;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2015, 2016, 2017, 2018, 2019, 2020 Ludovic Courtès ;;; Copyright © 2016 Chris Marusich ;;; Copyright © 2020 Jan (janneke) Nieuwenhuizen ;;; Copyright © 2020, 2021 Ricardo Wurmus ;;; ;;; 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 . (define-module (gnu services) #:use-module (guix gexp) #:use-module (guix monads) #:use-module (guix store) #:use-module (guix records) #:use-module (guix profiles) #:use-module (guix discovery) #:use-module (guix combinators) #:use-module (guix channels) #:use-module (guix describe) #:use-module (guix sets) #:use-module (guix ui) #:use-module (guix diagnostics) #:autoload (guix openpgp) (openpgp-format-fingerprint) #:use-module (guix modules) #:use-module (gnu packages base) #:use-module (gnu packages bash) #:use-module (gnu packages hurd) #:use-module (srfi srfi-1) #:use-module (srfi srfi-9) #:use-module (srfi srfi-9 gnu) #:use-module (srfi srfi-26) #:use-module (srfi srfi-34) #:use-module (srfi srfi-35) #:use-module (ice-9 vlist) #:use-module (ice-9 match) #:autoload (ice-9 pretty-print) (pretty-print) #:export (service-extension service-extension? service-extension-target service-extension-compute service-type service-type? service-type-name service-type-extensions service-type-compose service-type-extend service-type-default-value service-type-description service-type-location %service-type-path fold-service-types lookup-service-types service service? service-kind service-value service-parameters ;deprecated simple-service modify-services service-back-edges instantiate-missing-services fold-services service-error? missing-value-service-error? missing-value-service-error-type missing-value-service-error-location missing-target-service-error? missing-target-service-error-service missing-target-service-error-target-type ambiguous-target-service-error? ambiguous-target-service-error-service ambiguous-target-service-error-target-type system-service-type provenance-service-type sexp->system-provenance system-provenance boot-service-type cleanup-service-type activation-service-type activation-service->script %linux-bare-metal-service %hurd-rc-script %hurd-startup-service special-files-service-type extra-special-file etc-service-type etc-directory setuid-program-service-type profile-service-type firmware-service-type gc-root-service-type %boot-service %activation-service etc-service) #:re-export (;; Note: Re-export 'delete' to allow for proper syntax matching ;; in 'modify-services' forms. See ;; . delete)) ;;; Comment: ;;; ;;; This module defines a broad notion of "service types" and "services." ;;; ;;; A service type describe how its instances extend instances of other ;;; service types. For instance, some services extend the instance of ;;; ACCOUNT-SERVICE-TYPE by providing it with accounts and groups to create; ;;; others extend SHEPHERD-ROOT-SERVICE-TYPE by passing it instances of ;;; . ;;; ;;; When applicable, the service type defines how it can itself be extended, ;;; by providing one procedure to compose extensions, and one procedure to ;;; extend itself. ;;; ;;; A notable service type is SYSTEM-SERVICE-TYPE, which has a single ;;; instance, which is the root of the service DAG. Its value is the ;;; derivation that produces the 'system' directory as returned by ;;; 'operating-system-derivation'. ;;; ;;; The 'fold-services' procedure can be passed a list of procedures, which it ;;; "folds" by propagating extensions down the graph; it returns the root ;;; service after the applying all its extensions. ;;; ;;; Code: (define-record-type (service-extension target compute) service-extension? (target service-extension-target) ; (compute service-extension-compute)) ;params -> params (define &no-default-value ;; Value used to denote service types that have no associated default value. '(no default value)) (define-record-type* service-type make-service-type service-type? (name service-type-name) ;symbol (for debugging) ;; Things extended by services of this type. (extensions service-type-extensions) ;list of ;; Given a list of extensions, "compose" them. (compose service-type-compose ;list of Any -> Any (default #f)) ;; Extend the services' own parameters with the extension composition. (extend service-type-extend ;list of Any -> parameters (default #f)) ;; Optional default value for instances of this type. (default-value service-type-default-value ;Any (default &no-default-value)) ;; Meta-data. (description service-type-description ;string (default #f)) (location service-type-location ; (default (and=> (current-source-location) source-properties->location)) (innate))) (define (write-service-type type port) (format port "#" (service-type-name type) (number->string (object-address type) 16))) (set-record-type-printer! write-service-type) (define %distro-root-directory ;; Absolute file name of the module hierarchy. (dirname (search-path %load-path "guix.scm"))) (define %service-type-path ;; Search path for service types. (make-parameter `((,%distro-root-directory . "gnu/services") (,%distro-root-directory . "gnu/system")))) (define (all-service-modules) "Return the default set of service modules." (cons (resolve-interface '(gnu services)) (all-modules (%service-type-path) #:warn warn-about-load-error))) (define* (fold-service-types proc seed #:optional (modules (all-service-modules))) "For each service type exported by one of MODULES, call (PROC RESULT). SEED is used as the initial value of RESULT." (fold-module-public-variables (lambda (object result) (if (service-type? object) (proc object result) result)) seed modules)) (define lookup-service-types (let ((table (delay (fold-service-types (lambda (type result) (vhash-consq (service-type-name type) type result)) vlist-null)))) (lambda (name) "Return the list of services with the given NAME (a symbol)." (vhash-foldq* cons '() name (force table))))) ;; Services of a given type. (define-record-type (make-service type value) service? (type service-kind) (value service-value)) (define-syntax service (syntax-rules () "Return a service instance of TYPE. The service value is VALUE or, if omitted, TYPE's default value." ((_ type value) (make-service type value)) ((_ type) (%service-with-default-value (current-source-location) type)))) (define (%service-with-default-value location type) "Return a instance of service type TYPE with its default value, if any. If TYPE does not have a default value, an error is raised." ;; TODO: Currently this is a run-time error but with a little bit macrology ;; we could turn it into an expansion-time error. (let ((default (service-type-default-value type))) (if (eq? default &no-default-value) (let ((location (source-properties->location location))) (raise (make-compound-condition (condition (&missing-value-service-error (type type) (location location))) (formatted-message (G_ "~a: no value specified \ for service of type '~a'") (location->string location) (service-type-name type))))) (service type default)))) (define-condition-type &service-error &error service-error?) (define-condition-type &missing-value-service-error &service-error missing-value-service-error? (type missing-value-service-error-type) (location missing-value-service-error-location)) ;;; ;;; Helpers. ;;; (define service-parameters ;; Deprecated alias. service-value) (define (simple-service name target value) "Return a service that extends TARGET with VALUE. This works by creating a singleton service type NAME, of which the returned service is an instance." (let* ((extension (service-extension target identity)) (type (service-type (name name) (extensions (list extension))))) (service type value))) (define-syntax %modify-service (syntax-rules (=> delete) ((_ svc (delete kind) clauses ...) (if (eq? (service-kind svc) kind) #f (%modify-service svc clauses ...))) ((_ service) service) ((_ svc (kind param => exp ...) clauses ...) (if (eq? (service-kind svc) kind) (let ((param (service-value svc))) (service (service-kind svc) (begin exp ...))) (%modify-service svc clauses ...))))) (define-syntax modify-services (syntax-rules () "Modify the services listed in SERVICES according to CLAUSES and return the resulting list of services. Each clause must have the form: (TYPE VARIABLE => BODY) where TYPE is a service type, such as 'guix-service-type', and VARIABLE is an identifier that is bound within BODY to the value of the service of that TYPE. Consider this example: (modify-services %base-services (guix-service-type config => (guix-configuration (inherit config) (use-substitutes? #f) (extra-options '(\"--gc-keep-derivations\")))) (mingetty-service-type config => (mingetty-configuration (inherit config) (motd (plain-file \"motd\" \"Hi there!\")))) (delete udev-service-type)) It changes the configuration of the GUIX-SERVICE-TYPE instance, and that of all the MINGETTY-SERVICE-TYPE instances, and it deletes instances of the UDEV-SERVICE-TYPE. This is a shorthand for (filter-map (lambda (svc) ...) %base-services)." ((_ services clauses ...) (filter-map (lambda (service) (%modify-service service clauses ...)) services)))) ;;; ;;; Core services. ;;; (define (system-derivation entries mextensions) "Return as a monadic value the derivation of the 'system' directory containing the given entries." (mlet %store-monad ((extensions (mapm/accumulate-builds identity mextensions))) (lower-object (file-union "system" (append entries (concatenate extensions)))))) (define system-service-type ;; This is the ultimate service type, the root of the service DAG. The ;; service of this type is extended by monadic name/item pairs. These items ;; end up in the "system directory" as returned by ;; 'operating-system-derivation'. (service-type (name 'system) (extensions '()) (compose identity) (extend system-derivation) (description "Build the operating system top-level directory, which in turn refers to everything the operating system needs: its kernel, initrd, system profile, boot script, and so on."))) (define (compute-boot-script _ gexps) ;; Reverse GEXPS so that extensions appear in the boot script in the right ;; order. That is, user extensions would come first, and extensions added ;; by 'essential-services' (e.g., running shepherd) are guaranteed to come ;; last. (gexp->file "boot" ;; Clean up and activate the system, then spawn shepherd. #~(begin #$@(reverse gexps)))) (define (boot-script-entry mboot) "Return, as a monadic value, an entry for the boot script in the system directory." (mlet %store-monad ((boot mboot)) (return `(("boot" ,boot))))) (define boot-service-type ;; The service of this type is extended by being passed gexps. It ;; aggregates them in a single script, as a monadic value, which becomes its ;; value. (service-type (name 'boot) (extensions (list (service-extension system-service-type boot-script-entry))) (compose identity) (extend compute-boot-script) (description "Produce the operating system's boot script, which is spawned by the initrd once the root file system is mounted."))) (define %boot-service ;; The service that produces the boot script. (service boot-service-type #t)) ;;; ;;; Provenance tracking. ;;; (define (object->pretty-string obj) "Like 'object->string', but using 'pretty-print'." (call-with-output-string (lambda (port) (pretty-print obj port)))) (define (channel->code channel) "Return code to build CHANNEL, ready to be dropped in a 'channels.scm' file." ;; Since the 'introduction' field is backward-incompatible, and since it's ;; optional when using the "official" 'guix channel, include it if and only ;; if we're referring to a different channel. (let ((intro (and (not (equal? (list channel) %default-channels)) (channel-introduction channel)))) `(channel (name ',(channel-name channel)) (url ,(channel-url channel)) (branch ,(channel-branch channel)) (commit ,(channel-commit channel)) ,@(if intro `((introduction (make-channel-introduction ,(channel-introduction-first-signed-commit intro) (openpgp-fingerprint ,(openpgp-format-fingerprint (channel-introduction-first-commit-signer intro)))))) '())))) (define (channel->sexp channel) "Return an sexp describing CHANNEL. The sexp is _not_ code and is meant to be parsed by tools; it's potentially more future-proof than code." ;; TODO: Add CHANNEL's introduction. Currently we can't do that because ;; older 'guix system describe' expect exactly name/url/branch/commit ;; without any additional fields. `(channel (name ,(channel-name channel)) (url ,(channel-url channel)) (branch ,(channel-branch channel)) (commit ,(channel-commit channel)))) (define (sexp->channel sexp) "Return the channel corresponding to SEXP, an sexp as found in the \"provenance\" file produced by 'provenance-service-type'." (match sexp (('channel ('name name) ('url url) ('branch branch) ('commit commit) rest ...) ;; XXX: In the future REST may include a channel introduction. (channel (name name) (url url) (branch branch) (commit commit))))) (define (provenance-file channels config-file) "Return a 'provenance' file describing CHANNELS, a list of channels, and CONFIG-FILE, which can be either #f or a containing the OS configuration being used." (scheme-file "provenance" #~(provenance (version 0) (channels #+@(if channels (map channel->sexp channels) '())) (configuration-file #+config-file)))) (define (provenance-entry config-file) "Return system entries describing the operating system provenance: the channels in use and CONFIG-FILE, if it is true." (define profile (current-profile)) (define channels (and=> profile profile-channels)) (mbegin %store-monad (let ((config-file (cond ((string? config-file) ;; CONFIG-FILE has been passed typically via ;; 'guix system reconfigure CONFIG-FILE' so we ;; can assume it's valid: tell 'local-file' to ;; not emit a warning. (local-file (assume-valid-file-name config-file) "configuration.scm")) ((not config-file) #f) (else config-file)))) (return `(("provenance" ,(provenance-file channels config-file)) ,@(if channels `(("channels.scm" ,(plain-file "channels.scm" (object->pretty-string `(list ,@(map channel->code channels)))))) '()) ,@(if config-file `(("configuration.scm" ,config-file)) '())))))) (define provenance-service-type (service-type (name 'provenance) (extensions (list (service-extension system-service-type provenance-entry))) (default-value #f) ;the OS config file (description "Store provenance information about the system in the system itself: the channels used when building the system, and its configuration file, when available."))) (define (sexp->system-provenance sexp) "Parse SEXP, an s-expression read from /run/current-system/provenance or similar, and return two values: the list of channels listed therein, and the OS configuration file or #f." (match sexp (('provenance ('version 0) ('channels channels ...) ('configuration-file config-file)) (values (map sexp->channel channels) config-file)) (_ (values '() #f)))) (define (system-provenance system) "Given SYSTEM, the file name of a system generation, return two values: the list of channels SYSTEM is built from, and its configuration file. If that information is missing, return the empty list (for channels) and possibly #false (for the configuration file)." (catch 'system-error (lambda () (sexp->system-provenance (call-with-input-file (string-append system "/provenance") read))) (lambda _ (values '() #f)))) ;;; ;;; Cleanup. ;;; (define (cleanup-gexp _) "Return a gexp to clean up /tmp and similar places upon boot." (with-imported-modules '((guix build utils)) #~(begin (use-modules (guix build utils)) ;; Clean out /tmp and /var/run. ;; ;; XXX This needs to happen before service activations, so it ;; has to be here, but this also implicitly assumes that /tmp ;; and /var/run are on the root partition. (letrec-syntax ((fail-safe (syntax-rules () ((_ exp rest ...) (begin (catch 'system-error (lambda () exp) (const #f)) (fail-safe rest ...))) ((_) #t)))) ;; Ignore I/O errors so the system can boot. (fail-safe ;; Remove stale Shadow lock files as they would lead to ;; failures of 'useradd' & co. (delete-file "/etc/group.lock") (delete-file "/etc/passwd.lock") (delete-file "/etc/.pwd.lock") ;from 'lckpwdf' ;; Force file names to be decoded as UTF-8. See ;; . (setenv "GUIX_LOCPATH" #+(file-append glibc-utf8-locales "/lib/locale")) (setlocale LC_CTYPE "en_US.utf8") (delete-file-recursively "/tmp") (delete-file-recursively "/var/run") (mkdir "/tmp") (chmod "/tmp" #o1777) (mkdir "/var/run") (chmod "/var/run" #o755) (delete-file-recursively "/run/udev/watch.old")))))) (define cleanup-service-type ;; Service that cleans things up in /tmp and similar. (service-type (name 'cleanup) (extensions (list (service-extension boot-service-type cleanup-gexp))) (description "Delete files from @file{/tmp}, @file{/var/run}, and other temporary locations at boot time."))) (define* (activation-service->script service) "Return as a monadic value the activation script for SERVICE, a service of ACTIVATION-SCRIPT-TYPE." (activation-script (service-value service))) (define (activation-script gexps) "Return the system's activation script, which evaluates GEXPS." (define actions (map (cut program-file "activate-service.scm" <>) gexps)) (program-file "activate.scm" (with-imported-modules (source-module-closure '((gnu build activation) (guix build utils))) #~(begin (use-modules (gnu build activation) (guix build utils)) ;; Make sure the user accounting database exists. If it ;; does not exist, 'setutxent' does not create it and ;; thus there is no accounting at all. (close-port (open-file "/var/run/utmpx" "a0")) ;; Same for 'wtmp', which is populated by mingetty et ;; al. (mkdir-p "/var/log") (close-port (open-file "/var/log/wtmp" "a0")) ;; Set up /run/current-system. Among other things this ;; sets up locales, which the activation snippets ;; executed below may expect. (activate-current-system) ;; Run the services' activation snippets. ;; TODO: Use 'load-compiled'. (for-each primitive-load '#$actions))))) (define (gexps->activation-gexp gexps) "Return a gexp that runs the activation script containing GEXPS." #~(primitive-load #$(activation-script gexps))) (define (activation-profile-entry gexps) "Return, as a monadic value, an entry for the activation script in the system directory." (mlet %store-monad ((activate (lower-object (activation-script gexps)))) (return `(("activate" ,activate))))) (define (second-argument a b) b) (define activation-service-type (service-type (name 'activate) (extensions (list (service-extension boot-service-type gexps->activation-gexp) (service-extension system-service-type activation-profile-entry))) (compose identity) (extend second-argument) (description "Run @dfn{activation} code at boot time and upon @command{guix system reconfigure} completion."))) (define %activation-service ;; The activation service produces the activation script from the gexps it ;; receives. (service activation-service-type #t)) (define %modprobe-wrapper ;; Wrapper for the 'modprobe' command that knows where modules live. ;; ;; This wrapper is typically invoked by the Linux kernel ('call_modprobe', ;; in kernel/kmod.c), a situation where the 'LINUX_MODULE_DIRECTORY' ;; environment variable is not set---hence the need for this wrapper. (let ((modprobe "/run/current-system/profile/bin/modprobe")) (program-file "modprobe" #~(begin (setenv "LINUX_MODULE_DIRECTORY" "/run/booted-system/kernel/lib/modules") ;; FIXME: Remove this crutch when the patch #40422, ;; updating to kmod 27 is merged. (setenv "MODPROBE_OPTIONS" "-C /etc/modprobe.d") (apply execl #$modprobe (cons #$modprobe (cdr (command-line)))))))) (define %linux-kernel-activation ;; Activation of the Linux kernel running on the bare metal (as opposed to ;; running in a container.) #~(begin ;; Tell the kernel to use our 'modprobe' command. (activate-modprobe #$%modprobe-wrapper) ;; Let users debug their own processes! (activate-ptrace-attach))) (define %linux-bare-metal-service ;; The service that does things that are needed on the "bare metal", but not ;; necessary or impossible in a container. (simple-service 'linux-bare-metal activation-service-type %linux-kernel-activation)) (define %hurd-rc-script ;; The RC script to be started upon boot. (program-file "rc" (with-imported-modules (source-module-closure '((guix build utils) (gnu build hurd-boot) (guix build syscalls))) #~(begin (use-modules (guix build utils) (gnu build hurd-boot) (guix build syscalls) (ice-9 match) (system repl repl) (srfi srfi-1) (srfi srfi-26)) (boot-hurd-system))))) (define (hurd-rc-entry rc) "Return, as a monadic value, an entry for the RC script in the system directory." (mlet %store-monad ((rc (lower-object rc))) (return `(("rc" ,rc))))) (define hurd-startup-service-type ;; The service that creates the initial SYSTEM/rc startup file. (service-type (name 'startup) (extensions (list (service-extension system-service-type hurd-rc-entry))) (default-value %hurd-rc-script))) (define %hurd-startup-service ;; The service that produces the RC script. (service hurd-startup-service-type %hurd-rc-script)) (define special-files-service-type ;; Service to install "special files" such as /bin/sh and /usr/bin/env. (service-type (name 'special-files) (extensions (list (service-extension activation-service-type (lambda (files) #~(activate-special-files '#$files))))) (compose concatenate) (extend append) (description "Add special files to the root file system---e.g., @file{/usr/bin/env}."))) (define (extra-special-file file target) "Use TARGET as the \"special file\" FILE. For example, TARGET might be (file-append coreutils \"/bin/env\") and FILE could be \"/usr/bin/env\"." (simple-service (string->symbol (string-append "special-file-" file)) special-files-service-type `((,file ,target)))) (define (etc-directory service) "Return the directory for SERVICE, a service of type ETC-SERVICE-TYPE." (files->etc-directory (service-value service))) (define (files->etc-directory files) (define (assert-no-duplicates files) (let loop ((files files) (seen (set))) (match files (() #t) (((file _) rest ...) (when (set-contains? seen file) (raise (formatted-message (G_ "duplicate '~a' entry for /etc") file))) (loop rest (set-insert file seen)))))) ;; Detect duplicates early instead of letting them through, eventually ;; leading to a build failure of "etc.drv". (assert-no-duplicates files) (file-union "etc" files)) (define (etc-entry files) "Return an entry for the /etc directory consisting of FILES in the system directory." (with-monad %store-monad (return `(("etc" ,(files->etc-directory files)))))) (define etc-service-type (service-type (name 'etc) (extensions (list (service-extension activation-service-type (lambda (files) (let ((etc (files->etc-directory files))) #~(activate-etc #$etc)))) (service-extension system-service-type etc-entry))) (compose concatenate) (extend append) (description "Populate the @file{/etc} directory."))) (define (etc-service files) "Return a new service of ETC-SERVICE-TYPE that populates /etc with FILES. FILES must be a list of name/file-like object pairs." (service etc-service-type files)) (define setuid-program-service-type (service-type (name 'setuid-program) (extensions (list (service-extension activation-service-type (lambda (programs) #~(activate-setuid-programs (list #$@programs)))))) (compose concatenate) (extend append) (description "Populate @file{/run/setuid-programs} with the specified executables, making them setuid-root."))) (define (packages->profile-entry packages) "Return a system entry for the profile containing PACKAGES." ;; XXX: 'mlet' is needed here for one reason: to get the proper ;; '%current-target' and '%current-target-system' bindings when ;; 'packages->manifest' is called, and thus when the 'package-inputs' ;; etc. procedures are called on PACKAGES. That way, conditionals in those ;; inputs see the "correct" value of these two parameters. See ;; . (mlet %store-monad ((_ (current-target-system))) (return `(("profile" ,(profile (content (packages->manifest (delete-duplicates packages eq?))))))))) (define profile-service-type ;; The service that populates the system's profile---i.e., ;; /run/current-system/profile. It is extended by package lists. (service-type (name 'profile) (extensions (list (service-extension system-service-type packages->profile-entry))) (compose concatenate) (extend append) (description "This is the @dfn{system profile}, available as @file{/run/current-system/profile}. It contains packages that the sysadmin wants to be globally available to all the system users."))) (define (firmware->activation-gexp firmware) "Return a gexp to make the packages listed in FIRMWARE loadable by the kernel." (let ((directory (directory-union "firmware" firmware))) ;; Tell the kernel where firmware is. #~(activate-firmware (string-append #$directory "/lib/firmware")))) (define firmware-service-type ;; The service that collects firmware. (service-type (name 'firmware) (extensions (list (service-extension activation-service-type firmware->activation-gexp))) (compose concatenate) (extend append) (description "Make ``firmware'' files loadable by the operating system kernel. Firmware may then be uploaded to some of the machine's devices, such as Wifi cards."))) (define (gc-roots->system-entry roots) "Return an entry in the system's output containing symlinks to ROOTS." (mlet %store-monad ((entry (gexp->derivation "gc-roots" #~(let ((roots '#$roots)) (mkdir #$output) (chdir #$output) (for-each symlink roots (map number->string (iota (length roots)))))))) (return (if (null? roots) '() `(("gc-roots" ,entry)))))) (define gc-root-service-type ;; A service to associate extra garbage-collector roots to the system. This ;; is a simple hack that guarantees that the system retains references to ;; the given list of roots. Roots must be "lowerable" objects like ;; packages, or derivations. (service-type (name 'gc-roots) (extensions (list (service-extension system-service-type gc-roots->system-entry))) (compose concatenate) (extend append) (description "Register garbage-collector roots---i.e., store items that will not be reclaimed by the garbage collector.") (default-value '()))) ;;; ;;; Service folding. ;;; (define-condition-type &missing-target-service-error &service-error missing-target-service-error? (service missing-target-service-error-service) (target-type missing-target-service-error-target-type)) (define-condition-type &ambiguous-target-service-error &service-error ambiguous-target-service-error? (service ambiguous-target-service-error-service) (target-type ambiguous-target-service-error-target-type)) (define (missing-target-error service target-type) (raise (condition (&missing-target-service-error (service service) (target-type target-type)) (&message (message (format #f (G_ "no target of type '~a' for service '~a'") (service-type-name target-type) (service-type-name (service-kind service)))))))) (define (service-back-edges services) "Return a procedure that, when passed a , returns the list of objects that depend on it." (define (add-edges service edges) (define (add-edge extension edges) (let ((target-type (service-extension-target extension))) (match (filter (lambda (service) (eq? (service-kind service) target-type)) services) ((target) (vhash-consq target service edges)) (() (missing-target-error service target-type)) (x (raise (condition (&ambiguous-target-service-error (service service) (target-type target-type)) (&message (message (format #f (G_ "more than one target service of type '~a'") (service-type-name target-type)))))))))) (fold add-edge edges (service-type-extensions (service-kind service)))) (let ((edges (fold add-edges vlist-null services))) (lambda (node) (reverse (vhash-foldq* cons '() node edges))))) (define (instantiate-missing-services services) "Return SERVICES, a list, augmented with any services targeted by extensions and missing from SERVICES. Only service types with a default value can be instantiated; other missing services lead to a '&missing-target-service-error'." (define (adjust-service-list svc result instances) (fold2 (lambda (extension result instances) (define target-type (service-extension-target extension)) (match (vhash-assq target-type instances) (#f (let ((default (service-type-default-value target-type))) (if (eq? &no-default-value default) (missing-target-error svc target-type) (let ((new (service target-type))) (values (cons new result) (vhash-consq target-type new instances)))))) (_ (values result instances)))) result instances (service-type-extensions (service-kind svc)))) (let loop ((services services)) (define instances (fold (lambda (service result) (vhash-consq (service-kind service) service result)) vlist-null services)) (define adjusted (fold2 adjust-service-list services instances services)) ;; If we instantiated services, they might in turn depend on missing ;; services. Loop until we've reached fixed point. (if (= (length adjusted) (vlist-length instances)) adjusted (loop adjusted)))) (define* (fold-services services #:key (target-type system-service-type)) "Fold SERVICES by propagating their extensions down to the root of type TARGET-TYPE; return the root service adjusted accordingly." (define dependents (service-back-edges services)) (define (matching-extension target) (let ((target (service-kind target))) (match-lambda (($ type) (eq? type target))))) (define (apply-extension target) (lambda (service) (match (find (matching-extension target) (service-type-extensions (service-kind service))) (($ _ compute) (compute (service-value service)))))) (match (filter (lambda (service) (eq? (service-kind service) target-type)) services) ((sink) ;; Use the state monad to keep track of already-visited services in the ;; graph and to memoize their value once folded. (run-with-state (let loop ((sink sink)) (mlet %state-monad ((visited (current-state))) (match (vhash-assq sink visited) (#f (mlet* %state-monad ((dependents (mapm %state-monad loop (dependents sink))) (visited (current-state)) (extensions -> (map (apply-extension sink) dependents)) (extend -> (service-type-extend (service-kind sink))) (compose -> (service-type-compose (service-kind sink))) (params -> (service-value sink)) (service -> ;; Distinguish COMPOSE and EXTEND because PARAMS typically ;; has a different type than the elements of EXTENSIONS. (if extend (service (service-kind sink) (extend params (compose extensions))) sink))) (mbegin %state-monad (set-current-state (vhash-consq sink service visited)) (return service)))) ((_ . service) ;SINK was already visited (return service))))) vlist-null)) (() (raise (make-compound-condition (condition (&missing-target-service-error (service #f) (target-type target-type))) (formatted-message (G_ "service of type '~a' not found") (service-type-name target-type))))) (x (raise (condition (&ambiguous-target-service-error (service #f) (target-type target-type)) (&message (message (format #f (G_ "more than one target service of type '~a'") (service-type-name target-type))))))))) ;;; services.scm ends here.