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= Server-side file deletion =

Files are deleted from the data server's upload and download directories by two
programs:
 * The '''file_deleter''' daemon, which deletes input and output files
   as jobs are completed.
 * The '''antique file deleter''', which deletes files that have
   "fallen through the cracks".

== The File Deleter

Typically you don't need to customize this.
The default file deletion policy is:

 * A workunit's input files are deleted when all results are 'over'
   (reported or timed out) and the workunit is assimilated.
 * A result's output files are deleted after the workunit is assimilated.
   The canonical result is handled differently,
   since its output files may be needed to validate results
   that are reported after assimilation;
   hence its files are deleted only when all results are over,
   and all successful results have been validated.

Command-line options:

 -d N:: set debug output level (1/2/3/4)
 --mod M R:: handle only WUs with ID mod M == R
 --one_pass:: exit after one pass through DB
 --dry_run:: don't update DB (for debugging only)
 --download_dir D:: override download_dir from project config with D
 --sleep_interval N:: sleep for N seconds between scans (default 5)
 --appid N:: only process workunits with appid=N
 --app S:: only process workunits of app with name S
 --dont_retry_errors:: don't retry file deletions that failed previously
 --preserve_wu_files:: 	update the DB, but don't delete input files
 --preserve_result_files:: update the DB, but don't delete output files
 --dont_delete_batches:: don't delete anything with positive batch number
 --input_files_only:: don't delete output files
  If you store input and output files on different servers,
  you can improve performance by running separate file deleters,
  each one on the machine where the corresponding files are stored.
 --output_files_only:: don't delete input files
 --xml_doc_like L:: only process workunits where xml_doc LIKE 'L'

In some cases you may not want files to be deleted. There are three ways to accomplish this:

 * Use the --preserve_wu_files and/or the --preserve_result_files command-line options.
 * Include <no_delete/> in the [BoincFiles <file_info>]
 element for a file in a [WorkGeneration workunit or result template]. This lets you suppress deletion on a file-by-file basis.
 * Include nodelete in the workunit name. 

== The Antique File Deleter ==

Runs as a periodic task.
Removes 'antiques': output files that are older
than the oldest WU in the database.
These files are created when BOINC clients
return after the corresponding WU has been deleted from the database.

The antique files are deleted by using a Unix 'find' command to locate files
that are older than the oldest workunit.
The find command will work on NFS mounted file systems,
and will ignore .nfs stale file markers.
The output of find is limited by a 'head' to 50000 files by default.

If the web-server account on your system is not 'apache',
add a {{{<httpd_user>}}} element to your [ProjectOptions#file-deletion config.xml] file.
Otherwise antique deletion won't work.

Command-line options:

 -d N:: set debug output level (1/2/3/4)
 --dry_run:: don't delete any files, just log what would be deleted
 --usleep N:: sleep this number of usecs after each examined file (Throttles I/O if there are many files.)