touchDirectory: Touch a versioned directory

In LTLA/dir.expiry: Managing Expiration for Cache Directories

Touch a versioned directory

Description

Touch a versioned directory to indicate that it has been successfully accessed in the recent past.

Usage

touchDirectory(path, date = Sys.Date(), force = FALSE)

Arguments

path	String containing the path to a versioned directory. The dirname should be the package cache while the basename should be a version number.
date	A Date object containing the current date. Only provided for testing.
force	Logical scalar indicating whether to forcibly update the access date for path.

Details

This function should be called after any successful access to the contents of a versioned directory, to indicate that said directory is still in use by expiry-aware processes. A stub file is updated with the last access time to allow clearDirectories to accurately check for staleness.

For a given path and version, this function only modifies the files on its first call. All subsequent calls with the same two arguments, in the same R session and on the same day will have no effect. This avoids unnecessary touching of the file system during routine use.

The caller should lock the target directory with lockDirectory before calling this function. This ensures that another process calling clearDirectories does not delete this directory while its access time is being updated. If the target directory is locked, any writes to the stub file itself are thread-safe, even for shared locks.

By default, this function will remember the values of path that were passed in previous calls, and will avoid re-updating those same paths with the same date when called on the same day. This avoids unnecessary file system writes and locks when this function is repeatedly called. Advanced users can force an update by setting force=TRUE.

Value

The <version>_dir.expiry stub file within path is updated/created with the current date. A NULL is invisibly returned.

Author(s)

Aaron Lun

See Also

lockDirectory, which should always be called before this function.

Examples

# Creating the package cache.
cache.dir <- tempfile(pattern="expired_demo")
dir.create(cache.dir)

# Creating the versioned subdirectory.
version <- package_version("1.11.0")
version.dir <- file.path(cache.dir, version)
lck <- lockDirectory(version.dir)
dir.create(version.dir)

# Setting the last access time.
touchDirectory(version.dir)
list.files(cache.dir)
readLines(file.path(cache.dir, "1.11.0_dir.expiry"))

# Making sure we unlock it afterwards.
unlockDirectory(lck)

LTLA/dir.expiry documentation built on Sept. 14, 2022, 4:12 p.m.