vfs_preopen - Hide read latencies for applications reading numbered files

       The original Samba software and related utilities were created by Andrew Tridgell. Samba is now developed
       by the Samba Team as an Open Source project similar to the way the Linux kernel is developed.

       The PREOPEN VFS module was created with contributions from Volker Lendecke and the developers at IBM.

Samba 4.22.3-Ubuntu-4.22.3+dfs                     07/21/2025                                     VFS_PREOPEN(8)

       This VFS module is part of the samba(7) suite.

       This module assists applications that want to read numbered files in sequence with very strict latency
       requirements. One area where this happens in video streaming applications that want to read one file per
       frame.

       When you use this module, a number of helper processes is started that speculatively open files and read
       a number of bytes to prime the file system cache, so that later on when the real application's request
       comes along, no disk access is necessary.

       This module is stackable.

       vfs_preopen - Hide read latencies for applications reading numbered files

       preopen:posix-basic-regex = BOOL (default: no)
           preopen:posix-basic-regex = yes changes the meaning of the preopen:names option. Further details are
           described there.

       preopen:names = /pattern1/pattern2/
           preopen:names specifies the file name pattern(s) which should trigger the preopen helpers to do their
           work. We assume that the files are numbered incrementally. So if your file names are numbered
           FRAME00000.frm FRAME00001.frm and so on you would list them as preopen:names=/FRAME*.frm/. The
           default algorithm uses the first (at least 3) digits it finds in order to calculate the name of the
           next frames.

           preopen:posix-basic-regex = yes changes the meaning of the preopen:names option. It means 'POSIX
           Basic Regular Expression' strings are used as patterns. The key is each pattern requires exactly one
           'subexpression' starting with '\(' and ending with '\)' in order to specify the position of the
           digits representing the incrementing frame numbers. Given a file names like Movie7599Frame0v1234.txt,
           Movie7599Frame1v1234.txt, Movie7599Frame2v1234.txt up to Movie7599Frame9v1234.txt you can use
           preopen:names = /.*Frame\([0-9]\).*\.txt/ in order to match just a single digits, this might not be a
           real world example, but it shows the flexibility that is possible here.

       preopen:num_bytes = BYTES
           Specifies the number of bytes the helpers should speculatively read, defaults to 1.

       preopen:helpers = NUM-PROCS
           Number of forked helper processes, defaults to 1.

       preopen:queuelen = NUM-FILES
           Number of files that should be speculatively opened. Defaults to the 10 subsequent files.

       preopen:nomatch_log_level = LOGLEVEL
           In order to debug or audit the usage of the preopen logic you can use this option to specify at what
           log level details about filenames not matching any pattern from 'preopen:names' are logged.

           Defaults to the log level 5. See also smb.conf(5) in the 'loglevel' section for special handling of
           the 'preopen' debug class.

       preopen:match_log_level = LOGLEVEL
           In order to debug or audit the usage of the preopen logic you can use this option to specify at what
           log level details about filenames actually matching a pattern from 'preopen:names' are logged.

           See also 'preopen:founddigits_log_level' and 'preopen:push_log_level'.

           Defaults to the log level 5. See also smb.conf(5) in the 'loglevel' section for special handling of
           the 'preopen' debug class.

       preopen:nodigits_log_level = LOGLEVEL
           In order to debug or audit problems with the preopen configuration you can use this option to specify
           at what log level details about filenames actually matching a pattern from 'preopen:names', but at
           the same time don't contain the expected digits, are logged. This is typically something the
           administrator wants to notice and adjust the configuration in order to define more precisely where to
           find the digits in the filename.

           Defaults to the log level 1. See also smb.conf(5) in the 'loglevel' section for special handling of
           the 'preopen' debug class.

       preopen:founddigits_log_level = LOGLEVEL
           In order to debug or audit the usage of the preopen logic you can use this option to specify at what
           log level details about filenames actually matching a pattern from 'preopen:names', and at the same
           time having valid expected digits, are logged. This means enough information is available in order to
           queue preopens.

           Defaults to the log level 3. See also smb.conf(5) in the 'loglevel' section for special handling of
           the 'preopen' debug class.

       preopen:reset_log_level = LOGLEVEL
           If a matching filename belongs to a different pattern from 'preopen:names', a different parent
           directory or differs in a significant way from the last filename that was found before, the module
           needs to reset it's internal queue state. This means that no more preopens will be pushed to helper
           processes belonging to the former queue state. In order to debug or audit such queue resets you can
           use this option to specify at what log level details are logged.

           Defaults to the log level 5. See also smb.conf(5) in the 'loglevel' section for special handling of
           the 'preopen' debug class.

       preopen:push_log_level = LOGLEVEL
           In order to debug or audit the usage of the preopen logic you can use this option to specify at what
           log level details about filenames actually pushed to preopen helper processes are logged. This means
           they will actually be preopened soon.

           Defaults to the log level 3. See also smb.conf(5) in the 'loglevel' section for special handling of
           the 'preopen' debug class.

       preopen:queue_log_level = LOGLEVEL
           In order to debug details about internal queue processing you can use this option to specify at what
           log level the details are logged.

           Defaults to the log level 10. See also smb.conf(5) in the 'loglevel' section for special handling of
           the 'preopen' debug class.

       vfs objects = preopen

       This man page is part of version 4.22.3-Ubuntu-4.22.3+dfsg-4ubuntu1 of the Samba suite.