git-annex/doc/design/assistant/progressbars.mdwn

Currently, git-annex takes a very lazy approch to displaying
progress into. It just lets rsync or whatever display the progress
for it, in the terminal.

Something better is needed for the [[webapp]]. There needs to be a
way for the web app to know what the current progress is of all transfers.

This is one of those potentially hidden but time consuming problems.

## downloads

* Watch temp file as it's coming in and use its size.
  Can either poll every .5 seconds or so to check file size, or
  could use inotify. **done**
* When easily available, remotes call the MeterUpdate callback as downloads
  progress. **done**
* S3: TODO  
  While it has a download progress bar, `getObject` probably buffers the whole
  download in memory before returning. Leaving the progress bar to only
  display progress for writing the file out of memory. Fixing this would
  involve making hS3 stream better (also avoids it wasting memory).

## uploads

Each individual remote type needs to implement its own support for calling
the MeterUpdate callback as the upload progresses.

* git: **done**
* rsync: **done**
* directory: **done**
* web: Not applicable; does not upload 
* webdav: **done**
* S3: **done**
* glacier: **done**
* bup: **done**
* hook: Would require the hook interface to somehow do this, which seems
  too complicated. So skipping.

## communication

It may be worth using a better communication channel than files on disk for
the transfer progress. Shared memory could be used, or http posts to the
webapp.