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- ;;; GNU Guix --- Functional package management for GNU
- ;;; Copyright © 2013-2017, 2020-2021, 2023 Ludovic Courtès <ludo@gnu.org>
- ;;; Copyright © 2022 Simon Tournier <zimon.toutoune@gmail.com>
- ;;;
- ;;; This file is part of GNU Guix.
- ;;;
- ;;; GNU Guix is free software; you can redistribute it and/or modify it
- ;;; under the terms of the GNU General Public License as published by
- ;;; the Free Software Foundation; either version 3 of the License, or (at
- ;;; your option) any later version.
- ;;;
- ;;; GNU Guix is distributed in the hope that it will be useful, but
- ;;; WITHOUT ANY WARRANTY; without even the implied warranty of
- ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- ;;; GNU General Public License for more details.
- ;;;
- ;;; You should have received a copy of the GNU General Public License
- ;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
- (define-module (guix cache)
- #:use-module ((guix utils) #:select (with-atomic-file-output))
- #:use-module (srfi srfi-19)
- #:use-module (srfi srfi-26)
- #:use-module (ice-9 match)
- #:use-module ((ice-9 textual-ports) #:select (get-string-all))
- #:export (obsolete?
- delete-file*
- file-expiration-time
- remove-expired-cache-entries
- maybe-remove-expired-cache-entries))
- ;;; Commentary:
- ;;;
- ;;; This module provides tools to manage a simple on-disk cache consisting of
- ;;; individual files.
- ;;;
- ;;; Code:
- (define (obsolete? date now ttl)
- "Return #t if DATE is obsolete compared to NOW + TTL seconds."
- (time>? (subtract-duration now (make-time time-duration 0 ttl))
- (make-time time-monotonic 0 date)))
- (define (delete-file* file)
- "Like 'delete-file', but does not raise an error when FILE does not exist."
- (catch 'system-error
- (lambda ()
- (delete-file file))
- (lambda args
- (unless (= ENOENT (system-error-errno args))
- (apply throw args)))))
- (define* (file-expiration-time ttl #:optional (timestamp stat:atime))
- "Return a procedure that, when passed a file, returns its \"expiration
- time\" computed as its timestamp + TTL seconds. Call TIMESTAMP to obtain the
- relevant timestamp from the result of 'stat'."
- (lambda (file)
- (match (false-if-exception (lstat file))
- (#f 0) ;FILE may have been deleted in the meantime
- (st (+ (timestamp st) ttl)))))
- (define* (remove-expired-cache-entries entries
- #:key
- (now (current-time time-monotonic))
- (entry-expiration
- (file-expiration-time 3600))
- (delete-entry delete-file*))
- "Given ENTRIES, a list of file names, remove those whose expiration time,
- as returned by ENTRY-EXPIRATION, has passed. Use DELETE-ENTRY to delete
- them."
- (for-each (lambda (entry)
- (when (<= (entry-expiration entry) (time-second now))
- (delete-entry entry)))
- entries))
- (define* (maybe-remove-expired-cache-entries cache
- cache-entries
- #:key
- (entry-expiration
- (file-expiration-time 3600))
- (delete-entry delete-file*)
- (cleanup-period (* 24 3600)))
- "Remove expired narinfo entries from the cache if deemed necessary. Call
- CACHE-ENTRIES with CACHE to retrieve the list of cache entries.
- ENTRY-EXPIRATION must be a procedure that, when passed an entry, returns the
- expiration time of that entry in seconds since the Epoch. DELETE-ENTRY is a
- procedure that removes the entry passed as an argument. Finally,
- CLEANUP-PERIOD denotes the minimum time between two cache cleanups."
- (define now
- (current-time time-monotonic))
- (define expiry-file
- (string-append cache "/last-expiry-cleanup"))
- (define last-expiry-date
- (catch 'system-error
- (lambda ()
- (or (string->number
- (call-with-input-file expiry-file get-string-all))
- 0))
- (const 0)))
- (when (obsolete? last-expiry-date now cleanup-period)
- (remove-expired-cache-entries (cache-entries cache)
- #:now now
- #:entry-expiration entry-expiration
- #:delete-entry delete-entry)
- (catch 'system-error
- (lambda ()
- (with-atomic-file-output expiry-file
- (cute write (time-second now) <>)))
- (lambda args
- ;; ENOENT means CACHE does not exist.
- (unless (= ENOENT (system-error-errno args))
- (apply throw args))))))
- ;;; cache.scm ends here
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