Download link generator for snapshots

Three days expiration

apps/drivers/fs.go

@@ -1,6 +1,7 @@
 package drivers
 
 import (
+	"errors"
 	"io"
 	"io/ioutil"
 	"os"
@@ -83,3 +84,8 @@ func (f FSDriver) List(prefix string) ([]string, error) {
 func (f FSDriver) Delete(key string) error {
 	return os.Remove(path.Join(f.Path, key))
 }
+
+// GetDownloadLink is not implemented in this driver
+func (f FSDriver) GetDownloadLink(key string) (string, error) {
+	return "", errors.New("not implemented")
+}

apps/drivers/s3.go

@@ -5,11 +5,14 @@ import (
 	"context"
 	"fmt"
 	"io/ioutil"
+	"time"
 
 	"github.com/minio/minio-go/v7"
 	"github.com/minio/minio-go/v7/pkg/credentials"
 )
 
+const s3LinkExpiration = 72 // in hours
+
 // S3Driver provides basic interface for S3 storage compatible with Driver interface
 type S3Driver struct {
 	// S3 storage related things
@@ -155,3 +158,19 @@ func (s S3Driver) Delete(key string) error {
 
 	return nil
 }
+
+// GetDownloadLink returns URL of object with given key. That URL can be used to download the object.
+func (s S3Driver) GetDownloadLink(key string) (string, error) {
+	client, err := s.getMinioClient()
+	if err != nil {
+		return "", fmt.Errorf("getting minio client error: %v", err)
+	}
+
+	expiry := time.Second * s3LinkExpiration * 60 * 60 // 1 day.
+	presignedURL, err := client.PresignedPutObject(context.Background(), s.Bucket, key, expiry)
+	if err != nil {
+		return "", fmt.Errorf("generating presign URL error: %v", err)
+	}
+
+	return presignedURL.String(), nil
+}

apps/drivers/types.go

@@ -19,4 +19,7 @@ type DriverInterface interface {
 
 	// Delete deletes one object
 	Delete(key string) error
+
+	// GetDownloadLink returns URL of object with given key. That URL can be used to download the object.
+	GetDownloadLink(key string) (string, error)
 }

apps/snapshots.go

@@ -331,6 +331,16 @@ func (s *SnapshotProcessor) GetSnapshot(key string) (Snapshot, error) {
 	return snapshot, nil
 }
 
+// GetDownloadLink returns an URL for given snapshot
+func (s *SnapshotProcessor) GetDownloadLink(key string) (string, error) {
+	link, err := s.GetDownloadLink(key)
+	if err != nil {
+		return link, err
+	}
+
+	return link, nil
+}
+
 // DeleteSnapshot delete's one snapshot
 func (s *SnapshotProcessor) DeleteSnapshot(key string) error {
 	err := s.Driver.Delete(key)

handlers_nats.go

@@ -64,6 +64,7 @@ func _messageHandler(m *nats.Msg) error {
 		"list_apps_snapshots":        listAppsSnapshotsEventHandler,
 		"list_snapshots_by_label":    listSnapshotsByLabelEventHandler,
 		"get_snapshot":               getSnapshotEventHandler,
+		"get_snapshot_download_link": getSnapshotDownloadLinkEventHandler,
 		"delete_snapshot":            deleteSnapshotEventHandler,
 		"delete_app_snapshots":       deleteAppSnapshotsEventHandler,
 	}
@@ -1000,6 +1001,26 @@ func getSnapshotEventHandler(m *nats.Msg, message *RequestMessage) error {
 	return nil
 }
 
+/*
+getSnapshotDownloadLinkEventHandler return URL that can be used to download snapshot
+
+Payload: string with a snapshot name (key)
+Response: string with the URL
+*/
+func getSnapshotDownloadLinkEventHandler(m *nats.Msg, message *RequestMessage) error {
+	link, err := snapshotProcessor.GetDownloadLink(message.Payload)
+	if err != nil {
+		return errorReplyFormater(m, "backend error", err)
+	}
+
+	err = m.Respond([]byte(link))
+	if err != nil {
+		log.Println("ERROR: get snapshot:", err.Error())
+	}
+
+	return nil
+}
+
 /*
 deleteSnapshotEventHandler delete a single snapshot. This is not bound to application name.