path: root/guix/scripts/substitute-binary.scm

;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013, 2014 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 (guix scripts substitute-binary)
  #:use-module (guix ui)
  #:use-module (guix store)
  #:use-module (guix utils)
  #:use-module (guix config)
  #:use-module (guix records)
  #:use-module (guix nar)
  #:use-module ((guix build utils) #:select (mkdir-p))
  #:use-module ((guix build download)
                #:select (progress-proc uri-abbreviation))
  #:use-module (ice-9 rdelim)
  #:use-module (ice-9 regex)
  #:use-module (ice-9 match)
  #:use-module (ice-9 threads)
  #:use-module (ice-9 format)
  #:use-module (ice-9 ftw)
  #:use-module (ice-9 binary-ports)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-9)
  #:use-module (srfi srfi-11)
  #:use-module (srfi srfi-19)
  #:use-module (srfi srfi-26)
  #:use-module (web uri)
  #:use-module (guix http-client)
  #:export (guix-substitute-binary))

;;; Comment:
;;;
;;; This is the "binary substituter".  It is invoked by the daemon do check
;;; for the existence of available "substitutes" (pre-built binaries), and to
;;; actually use them as a substitute to building things locally.
;;;
;;; If possible, substitute a binary for the requested store path, using a Nix
;;; "binary cache".  This program implements the Nix "substituter" protocol.
;;;
;;; Code:

(define %narinfo-cache-directory
  ;; A local cache of narinfos, to avoid going to the network.
  (or (and=> (getenv "XDG_CACHE_HOME")
             (cut string-append <> "/guix/substitute-binary"))
      (string-append %state-directory "/substitute-binary/cache")))

(define %narinfo-ttl
  ;; Number of seconds during which cached narinfo lookups are considered
  ;; valid.
  (* 24 3600))

(define %narinfo-negative-ttl
  ;; Likewise, but for negative lookups---i.e., cached lookup failures.
  (* 3 3600))

(define %narinfo-expired-cache-entry-removal-delay
  ;; How often we want to remove files corresponding to expired cache entries.
  (* 7 24 3600))

;; In Guile 2.0.9, `regexp-exec' is thread-unsafe, so work around it.
;; See <http://bugs.gnu.org/14404>.
(set! regexp-exec
      (let ((real regexp-exec)
            (lock (make-mutex)))
        (lambda args
          (with-mutex lock
            (apply real args)))))

(define fields->alist
  ;; The narinfo format is really just like recutils.
  recutils->alist)

(define %fetch-timeout
  ;; Number of seconds after which networking is considered "slow".
  5)

(define %random-state
  (seed->random-state (+ (ash (cdr (gettimeofday)) 32) (getpid))))

(define-syntax-rule (with-timeout duration handler body ...)
  "Run BODY; when DURATION seconds have expired, call HANDLER, and run BODY
again."
  (begin
    (sigaction SIGALRM
      (lambda (signum)
        (sigaction SIGALRM SIG_DFL)
        handler))
    (alarm duration)
    (call-with-values
        (lambda ()
          (let try ()
            (catch 'system-error
              (lambda ()
                body ...)
              (lambda args
                ;; Before Guile v2.0.9-39-gfe51c7b, the SIGALRM triggers EINTR
                ;; because of the bug at
                ;; <http://lists.gnu.org/archive/html/guile-devel/2013-06/msg00050.html>.
                ;; When that happens, try again.  Note: SA_RESTART cannot be
                ;; used because of <http://bugs.gnu.org/14640>.
                (if (= EINTR (system-error-errno args))
                    (begin
                      ;; Wait a little to avoid bursts.
                      (usleep (random 3000000 %random-state))
                      (try))
                    (apply throw args))))))
      (lambda result
        (alarm 0)
        (sigaction SIGALRM SIG_DFL)
        (apply values result)))))

(define* (fetch uri #:key (buffered? #t) (timeout? #t))
  "Return a binary input port to URI and the number of bytes it's expected to
provide."
  (case (uri-scheme uri)
    ((file)
     (let ((port (open-file (uri-path uri)
                            (if buffered? "rb" "r0b"))))
       (values port (stat:size (stat port)))))
    ((http)
     ;; On Guile 2.0.5, `http-fetch' fetches the whole thing at once.  So
     ;; honor TIMEOUT? to disable the timeout when fetching a nar.
     ;;
     ;; Test this with:
     ;;   sudo tc qdisc add dev eth0 root netem delay 1500ms
     ;; and then cancel with:
     ;;   sudo tc qdisc del dev eth0 root
     (let ((port #f))
       (with-timeout (if (or timeout? (guile-version>? "2.0.5"))
                         %fetch-timeout
                         0)
         (begin
           (warning (_ "while fetching ~a: server is unresponsive~%")
                    (uri->string uri))
           (warning (_ "try `--no-substitutes' if the problem persists~%"))

           ;; Before Guile v2.0.9-39-gfe51c7b, EINTR was reported to the user,
           ;; and thus PORT had to be closed and re-opened.  This is not the
           ;; case afterward.
           (unless (or (guile-version>? "2.0.9")
                       (version>? (version) "2.0.9.39"))
             (when port
               (close-port port))))
         (begin
           (when (or (not port) (port-closed? port))
             (set! port (open-socket-for-uri uri #:buffered? buffered?)))
           (http-fetch uri #:text? #f #:port port)))))))

(define-record-type <cache>
  (%make-cache url store-directory wants-mass-query?)
  cache?
  (url               cache-url)
  (store-directory   cache-store-directory)
  (wants-mass-query? cache-wants-mass-query?))

(define (open-cache url)
  "Open the binary cache at URL.  Return a <cache> object on success, or #f on
failure."
  (define (download-cache-info url)
    ;; Download the `nix-cache-info' from URL, and return its contents as an
    ;; list of key/value pairs.
    (and=> (false-if-exception (fetch (string->uri url)))
           fields->alist))

  (and=> (download-cache-info (string-append url "/nix-cache-info"))
         (lambda (properties)
           (alist->record properties
                          (cut %make-cache url <...>)
                          '("StoreDir" "WantMassQuery")))))

(define-record-type <narinfo>
  (%make-narinfo path uri compression file-hash file-size nar-hash nar-size
                 references deriver system)
  narinfo?
  (path         narinfo-path)
  (uri          narinfo-uri)
  (compression  narinfo-compression)
  (file-hash    narinfo-file-hash)
  (file-size    narinfo-file-size)
  (nar-hash     narinfo-hash)
  (nar-size     narinfo-size)
  (references   narinfo-references)
  (deriver      narinfo-deriver)
  (system       narinfo-system))

(define (narinfo-maker cache-url)
  "Return a narinfo constructor for narinfos originating from CACHE-URL."
  (lambda (path url compression file-hash file-size nar-hash nar-size
                references deriver system)
    "Return a new <narinfo> object."
    (%make-narinfo path

                   ;; Handle the case where URL is a relative URL.
                   (or (string->uri url)
                       (string->uri (string-append cache-url "/" url)))

                   compression file-hash
                   (and=> file-size string->number)
                   nar-hash
                   (and=> nar-size string->number)
                   (string-tokenize references)
                   (match deriver
                     ((or #f "") #f)
                     (_ deriver))
                   system)))

(define* (read-narinfo port #:optional url)
  "Read a narinfo from PORT in its standard external form.  If URL is true, it
must be a string used to build full URIs from relative URIs found while
reading PORT."
  (alist->record (fields->alist port)
                 (narinfo-maker url)
                 '("StorePath" "URL" "Compression"
                   "FileHash" "FileSize" "NarHash" "NarSize"
                   "References" "Deriver" "System")))

(define (write-narinfo narinfo port)
  "Write NARINFO to PORT."
  (define (empty-string-if-false x)
    (or x ""))

  (define (number-or-empty-string x)
    (if (number? x)
        (number->string x)
        ""))

  (object->fields narinfo
                  `(("StorePath" . ,narinfo-path)
                    ("URL" . ,(compose uri->string narinfo-uri))
                    ("Compression" . ,narinfo-compression)
                    ("FileHash" . ,(compose empty-string-if-false
                                            narinfo-file-hash))
                    ("FileSize" . ,(compose number-or-empty-string
                                            narinfo-file-size))
                    ("NarHash" . ,(compose empty-string-if-false
                                           narinfo-hash))
                    ("NarSize" . ,(compose number-or-empty-string
                                           narinfo-size))
                    ("References" . ,(compose string-join narinfo-references))
                    ("Deriver" . ,(compose empty-string-if-false
                                           narinfo-deriver))
                    ("System" . ,narinfo-system))
                  port))

(define (narinfo->string narinfo)
  "Return the external representation of NARINFO."
  (call-with-output-string (cut write-narinfo narinfo <>)))

(define (string->narinfo str)
  "Return the narinfo represented by STR."
  (call-with-input-string str (cut read-narinfo <>)))

(define (fetch-narinfo cache path)
  "Return the <narinfo> record for PATH, or #f if CACHE does not hold PATH."
  (define (download url)
    ;; Download the .narinfo from URL, and return its contents as a list of
    ;; key/value pairs.
    (false-if-exception (fetch (string->uri url))))

  (and (string=? (cache-store-directory cache) (%store-prefix))
       (and=> (download (string-append (cache-url cache) "/"
                                       (store-path-hash-part path)
                                       ".narinfo"))
              (cute read-narinfo <> (cache-url cache)))))

(define (obsolete? date now ttl)
  "Return #t if DATE is obsolete compared to NOW + TTL seconds."
  (time>? (subtract-duration now (make-time time-duration 0 ttl))
          (make-time time-monotonic 0 date)))

(define %lookup-threads
  ;; Number of threads spawned to perform lookup operations.  This means we
  ;; can have this many simultaneous HTTP GET requests to the server, which
  ;; limits the impact of connection latency.
  20)

(define (lookup-narinfo cache path)
  "Check locally if we have valid info about PATH, otherwise go to CACHE and
check what it has."
  (define now
    (current-time time-monotonic))

  (define cache-file
    (string-append %narinfo-cache-directory "/"
                   (store-path-hash-part path)))

  (define (cache-entry narinfo)
    `(narinfo (version 0)
              (date ,(time-second now))
              (value ,(and=> narinfo narinfo->string))))

  (let*-values (((valid? cached)
                 (catch 'system-error
                   (lambda ()
                     (call-with-input-file cache-file
                       (lambda (p)
                         (match (read p)
                           (('narinfo ('version 0) ('date date)
                                      ('value #f))
                            ;; A cached negative lookup.
                            (if (obsolete? date now %narinfo-negative-ttl)
                                (values #f #f)
                                (values #t #f)))
                           (('narinfo ('version 0) ('date date)
                                      ('value value))
                            ;; A cached positive lookup
                            (if (obsolete? date now %narinfo-ttl)
                                (values #f #f)
                                (values #t (string->narinfo value))))))))
                   (lambda _
                     (values #f #f)))))
    (if valid?
        cached                                    ; including negative caches
        (let* ((cache   (force cache))
               (narinfo (and cache (fetch-narinfo cache path))))
          ;; Cache NARINFO only when CACHE was actually accessible.  This
          ;; avoids caching negative hits when in fact we just lacked network
          ;; access.
          (when cache
            (with-atomic-file-output cache-file
              (lambda (out)
                (write (cache-entry narinfo) out))))
          narinfo))))

(define (remove-expired-cached-narinfos)
  "Remove expired narinfo entries from the cache.  The sole purpose of this
function is to make sure `%narinfo-cache-directory' doesn't grow
indefinitely."
  (define now
    (current-time time-monotonic))

  (define (expired? file)
    (catch 'system-error
      (lambda ()
        (call-with-input-file file
          (lambda (port)
            (match (read port)
              (('narinfo ('version 0) ('date date)
                         ('value #f))
               (obsolete? date now %narinfo-negative-ttl))
              (('narinfo ('version 0) ('date date)
                         ('value _))
               (obsolete? date now %narinfo-ttl))
              (_ #t)))))
      (lambda args
        ;; FILE may have been deleted.
        #t)))

  (for-each (lambda (file)
              (let ((file (string-append %narinfo-cache-directory
                                         "/" file)))
                (when (expired? file)
                  ;; Wrap in `false-if-exception' because FILE might have been
                  ;; deleted in the meantime (TOCTTOU).
                  (false-if-exception (delete-file file)))))
            (scandir %narinfo-cache-directory
                     (lambda (file)
                       (= (string-length file) 32)))))

(define (maybe-remove-expired-cached-narinfo)
  "Remove expired narinfo entries from the cache if deemed necessary."
  (define now
    (current-time time-monotonic))

  (define expiry-file
    (string-append %narinfo-cache-directory "/last-expiry-cleanup"))

  (define last-expiry-date
    (or (false-if-exception
         (call-with-input-file expiry-file read))
        0))

  (when (obsolete? last-expiry-date now %narinfo-expired-cache-entry-removal-delay)
    (remove-expired-cached-narinfos)
    (call-with-output-file expiry-file
      (cute write (time-second now) <>))))

(define (decompressed-port compression input)
  "Return an input port where INPUT is decompressed according to COMPRESSION,
along with a list of PIDs to wait for."
  (match compression
    ("none"  (values input '()))
    ("bzip2" (filtered-port `(,%bzip2 "-dc") input))
    ("xz"    (filtered-port `(,%xz "-dc") input))
    ("gzip"  (filtered-port `(,%gzip "-dc") input))
    (else    (error "unsupported compression scheme" compression))))

(define (progress-report-port report-progress port)
  "Return a port that calls REPORT-PROGRESS every time something is read from
PORT.  REPORT-PROGRESS is a two-argument procedure such as that returned by
`progress-proc'."
  (define total 0)
  (define (read! bv start count)
    (let ((n (match (get-bytevector-n! port bv start count)
               ((? eof-object?) 0)
               (x x))))
      (set! total (+ total n))
      (report-progress total (const n))
      ;; XXX: We're not in control, so we always return anyway.
      n))

  ;; Since `http-fetch' in Guile 2.0.5 returns all the data once it's done,
  ;; don't pretend to report any progress in that case.
  (if (guile-version>? "2.0.5")
      (make-custom-binary-input-port "progress-port-proc"
                                     read! #f #f
                                     (cut close-port port))
      (begin
        (format (current-error-port) (_ "Downloading, please wait...~%"))
        (format (current-error-port)
                (_ "(Please consider upgrading Guile to get proper progress report.)~%"))
        port)))

(define %cache-url
  (or (getenv "GUIX_BINARY_SUBSTITUTE_URL")
      "http://hydra.gnu.org"))

(define-syntax with-networking
  (syntax-rules ()
    "Catch DNS lookup errors and gracefully exit."
    ;; Note: no attempt is made to catch other networking errors, because DNS
    ;; lookup errors are typically the first one, and because other errors are
    ;; a subset of `system-error', which is harder to filter.
    ((_ exp ...)
     (catch 'getaddrinfo-error
       (lambda () exp ...)
       (lambda (key error)
         (leave (_ "host name lookup error: ~a~%")
                (gai-strerror error)))))))


;;;
;;; Help.
;;;

(define (show-help)
  (display (_ "Usage: guix substitute-binary [OPTION]...
Internal tool to substitute a pre-built binary to a local build.\n"))
  (display (_ "
      --query            report on the availability of substitutes for the
                         store file names passed on the standard input"))
  (display (_ "
      --substitute STORE-FILE DESTINATION
                         download STORE-FILE and store it as a Nar in file
                         DESTINATION"))
  (newline)
  (display (_ "
  -h, --help             display this help and exit"))
  (display (_ "
  -V, --version          display version information and exit"))
  (newline)
  (show-bug-report-information))



;;;
;;; Entry point.
;;;

(define n-par-map*
  ;; We want the ability to run many threads in parallel, regardless of the
  ;; number of cores.  However, Guile 2.0.5 has a bug whereby 'n-par-map' ends
  ;; up consuming a lot of memory, possibly leading to death.  Thus, resort to
  ;; 'par-map' on 2.0.5.
  (if (guile-version>? "2.0.5")
      n-par-map
      (lambda (n proc lst)
        (par-map proc lst))))

(define (guix-substitute-binary . args)
  "Implement the build daemon's substituter protocol."
  (mkdir-p %narinfo-cache-directory)
  (maybe-remove-expired-cached-narinfo)

  ;; Starting from commit 22144afa in Nix, we are allowed to bail out directly
  ;; when we know we cannot substitute, but we must emit a newline on stdout
  ;; when everything is alright.
  (let ((uri (string->uri %cache-url)))
    (case (uri-scheme uri)
      ((http)
       ;; Exit gracefully if there's no network access.
       (let ((host (uri-host uri)))
         (catch 'getaddrinfo-error
           (lambda ()
             (getaddrinfo host))
           (lambda (key error)
             (warning (_ "failed to look up host '~a' (~a), \
substituter disabled~%")
                      host (gai-strerror error))
             (exit 0)))))
      (else #t)))

  ;; Say hello (see above.)
  (newline)
  (force-output (current-output-port))

  (with-networking
   (match args
     (("--query")
      (let ((cache (delay (open-cache %cache-url))))
        (let loop ((command (read-line)))
          (or (eof-object? command)
              (begin
                (match (string-tokenize command)
                  (("have" paths ..1)
                   ;; Return the subset of PATHS available in CACHE.
                   (let ((substitutable
                          (if cache
                              (n-par-map* %lookup-threads
                                          (cut lookup-narinfo cache <>)
                                          paths)
                              '())))
                     (for-each (lambda (narinfo)
                                 (when narinfo
                                   (format #t "~a~%" (narinfo-path narinfo))))
                               (filter narinfo? substitutable))
                     (newline)))
                  (("info" paths ..1)
                   ;; Reply info about PATHS if it's in CACHE.
                   (let ((substitutable
                          (if cache
                              (n-par-map* %lookup-threads
                                          (cut lookup-narinfo cache <>)
                                          paths)
                              '())))
                     (for-each (lambda (narinfo)
                                 (format #t "~a\n~a\n~a\n"
                                         (narinfo-path narinfo)
                                         (or (and=> (narinfo-deriver narinfo)
                                                    (cute string-append
                                                          (%store-prefix) "/"
                                                          <>))
                                             "")
                                         (length (narinfo-references narinfo)))
                                 (for-each (cute format #t "~a/~a~%"
                                                 (%store-prefix) <>)
                                           (narinfo-references narinfo))
                                 (format #t "~a\n~a\n"
                                         (or (narinfo-file-size narinfo) 0)
                                         (or (narinfo-size narinfo) 0)))
                               (filter narinfo? substitutable))
                     (newline)))
                  (wtf
                   (error "unknown `--query' command" wtf)))
                (loop (read-line)))))))
     (("--substitute" store-path destination)
      ;; Download STORE-PATH and add store it as a Nar in file DESTINATION.
      (let* ((cache   (delay (open-cache %cache-url)))
             (narinfo (lookup-narinfo cache store-path))
             (uri     (narinfo-uri narinfo)))
        ;; Tell the daemon what the expected hash of the Nar itself is.
        (format #t "~a~%" (narinfo-hash narinfo))

        (format (current-error-port) "downloading `~a' from `~a'~:[~*~; (~,1f MiB installed)~]...~%"
                store-path (uri->string uri)

                ;; Use the Nar size as an estimate of the installed size.
                (narinfo-size narinfo)
                (and=> (narinfo-size narinfo)
                       (cute / <> (expt 2. 20))))
        (let*-values (((raw download-size)
                       ;; Note that Hydra currently generates Nars on the fly
                       ;; and doesn't specify a Content-Length, so
                       ;; DOWNLOAD-SIZE is #f in practice.
                       (fetch uri #:buffered? #f #:timeout? #f))
                      ((progress)
                       (let* ((comp     (narinfo-compression narinfo))
                              (dl-size  (or download-size
                                            (and (equal? comp "none")
                                                 (narinfo-size narinfo))))
                              (progress (progress-proc (uri-abbreviation uri)
                                                       dl-size
                                                       (current-error-port))))
                         (progress-report-port progress raw)))
                      ((input pids)
                       (decompressed-port (narinfo-compression narinfo)
                                          progress)))
          ;; Unpack the Nar at INPUT into DESTINATION.
          (restore-file input destination)
          (every (compose zero? cdr waitpid) pids))))
     (("--version")
      (show-version-and-exit "guix substitute-binary"))
     (("--help")
      (show-help))
     (opts
      (leave (_ "~a: unrecognized options~%") opts)))))


;;; Local Variables:
;;; eval: (put 'with-timeout 'scheme-indent-function 1)
;;; End:

;;; substitute-binary.scm ends here