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nar: Deduplicate files right as they are restored. 

This avoids having to traverse and re-read the files that we have just
restored, thereby reducing I/O.

* guix/serialization.scm (dump-file): New procedure.
(restore-file): Add #:dump-file parameter and honor it.
* guix/store/deduplication.scm (tee, dump-file/deduplicate): New
procedures.
* guix/nar.scm (restore-one-item): Pass #:dump-file to 'restore-file'.
(finalize-store-file): Pass #:deduplicate? #f to 'register-items'.
* tests/nar.scm <top level>: Call 'setenv' to set "NIX_STORE".
master
Ludovic Courtès 2020-12-10 11:21:14 +01:00
parent ed7d02f7c1
commit 2718c29c3f
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GPG Key ID: 090B11993D9AEBB5
4 changed files with 85 additions and 14 deletions
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12
guix/nar.scm
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@ -27,6 +27,7 @@
;; (guix store) since this is "daemon-side" code.
#:use-module (guix store)
#:use-module (guix store database)
#:use-module ((guix store deduplication) #:select (dump-file/deduplicate))
#:use-module ((guix build store-copy) #:select (store-info))
#:use-module (guix i18n)
@ -114,12 +115,12 @@ held."
;; Install the new TARGET.
(rename-file source target)
;; Register TARGET. As a side effect, run a deduplication pass.
;; Timestamps and permissions are already correct thanks to
;; 'restore-file'.
;; Register TARGET. The 'restore-file' call took care of
;; deduplication, timestamps, and permissions.
(register-items db
(list (store-info target deriver references))
#:reset-timestamps? #f))
#:reset-timestamps? #f
#:deduplicate? #f))
(when lock?
(delete-file (string-append target ".lock"))
@ -212,7 +213,8 @@ s-expression"))
(let-values (((port get-hash)
(open-sha256-input-port port)))
(with-temporary-store-file temp
(restore-file port temp)
(restore-file port temp
#:dump-file dump-file/deduplicate)
(let ((magic (read-int port)))
(unless (= magic %export-magic)

27
guix/serialization.scm
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@ -457,9 +457,22 @@ depends on TYPE."
(&message (message "unsupported nar entry type"))
(&nar-read-error (port port) (file file) (token x)))))))))
(define (restore-file port file)
(define (dump-file file input size type)
"Dump SIZE bytes from INPUT to FILE."
(call-with-output-file file
(lambda (output)
(dump input output size))))
(define* (restore-file port file
#:key (dump-file dump-file))
"Read a file (possibly a directory structure) in Nar format from PORT.
Restore it as FILE with canonical permissions and timestamps."
Restore it as FILE with canonical permissions and timestamps. To write a
regular or executable file, call:
(DUMP-FILE FILE INPUT SIZE TYPE)
The default is to dump SIZE bytes from INPUT to FILE, but callers can provide
a custom procedure, for instance to deduplicate FILE on the fly."
(fold-archive (lambda (file type content result)
(match type
('directory
@ -473,12 +486,10 @@ Restore it as FILE with canonical permissions and timestamps."
((or 'regular 'executable)
(match content
((input . size)
(call-with-output-file file
(lambda (output)
(dump input output size)
(chmod output (if (eq? type 'executable)
#o555
#o444))))
(dump-file file input size type)
(chmod file (if (eq? type 'executable)
#o555
#o444))
(utime file 1 1 0 0))))))
#t
port

57
guix/store/deduplication.scm
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@ -26,12 +26,15 @@
#:use-module (guix build syscalls)
#:use-module (guix base32)
#:use-module (srfi srfi-11)
#:use-module (srfi srfi-34)
#:use-module (srfi srfi-35)
#:use-module (rnrs io ports)
#:use-module (ice-9 ftw)
#:use-module (ice-9 match)
#:use-module (guix serialization)
#:export (nar-sha256
deduplicate))
deduplicate
dump-file/deduplicate))
;; XXX: This port is used as a workaround on Guile <= 2.2.4 where
;; 'port-position' throws to 'out-of-range' when the offset is great than or
@ -201,3 +204,55 @@ under STORE."
;; that's OK: we just can't deduplicate it more.
#f)
(else (apply throw args)))))))))))
(define (tee input len output)
"Return a port that reads up to LEN bytes from INPUT and writes them to
OUTPUT as it goes."
(define bytes-read 0)
(define (fail)
;; Reached EOF before we had read LEN bytes from INPUT.
(raise (condition
(&nar-error (port input)
(file (port-filename output))))))
(define (read! bv start count)
;; Read at most LEN bytes in total.
(let ((count (min count (- len bytes-read))))
(let loop ((ret (get-bytevector-n! input bv start count)))
(cond ((eof-object? ret)
(if (= bytes-read len)
0 ; EOF
(fail)))
((and (zero? ret) (> count 0))
;; Do not return zero since zero means EOF, so try again.
(loop (get-bytevector-n! input bv start count)))
(else
(put-bytevector output bv start ret)
(set! bytes-read (+ bytes-read ret))
ret)))))
(make-custom-binary-input-port "tee input port" read! #f #f #f))
(define* (dump-file/deduplicate file input size type
#:key (store (%store-directory)))
"Write SIZE bytes read from INPUT to FILE. TYPE is a symbol, either
'regular or 'executable.
This procedure is suitable as a #:dump-file argument to 'restore-file'. When
used that way, it deduplicates files on the fly as they are restored, thereby
removing the need to a deduplication pass that would re-read all the files
down the road."
(define hash
(call-with-output-file file
(lambda (output)
(let-values (((hash-port get-hash)
(open-hash-port (hash-algorithm sha256))))
(write-file-tree file hash-port
#:file-type+size (lambda (_) (values type size))
#:file-port
(const (tee input size output)))
(close-port hash-port)
(get-hash)))))
(deduplicate file hash #:store store))

3
tests/nar.scm
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@ -452,6 +452,9 @@
(false-if-exception (rm-rf %test-dir))
(setlocale LC_ALL locale)))))
;; XXX: Tell the 'deduplicate' procedure what store we're actually using.
(setenv "NIX_STORE" (%store-prefix))
(test-assert "restore-file-set (signed, valid)"
(with-store store
(let* ((texts (unfold (cut >= <> 10)