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guix: docker: Build layered images.

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* guix/docker.scm (%docker-image-max-layers): New variable.
(size-sorted-store-items, create-empty-tar): New procedures.
(config, manifest, build-docker-image): Build layered images.

Change-Id: I4c8846bff0a3ceccb77e6bdf95d4942e5c3efe41
This commit is contained in:
Oleg Pykhalov 2023-12-26 03:46:35 +03:00
parent bdf0ba4ca1
commit d3d3eedf7f
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1 changed files with 166 additions and 46 deletions
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212
guix/docker.scm
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@ -3,6 +3,7 @@
;;; Copyright © 2017, 2018, 2019, 2021 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2018 Chris Marusich <cmmarusich@gmail.com>
;;; Copyright © 2021 Maxim Cournoyer <maxim.cournoyer@gmail.com>
;;; Copyright © 2023 Oleg Pykhalov <go.wigust@gmail.com>
;;;
;;; This file is part of GNU Guix.
;;;
@ -29,16 +30,27 @@ (define-module (guix docker)
with-directory-excursion
invoke))
#:use-module (gnu build install)
#:use-module ((guix build store-copy)
#:select (file-size))
#:use-module (json) ;guile-json
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-19)
#:use-module (srfi srfi-26)
#:use-module (srfi srfi-71)
#:use-module ((texinfo string-utils)
#:select (escape-special-chars))
#:use-module (rnrs bytevectors)
#:use-module (ice-9 ftw)
#:use-module (ice-9 match)
#:export (build-docker-image))
#:export (%docker-image-max-layers
build-docker-image))
;; The maximum number of layers allowed in a Docker image is typically around
;; 128, although it may vary depending on the Docker daemon. However, we
;; recommend setting the limit to 100 to ensure sufficient room for future
;; extensions.
(define %docker-image-max-layers
#f)
;; Generate a 256-bit identifier in hexadecimal encoding for the Docker image.
(define docker-id
@ -92,12 +104,12 @@ (define normalized-name
(make-string (- min-length l) padding-character)))
(_ normalized-name))))
(define* (manifest path id #:optional (tag "guix"))
(define* (manifest path layers #:optional (tag "guix"))
"Generate a simple image manifest."
(let ((tag (canonicalize-repository-name tag)))
`#(((Config . "config.json")
(RepoTags . #(,(string-append tag ":latest")))
(Layers . #(,(string-append id "/layer.tar")))))))
(Layers . ,(list->vector layers))))))
;; According to the specifications this is required for backwards
;; compatibility. It duplicates information provided by the manifest.
@ -106,8 +118,8 @@ (define* (repositories path id #:optional (tag "guix"))
`((,(canonicalize-repository-name tag) . ((latest . ,id)))))
;; See https://github.com/opencontainers/image-spec/blob/master/config.md
(define* (config layer time arch #:key entry-point (environment '()))
"Generate a minimal image configuration for the given LAYER file."
(define* (config layers-diff-ids time arch #:key entry-point (environment '()))
"Generate a minimal image configuration for the given LAYERS files."
;; "architecture" must be values matching "platform.arch" in the
;; runtime-spec at
;; https://github.com/opencontainers/runtime-spec/blob/v1.0.0-rc2/config.md#platform
@ -125,7 +137,7 @@ (define* (config layer time arch #:key entry-point (environment '()))
(container_config . #nil)
(os . "linux")
(rootfs . ((type . "layers")
(diff_ids . #(,(layer-diff-id layer)))))))
(diff_ids . ,(list->vector layers-diff-ids))))))
(define directive-file
;; Return the file or directory created by a 'evaluate-populate-directive'
@ -136,6 +148,26 @@ (define directive-file
(('directory name _ ...)
(string-trim name #\/))))
(define (size-sorted-store-items items max-layers)
"Split list of ITEMS at %MAX-LAYERS and sort by disk usage."
(let* ((items-length (length items))
(head tail
(split-at
(map (match-lambda ((size . item) item))
(sort (map (lambda (item)
(cons (file-size item) item))
items)
(lambda (item1 item2)
(< (match item2 ((size . _) size))
(match item1 ((size . _) size))))))
(if (>= items-length max-layers)
(- max-layers 2)
(1- items-length)))))
(list head tail)))
(define (create-empty-tar file)
(invoke "tar" "-cf" file "--files-from" "/dev/null"))
(define* (build-docker-image image paths prefix
#:key
(repository "guix")
@ -146,11 +178,13 @@ (define* (build-docker-image image paths prefix
entry-point
(environment '())
compressor
(creation-time (current-time time-utc)))
"Write to IMAGE a Docker image archive containing the given PATHS. PREFIX
must be a store path that is a prefix of any store paths in PATHS. REPOSITORY
is a descriptive name that will show up in \"REPOSITORY\" column of the output
of \"docker images\".
(creation-time (current-time time-utc))
max-layers
root-system)
"Write to IMAGE a layerer Docker image archive containing the given PATHS.
PREFIX must be a store path that is a prefix of any store paths in PATHS.
REPOSITORY is a descriptive name that will show up in \"REPOSITORY\" column of
the output of \"docker images\".
When DATABASE is true, copy it to /var/guix/db in the image and create
/var/guix/gcroots and friends.
@ -172,7 +206,14 @@ (define* (build-docker-image image paths prefix
SYSTEM is a GNU triplet (or prefix thereof) of the system the binaries in
PATHS are for; it is used to produce metadata in the image. Use COMPRESSOR, a
command such as '(\"gzip\" \"-9n\"), to compress IMAGE. Use CREATION-TIME, a
SRFI-19 time-utc object, as the creation time in metadata."
SRFI-19 time-utc object, as the creation time in metadata.
When MAX-LAYERS is not false build layered image, providing a Docker
image with store paths splitted in their own layers to improve sharing
between images.
ROOT-SYSTEM is a directory with a provisioned root file system, which will be
added to image as a layer."
(define (sanitize path-fragment)
(escape-special-chars
;; GNU tar strips the leading slash off of absolute paths before applying
@ -203,6 +244,59 @@ (define transformation-options
(if (eq? '() transformations)
'()
`("--transform" ,(transformations->expression transformations))))
(define (seal-layer)
;; Add 'layer.tar' to 'image.tar' under the right name. Return its hash.
(let* ((file-hash (layer-diff-id "layer.tar"))
(file-name (string-append file-hash "/layer.tar")))
(mkdir file-hash)
(rename-file "layer.tar" file-name)
(invoke "tar" "-rf" "image.tar" file-name)
(delete-file file-name)
file-hash))
(define layers-hashes
;; Generate a tarball that includes container image layers as tarballs,
;; along with a manifest.json file describing the layer and config file
;; locations.
(match-lambda
(((head ...) (tail ...) id)
(create-empty-tar "image.tar")
(let* ((head-layers
(map
(lambda (file)
(invoke "tar" "cf" "layer.tar" file)
(seal-layer))
head))
(tail-layer
(begin
(create-empty-tar "layer.tar")
(for-each (lambda (file)
(invoke "tar" "-rf" "layer.tar" file))
tail)
(let* ((file-hash (layer-diff-id "layer.tar"))
(file-name (string-append file-hash "/layer.tar")))
(mkdir file-hash)
(rename-file "layer.tar" file-name)
(invoke "tar" "-rf" "image.tar" file-name)
(delete-file file-name)
file-hash)))
(customization-layer
(let* ((file-id (string-append id "/layer.tar"))
(file-hash (layer-diff-id file-id))
(file-name (string-append file-hash "/layer.tar")))
(mkdir file-hash)
(rename-file file-id file-name)
(invoke "tar" "-rf" "image.tar" file-name)
file-hash))
(all-layers
(append head-layers (list tail-layer customization-layer))))
(with-output-to-file "manifest.json"
(lambda ()
(scm->json (manifest prefix
(map (cut string-append <> "/layer.tar")
all-layers)
repository))))
(invoke "tar" "-rf" "image.tar" "manifest.json")
all-layers))))
(let* ((directory "/tmp/docker-image") ;temporary working directory
(id (docker-id prefix))
(time (date->string (time-utc->date creation-time) "~4"))
@ -229,26 +323,39 @@ (define transformation-options
(with-output-to-file "json"
(lambda () (scm->json (image-description id time))))
;; Create a directory for the non-store files that need to go into the
;; archive.
(mkdir "extra")
(if root-system
(let ((directory (getcwd)))
(with-directory-excursion root-system
(apply invoke "tar"
"-cf" (string-append directory "/layer.tar")
`(,@transformation-options
,@(tar-base-options)
,@(scandir "."
(lambda (file)
(not (member file '("." "..")))))))))
(begin
;; Create a directory for the non-store files that need to go
;; into the archive.
(mkdir "extra")
(with-directory-excursion "extra"
;; Create non-store files.
(for-each (cut evaluate-populate-directive <> "./")
extra-files)
(with-directory-excursion "extra"
;; Create non-store files.
(for-each (cut evaluate-populate-directive <> "./")
extra-files)
(when database
;; Initialize /var/guix, assuming PREFIX points to a profile.
(install-database-and-gc-roots "." database prefix))
(when database
;; Initialize /var/guix, assuming PREFIX points to a
;; profile.
(install-database-and-gc-roots "." database prefix))
(apply invoke "tar" "-cf" "../layer.tar"
`(,@transformation-options
,@(tar-base-options)
,@paths
,@(scandir "."
(lambda (file)
(not (member file '("." ".."))))))))
(apply invoke "tar" "-cf" "../layer.tar"
`(,@transformation-options
,@(tar-base-options)
,@(if max-layers '() paths)
,@(scandir "."
(lambda (file)
(not (member file '("." ".."))))))))
(delete-file-recursively "extra")))
;; It is possible for "/" to show up in the archive, especially when
;; applying transformations. For example, the transformation
@ -261,24 +368,37 @@ (define transformation-options
;; error messages.
(with-error-to-port (%make-void-port "w")
(lambda ()
(system* "tar" "--delete" "/" "-f" "layer.tar")))
(delete-file-recursively "extra"))
(system* "tar" "--delete" "/" "-f" "layer.tar"))))
(with-output-to-file "config.json"
(lambda ()
(scm->json (config (string-append id "/layer.tar")
time arch
#:environment environment
#:entry-point entry-point))))
(with-output-to-file "manifest.json"
(lambda ()
(scm->json (manifest prefix id repository))))
(with-output-to-file "repositories"
(lambda ()
(scm->json (repositories prefix id repository)))))
(apply invoke "tar" "-cf" image "-C" directory
`(,@(tar-base-options #:compressor compressor)
"."))
(scm->json
(config (if max-layers
(layers-hashes
(append (size-sorted-store-items paths max-layers)
(list id)))
(list (layer-diff-id (string-append id "/layer.tar"))))
time arch
#:environment environment
#:entry-point entry-point))))
(if max-layers
(begin
(invoke "tar" "-rf" "image.tar" "config.json")
(if compressor
(begin
(apply invoke `(,@compressor "image.tar"))
(copy-file "image.tar.gz" image))
(copy-file "image.tar" image)))
(begin
(with-output-to-file "manifest.json"
(lambda ()
(scm->json (manifest prefix
(list (string-append id "/layer.tar"))
repository))))
(with-output-to-file "repositories"
(lambda ()
(scm->json (repositories prefix id repository))))
(apply invoke "tar" "-cf" image
`(,@(tar-base-options #:compressor compressor)
".")))))
(delete-file-recursively directory)))