	if err != nil {
 		if err := s.notifyPanelOfBackup(b.Identifier(), &backup.ArchiveDetails{}, false); err != nil {
 			s.Log().WithFields(log.Fields{
@@ -150,7 +150,7 @@ func (s *Server) RestoreBackup(b backup.BackupInterface, reader io.ReadCloser) (
 	// Attempt to restore the backup to the server by running through each entry
 	// in the file one at a time and writing them to the disk.
 	s.Log().Debug("starting file writing process for backup restoration")
-	err = b.Restore(reader, func(file string, r io.Reader) error {
+	err = b.Restore(s.Context(), reader, func(file string, r io.Reader) error {
 		s.Events().Publish(DaemonMessageEvent, "(restoring): "+file)
 		return s.Filesystem().Writefile(file, r)
 	})

server/backup/backup.go

@@ -1,16 +1,18 @@
 package backup
 
 import (
+	"context"
 	"crypto/sha1"
 	"encoding/hex"
 	"io"
 	"os"
 	"path"
-	"sync"
 
+	"emperror.dev/errors"
 	"github.com/apex/log"
 	"github.com/pterodactyl/wings/config"
 	"github.com/pterodactyl/wings/remote"
+	"golang.org/x/sync/errgroup"
 )
 
 type AdapterType string
@@ -24,20 +26,37 @@ const (
 // and remote backups allowing the files to be restored.
 type RestoreCallback func(file string, r io.Reader) error
 
-type ArchiveDetails struct {
+// noinspection GoNameStartsWithPackageName
-	Checksum     string `json:"checksum"`
+type BackupInterface interface {
-	ChecksumType string `json:"checksum_type"`
+	// SetClient sets the API request client on the backup interface.
-	Size         int64  `json:"size"`
+	SetClient(c remote.Client)
-}
+	// Identifier returns the UUID of this backup as tracked by the panel
-
+	// instance.
-// ToRequest returns a request object.
+	Identifier() string
-func (ad *ArchiveDetails) ToRequest(successful bool) remote.BackupRequest {
+	// WithLogContext attaches additional context to the log output for this
-	return remote.BackupRequest{
+	// backup.
-		Checksum:     ad.Checksum,
+	WithLogContext(map[string]interface{})
-		ChecksumType: ad.ChecksumType,
+	// Generate creates a backup in whatever the configured source for the
-		Size:         ad.Size,
+	// specific implementation is.
-		Successful:   successful,
+	Generate(ctx context.Context, basePath string, ignore string) (*ArchiveDetails, error)
-	}
+	// Ignored returns the ignored files for this backup instance.
+	Ignored() string
+	// Checksum returns a SHA1 checksum for the generated backup.
+	Checksum() ([]byte, error)
+	// Size returns the size of the generated backup.
+	Size() (int64, error)
+	// Path returns the path to the backup on the machine. This is not always
+	// the final storage location of the backup, simply the location we're using
+	// to store it until it is moved to the final spot.
+	Path() string
+	// Details returns details about the archive.
+	Details(ctx context.Context) (*ArchiveDetails, error)
+	// Remove removes a backup file.
+	Remove() error
+	// Restore is called when a backup is ready to be restored to the disk from
+	// the given source. Not every backup implementation will support this nor
+	// will every implementation require a reader be provided.
+	Restore(ctx context.Context, reader io.Reader, callback RestoreCallback) error
 }
 
 type Backup struct {
@@ -54,39 +73,6 @@ type Backup struct {
 	logContext map[string]interface{}
 }
 
-// noinspection GoNameStartsWithPackageName
-type BackupInterface interface {
-	// SetClient sets the API request client on the backup interface.
-	SetClient(c remote.Client)
-	// Identifier returns the UUID of this backup as tracked by the panel
-	// instance.
-	Identifier() string
-	// WithLogContext attaches additional context to the log output for this
-	// backup.
-	WithLogContext(map[string]interface{})
-	// Generate creates a backup in whatever the configured source for the
-	// specific implementation is.
-	Generate(string, string) (*ArchiveDetails, error)
-	// Ignored returns the ignored files for this backup instance.
-	Ignored() string
-	// Checksum returns a SHA1 checksum for the generated backup.
-	Checksum() ([]byte, error)
-	// Size returns the size of the generated backup.
-	Size() (int64, error)
-	// Path returns the path to the backup on the machine. This is not always
-	// the final storage location of the backup, simply the location we're using
-	// to store it until it is moved to the final spot.
-	Path() string
-	// Details returns details about the archive.
-	Details() *ArchiveDetails
-	// Remove removes a backup file.
-	Remove() error
-	// Restore is called when a backup is ready to be restored to the disk from
-	// the given source. Not every backup implementation will support this nor
-	// will every implementation require a reader be provided.
-	Restore(reader io.Reader, callback RestoreCallback) error
-}
-
 func (b *Backup) SetClient(c remote.Client) {
 	b.client = c
 }
@@ -95,12 +81,12 @@ func (b *Backup) Identifier() string {
 	return b.Uuid
 }
 
-// Returns the path for this specific backup.
+// Path returns the path for this specific backup.
 func (b *Backup) Path() string {
 	return path.Join(config.Get().System.BackupDirectory, b.Identifier()+".tar.gz")
 }
 
-// Return the size of the generated backup.
+// Size returns the size of the generated backup.
 func (b *Backup) Size() (int64, error) {
 	st, err := os.Stat(b.Path())
 	if err != nil {
@@ -110,7 +96,7 @@ func (b *Backup) Size() (int64, error) {
 	return st.Size(), nil
 }
 
-// Returns the SHA256 checksum of a backup.
+// Checksum returns the SHA256 checksum of a backup.
 func (b *Backup) Checksum() ([]byte, error) {
 	h := sha1.New()
 
@@ -128,51 +114,34 @@ func (b *Backup) Checksum() ([]byte, error) {
 	return h.Sum(nil), nil
 }
 
-// Returns details of the archive by utilizing two go-routines to get the checksum and
+// Details returns both the checksum and size of the archive currently stored on
-// the size of the archive.
+// the disk to the caller.
-func (b *Backup) Details() *ArchiveDetails {
+func (b *Backup) Details(ctx context.Context) (*ArchiveDetails, error) {
-	wg := sync.WaitGroup{}
+	ad := ArchiveDetails{ChecksumType: "sha1"}
-	wg.Add(2)
+	g, ctx := errgroup.WithContext(ctx)
 
-	l := log.WithField("backup_id", b.Uuid)
+	g.Go(func() error {
-
-	var checksum string
-	// Calculate the checksum for the file.
-	go func() {
-		defer wg.Done()
-
-		l.Info("computing checksum for backup...")
 		resp, err := b.Checksum()
 		if err != nil {
-			log.WithFields(log.Fields{
+			return err
-				"backup": b.Identifier(),
-				"error":  err,
-			}).Error("failed to calculate checksum for backup")
-			return
 		}
+		ad.Checksum = hex.EncodeToString(resp)
+		return nil
+	})
 
-		checksum = hex.EncodeToString(resp)
+	g.Go(func() error {
-		l.WithField("checksum", checksum).Info("computed checksum for backup")
+		s, err := b.Size()
-	}()
+		if err != nil {
-
+			return err
-	var sz int64
-	go func() {
-		defer wg.Done()
-
-		if s, err := b.Size(); err != nil {
-			return
-		} else {
-			sz = s
 		}
-	}()
+		ad.Size = s
+		return nil
+	})
 
-	wg.Wait()
+	if err := g.Wait(); err != nil {
-
+		return nil, errors.WithStackDepth(err, 1)
-	return &ArchiveDetails{
-		Checksum:     checksum,
-		ChecksumType: "sha1",
-		Size:         sz,
 	}
+	return &ad, nil
 }
 
 func (b *Backup) Ignored() string {
@@ -188,3 +157,19 @@ func (b *Backup) log() *log.Entry {
 	}
 	return l
 }
+
+type ArchiveDetails struct {
+	Checksum     string `json:"checksum"`
+	ChecksumType string `json:"checksum_type"`
+	Size         int64  `json:"size"`
+}
+
+// ToRequest returns a request object.
+func (ad *ArchiveDetails) ToRequest(successful bool) remote.BackupRequest {
+	return remote.BackupRequest{
+		Checksum:     ad.Checksum,
+		ChecksumType: ad.ChecksumType,
+		Size:         ad.Size,
+		Successful:   successful,
+	}
+}

server/backup/backup_local.go

@@ -1,10 +1,11 @@
 package backup
 
 import (
-	"errors"
+	"context"
 	"io"
 	"os"
 
+	"emperror.dev/errors"
 	"github.com/pterodactyl/wings/server/filesystem"
 
 	"github.com/mholt/archiver/v3"
@@ -56,28 +57,40 @@ func (b *LocalBackup) WithLogContext(c map[string]interface{}) {
 
 // Generate generates a backup of the selected files and pushes it to the
 // defined location for this instance.
-func (b *LocalBackup) Generate(basePath, ignore string) (*ArchiveDetails, error) {
+func (b *LocalBackup) Generate(ctx context.Context, basePath, ignore string) (*ArchiveDetails, error) {
 	a := &filesystem.Archive{
 		BasePath: basePath,
 		Ignore:   ignore,
 	}
 
-	b.log().Info("creating backup for server...")
+	b.log().WithField("path", b.Path()).Info("creating backup for server")
 	if err := a.Create(b.Path()); err != nil {
 		return nil, err
 	}
 	b.log().Info("created backup successfully")
 
-	return b.Details(), nil
+	ad, err := b.Details(ctx)
+	if err != nil {
+		return nil, errors.WrapIf(err, "backup: failed to get archive details for local backup")
+	}
+	return ad, nil
 }
 
 // Restore will walk over the archive and call the callback function for each
 // file encountered.
-func (b *LocalBackup) Restore(_ io.Reader, callback RestoreCallback) error {
+func (b *LocalBackup) Restore(ctx context.Context, _ io.Reader, callback RestoreCallback) error {
 	return archiver.Walk(b.Path(), func(f archiver.File) error {
-		if f.IsDir() {
+		select {
-			return nil
+		case <-ctx.Done():
+			// Stop walking if the context is canceled.
+			return archiver.ErrStopWalk
+		default:
+			{
+				if f.IsDir() {
+					return nil
+				}
+				return callback(filesystem.ExtractNameFromArchive(f), f)
+			}
 		}
-		return callback(filesystem.ExtractNameFromArchive(f), f)
 	})
 }

server/backup/backup_s3.go

@@ -5,11 +5,15 @@ import (
 	"compress/gzip"
 	"context"
 	"fmt"
-	"github.com/pterodactyl/wings/server/filesystem"
 	"io"
 	"net/http"
 	"os"
 	"strconv"
+	"time"
+
+	"emperror.dev/errors"
+	"github.com/cenkalti/backoff/v4"
+	"github.com/pterodactyl/wings/server/filesystem"
 
 	"github.com/juju/ratelimit"
 	"github.com/pterodactyl/wings/config"
@@ -45,7 +49,7 @@ func (s *S3Backup) WithLogContext(c map[string]interface{}) {
 
 // Generate creates a new backup on the disk, moves it into the S3 bucket via
 // the provided presigned URL, and then deletes the backup from the disk.
-func (s *S3Backup) Generate(basePath, ignore string) (*ArchiveDetails, error) {
+func (s *S3Backup) Generate(ctx context.Context, basePath, ignore string) (*ArchiveDetails, error) {
 	defer s.Remove()
 
 	a := &filesystem.Archive{
@@ -53,7 +57,7 @@ func (s *S3Backup) Generate(basePath, ignore string) (*ArchiveDetails, error) {
 		Ignore:   ignore,
 	}
 
-	s.log().Info("creating backup for server...")
+	s.log().WithField("path", s.Path()).Info("creating backup for server")
 	if err := a.Create(s.Path()); err != nil {
 		return nil, err
 	}
@@ -61,29 +65,65 @@ func (s *S3Backup) Generate(basePath, ignore string) (*ArchiveDetails, error) {
 
 	rc, err := os.Open(s.Path())
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrap(err, "backup: could not read archive from disk")
 	}
 	defer rc.Close()
 
-	if err := s.generateRemoteRequest(rc); err != nil {
+	if err := s.generateRemoteRequest(ctx, rc); err != nil {
 		return nil, err
 	}
-
+	ad, err := s.Details(ctx)
-	return s.Details(), nil
+	if err != nil {
+		return nil, errors.WrapIf(err, "backup: failed to get archive details after upload")
+	}
+	return ad, nil
 }
 
-// Reader provides a wrapper around an existing io.Reader
+// Restore will read from the provided reader assuming that it is a gzipped
-// but implements io.Closer in order to satisfy an io.ReadCloser.
+// tar reader. When a file is encountered in the archive the callback function
-type Reader struct {
+// will be triggered. If the callback returns an error the entire process is
-	io.Reader
+// stopped, otherwise this function will run until all files have been written.
-}
+//
-
+// This restoration uses a workerpool to use up to the number of CPUs available
-func (Reader) Close() error {
+// on the machine when writing files to the disk.
+func (s *S3Backup) Restore(ctx context.Context, r io.Reader, callback RestoreCallback) error {
+	reader := r
+	// Steal the logic we use for making backups which will be applied when restoring
+	// this specific backup. This allows us to prevent overloading the disk unintentionally.
+	if writeLimit := int64(config.Get().System.Backups.WriteLimit * 1024 * 1024); writeLimit > 0 {
+		reader = ratelimit.Reader(r, ratelimit.NewBucketWithRate(float64(writeLimit), writeLimit))
+	}
+	gr, err := gzip.NewReader(reader)
+	if err != nil {
+		return err
+	}
+	defer gr.Close()
+	tr := tar.NewReader(gr)
+	for {
+		select {
+		case <-ctx.Done():
+			return nil
+		default:
+			// Do nothing, fall through to the next block of code in this loop.
+		}
+		header, err := tr.Next()
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			return err
+		}
+		if header.Typeflag == tar.TypeReg {
+			if err := callback(header.Name, tr); err != nil {
+				return err
+			}
+		}
+	}
 	return nil
 }
 
 // Generates the remote S3 request and begins the upload.
-func (s *S3Backup) generateRemoteRequest(rc io.ReadCloser) error {
+func (s *S3Backup) generateRemoteRequest(ctx context.Context, rc io.ReadCloser) error {
 	defer rc.Close()
 
 	s.log().Debug("attempting to get size of backup...")
@@ -101,37 +141,7 @@ func (s *S3Backup) generateRemoteRequest(rc io.ReadCloser) error {
 	s.log().Debug("got S3 upload urls from the Panel")
 	s.log().WithField("parts", len(urls.Parts)).Info("attempting to upload backup to s3 endpoint...")
 
-	handlePart := func(part string, size int64) (string, error) {
+	uploader := newS3FileUploader(rc)
-		r, err := http.NewRequest(http.MethodPut, part, nil)
-		if err != nil {
-			return "", err
-		}
-
-		r.ContentLength = size
-		r.Header.Add("Content-Length", strconv.Itoa(int(size)))
-		r.Header.Add("Content-Type", "application/x-gzip")
-
-		// Limit the reader to the size of the part.
-		r.Body = Reader{Reader: io.LimitReader(rc, size)}
-
-		// This http request can block forever due to it not having a timeout,
-		// but we are uploading up to 5GB of data, so there is not really
-		// a good way to handle a timeout on this.
-		res, err := http.DefaultClient.Do(r)
-		if err != nil {
-			return "", err
-		}
-		defer res.Body.Close()
-
-		// Handle non-200 status codes.
-		if res.StatusCode != http.StatusOK {
-			return "", fmt.Errorf("failed to put S3 object part, %d:%s", res.StatusCode, res.Status)
-		}
-
-		// Get the ETag from the uploaded part, this should be sent with the CompleteMultipartUpload request.
-		return res.Header.Get("ETag"), nil
-	}
-
 	for i, part := range urls.Parts {
 		// Get the size for the current part.
 		var partSize int64
@@ -144,7 +154,7 @@ func (s *S3Backup) generateRemoteRequest(rc io.ReadCloser) error {
 		}
 
 		// Attempt to upload the part.
-		if _, err := handlePart(part, partSize); err != nil {
+		if _, err := uploader.uploadPart(ctx, part, partSize); err != nil {
 			s.log().WithField("part_id", i+1).WithError(err).Warn("failed to upload part")
 			return err
 		}
@@ -157,39 +167,97 @@ func (s *S3Backup) generateRemoteRequest(rc io.ReadCloser) error {
 	return nil
 }
 
-// Restore will read from the provided reader assuming that it is a gzipped
+type s3FileUploader struct {
-// tar reader. When a file is encountered in the archive the callback function
+	io.ReadCloser
-// will be triggered. If the callback returns an error the entire process is
+	client *http.Client
-// stopped, otherwise this function will run until all files have been written.
+}
+
+// newS3FileUploader returns a new file uploader instance.
+func newS3FileUploader(file io.ReadCloser) *s3FileUploader {
+	return &s3FileUploader{
+		ReadCloser: file,
+		// We purposefully use a super high timeout on this request since we need to upload
+		// a 5GB file. This assumes at worst a 10Mbps connection for uploading. While technically
+		// you could go slower we're targeting mostly hosted servers that should have 100Mbps
+		// connections anyways.
+		client: &http.Client{Timeout: time.Hour * 2},
+	}
+}
+
+// backoff returns a new expoential backoff implementation using a context that
+// will also stop the backoff if it is canceled.
+func (fu *s3FileUploader) backoff(ctx context.Context) backoff.BackOffContext {
+	b := backoff.NewExponentialBackOff()
+	b.Multiplier = 2
+	b.MaxElapsedTime = time.Minute
+
+	return backoff.WithContext(b, ctx)
+}
+
+// uploadPart attempts to upload a given S3 file part to the S3 system. If a
+// 5xx error is returned from the endpoint this will continue with an exponential
+// backoff to try and successfully upload the part.
 //
-// This restoration uses a workerpool to use up to the number of CPUs available
+// Once uploaded the ETag is returned to the caller.
-// on the machine when writing files to the disk.
+func (fu *s3FileUploader) uploadPart(ctx context.Context, part string, size int64) (string, error) {
-func (s *S3Backup) Restore(r io.Reader, callback RestoreCallback) error {
+	r, err := http.NewRequestWithContext(ctx, http.MethodPut, part, nil)
-	reader := r
-	// Steal the logic we use for making backups which will be applied when restoring
-	// this specific backup. This allows us to prevent overloading the disk unintentionally.
-	if writeLimit := int64(config.Get().System.Backups.WriteLimit * 1024 * 1024); writeLimit > 0 {
-		reader = ratelimit.Reader(r, ratelimit.NewBucketWithRate(float64(writeLimit), writeLimit))
-	}
-	gr, err := gzip.NewReader(reader)
 	if err != nil {
-		return err
+		return "", errors.Wrap(err, "backup: could not create request for S3")
 	}
-	defer gr.Close()
+
-	tr := tar.NewReader(gr)
+	r.ContentLength = size
-	for {
+	r.Header.Add("Content-Length", strconv.Itoa(int(size)))
-		header, err := tr.Next()
+	r.Header.Add("Content-Type", "application/x-gzip")
+
+	// Limit the reader to the size of the part.
+	r.Body = Reader{Reader: io.LimitReader(fu.ReadCloser, size)}
+
+	var etag string
+	err = backoff.Retry(func() error {
+		res, err := fu.client.Do(r)
 		if err != nil {
-			if err == io.EOF {
+			if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, context.Canceled) {
-				break
+				return backoff.Permanent(err)
 			}
-			return err
+			// Don't use a permanent error here, if there is a temporary resolution error with
+			// the URL due to DNS issues we want to keep re-trying.
+			return errors.Wrap(err, "backup: S3 HTTP request failed")
 		}
-		if header.Typeflag == tar.TypeReg {
+		_ = res.Body.Close()
-			if err := callback(header.Name, tr); err != nil {
+
+		if res.StatusCode != http.StatusOK {
+			err := errors.New(fmt.Sprintf("backup: failed to put S3 object: [HTTP/%d] %s", res.StatusCode, res.Status))
+			// Only attempt a backoff retry if this error is because of a 5xx error from
+			// the S3 endpoint. Any 4xx error should be treated as an error that a retry
+			// would not fix.
+			if res.StatusCode >= http.StatusInternalServerError {
 				return err
 			}
+			return backoff.Permanent(err)
 		}
+
+		// Get the ETag from the uploaded part, this should be sent with the
+		// CompleteMultipartUpload request.
+		etag = res.Header.Get("ETag")
+
+		return nil
+	}, fu.backoff(ctx))
+
+	if err != nil {
+		if v, ok := err.(*backoff.PermanentError); ok {
+			return "", v.Unwrap()
+		}
+		return "", err
 	}
+	return etag, nil
+}
+
+// Reader provides a wrapper around an existing io.Reader
+// but implements io.Closer in order to satisfy an io.ReadCloser.
+type Reader struct {
+	io.Reader
+}
+
+func (Reader) Close() error {
 	return nil
 }