guix - Wojtek's customized Guix

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Commentary: ;;; ;;; This module provides an interface to the GNU Shepherd, similar to the ;;; 'herd' command. Essentially it implements a subset of the (shepherd comm) ;;; module, but focusing only on the parts relevant to 'guix system ;;; reconfigure'. ;;; ;;; Code: (define %shepherd-socket-file (make-parameter "/var/run/shepherd/socket")) (define* (open-connection #:optional (file (%shepherd-socket-file))) "Open a connection to the daemon, using the Unix-domain socket at FILE, and return the socket." ;; The protocol is sexp-based and UTF-8-encoded. (with-fluids ((%default-port-encoding "UTF-8")) (let ((sock (socket PF_UNIX SOCK_STREAM 0)) (address (make-socket-address PF_UNIX file))) (catch 'system-error (lambda () (connect sock address) (setvbuf sock 'block 1024) sock) (lambda args (close-port sock) (apply throw args)))))) (define-syntax-rule (with-shepherd connection body ...) "Evaluate BODY... with CONNECTION bound to an open socket to PID 1." (let ((connection (open-connection))) (dynamic-wind (const #t) (lambda () body ...) (lambda () (close-port connection))))) (define-condition-type &shepherd-error &error shepherd-error?) (define-condition-type &service-not-found-error &shepherd-error service-not-found-error? (service service-not-found-error-service)) (define-condition-type &action-not-found-error &shepherd-error action-not-found-error? (service action-not-found-error-service) (action action-not-found-error-action)) (define-condition-type &action-exception-error &shepherd-error action-exception-error? (service action-exception-error-service) (action action-exception-error-action) (key action-exception-error-key) (args action-exception-error-arguments)) (define-condition-type &unknown-shepherd-error &shepherd-error unknown-shepherd-error? (sexp unknown-shepherd-error-sexp)) (define (raise-shepherd-error error) "Raise an error condition corresponding to ERROR, an sexp received by a shepherd client in reply to COMMAND, a command object. Return #t if ERROR does not denote an error." (match error (('error ('version 0 x ...) 'service-not-found service) (raise (condition (&service-not-found-error (service service))))) (('error ('version 0 x ...) 'action-not-found action service) (raise (condition (&action-not-found-error (service service) (action action))))) (('error ('version 0 x ...) 'action-exception action service key (args ...)) (raise (condition (&action-exception-error (service service) (action action) (key key) (args args))))) (('error . _) (raise (condition (&unknown-shepherd-error (sexp error))))) (#f ;not an error #t))) (define shepherd-message-port ;; Port where messages coming from shepherd are printed. (make-parameter (current-error-port))) (define (display-message message) (format (shepherd-message-port) "shepherd: ~a~%" message)) (define* (invoke-action service action arguments cont) "Invoke ACTION on SERVICE with ARGUMENTS. On success, call CONT with the list of results (one result per instance with the name SERVICE). Otherwise return #f." (with-shepherd sock (write `(shepherd-command (version 0) (action ,action) (service ,service) (arguments ,arguments) (directory ,(getcwd))) sock) (force-output sock) (match (read sock) (('reply ('version 0 _ ...) ('result result) ('error #f) ('messages messages)) (for-each display-message messages) (cont result)) (('reply ('version 0 x ...) ('result y) ('error error) ('messages messages)) (for-each display-message messages) (raise-shepherd-error error) #f) (x ;; invalid reply #f)))) (define-syntax-rule (with-shepherd-action service (action args ...) result body ...) "Invoke ACTION on SERVICE with the given ARGS, and evaluate BODY with RESULT bound to the action's result." (invoke-action service action (list args ...) (lambda (result) body ...))) (define-syntax alist-let* (syntax-rules () "Bind the given KEYs in EXP to the corresponding items in ALIST. ALIST is assumed to be a list of two-element tuples rather than a traditional list of pairs." ((_ alist (key ...) exp ...) (let ((key (and=> (assoc-ref alist 'key) car)) ...) exp ...)))) ;; Information about live Shepherd services. (define-record-type <live-service> (live-service provision requirement transient? running) live-service? (provision live-service-provision) ;list of symbols (requirement live-service-requirement) ;list of symbols (transient? live-service-transient?) ;Boolean (running live-service-running)) ;#f | object (define (live-service-canonical-name service) "Return the 'canonical name' of SERVICE." (first (live-service-provision service))) (define (current-service name) "Return the currently defined Shepherd service NAME, as a <live-service> object. Return #f if the service could not be obtained. As a special case, @code{(current-service 'root)} returns all the current services." (define (process-services services) (resolve-transients (map (lambda (service) (alist-let* service (provides requires running transient?) ;; The Shepherd 0.9.0 would not provide 'transient?' in ;; its status sexp. Thus, when it's missing, query it ;; via an "eval" request. (live-service provides requires (if (sloppy-assq 'transient? service) transient? (and running *unspecified*)) running))) services))) (with-shepherd-action name ('status) results ;; We get a list of results, one for each service with the name NAME. ;; In practice there's only one such service though. (match results ((services _ ...) (match services ((('service ('version 0 _ ...) _ ...) ...) ;; Summary of all services (when NAME is 'root or 'shepherd). (process-services services)) (('service ('version 0 _ ...) _ ...) ;single service (first (process-services (list services)))) (x #f)))))) ;singleton (define (current-services) "Return the list of currently defined Shepherd services, represented as <live-service> objects. Return #f if the list of services could not be obtained." (current-service 'root)) (define (resolve-transients services) "Resolve the subset of SERVICES whose 'transient?' field is undefined. This is necessary to deal with Shepherd 0.9.0, which did not communicate whether a service is transient." ;; All the fuss here is to make sure we make a single "eval root" request ;; for all of SERVICES. (let* ((unresolved (filter (compose unspecified? live-service-transient?) services)) (values (or (and (pair? unresolved) (eval-there `(and (defined? 'transient?) ;shepherd >= 0.9.0 (map (compose transient? lookup-running) ',(map (compose first live-service-provision) unresolved))))) (make-list (length unresolved) #f))) (resolved (map (lambda (unresolved transient?) (cons unresolved (set-field unresolved (live-service-transient?) transient?))) unresolved values))) (map (lambda (service) (or (assq-ref resolved service) service)) services))) (define (unload-service service) "Unload SERVICE, a symbol name; return #t on success." (with-shepherd-action 'root ('unload (symbol->string service)) result (first result))) (define (%load-file file) "Load FILE in the Shepherd." (with-shepherd-action 'root ('load file) result (first result))) (define (eval-there exp) "Eval EXP in the Shepherd." (with-shepherd-action 'root ('eval (object->string exp)) result (first result))) (define (load-services files) "Load and register the services from FILES, where FILES contain code that returns a shepherd <service> object." (eval-there `(register-services ,@(map (lambda (file) `(primitive-load ,file)) files)))) (define load-services/safe ;; Deprecated. It used to behave differently before service replacements ;; were a thing. load-services) (define* (start-service name #:optional (arguments '())) (invoke-action name 'start arguments (lambda (result) result))) (define (stop-service name) (with-shepherd-action name ('stop) result result)) (define (restart-service name) (with-shepherd-action name ('restart) result result)) (define* (wait-for-service name #:key (timeout 20)) "Wait for the service providing NAME, a symbol, to be up and running, and return its \"running value\". Give up after TIMEOUT seconds and raise a '&shepherd-error' exception. Raise a '&service-not-found-error' exception when NAME is not found." (define (relevant-service? service) (memq name (live-service-provision service))) (define start (car (gettimeofday))) ;; Note: As of Shepherd 0.9.1, we cannot just call the 'start' method and ;; wait for it: it would spawn an additional elogind process. Thus, poll. (let loop ((attempts 0)) (define services (current-services)) (define now (car (gettimeofday))) (when (>= (- now start) timeout) (raise (condition (&shepherd-error)))) ;XXX: better exception? (match (find relevant-service? services) (#f (raise (condition (&service-not-found-error (service name))))) (service (or (live-service-running service) (begin (sleep 1) (loop (+ attempts 1)))))))) ;; Local Variables: ;; eval: (put 'alist-let* 'scheme-indent-function 2) ;; eval: (put 'with-shepherd 'scheme-indent-function 1) ;; eval: (put 'with-shepherd-action 'scheme-indent-function 3) ;; End: ;;; herd.scm ends here


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