daemon, store: support download resume from /v2/downloadapi-download-resume

This commit adds support for resuming downloads from the /v2/download endpoint. 

7 files changed, 75 insertions, 11 deletions

diff --git a/daemon/api_download.go b/daemon/api_download.go
index 4c7bf3b129..1bc0a52897 100644
--- a/daemon/api_download.go
+++ b/daemon/api_download.go
@@ -39,6 +39,7 @@ var snapDownloadCmd = &Command{
 // SnapDownloadAction is used to request a snap download
 type snapDownloadAction struct {
	SnapName string `json:"snap-name,omitempty"`
+	Resume int64 `json:"resume,omitempty"`
	snapRevisionOptions
 }
 
@@ -86,7 +87,8 @@ func streamOneSnap(c *Command, action snapDownloadAction, user *auth.UserState)
	info := sars[0].Info
 
	downloadInfo := info.DownloadInfo
-	r, err := getStore(c).DownloadStream(context.TODO(), action.SnapName, &downloadInfo, user)
+	dlOpts := &store.DownloadOptions{Resume: action.Resume}
+	r, err := getStore(c).DownloadStream(context.TODO(), action.SnapName, &downloadInfo, user, dlOpts)
	if err != nil {
	return InternalError(err.Error())
	}
diff --git a/daemon/api_download_test.go b/daemon/api_download_test.go
index d595890457..89618a477e 100644
--- a/daemon/api_download_test.go
+++ b/daemon/api_download_test.go
@@ -104,6 +104,17 @@ var storeSnaps = map[string]*snap.Info{
	Sha3_384: "sha3sha3sha3",
	},
	},
+	"foo-resume": {
+	SideInfo: snap.SideInfo{
+	RealName: "foo-resume",
+	Revision: snap.R(1),
+	},
+	DownloadInfo: snap.DownloadInfo{
+	Size: int64(len(snapContent)),
+	AnonDownloadURL: "http://localhost/foo-resume",
+	Sha3_384: "sha3sha3sha3",
+	},
+	},
	"download-error-trigger-snap": {
	DownloadInfo: snap.DownloadInfo{
	Size: 100,
@@ -134,10 +145,13 @@ func (s *snapDownloadSuite) SnapAction(ctx context.Context, currentSnaps []*stor
	return []store.SnapActionResult{{Info: info}}, nil
 }
 
-func (s *snapDownloadSuite) DownloadStream(ctx context.Context, name string, downloadInfo *snap.DownloadInfo, user *auth.UserState) (io.ReadCloser, error) {
+func (s *snapDownloadSuite) DownloadStream(ctx context.Context, name string, downloadInfo *snap.DownloadInfo, user *auth.UserState, dlOpts *store.DownloadOptions) (io.ReadCloser, error) {
	if name == "download-error-trigger-snap" {
	return nil, fmt.Errorf("error triggered by download-error-trigger-snap")
	}
+	if name == "foo-resume" && dlOpts.Resume != 77 {
+	panic("foo-resume should set dlOpts.Resume to 77")
+	}
	if _, ok := storeSnaps[name]; ok {
	return ioutil.NopCloser(bytes.NewReader([]byte(snapContent))), nil
	}
@@ -223,6 +237,12 @@ func (s *snapDownloadSuite) TestStreamOneSnap(c *check.C) {
	status: 200,
	err: "",
	},
+	{
+	snapName: "foo-resume",
+	dataJSON: `{"snap-name": "foo-resume", "resume":77}`,
+	status: 200,
+	err: "",
+	},
	} {
	req, err := http.NewRequest("POST", "/v2/download", strings.NewReader(s.dataJSON))
	c.Assert(err, check.IsNil)
diff --git a/overlord/snapstate/backend.go b/overlord/snapstate/backend.go
index f8ca02411d..4b1719c7b6 100644
--- a/overlord/snapstate/backend.go
+++ b/overlord/snapstate/backend.go
@@ -47,7 +47,7 @@ type StoreService interface {
	WriteCatalogs(ctx context.Context, names io.Writer, adder store.SnapAdder) error
 
	Download(context.Context, string, string, *snap.DownloadInfo, progress.Meter, *auth.UserState, *store.DownloadOptions) error
-	DownloadStream(context.Context, string, *snap.DownloadInfo, *auth.UserState) (io.ReadCloser, error)
+	DownloadStream(context.Context, string, *snap.DownloadInfo, *auth.UserState, *store.DownloadOptions) (io.ReadCloser, error)
 
	Assertion(assertType *asserts.AssertionType, primaryKey []string, user *auth.UserState) (asserts.Assertion, error)
 
diff --git a/store/export_test.go b/store/export_test.go
index 73820da253..74b893fbde 100644
--- a/store/export_test.go
+++ b/store/export_test.go
@@ -113,7 +113,7 @@ func MockDownload(f func(ctx context.Context, name, sha3_384, downloadURL string
	}
 }
 
-func MockDoDownloadReq(f func(ctx context.Context, storeURL *url.URL, cdnHeader string, s *Store, user *auth.UserState) (*http.Response, error)) (restore func()) {
+func MockDoDownloadReq(f func(ctx context.Context, storeURL *url.URL, cdnHeader string, opts *DownloadOptions, s *Store, user *auth.UserState) (*http.Response, error)) (restore func()) {
	orig := doDownloadReq
	doDownloadReq = f
	return func() {
diff --git a/store/store.go b/store/store.go
index 5ed78b4dd6..5faf61cbd6 100644
--- a/store/store.go
+++ b/store/store.go
@@ -1338,6 +1338,7 @@ type DownloadOptions struct {
	RateLimit int64
	IsAutoRefresh bool
	LeavePartialOnError bool
+	Resume int64
 }
 
 // Download downloads the snap addressed by download info and returns its
@@ -1470,6 +1471,9 @@ func downloadReqOpts(storeURL *url.URL, cdnHeader string, opts *DownloadOptions)
	if opts != nil && opts.IsAutoRefresh {
	reqOptions.ExtraHeaders["Snap-Refresh-Reason"] = "scheduled"
	}
+	if opts != nil && opts.Resume > 0 {
+	reqOptions.ExtraHeaders["Range"] = fmt.Sprintf("bytes=%d-", opts.Resume)
+	}
 
	return &reqOptions
 }
@@ -1606,13 +1610,23 @@ func downloadImpl(ctx context.Context, name, sha3_384, downloadURL string, user
 }
 
 // DownloadStream will copy the snap from the request to the io.Reader
-func (s *Store) DownloadStream(ctx context.Context, name string, downloadInfo *snap.DownloadInfo, user *auth.UserState) (io.ReadCloser, error) {
+func (s *Store) DownloadStream(ctx context.Context, name string, downloadInfo *snap.DownloadInfo, user *auth.UserState, dlOpts *DownloadOptions) (io.ReadCloser, error) {
+	if dlOpts == nil {
+	dlOpts = &DownloadOptions{}
+	}
	if path := s.cacher.GetPath(downloadInfo.Sha3_384); path != "" {
	logger.Debugf("Cache hit for SHA3_384 …%.5s.", downloadInfo.Sha3_384)
	file, err := os.OpenFile(path, os.O_RDONLY, 0600)
	if err != nil {
	return nil, err
	}
+
+	if dlOpts.Resume > 0 {
+	if _, err := file.Seek(dlOpts.Resume, 0); err != nil {
+	return nil, err
+	}
+	}
+
	return file, nil
	}
 
@@ -1636,7 +1650,7 @@ func (s *Store) DownloadStream(ctx context.Context, name string, downloadInfo *s
	return nil, err
	}
 
-	resp, err := doDownloadReq(ctx, storeURL, cdnHeader, s, user)
+	resp, err := doDownloadReq(ctx, storeURL, cdnHeader, dlOpts, s, user)
	if err != nil {
	return nil, err
	}
@@ -1645,8 +1659,8 @@ func (s *Store) DownloadStream(ctx context.Context, name string, downloadInfo *s
 
 var doDownloadReq = doDownloadReqImpl
 
-func doDownloadReqImpl(ctx context.Context, storeURL *url.URL, cdnHeader string, s *Store, user *auth.UserState) (*http.Response, error) {
-	reqOptions := downloadReqOpts(storeURL, cdnHeader, nil)
+func doDownloadReqImpl(ctx context.Context, storeURL *url.URL, cdnHeader string, opts *DownloadOptions, s *Store, user *auth.UserState) (*http.Response, error) {
+	reqOptions := downloadReqOpts(storeURL, cdnHeader, opts)
	return s.doRequest(ctx, httputil.NewHTTPClient(&httputil.ClientOptions{Proxy: s.proxy}), reqOptions, user)
 }
 
diff --git a/store/store_test.go b/store/store_test.go
index 738135c28d..8a2687e31f 100644
--- a/store/store_test.go
+++ b/store/store_test.go
@@ -454,7 +454,7 @@ func (s *storeTestSuite) expectedAuthorization(c *C, user *auth.UserState) strin
 
 func (s *storeTestSuite) TestDownloadStreamOK(c *C) {
	expectedContent := []byte("I was downloaded")
-	restore := store.MockDoDownloadReq(func(ctx context.Context, url *url.URL, cdnHeader string, s *store.Store, user *auth.UserState) (*http.Response, error) {
+	restore := store.MockDoDownloadReq(func(ctx context.Context, url *url.URL, cdnHeader string, opts *store.DownloadOptions, s *store.Store, user *auth.UserState) (*http.Response, error) {
	c.Check(url.String(), Equals, "http://anon-url")
	r := &http.Response{
	Body: ioutil.NopCloser(bytes.NewReader(expectedContent)),
@@ -469,7 +469,7 @@ func (s *storeTestSuite) TestDownloadStreamOK(c *C) {
	snap.DownloadURL = "AUTH-URL"
	snap.Size = int64(len(expectedContent))
 
-	stream, err := s.store.DownloadStream(context.TODO(), "foo", &snap.DownloadInfo, nil)
+	stream, err := s.store.DownloadStream(context.TODO(), "foo", &snap.DownloadInfo, nil, nil)
	c.Assert(err, IsNil)
 
	buf := new(bytes.Buffer)
@@ -477,6 +477,34 @@ func (s *storeTestSuite) TestDownloadStreamOK(c *C) {
	c.Check(buf.String(), Equals, string(expectedContent))
 }
 
+func (s *storeTestSuite) TestDownloadStreamResumeOk(c *C) {
+	expectedContent := []byte("I was downloaded")
+	restore := store.MockDoDownloadReq(func(ctx context.Context, url *url.URL, cdnHeader string, opts *store.DownloadOptions, s *store.Store, user *auth.UserState) (*http.Response, error) {
+	c.Check(url.String(), Equals, "http://anon-url")
+	r := &http.Response{
+	Body: ioutil.NopCloser(bytes.NewReader(expectedContent[opts.Resume:])),
+	}
+	return r, nil
+	})
+	defer restore()
+
+	snap := &snap.Info{}
+	snap.RealName = "foo"
+	snap.AnonDownloadURL = "http://anon-url"
+	snap.DownloadURL = "AUTH-URL"
+	snap.Size = int64(len(expectedContent))
+
+	resumePoint := int64(5)
+	dlOpts := &store.DownloadOptions{Resume: resumePoint}
+
+	stream, err := s.store.DownloadStream(context.TODO(), "foo", &snap.DownloadInfo, nil, dlOpts)
+	c.Assert(err, IsNil)
+
+	buf := bytes.NewBuffer(expectedContent[:resumePoint])
+	buf.ReadFrom(stream)
+	c.Check(buf.String(), Equals, string(expectedContent))
+}
+
 func (s *storeTestSuite) TestDownloadOK(c *C) {
	expectedContent := []byte("I was downloaded")
 
diff --git a/store/storetest/storetest.go b/store/storetest/storetest.go
index 0aeca31e4e..74d76ebdc7 100644
--- a/store/storetest/storetest.go
+++ b/store/storetest/storetest.go
@@ -61,7 +61,7 @@ func (Store) Download(context.Context, string, string, *snap.DownloadInfo, progr
	panic("Store.Download not expected")
 }
 
-func (Store) DownloadStream(ctx context.Context, name string, downloadInfo *snap.DownloadInfo, user *auth.UserState) (io.ReadCloser, error) {
+func (Store) DownloadStream(ctx context.Context, name string, downloadInfo *snap.DownloadInfo, user *auth.UserState, dlOpts *store.DownloadOptions) (io.ReadCloser, error) {
	panic("Store.DownloadStream not expected")
 }