--- /dev/null
+.. -*- coding: utf-8-with-signature -*-
+
+================================
+Tahoe-LAFS Magic Folder Frontend
+================================
+
+1. `Introduction`_
+2. `Configuration`_
+3. `Known Issues and Limitations`_
+
+
+Introduction
+============
+
+The Magic Folder frontend synchronizes local directories on two or more
+clients, using a Tahoe-LAFS grid for storage. Whenever a file is created
+or changed under the local directory of one of the clients, the change is
+propagated to the grid and then to the other clients.
+
+The implementation of the "drop-upload" frontend, on which Magic Folder is
+based, was written as a prototype at the First International Tahoe-LAFS
+Summit in June 2011. In 2015, with the support of a grant from the
+`Open Technology Fund`_, it was redesigned and extended to support
+synchronization between clients. It currently works on Linux and Windows.
+
+Magic Folder is not currently in as mature a state as the other frontends
+(web, CLI, SFTP and FTP). This means that you probably should not rely on
+all changes to files in the local directory to result in successful uploads.
+There might be (and have been) incompatible changes to how the feature is
+configured.
+
+We are very interested in feedback on how well this feature works for you, and
+suggestions to improve its usability, functionality, and reliability.
+
+.. _`Open Technology Fund`: https://www.opentech.fund/
+
+
+Configuration
+=============
+
+The Magic Folder frontend runs as part of a gateway node. To set it up, you
+must use the tahoe magic-folder CLI. For detailed information see our
+`Magic-Folder CLI design documentation`_. For a given Magic-Folder collective
+directory you need to run the ``tahoe magic-folder create`` command. After
+that the ``tahoe magic-folder invite`` command must used to generate an
+*invite code* for each member of the magic-folder collective. A confidential,
+authenticated communications channel should be used to transmit the invite code
+to each member, who will be joining using the ``tahoe magic-folder join``
+command.
+
+These settings are persisted in the ``[magic_folder]`` section of the
+gateway's ``tahoe.cfg`` file.
+
+``[magic_folder]``
+
+``enabled = (boolean, optional)``
+
+ If this is ``True``, Magic Folder will be enabled. The default value is
+ ``False``.
+
+``local.directory = (UTF-8 path)``
+
+ This specifies the local directory to be monitored for new or changed
+ files. If the path contains non-ASCII characters, it should be encoded
+ in UTF-8 regardless of the system's filesystem encoding. Relative paths
+ will be interpreted starting from the node's base directory.
+
+You should not normally need to set these fields manually because they are
+set by the ``tahoe magic-folder create`` and/or ``tahoe magic-folder join``
+commands. Use the ``--help`` option to these commands for more information.
+
+After setting up a Magic Folder collective and starting or restarting each
+gateway, you can confirm that the feature is working by copying a file into
+any local directory, and checking that it appears on other clients.
+Large files may take some time to appear.
+
+The 'Operational Statistics' page linked from the Welcome page shows
+counts of the number of files uploaded, the number of change events currently
+queued, and the number of failed uploads. The 'Recent Uploads and Downloads'
+page and the node log_ may be helpful to determine the cause of any failures.
+
+.. _log: ../logging.rst
+
+
+Known Issues and Limitations
+============================
+
+This feature only works on Linux and Windows. There is a ticket to add
+support for Mac OS X and BSD-based systems (`#1432`_).
+
+The only way to determine whether uploads have failed is to look at the
+'Operational Statistics' page linked from the Welcome page. This only shows
+a count of failures, not the names of files. Uploads are never retried.
+
+The Magic Folder frontend performs its uploads sequentially (i.e. it waits
+until each upload is finished before starting the next), even when there
+would be enough memory and bandwidth to efficiently perform them in parallel.
+A Magic Folder upload can occur in parallel with an upload by a different
+frontend, though. (`#1459`_)
+
+On Linux, if there are a large number of near-simultaneous file creation or
+change events (greater than the number specified in the file
+``/proc/sys/fs/inotify/max_queued_events``), it is possible that some events
+could be missed. This is fairly unlikely under normal circumstances, because
+the default value of ``max_queued_events`` in most Linux distributions is
+16384, and events are removed from this queue immediately without waiting for
+the corresponding upload to complete. (`#1430`_)
+
+The Windows implementation might also occasionally miss file creation or
+change events, due to limitations of the underlying Windows API
+(ReadDirectoryChangesW). We do not know how likely or unlikely this is.
+(`#1431`_)
+
+Some filesystems may not support the necessary change notifications.
+So, it is recommended for the local directory to be on a directly attached
+disk-based filesystem, not a network filesystem or one provided by a virtual
+machine.
+
+The ``private/magic_folder_dircap`` and ``private/collective_dircap`` files
+cannot use an alias or path to specify the upload directory. (`#1711`_)
+
+If a file in the upload directory is changed (actually relinked to a new
+file), then the old file is still present on the grid, and any other caps
+to it will remain valid. Eventually it will be possible to use
+`garbage collection`_ to reclaim the space used by these files; however
+currently they are retained indefinitely. (`#2440`_)
+
+Unicode filenames are supported on both Linux and Windows, but on Linux, the
+local name of a file must be encoded correctly in order for it to be uploaded.
+The expected encoding is that printed by
+``python -c "import sys; print sys.getfilesystemencoding()"``.
+
+On Windows, local directories with non-ASCII names are not currently working.
+(`#2219`_)
+
+On Windows, when a node has Magic Folder enabled, it is unresponsive to Ctrl-C
+(it can only be killed using Task Manager or similar). (`#2218`_)
+
+.. _`#1430`: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1430
+.. _`#1431`: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1431
+.. _`#1432`: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1432
+.. _`#1459`: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1459
+.. _`#1711`: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1711
+.. _`#2218`: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2218
+.. _`#2219`: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2219
+.. _`#2440`: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2440
+
+.. _`garbage collection`: ../garbage-collection.rst
+.. _`Magic-Folder CLI design documentation`: ../proposed/magic-folder/user-interface-design.rst
projects / tahoe-lafs / tahoe-lafs.git / blobdiff