(define-module (guix-build-coordinator utils)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-11)
  #:use-module (srfi srfi-19)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-60)
  #:use-module (ice-9 q)
  #:use-module (ice-9 ftw)
  #:use-module (ice-9 popen)
  #:use-module (ice-9 iconv)
  #:use-module (ice-9 match)
  #:use-module (ice-9 format)
  #:use-module (ice-9 threads)
  #:use-module (ice-9 textual-ports)
  #:use-module (ice-9 rdelim)
  #:use-module (ice-9 binary-ports)
  #:use-module (ice-9 suspendable-ports)
  #:use-module ((ice-9 ports internal) #:select (port-poll))
  #:use-module (ice-9 exceptions)
  #:use-module (rnrs bytevectors)
  #:use-module (web uri)
  #:use-module (web http)
  #:use-module (web client)
  #:use-module (web request)
  #:use-module (web response)
  #:use-module (gcrypt pk-crypto)
  #:use-module (gcrypt hash)
  #:use-module (gcrypt random)
  #:use-module (json)
  #:use-module (prometheus)
  #:use-module (guix pki)
  #:use-module (guix utils)
  #:use-module (guix config)
  #:use-module (guix store)
  #:use-module (guix status)
  #:use-module (guix base64)
  #:use-module (guix progress)
  #:use-module (guix derivations)
  #:use-module ((guix http-client)
                #:select (http-fetch))
  #:use-module (guix serialization)
  #:use-module ((guix build syscalls)
                #:select (set-thread-name))
  #:use-module (guix scripts substitute)
  #:export (random-v4-uuid

            &port-timeout
            &port-read-timeout
            &port-write-timeout

            port-timeout-error?
            port-read-timeout-error?
            port-write-timeout-error?

            with-port-timeouts

            request-query-parameters

            call-with-streaming-http-request

            find-missing-substitutes-for-output
            has-substiutes-no-cache?

            read-derivation-from-file*

            non-blocking-port
            ensure-non-blocking-store-connection
            with-store/non-blocking

            substitute-derivation
            read-derivation-through-substitutes

            narinfo-string

            retry-on-error

            s3-list-objects
            s3-cp

            log-delay
            call-with-delay-logging

            with-time-logging

            create-work-queue
            create-thread-pool

            with-timeout
            reset-timeout

            throttle

            get-load-average
            get-uptime

            running-on-the-hurd?

            get-guix-memory-metrics-updater

            open-socket-for-uri*

            check-locale!))

(eval-when (eval load compile)
  (begin
    (when (defined? 'narinfo-references (resolve-module '(guix narinfo)))
      ;; This module contains narinfo-references in newer version of Guix
      (use-modules (guix narinfo)))

    (when (defined? 'lookup-narinfos (resolve-module '(guix substitutes)))
      ;; This module may contain lookup-narinfos in newer version of Guix
      (use-modules (guix substitutes)))))

(define (random-v4-uuid)
  ;; https://tools.ietf.org/html/rfc4122#page-14
  ;;
  ;; The pattern in characters is: 8, 4, 4, 4, 12
  ;; The pattern in bytes is:      4, 2, 2, 2, 6
  ;;
  ;; time-low "-" time-mid "-" time-high-and-version "-"
  ;;   clock-seq-and-reserved clock-seq-low "-" node
  ;;
  ;; - Set the two most significant bits (bits 6 and 7) of the
  ;;   clock_seq_hi_and_reserved to zero and one, respectively.
  ;; - Set the four most significant bits (bits 12 through 15) of the
  ;;   time_hi_and_version field to the 4-bit version number from
  ;;   Section 4.1.3.

  (let* ((bytes 16)
         (bv (gen-random-bv bytes)))

    (let ((version 4)
          (6th-byte (array-ref bv 6))   ; Most significant byte in
                                        ; time_hi_and_version
          (8th-byte (array-ref bv 8)))  ; Most significant byte in
                                        ; clock_seq_hi_and_reserved

      (array-set!
       bv
       (logior (logand #b00001111 6th-byte)
               (rotate-bit-field version 4 0 8))
       6)

      (array-set!
       bv
       ;; Set bits 6 and 7 to 0 and 1 respectively
       (logior #b10000000
               (logand #b00111111
                       8th-byte))
       8))

    (let* ((int
            (bytevector-uint-ref bv 0 (endianness big) bytes))
           (hex-string
            (format #f "~32,'0x" int)))
      (string-join
       (fold (lambda (part-length result)
               (let ((start (string-length
                             (string-join result ""))))
                 (append
                  result
                  (list (substring hex-string
                                   start
                                   (+ start part-length))))))
             '()
             (list 8 4 4 4 12))
       "-"))))


(define (request-query-parameters request)
  (define (parse-query-string query)
    "Parse and decode the URI query string QUERY and return an alist."
    (let lp ((lst (map uri-decode (string-split query (char-set #\& #\=)))))
      (match lst
        ((key value . rest)
         (cons (cons key value) (lp rest)))
        (("") '())
        (() '()))))

  (let ((query (uri-query (request-uri request))))
    (if (and query
             (not (string-null? query)))
        (map (match-lambda
               ((name . value)
                (cons (string->symbol name)
                      value)))
             (parse-query-string query))
        '())))

(define &port-timeout
  (make-exception-type '&port-timeout
                       &external-error
                       '(port)))

(define make-port-timeout-error
  (record-constructor &port-timeout))

(define port-timeout-error?
  (record-predicate &port-timeout))

(define &port-read-timeout
  (make-exception-type '&port-read-timeout
                       &port-timeout
                       '()))

(define make-port-read-timeout-error
  (record-constructor &port-read-timeout))

(define port-read-timeout-error?
  (record-predicate &port-read-timeout))

(define &port-write-timeout
  (make-exception-type '&port-write-timeout
                       &port-timeout
                       '()))

(define make-port-write-timeout-error
  (record-constructor &port-write-timeout))

(define port-write-timeout-error?
  (record-predicate &port-write-timeout))

(define* (with-port-timeouts thunk #:key (timeout (* 120 1000)))

  ;; When the GC runs, it restarts the poll syscall, but the timeout remains
  ;; unchanged! When the timeout is longer than the time between the syscall
  ;; restarting, I think this renders the timeout useless. Therefore, this
  ;; code uses a short timeout, and repeatedly calls poll while watching the
  ;; clock to see if it has timed out overall.
  (define poll-timeout-ms 200)

  (define (wait port mode)
    (let ((timeout-internal
           (+ (get-internal-real-time)
              (* internal-time-units-per-second
                 (/ timeout 1000)))))
      (let loop ((poll-value
                  (port-poll port mode poll-timeout-ms)))
        (if (= poll-value 0)
            (if (> (get-internal-real-time)
                   timeout-internal)
                (raise-exception
                 (if (string=? mode "r")
                     (make-port-read-timeout-error port)
                     (make-port-write-timeout-error port)))
                (loop (port-poll port mode poll-timeout-ms)))
            poll-value))))

  (parameterize
      ((current-read-waiter
        (lambda (port)
          (wait port "r")))
       (current-write-waiter
        (lambda (port)
          (wait port "w"))))
    (thunk)))

(define* (call-with-streaming-http-request uri
                                           content-length
                                           callback
                                           #:key (headers '())
                                           (method 'PUT)
                                           streaming?)
  (with-port-timeouts
   (lambda ()
     (let* ((port (open-socket-for-uri* uri))
            (request
             (build-request
              uri
              #:method method
              #:version '(1 . 1)
              #:headers `((connection close)
                          (content-length . ,content-length)
                          (Content-Type . "application/octet-stream")
                          ;; read-request-body/patch looks for this header
                          (Stream-Body . "true")
                          ,@headers)
              #:port port)))

       (set-port-encoding! port "ISO-8859-1")
       (setvbuf port 'block (expt 2 13))
       (with-exception-handler
           (lambda (exp)
             (simple-format #t "error: ~A ~A: ~A\n"
                            method (uri-path uri) exp)
             (close-port port)
             (raise-exception exp))
         (lambda ()
           (let ((request (write-request request port)))
             (callback port)
             (force-output port)

             (let ((response (read-response port)))
               (if streaming?
                   (values response
                           (response-body-port response))
                   (let ((body (read-response-body response)))
                     (close-port port)
                     (values response
                             body)))))))))))

(define (find-missing-substitutes-for-output store substitute-urls output)
  (if (valid-path? store output)
      '()
      (let ((narinfo
             (any (lambda (substitute-url)
                    (let ((result (lookup-narinfos substitute-url (list output))))
                      (if (null? result)
                          #f
                          (first result))))
                  substitute-urls)))
        (if narinfo
            (append-map
             (lambda (reference)
               (let ((referenced-output
                      (string-append (%store-prefix) "/" reference)))
                 (if (string=? referenced-output output)
                     '()
                     (find-missing-substitutes-for-output store
                                                          substitute-urls
                                                          referenced-output))))
             (narinfo-references narinfo))
            (list output)))))

;; Work around Guix holding on to broken connections to substitute servers
;; (because of mishandling gnutls errors).
(let ((mod (resolve-module '(guix scripts substitute))))
  (when (module-variable mod '%max-cached-connections)
    (module-set! mod '%max-cached-connections 0)))

(define (has-substiutes-no-cache? substitute-urls file)
  (define %narinfo-cache-directory
    (if (zero? (getuid))
        (or (and=> (getenv "XDG_CACHE_HOME")
                   (cut string-append <> "/guix/substitute"))
            (string-append %state-directory "/substitute/cache"))
        (string-append (cache-directory #:ensure? #f) "/substitute")))

  ;; Because there's no control over the caching of 404 lookups, and I'd
  ;; rather not reach inside and monkey patch the Guix code, just delete any
  ;; cache files
  (let ((hash-part (store-path-hash-part file))
        (directories
         (scandir %narinfo-cache-directory
                  (lambda (s) (= (string-length s) 52)))))

    (for-each (lambda (directory)
                (let ((cache-file
                       (string-append
                        %narinfo-cache-directory "/"
                        directory "/" hash-part)))
                  ;; Use monitor to avoid multiple threads trying to delete
                  ;; the same file at the same time
                  (monitor
                   (when (file-exists? cache-file)
                     (with-exception-handler
                         (lambda (exn)
                           (simple-format
                            (current-error-port)
                            "error: when deleting substitute cache file: ~A\n"
                            exn))
                       (lambda ()
                         (delete-file cache-file))
                       #:unwind? #t)))))
              (or directories '())))

  (let ((substitute-urls
         (append-map (lambda (substitute-url)
                       (let ((log-port (open-output-string)))
                         (with-throw-handler #t
                           (lambda ()
                             (if (null?
                                  ;; I doubt the caching is thread safe, so
                                  ;; only make one request at a time.
                                  (monitor
                                   (parameterize ((current-error-port log-port))
                                     (lookup-narinfos substitute-url
                                                      (list file)))))
                                 '()
                                 (list substitute-url)))
                           (lambda (key . args)
                             (simple-format
                              (current-error-port)
                              "exception in has-substiutes-no-cache? (~A) ~A: ~A\n"
                              substitute-url key args)
                             (display (string-append
                                       (get-output-string log-port)
                                       "\n")
                                      (current-error-port))
                             (close-output-port log-port)))))
                     substitute-urls)))
    substitute-urls))

(define (non-blocking-port port)
  "Make PORT non-blocking and return it."
  (let ((flags (fcntl port F_GETFL)))
    (when (zero? (logand O_NONBLOCK flags))
      (fcntl port F_SETFL (logior O_NONBLOCK flags)))
    port))

(define (ensure-non-blocking-store-connection store)
  "Mark the file descriptor that backs STORE, a <store-connection>, as
O_NONBLOCK."
  (match (store-connection-socket store)
    ((? file-port? port)
     (non-blocking-port port))
    (_ #f)))

(define-syntax-rule (with-store/non-blocking store exp ...)
  "Like 'with-store', bind STORE to a connection to the store, but ensure that
said connection is non-blocking (O_NONBLOCK).  Evaluate EXP... in that
context."
  (with-store store
    (ensure-non-blocking-store-connection store)
    (let ()
      exp ...)))

(define* (substitute-derivation store
                                derivation-name
                                #:key substitute-urls)
  (let ((log-port (open-output-string)))
    (apply set-build-options
           store
           `(,@(if substitute-urls
                   `(#:substitute-urls ,substitute-urls)
                   '())
             #:max-silent-time 60
             #:timeout ,(* 10 60)))

    (with-exception-handler
        (lambda (exn)
          (let* ((log-string
                  (get-output-string log-port))
                 (lines
                  (string-split log-string #\newline))
                 (last-n-lines
                  (if (< 10 (length lines))
                      (take-right lines 10)
                      lines)))
            (close-output-port log-port)
            (simple-format
             (current-error-port)
             "exception when substituting derivation: ~A:\n  ~A\n"
             exn (string-join last-n-lines "\n"))
            (raise-exception exn)))
      (lambda ()
        (parameterize ((current-build-output-port log-port))
          (ensure-path store derivation-name)))
      #:unwind? #t)))

(define read-derivation-from-file*
  (let ((%derivation-cache
         (@@ (guix derivations) %derivation-cache)))
    (lambda (file)
      (or (and file (hash-ref %derivation-cache file))
          (let ((drv
                 ;; read-derivation can call read-derivation-from-file, so to
                 ;; avoid having many open files when reading a derivation with
                 ;; inputs, read it in to a string first.
                 (call-with-input-string
                     ;; Avoid calling scm_i_relativize_path in
                     ;; fport_canonicalize_filename since this leads to lots
                     ;; of readlink calls
                     (with-fluids ((%file-port-name-canonicalization 'none))
                       (call-with-input-file file
                         get-string-all))
                   (lambda (port)
                     (set-port-filename! port file)
                     (read-derivation port read-derivation-from-file*)))))
            (hash-set! %derivation-cache file drv)
            drv)))))

(define (read-derivation-through-substitutes derivation-name
                                             substitute-urls)
  (define %fetch-timeout
    5)

  (define open-connection-for-uri/cached
    (let ((cache '()))
      (lambda* (uri #:key fresh? (timeout %fetch-timeout) verify-certificate?)
        (define host (uri-host uri))
        (define scheme (uri-scheme uri))
        (define key (list host scheme (uri-port uri)))

        (and (not (memq scheme '(file #f)))
             (match (assoc-ref cache key)
               (#f
                (let ((socket
                       (open-socket-for-uri*
                        uri
                        #:verify-certificate? verify-certificate?)))
                  (set! cache (alist-cons key socket cache))
                  socket))
               (socket
                (if (or fresh? (port-closed? socket))
                    (begin
                      (false-if-exception (close-port socket))
                      (set! cache (alist-delete key cache))
                      (open-connection-for-uri/cached uri #:timeout timeout
                                                      #:verify-certificate?
                                                      verify-certificate?))
                    (begin
                      ;; Drain input left from the previous use.
                      (drain-input socket)
                      socket))))))))

  (define (derivation-name->bytevector derivation-name)
    (let ((narinfo
           (any (lambda (substitute-url)
                  (let ((result (lookup-narinfos substitute-url
                                                 (list derivation-name)
                                                 #:open-connection
                                                 open-connection-for-uri/cached)))
                    (if (null? result)
                        #f
                        (first result))))
                substitute-urls)))
      (if narinfo
          (let*-values (((uri compression file-size)
                         (narinfo-best-uri narinfo))
                        ((raw download-size)
                         (http-fetch
                          (first (narinfo-uris narinfo))
                          #:open-connection open-connection-for-uri/cached
                          #:keep-alive? #t))
                        ((progress)
                         (let* ((dl-size  (or download-size
                                              (and (equal? compression "none")
                                                   (narinfo-size narinfo)))))
                           ;; Keep RAW open upon completion so we can later
                           ;; reuse the underlying connection.  Pass the
                           ;; download size so that this procedure won't block
                           ;; reading from RAW.
                           (progress-report-port progress-reporter/silent
                                                 raw
                                                 #:close? #f
                                                 #:download-size dl-size)))
                        ((input pids)
                         ;; NOTE: This 'progress' port of current process will be
                         ;; closed here, while the child process doing the
                         ;; reporting will close it upon exit.
                         (decompressed-port (string->symbol compression)
                                            progress)))

            ;; The decompressor can be an external program, so wait for it to
            ;; exit
            (every (compose zero? cdr waitpid) pids)

            (fold-archive (lambda (file type contents result)
                            (match contents
                              ((port . bytes)
                               (get-bytevector-n port bytes))))
                          #f
                          input
                          #f))
          (error "could not fetch narinfo"))))

  (define (read-derivation-from-file/custom derivation-name)
    ;; Try the local store
    (or (and (file-exists? derivation-name)
             (with-store/non-blocking
              store
              (valid-path? store derivation-name))
             (read-derivation-from-file* derivation-name))

        ;; Otherwise try the network
        (call-with-input-bytevector
         (derivation-name->bytevector derivation-name)
         (lambda (port)
           (set-port-filename! port derivation-name)
           (read-derivation port
                            read-derivation-from-file/custom)))))

  (read-derivation-from-file/custom derivation-name))

(define* (narinfo-string store-path hash size references
                         compressed-files
                         #:key (nar-path "nar")
                         system derivation
                         public-key private-key)
  (define (signed-string s)
    (let* ((hash (bytevector->hash-data (sha256 (string->utf8 s))
                                        #:key-type (key-type public-key))))
      (signature-sexp hash private-key public-key)))

  (define base64-encode-string
    (compose base64-encode string->utf8))

  (define* (store-item->recutils compression file-size)
    (let ((url (encode-and-join-uri-path
                `(,@(split-and-decode-uri-path nar-path)
                  ,@(if compression
                        (list (symbol->string compression))
                        '())
                  ,(basename store-path)))))
      (format #f "URL: ~a~%Compression: ~a~%~@[FileSize: ~a~%~]"
              url
              (or compression "none")
              file-size)))

  (let* ((base-info  (format #f
                             "\
StorePath: ~a
NarHash: sha256:~a
NarSize: ~d
References: ~a~%"
                             store-path
                             hash
                             size
                             (string-join references " ")))
         ;; Do not render a "Deriver" or "System" line if we are rendering
         ;; info for a derivation.
         (info       (if derivation
                         (format #f "~aSystem: ~a~%Deriver: ~a~%"
                                 base-info
                                 system
                                 (basename derivation))
                         base-info))
         (signature  (base64-encode-string
                      (canonical-sexp->string (signed-string info)))))
    (format #f "~aSignature: 1;~a;~a~%~{~a~}"
            info
            (gethostname)
            signature
            (map (match-lambda
                   ((compression compressed-size)
                    (store-item->recutils compression
                                          compressed-size)))
                 compressed-files))))

(define* (retry-on-error f #:key times delay ignore no-retry error-hook
                         (sleep-impl sleep))
  (let loop ((attempt 1))
    (match (with-exception-handler
               (lambda (exn)
                 (if (cond
                      ((list? ignore)
                       (any (lambda (test)
                              (test exn))
                            ignore))
                      ((procedure? ignore)
                       (ignore exn))
                      (else #f))
                     `(#t . (,exn))
                     (begin
                       (when (cond
                              ((list? no-retry)
                               (any (lambda (test)
                                      (test exn))
                                    no-retry))
                              ((procedure? no-retry)
                               (no-retry exn))
                              (else #f))
                         (raise-exception exn))

                       (cons #f exn))))
             (lambda ()
               (call-with-values f
                 (lambda vals
                   (cons #t vals))))
             #:unwind? #t)
      ((#t . return-values)
       (when (> attempt 1)
         (simple-format
          (current-error-port)
          "retry success: ~A\n  on attempt ~A of ~A\n"
          f
          attempt
          times))
       (apply values return-values))
      ((#f . exn)
       (if (>= attempt
               (- times 1))
           (begin
             (simple-format
              (current-error-port)
              "error: ~A:\n  ~A,\n  attempt ~A of ~A, last retry in ~A\n"
              f
              exn
              attempt
              times
              delay)
             (when error-hook
               (error-hook attempt exn))
             (sleep-impl delay)
             (simple-format
              (current-error-port)
              "running last retry of ~A after ~A failed attempts\n"
              f
              attempt)
             (f))
           (begin
             (simple-format
              (current-error-port)
              "error: ~A:\n  ~A,\n  attempt ~A of ~A, retrying in ~A\n"
              f
              exn
              attempt
              times
              delay)
             (when error-hook
               (error-hook attempt exn))
             (sleep-impl delay)
             (loop (+ 1 attempt))))))))

(define* (s3-list-objects s3-bucket prefix
                          #:key
                          (command "aws")
                          (command-line-arguments '()))
  (let ((command
         `(,command
           "s3api"
           ,@command-line-arguments
           "list-objects"
           "--bucket" ,s3-bucket
           "--prefix" ,prefix)))
    (simple-format
     #t
     "running: ~A\n"
     (string-join command))
    (let ((pipe (apply open-pipe*
                       OPEN_READ
                       command)))

      (let ((output    (get-string-all pipe))
            (exit-code (status:exit-val
                        (close-pipe pipe))))
        (if (zero? exit-code)
            (if (string-null? output)
                '()
                (json-string->scm output))
            (raise-exception
             (make-exception-with-message
              output)))))))

(define* (s3-cp s3-bucket source destination
                #:key
                (command "aws")
                (command-line-arguments '()))
  (let ((command
         `(,command
           "s3"
           ,@command-line-arguments
           "cp"
           ,source
           ,(simple-format #f "s3://~A/~A"
                           s3-bucket destination))))
    (simple-format
     #t
     "running: ~A\n"
     (string-join command))
    (let ((exit-code
           (status:exit-val
            (apply system* command))))
      (unless (zero? exit-code)
        (raise-exception
         (make-exception-with-message
          (simple-format
           #f
           "error: command failed (~A): ~A\n"
           exit-code
           command))))
      #t)))

(define delay-logging-fluid
  (make-thread-local-fluid))
(define delay-logging-depth-fluid
  (make-thread-local-fluid 0))

(define (log-delay proc duration)
  (and=> (fluid-ref delay-logging-fluid)
         (lambda (recorder)
           (recorder proc duration))))

(define* (call-with-delay-logging proc #:key (threshold 1) (args '()))
  (let ((start (get-internal-real-time))
        (trace '())
        (root-logger? (eq? #f (fluid-ref delay-logging-fluid))))

    (define (format-seconds seconds)
      (format #f "~5f" seconds))

    (call-with-values
        (lambda ()
          (with-fluid* delay-logging-depth-fluid
            (+ 1 (fluid-ref delay-logging-depth-fluid))
            (lambda ()
              (if root-logger?
                  (with-fluid* delay-logging-fluid
                    (lambda (proc duration)
                      (set! trace
                            (cons (list proc
                                        duration
                                        (fluid-ref delay-logging-depth-fluid))
                                  trace))
                      #t)
                    (lambda ()
                      (apply proc args)))
                  (apply proc args)))))
      (lambda vals
        (let ((elapsed-seconds
               (/ (- (get-internal-real-time)
                     start)
                  internal-time-units-per-second)))
          (if (and (> elapsed-seconds threshold)
                   root-logger?)
              (let ((lines
                     (cons
                      (simple-format #f "warning: delay of ~A seconds: ~A"
                                     (format-seconds elapsed-seconds)
                                     proc)
                      (filter-map
                       (match-lambda
                         ((proc duration depth)
                          (if (>= duration 0.001)
                              (string-append
                               (make-string (* 2 depth) #\space)
                               (simple-format #f "~A: ~A"
                                              (format-seconds duration)
                                              proc))
                              #f)))
                       trace))))
                (display (string-append
                          (string-join lines "\n")
                          "\n")))
              (unless root-logger?
                ((fluid-ref delay-logging-fluid) proc elapsed-seconds))))
        (apply values vals)))))

(define (call-with-time-logging name thunk)
  (let ((start   (current-time time-utc)))
    (call-with-values
        thunk
      (lambda vals
        (let* ((end     (current-time time-utc))
               (elapsed (time-difference end start)))
          (display
           (format #f
                   "~a took ~f seconds~%"
                   name
                   (+ (time-second elapsed)
                      (/ (time-nanosecond elapsed) 1e9))))
          (apply values vals))))))

(define-syntax-rule (with-time-logging name exp ...)
  "Log under NAME the time taken to evaluate EXP."
  (call-with-time-logging name (lambda () exp ...)))

(define* (create-work-queue thread-count-parameter proc
                            #:key thread-start-delay
                            (thread-stop-delay
                             (make-time time-duration 0 0))
                            (name "unnamed")
                            priority<?)
  (let ((queue (make-q))
        (queue-mutex (make-mutex))
        (job-available (make-condition-variable))
        (running-job-args (make-hash-table)))

    (define get-thread-count
      (cond
       ((number? thread-count-parameter)
        (const thread-count-parameter))
       ((eq? thread-count-parameter #f)
        ;; Run one thread per job
        (lambda ()
          (+ (q-length queue)
             (hash-count (lambda (index val)
                           (list? val))
                         running-job-args))))
       (else
        thread-count-parameter)))

    (define process-job
      (if priority<?
          (lambda* (args #:key priority)
            (with-mutex queue-mutex
              (enq! queue (cons priority args))
              (set-car!
               queue
               (stable-sort! (car queue)
                             (lambda (a b)
                               (priority<?
                                (car a)
                                (car b)))))
              (sync-q! queue)
              (start-new-threads-if-necessary (get-thread-count))
              (signal-condition-variable job-available)))
          (lambda args
            (with-mutex queue-mutex
              (enq! queue args)
              (start-new-threads-if-necessary (get-thread-count))
              (signal-condition-variable job-available)))))

    (define (count-threads)
      (with-mutex queue-mutex
        (hash-count (const #t) running-job-args)))

    (define (count-jobs)
      (with-mutex queue-mutex
        (+ (q-length queue)
           (hash-count (lambda (index val)
                         (list? val))
                       running-job-args))))

    (define (list-jobs)
      (with-mutex queue-mutex
        (append (if priority<?
                    (map cdr (car queue))
                    (list-copy (car queue)))
                (hash-fold (lambda (key val result)
                             (if val
                                 (cons val result)
                                 result))
                           '()
                           running-job-args))))

    (define (thread-process-job job-args)
      (with-exception-handler
          (lambda (exn)
            (simple-format (current-error-port)
                           "~A work queue, job raised exception ~A: ~A\n"
                           name job-args exn))
        (lambda ()
          (with-throw-handler #t
            (lambda ()
              (apply proc job-args))
            (lambda (key . args)
              (simple-format
               (current-error-port)
               "~A work queue, exception when handling job: ~A ~A\n"
               name key args)
              (let* ((stack (make-stack #t 3))
                     (backtrace
                      (call-with-output-string
                        (lambda (port)
                          (display-backtrace stack port)
                          (newline port)))))
                (display
                 backtrace
                 (current-error-port))))))
        #:unwind? #t))

    (define (start-thread thread-index)
      (define (too-many-threads?)
        (let ((running-jobs-count
               (hash-count (lambda (index val)
                             (list? val))
                           running-job-args))
              (desired-thread-count (get-thread-count)))

          (>= running-jobs-count
              desired-thread-count)))

      (define (thread-idle-for-too-long? last-job-finished-at)
        (time>=?
         (time-difference (current-time time-monotonic)
                          last-job-finished-at)
         thread-stop-delay))

      (define (stop-thread)
        (hash-remove! running-job-args
                      thread-index)
        (unlock-mutex queue-mutex))

      (call-with-new-thread
       (lambda ()
         (catch 'system-error
           (lambda ()
             (set-thread-name
              (string-append name " q t "
                             (number->string thread-index))))
           (const #t))

         (let loop ((last-job-finished-at (current-time time-monotonic)))
           (lock-mutex queue-mutex)

           (if (too-many-threads?)
               (stop-thread)
               (let ((job-args
                      (if (q-empty? queue)
                          ;; #f from wait-condition-variable indicates a timeout
                          (if (wait-condition-variable
                               job-available
                               queue-mutex)
                              ;; Another thread could have taken
                              ;; the job in the mean time
                              (if (q-empty? queue)
                                  #f
                                  (if priority<?
                                      (cdr (deq! queue))
                                      (deq! queue)))
                              #f)
                          (if priority<?
                              (cdr (deq! queue))
                              (deq! queue)))))

                 (if job-args
                     (begin
                       (hash-set! running-job-args
                                  thread-index
                                  job-args)

                       (unlock-mutex queue-mutex)
                       (thread-process-job job-args)

                       (with-mutex queue-mutex
                         (hash-set! running-job-args
                                    thread-index
                                    #f))

                       (loop (current-time time-monotonic)))
                     (if (thread-idle-for-too-long? last-job-finished-at)
                         (stop-thread)
                         (begin
                           (unlock-mutex queue-mutex)

                           (loop last-job-finished-at))))))))))


    (define start-new-threads-if-necessary
      (let ((previous-thread-started-at (make-time time-monotonic 0 0)))
        (lambda (desired-count)
          (let* ((thread-count
                  (hash-count (const #t) running-job-args))
                 (threads-to-start
                  (- desired-count thread-count)))
            (when (> threads-to-start 0)
              (for-each
               (lambda (thread-index)
                 (when (eq? (hash-ref running-job-args
                                      thread-index
                                      'slot-free)
                            'slot-free)
                   (let* ((now     (current-time time-monotonic))
                          (elapsed (time-difference now
                                                    previous-thread-started-at)))
                     (when (or (eq? #f thread-start-delay)
                               (time>=? elapsed thread-start-delay))
                       (set! previous-thread-started-at now)
                       (hash-set! running-job-args
                                  thread-index
                                  #f)
                       (start-thread thread-index)))))
               (iota desired-count)))))))

    (if (procedure? thread-count-parameter)
        (call-with-new-thread
         (lambda ()
           (catch 'system-error
             (lambda ()
               (set-thread-name
                (string-append name " q t")))
             (const #t))

           (while #t
             (sleep 15)
             (with-mutex queue-mutex
               (let ((idle-threads (hash-count (lambda (index val)
                                                 (eq? #f val))
                                               running-job-args)))
                 (when (= 0 idle-threads)
                   (start-new-threads-if-necessary (get-thread-count))))))))
        (start-new-threads-if-necessary (get-thread-count)))

    (values process-job count-jobs count-threads list-jobs)))

(define* (create-thread-pool thread-count-parameter get-job proc
                             #:key thread-start-delay
                             (thread-stop-delay
                              (make-time time-duration 0 0))
                             (name "unnamed"))
  (let ((pool-mutex (make-mutex))
        (job-available (make-condition-variable))
        (running-job-args (make-hash-table)))

    (define get-thread-count
      (cond
       ((number? thread-count-parameter)
        (const thread-count-parameter))
       (else
        (lambda ()
          (with-exception-handler
              (lambda (exn)
                (count-threads))
            thread-count-parameter
            #:unwind? #t)))))

    (define (get-job/safe running-jobs)
      (with-exception-handler
          (lambda (exn)
            #f)
        (lambda ()
          (get-job running-jobs))
        #:unwind? #t))

    (define (count-threads)
      (hash-count (const #t) running-job-args))

    (define (list-jobs)
      (append (hash-fold (lambda (key val result)
                           (or (and val
                                    (cons val result))
                               result))
                         '()
                         running-job-args)))

    (define (thread-process-job job-args)
      (with-exception-handler
          (lambda (exn)
            (with-exception-handler
                (lambda _
                  #f)
              (lambda ()
                ;; Logging may raise an exception, so try and just keep going.
                (display
                 (simple-format
                  #f
                  "~A thread pool, job raised exception ~A: ~A\n"
                  name job-args exn)
                 (current-error-port)))
              #:unwind? #t))
        (lambda ()
          (with-throw-handler #t
            (lambda ()
              (apply proc job-args))
            (lambda (key . args)
              (simple-format
               (current-error-port)
               "~A thread pool, exception when handling job: ~A ~A\n"
               name key args)
              (let* ((stack (make-stack #t 3))
                     (backtrace
                      (call-with-output-string
                        (lambda (port)
                          (display-backtrace stack port)
                          (newline port)))))
                (display
                 backtrace
                 (current-error-port))))))
        #:unwind? #t))

    (define (start-thread thread-index)
      (define (too-many-threads?)
        (let ((running-jobs-count
               (hash-count (lambda (index val)
                             (list? val))
                           running-job-args))
              (desired-thread-count (get-thread-count)))

          (>= running-jobs-count
              desired-thread-count)))

      (define (thread-idle-for-too-long? last-job-finished-at)
        (time>=?
         (time-difference (current-time time-monotonic)
                          last-job-finished-at)
         thread-stop-delay))

      (define (stop-thread)
        (hash-remove! running-job-args
                      thread-index)
        (unlock-mutex pool-mutex))

      (call-with-new-thread
       (lambda ()
         (catch 'system-error
           (lambda ()
             (set-thread-name
              (string-append name " p t "
                             (number->string thread-index))))
           (const #t))

         (let loop ((last-job-finished-at (current-time time-monotonic)))
           (lock-mutex pool-mutex)

           (hash-set! running-job-args
                      thread-index
                      #f)

           (let ((job-args
                  (or (get-job/safe (list-jobs))
                      ;; #f from wait-condition-variable indicates a timeout
                      (if (wait-condition-variable
                           job-available
                           pool-mutex)
                          (get-job/safe (list-jobs))
                          #f))))
             (if job-args
                 (begin
                   (hash-set! running-job-args
                              thread-index
                              job-args)

                   (unlock-mutex pool-mutex)
                   (thread-process-job job-args)

                   (loop (current-time time-monotonic)))
                 (if (or (thread-idle-for-too-long? last-job-finished-at)
                         (too-many-threads?))
                     (stop-thread)
                     (begin
                       (unlock-mutex pool-mutex)

                       (loop last-job-finished-at)))))))))

    (define start-new-threads-if-necessary
      (let ((previous-thread-started-at (make-time time-monotonic 0 0)))
        (lambda (desired-count)
            (let* ((thread-count
                    (hash-count (const #t) running-job-args))
                   (threads-to-start
                    (- desired-count thread-count)))
              (when (> threads-to-start 0)
                (for-each
                 (lambda (thread-index)
                   (when (eq? (hash-ref running-job-args
                                        thread-index
                                        'slot-free)
                              'slot-free)
                     (let* ((now     (current-time time-monotonic))
                            (elapsed (time-difference now
                                                      previous-thread-started-at)))
                       (when (or (eq? #f thread-start-delay)
                                 (time>=? elapsed thread-start-delay))
                         (set! previous-thread-started-at now)
                         (hash-set! running-job-args
                                    thread-index
                                    #f)
                         (start-thread thread-index)))))
                 (iota desired-count)))))))

    (if (procedure? thread-count-parameter)
        (call-with-new-thread
         (lambda ()
           (catch 'system-error
             (lambda ()
               (set-thread-name
                (string-append name " p t ")))
             (const #t))

           (lock-mutex pool-mutex)
           (while #t
             (with-exception-handler
                 (lambda _
                   ;; Things are going really wrong, we probably can't even
                   ;; log without risking another exception, so just sleep and
                   ;; try again.
                   (sleep 10))
               (lambda ()
                 (let ((idle-threads (hash-count (lambda (index val)
                                                   (eq? #f val))
                                                 running-job-args)))
                   (when (= 0 idle-threads)
                     (start-new-threads-if-necessary (get-thread-count))))

                 ;; Wake a worker thread to check if a job is available
                 (signal-condition-variable job-available)

                 (wait-condition-variable
                  job-available
                  pool-mutex))
               #:unwind? #t))))

        (start-new-threads-if-necessary (get-thread-count)))

    (values pool-mutex job-available count-threads list-jobs)))

;; copied from (guix scripts substitute)
(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 ()
          body ...)
      (lambda result
        (alarm 0)
        (sigaction SIGALRM SIG_DFL)
        (apply values result)))))

(define (reset-timeout duration)
  (alarm duration))

(define (throttle min-duration thunk)
  (let ((next-min-runtime 0))
    (lambda ()
      (if (> (get-internal-real-time)
             next-min-runtime)
          (begin
            (set! next-min-runtime
                  (+ (get-internal-real-time)
                     (* min-duration internal-time-units-per-second)))
            (thunk))
          #f))))

(define* (get-load-average #:key (period 5))
  (if (file-exists? "/proc/loadavg")
      (let ((line (call-with-input-file "/proc/loadavg" get-line)))
        (match (string-split line #\space)
          ((1min 5min 15min _ _)
           (string->number
            (cond
             ((= period 1) 1min)
             ((= period 5) 5min)
             ((= period 15) 15min))))))
      #f))

(define (get-uptime)
  (if (file-exists? "/proc/uptime")
      (let ((line (call-with-input-file "/proc/uptime" get-line)))
        (match (string-split line #\space)
          ((uptime _)
           (string->number uptime))))
      #f))

(define (running-on-the-hurd?)
  (let ((cached-system #f))
    (unless cached-system
      (set! cached-system (utsname:sysname (uname))))
    (string=? cached-system "GNU")))

(define (get-guix-memory-metrics-updater registry)
  (define %memoization-tables
    (@@ (guix memoization) %memoization-tables))

  (define memoization-table-entry-count-metric
    (make-gauge-metric
     registry "guix_memoization_table_entry_count"
     #:labels '(procedure)))

  (define %derivation-cache
    (@@ (guix derivations) %derivation-cache))

  (define derivation-cache-entry-count-metric
    (make-gauge-metric
     registry "guix_derivation_cache_entry_count"))

  (lambda ()
    (metric-set
     derivation-cache-entry-count-metric
     ;; hash-count doesn't work for weak tables?
     (hash-fold (lambda (k v result)
                  (+ 1 result))
                0
                %derivation-cache))

    (hash-for-each
     (lambda (proc table)
       (metric-set
        memoization-table-entry-count-metric
        (hash-count (const #t) table)
        #:label-values `((procedure . ,(simple-format
                                        #f "~A"
                                        proc)))))
     %memoization-tables)))

;; Returns the port as well as the raw socket
(define* (open-socket-for-uri* uri
                               #:key (verify-certificate? #t)
                               (non-blocking? #t))
  (define tls-wrap
    (@@ (web client) tls-wrap))

  (define https?
    (eq? 'https (uri-scheme uri)))

  (define plain-uri
    (if https?
        (build-uri
         'http
         #:userinfo (uri-userinfo uri)
         #:host (uri-host uri)
         #:port (or (uri-port uri) 443)
         #:path (uri-path uri)
         #:query (uri-query uri)
         #:fragment (uri-fragment uri))
        uri))

  (let* ((s (open-socket-for-uri plain-uri))
         (port
          (if https?
              (tls-wrap s (uri-host uri)
                        #:verify-certificate? verify-certificate?)
              s)))
    (values port
            (if non-blocking?
                ;; Guile/guile-gnutls don't handle the handshake happening on
                ;; a non blocking socket, so change the behavior here.
                (non-blocking-port s)
                s))))

(define (check-locale!)
  (with-exception-handler
      (lambda (exn)
        (display
         (simple-format
          #f
          "exception when calling setlocale: ~A
falling back to en_US.utf8\n"
          exn)
         (current-error-port))

        (with-exception-handler
            (lambda (exn)
              (display
               (simple-format
                #f
                "exception when calling setlocale with en_US.utf8: ~A\n"
                exn)
               (current-error-port))

              (exit 1))
          (lambda _
            (setlocale LC_ALL "en_US.utf8"))
          #:unwind? #t))
    (lambda _
      (setlocale LC_ALL ""))
    #:unwind? #t))