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Add (guix store deduplication).

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* guix/store/database.scm (register-path): Add #:deduplicate? and call
'deduplicate' when it's true.
(counting-wrapper-port, nar-sha256): Move to...
* guix/store/deduplication.scm: ... here.  New file.
* tests/store-deduplication.scm: New file.
* Makefile.am (STORE_MODULES): Add deduplication.scm.
(SCM_TESTS) [HAVE_GUILE_SQLITE3]: Add store-deduplication.scm.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>
This commit is contained in:
Caleb Ristvedt 2018-05-27 23:20:54 +02:00 committed by Ludovic Courtès
parent 285cc75c31
commit bf5bf5778c
No known key found for this signature in database
GPG key ID: 090B11993D9AEBB5
4 changed files with 222 additions and 39 deletions
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6
Makefile.am
View file

@ -259,7 +259,8 @@ endif BUILD_DAEMON_OFFLOAD
# Scheme implementation of the build daemon and related functionality.
STORE_MODULES = \
guix/store/database.scm
guix/store/database.scm \
guix/store/deduplication.scm
if HAVE_GUILE_SQLITE3
MODULES += $(STORE_MODULES)
@ -392,7 +393,8 @@ endif
if HAVE_GUILE_SQLITE3
SCM_TESTS += \
tests/store-database.scm
tests/store-database.scm \
tests/store-deduplication.scm
endif

43
guix/store/database.scm
View file

@ -21,10 +21,9 @@ (define-module (guix store database)
#:use-module (sqlite3)
#:use-module (guix config)
#:use-module (guix serialization)
#:use-module (guix store deduplication)
#:use-module (guix base16)
#:use-module (guix hash)
#:use-module (guix build syscalls)
#:use-module (rnrs io ports)
#:use-module (srfi srfi-11)
#:use-module (srfi srfi-19)
#:use-module (ice-9 match)
@ -140,39 +139,6 @@ (define* (sqlite-register #:key db-file path (references '())
;;; High-level interface.
;;;
;; XXX: Would it be better to just make WRITE-FILE give size as well? I question
;; the general utility of this approach.
(define (counting-wrapper-port output-port)
"Some custom ports don't implement GET-POSITION at all. But if we want to
figure out how many bytes are being written, we will want to use that. So this
makes a wrapper around a port which implements GET-POSITION."
(let ((byte-count 0))
(make-custom-binary-output-port "counting-wrapper"
(lambda (bytes offset count)
(set! byte-count
(+ byte-count count))
(put-bytevector output-port bytes
offset count)
count)
(lambda ()
byte-count)
#f
(lambda ()
(close-port output-port)))))
(define (nar-sha256 file)
"Gives the sha256 hash of a file and the size of the file in nar form."
(let-values (((port get-hash) (open-sha256-port)))
(let ((wrapper (counting-wrapper-port port)))
(write-file file wrapper)
(force-output wrapper)
(force-output port)
(let ((hash (get-hash))
(size (port-position wrapper)))
(close-port wrapper)
(values hash size)))))
;; TODO: Factorize with that in (gnu build install).
(define (reset-timestamps file)
"Reset the modification time on FILE and on all the files it contains, if
@ -211,7 +177,7 @@ (define (reset-timestamps file)
(define* (register-path path
#:key (references '()) deriver prefix
state-directory)
state-directory (deduplicate? #t))
;; Priority for options: first what is given, then environment variables,
;; then defaults. %state-directory, %store-directory, and
;; %store-database-directory already handle the "environment variables /
@ -262,4 +228,7 @@ (define* (register-path path
#:deriver deriver
#:hash (string-append "sha256:"
(bytevector->base16-string hash))
#:nar-size nar-size))))
#:nar-size nar-size)
(when deduplicate?
(deduplicate real-path hash #:store store-dir)))))

148
guix/store/deduplication.scm Normal file
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@ -0,0 +1,148 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2017 Caleb Ristvedt <caleb.ristvedt@cune.org>
;;; Copyright © 2018 Ludovic Courtès <ludo@gnu.org>
;;;
;;; 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/>.
;;; This houses stuff we do to files when they arrive at the store - resetting
;;; timestamps, deduplicating, etc.
(define-module (guix store deduplication)
#:use-module (guix hash)
#:use-module (guix build utils)
#:use-module (guix base16)
#:use-module (srfi srfi-11)
#:use-module (rnrs io ports)
#:use-module (ice-9 ftw)
#:use-module (guix serialization)
#:export (nar-sha256
deduplicate))
;; Would it be better to just make WRITE-FILE give size as well? I question
;; the general utility of this approach.
(define (counting-wrapper-port output-port)
"Some custom ports don't implement GET-POSITION at all. But if we want to
figure out how many bytes are being written, we will want to use that. So this
makes a wrapper around a port which implements GET-POSITION."
(let ((byte-count 0))
(make-custom-binary-output-port "counting-wrapper"
(lambda (bytes offset count)
(set! byte-count
(+ byte-count count))
(put-bytevector output-port bytes
offset count)
count)
(lambda ()
byte-count)
#f
(lambda ()
(close-port output-port)))))
(define (nar-sha256 file)
"Gives the sha256 hash of a file and the size of the file in nar form."
(let-values (((port get-hash) (open-sha256-port)))
(let ((wrapper (counting-wrapper-port port)))
(write-file file wrapper)
(force-output wrapper)
(force-output port)
(let ((hash (get-hash))
(size (port-position wrapper)))
(close-port wrapper)
(values hash size)))))
(define (tempname-in directory)
"Gives an unused temporary name under DIRECTORY. Not guaranteed to still be
unused by the time you create anything with that name, but a good shot."
(let ((const-part (string-append directory "/.tmp-link-"
(number->string (getpid)))))
(let try ((guess-part
(number->string (random most-positive-fixnum) 16)))
(if (file-exists? (string-append const-part "-" guess-part))
(try (number->string (random most-positive-fixnum) 16))
(string-append const-part "-" guess-part)))))
(define* (get-temp-link target #:optional (link-prefix (dirname target)))
"Like mkstemp!, but instead of creating a new file and giving you the name,
it creates a new hardlink to TARGET and gives you the name. Since
cross-filesystem hardlinks don't work, the temp link must be created on the
same filesystem - where in that filesystem it is can be controlled by
LINK-PREFIX."
(let try ((tempname (tempname-in link-prefix)))
(catch 'system-error
(lambda ()
(link target tempname)
tempname)
(lambda (args)
(if (= (system-error-errno args) EEXIST)
(try (tempname-in link-prefix))
(throw 'system-error args))))))
;; There are 3 main kinds of errors we can get from hardlinking: "Too many
;; things link to this" (EMLINK), "this link already exists" (EEXIST), and
;; "can't fit more stuff in this directory" (ENOSPC).
(define (replace-with-link target to-replace)
"Atomically replace the file TO-REPLACE with a link to TARGET. Note: TARGET
and TO-REPLACE must be on the same file system."
(let ((temp-link (get-temp-link target (dirname to-replace))))
(rename-file temp-link to-replace)))
(define-syntax-rule (false-if-system-error (errors ...) exp ...)
"Given ERRORS, a list of system error codes to ignore, evaluates EXP... and
return #f if any of the system error codes in the given list are thrown."
(catch 'system-error
(lambda ()
exp ...)
(lambda args
(if (member (system-error-errno args) (list errors ...))
#f
(apply throw args)))))
(define* (deduplicate path hash #:key (store %store-directory))
"Check if a store item with sha256 hash HASH already exists. If so,
replace PATH with a hardlink to the already-existing one. If not, register
PATH so that future duplicates can hardlink to it. PATH is assumed to be
under STORE."
(let* ((links-directory (string-append store "/.links"))
(link-file (string-append links-directory "/"
(bytevector->base16-string hash))))
(mkdir-p links-directory)
(if (file-is-directory? path)
;; Can't hardlink directories, so hardlink their atoms.
(for-each (lambda (file)
(unless (member file '("." ".."))
(deduplicate file (nar-sha256 file)
#:store store)))
(scandir path))
(if (file-exists? link-file)
(false-if-system-error (EMLINK)
(replace-with-link link-file path))
(catch 'system-error
(lambda ()
(link path link-file))
(lambda args
(let ((errno (system-error-errno args)))
(cond ((= errno EEXIST)
;; Someone else put an entry for PATH in
;; LINKS-DIRECTORY before we could. Let's use it.
(false-if-system-error (EMLINK)
(replace-with-link path link-file)))
((= errno ENOSPC)
;; There's not enough room in the directory index for
;; more entries in .links, but that's fine: we can
;; just stop.
#f)
(else (apply throw args))))))))))

64
tests/store-deduplication.scm Normal file
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@ -0,0 +1,64 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2018 Ludovic Courtès <ludo@gnu.org>
;;;
;;; 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 (test-store-deduplication)
#:use-module (guix tests)
#:use-module (guix store deduplication)
#:use-module (guix hash)
#:use-module ((guix utils) #:select (call-with-temporary-directory))
#:use-module (guix build utils)
#:use-module (rnrs bytevectors)
#:use-module (ice-9 binary-ports)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-64))
(test-begin "store-deduplication")
(test-equal "deduplicate"
(cons* #t #f ;inode comparisons
2 (make-list 5 6)) ;'nlink' values
(call-with-temporary-directory
(lambda (store)
(let ((data (string->utf8 "Hello, world!"))
(identical (map (lambda (n)
(string-append store "/" (number->string n)))
(iota 5)))
(unique (string-append store "/unique")))
(for-each (lambda (file)
(call-with-output-file file
(lambda (port)
(put-bytevector port data))))
identical)
(call-with-output-file unique
(lambda (port)
(put-bytevector port (string->utf8 "This is unique."))))
(for-each (lambda (file)
(deduplicate file (sha256 data) #:store store))
identical)
(deduplicate unique (nar-sha256 unique) #:store store)
;; (system (string-append "ls -lRia " store))
(cons* (apply = (map (compose stat:ino stat) identical))
(= (stat:ino (stat unique))
(stat:ino (stat (car identical))))
(stat:nlink (stat unique))
(map (compose stat:nlink stat) identical))))))
(test-end "store-deduplication")