Method getRemoteFile

mediaapi/routing/download.go:514–567

getRemoteFile fetches the remote file and caches it locally A hash map of active remote requests to a struct containing a sync.Cond is used to only download remote files once, regardless of how many download requests are received. Note: The named errorResponse return variable is used in a deferred b

(
	ctx context.Context,
	client *gomatrixserverlib.Client,
	cfg *config.MediaAPI,
	db storage.Database,
	activeRemoteRequests *types.ActiveRemoteRequests,
	activeThumbnailGeneration *types.ActiveThumbnailGeneration,
)

// regardless of how many download requests are received.
// Note: The named errorResponse return variable is used in a deferred broadcast of the metadata and error response to waiting goroutines.
func (r *downloadRequest) getRemoteFile(
	ctx context.Context,
	client *gomatrixserverlib.Client,
	cfg *config.MediaAPI,
	db storage.Database,
	activeRemoteRequests *types.ActiveRemoteRequests,
	activeThumbnailGeneration *types.ActiveThumbnailGeneration,
) (errorResponse error) {
	// Note: getMediaMetadataFromActiveRequest uses mutexes and conditions from activeRemoteRequests
	mediaMetadata, resErr := r.getMediaMetadataFromActiveRequest(activeRemoteRequests)
	if resErr != nil {
		return resErr
	} else if mediaMetadata != nil {
		// If we got metadata from an active request, we can respond from the local file
		r.MediaMetadata = mediaMetadata
	} else {
		// Note: This is an active request that MUST broadcastMediaMetadata to wake up waiting goroutines!
		// Note: broadcastMediaMetadata uses mutexes and conditions from activeRemoteRequests
		defer func() {
			// Note: errorResponse is the named return variable so we wrap this in a closure to re-evaluate the arguments at defer-time
			if err := recover(); err != nil {
				r.broadcastMediaMetadata(activeRemoteRequests, errors.New("paniced"))
				panic(err)
			}
			r.broadcastMediaMetadata(activeRemoteRequests, errorResponse)
		}()

		// check if we have a record of the media in our database
		mediaMetadata, err := db.GetMediaMetadata(
			ctx, r.MediaMetadata.MediaID, r.MediaMetadata.Origin,
		)
		if err != nil {
			return fmt.Errorf("db.GetMediaMetadata: %w", err)
		}

		if mediaMetadata == nil {
			// If we do not have a record, we need to fetch the remote file first and then respond from the local file
			err := r.fetchRemoteFileAndStoreMetadata(
				ctx, client,
				cfg.AbsBasePath, cfg.MaxFileSizeBytes, db,
				cfg.ThumbnailSizes, activeThumbnailGeneration,
				cfg.MaxThumbnailGenerators,
			)
			if err != nil {
				r.Logger.WithError(err).Errorf("r.fetchRemoteFileAndStoreMetadata: failed to fetch remote file")
				return err
			}
		} else {
			// If we have a record, we can respond from the local file
			r.MediaMetadata = mediaMetadata
		}
	}
	return nil
}

func (r *downloadRequest) getMediaMetadataFromActiveRequest(activeRemoteRequests *types.ActiveRemoteRequests) (*types.MediaMetadata, error) {
	// Check if there is an active remote request for the file