From: david-sarah Date: Mon, 8 Aug 2011 18:21:46 +0000 (-0700) Subject: Documentation for drop-upload frontend. refs #1429 X-Git-Url: https://git.rkrishnan.org/%5B/%5D%20/reliability?a=commitdiff_plain;h=667b086b59ee37d38579f5cea8ec6f61122390ae;p=tahoe-lafs%2Ftahoe-lafs.git Documentation for drop-upload frontend. refs #1429 --- diff --git a/docs/configuration.rst b/docs/configuration.rst index 4f414f66..634d063f 100644 --- a/docs/configuration.rst +++ b/docs/configuration.rst @@ -359,6 +359,12 @@ FTP, SFTP for instructions on configuring these services, and the ``[ftpd]`` and ``[sftpd]`` sections of ``tahoe.cfg``. +Drop-Upload + + As of Tahoe-LAFS v1.9.0, a node running on Linux can be configured to + automatically upload files that are created or changed in a specified + local directory. See ``_ for details. + Storage Server Configuration diff --git a/docs/frontends/drop-upload.rst b/docs/frontends/drop-upload.rst new file mode 100644 index 00000000..ed2d4167 --- /dev/null +++ b/docs/frontends/drop-upload.rst @@ -0,0 +1,141 @@ +=============================== +Tahoe-LAFS Drop-Upload Frontend +=============================== + +1. `Introduction`_ +2. `Configuration`_ +3. `Known Issues and Limitations`_ + + +Introduction +============ + +The drop-upload frontend allows an upload to a Tahoe-LAFS grid to be triggered +automatically whenever a file is created or changed in a specific local +directory. This is a preview of a feature that we expect to support across +several platforms, but it currently works only on Linux. + +The implementation was written as a prototype at the First International +Tahoe-LAFS Summit in June 2011, and is not currently in as mature a state as +the other frontends (web, CLI, FTP and SFTP). This means that you probably +should not keep important data in the upload directory, and should not rely +on all changes to files in the local directory to result in successful uploads. +There might be incompatible changes to how the feature is configured in +future versions. There is even the possibility that it may be abandoned, for +example if unsolveable reliability issues are found. + +We are very interested in feedback on how well this feature works for you, and +suggestions to improve its usability, functionality, and reliability. + + +Configuration +============= + +The drop-upload frontend runs as part of a gateway node. To set it up, you +need to choose the local directory to monitor for file changes, and a mutable +directory on the grid to which files will be uploaded. + +These settings are configured in the ``[drop_upload]`` section of the +gateway's ``tahoe.cfg`` file. + +``[drop_upload]`` + +``enabled = (boolean, optional)`` + + If this is ``True``, drop-upload will be enabled (provided that the + ``upload.uri`` and ``local.directory`` fields are also set). The default + value is ``False``. + +``upload.uri = (URI)`` + + This is the Tahoe URI of an existing mutable directory to be used as + the target of uploads. It must be the full URI of the directory + (starting with ``URI:DIR2:``), and cannot include an alias or path. + +``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. + +After setting the above fields and starting or restarting the gateway, +you can confirm that the feature is working by copying a file into the +local directory. Then, use the WUI or CLI to check that it has appeared +in the upload directory with the same filename. A large file may take some +time to appear, since it is only linked into the directory after the upload +has completed. + +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 frontend only works on Linux. There is an even-more-experimental +implementation for Windows (`#1431`_), and a ticket to add support for +Mac OS X and BSD-based systems (`#1432`_). + +Subdirectories of the local directory are not monitored. If a subdirectory +is created, it will be ignored. (`#1433`_) + +If files are created or changed in the local directory just after the gateway +has started, it might not have connected to a sufficient number of servers +when the upload is attempted, causing the upload to fail. (`#1449`_) + +Files that were created or changed in the local directory while the gateway +was not running, will not be uploaded. (`#1458`_) + +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 drop-upload 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 drop-upload can occur in parallel with an upload by a different frontend, +though. (`#1459`_) + +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`_) + +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. + +Attempts to read the mutable directory at about the same time as an uploaded +file is being linked into it, might fail, even if they are done through the +same gateway. (`#1105`_) + +Files are always uploaded as immutable. If there is an existing mutable file +of the same name in the upload directory, it will be unlinked and replaced +with an immutable file. + +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. See `docs/garbage-collection.rst +<../garbage-collection.rst>`_ for how to reclaim the space used by files +that are no longer needed. + +Unicode names are supported, but 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()"``. + +.. _`#1105`: http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1105 +.. _`#1430`: http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1430 +.. _`#1431`: http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1431 +.. _`#1432`: http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1432 +.. _`#1449`: http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1449 +.. _`#1458`: http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1458 +.. _`#1459`: http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1459