Add 'guix processes'.

* guix/scripts/processes.scm, tests/processes.scm: New files.
* Makefile.am (MODULES): Add the former.
(SCM_TESTS): Add the latter.
* po/guix/POTFILES.in: Add guix/scripts/processes.scm.
* doc/guix.texi (Invoking guix processes): New node.
(Invoking guix-daemon): Reference it.

1 files changed, 223 insertions, 0 deletions

diff --git a/guix/scripts/processes.scm b/guix/scripts/processes.scm
new file mode 100644
index 0000000000..6a2f603599
--- /dev/null
+++ b/guix/scripts/processes.scm
@@ -0,0 +1,223 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2018 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 processes)
+  #:use-module ((guix store) #:select (%store-prefix))
+  #:use-module (guix scripts)
+  #:use-module (guix ui)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-9 gnu)
+  #:use-module (srfi srfi-37)
+  #:use-module (ice-9 ftw)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 rdelim)
+  #:use-module (ice-9 format)
+  #:export (process?
+            process-id
+            process-parent-id
+            process-command
+            processes
+
+            daemon-session?
+            daemon-session-process
+            daemon-session-client
+            daemon-session-children
+            daemon-session-locks-held
+            daemon-sessions
+
+            guix-processes))
+
+;; Process as can be found in /proc on GNU/Linux.
+(define-record-type <process>
+  (process id parent command)
+  process?
+  (id       process-id)                           ;integer
+  (parent   process-parent-id)                    ;integer | #f
+  (command  process-command))                     ;list of strings
+
+(define (write-process process port)
+  (format port "#<process ~a>" (process-id process)))
+
+(set-record-type-printer! <process> write-process)
+
+(define (read-status-ppid port)
+  "Read the PPID from PORT, an input port on a /proc/PID/status file.  Return
+#f for PID 1 and kernel pseudo-processes."
+  (let loop ()
+    (match (read-line port)
+      ((? eof-object?) #f)
+      (line
+       (if (string-prefix? "PPid:" line)
+           (string->number (string-trim-both (string-drop line 5)))
+           (loop))))))
+
+(define %not-nul
+  (char-set-complement (char-set #\nul)))
+
+(define (read-command-line port)
+  "Read the zero-split command line from PORT, a /proc/PID/cmdline file, and
+return it as a list."
+  (string-tokenize (read-string port) %not-nul))
+
+(define (processes)
+  "Return a list of process records representing the currently alive
+processes."
+  ;; This assumes a Linux-compatible /proc file system.  There exists one for
+  ;; GNU/Hurd.
+  (filter-map (lambda (pid)
+                ;; There's a TOCTTOU race here.  If we get ENOENT, simply
+                ;; ignore PID.
+                (catch 'system-error
+                  (lambda ()
+                    (define ppid
+                      (call-with-input-file (string-append "/proc/" pid "/status")
+                        read-status-ppid))
+                    (define command
+                      (call-with-input-file (string-append "/proc/" pid "/cmdline")
+                        read-command-line))
+                    (process (string->number pid) ppid command))
+                  (lambda args
+                    (if (= ENOENT (system-error-errno args))
+                        #f
+                        (apply throw args)))))
+              (scandir "/proc" string->number)))
+
+(define (process-open-files process)
+  "Return the list of files currently open by PROCESS."
+  (let ((directory (string-append "/proc/"
+                                  (number->string (process-id process))
+                                  "/fd")))
+    (map (lambda (fd)
+           (readlink (string-append directory "/" fd)))
+         (or (scandir directory string->number) '()))))
+
+;; Daemon session.
+(define-record-type <daemon-session>
+  (daemon-session process client children locks)
+  daemon-session?
+  (process    daemon-session-process)             ;<process>
+  (client     daemon-session-client)              ;<process>
+  (children   daemon-session-children)            ;list of <process>
+  (locks      daemon-session-locks-held))         ;list of strings
+
+(define (daemon-sessions)
+  "Return two values: the list of <daemon-session> denoting the currently
+active sessions, and the master 'guix-daemon' process."
+  (define (lock-file? file)
+    (and (string-prefix? (%store-prefix) file)
+         (string-suffix? ".lock" file)))
+
+  (let* ((processes (processes))
+         (daemons   (filter (lambda (process)
+                              (match (process-command process)
+                                ((argv0 _ ...)
+                                 (string=? (basename argv0) "guix-daemon"))
+                                (_ #f)))
+                            processes))
+         (children  (filter (lambda (process)
+                              (match (process-command process)
+                                ((argv0 (= string->number argv1) _ ...)
+                                 (integer? argv1))
+                                (_ #f)))
+                            daemons))
+         (master    (remove (lambda (process)
+                              (memq process children))
+                            daemons)))
+    (define (lookup-process pid)
+      (find (lambda (process)
+              (and (process-id process)
+                   (= pid (process-id process))))
+            processes))
+
+    (define (lookup-children pid)
+      (filter (lambda (process)
+                (and (process-parent-id process)
+                     (= pid (process-parent-id process))))
+              processes))
+
+    (values (map (lambda (process)
+                   (match (process-command process)
+                     ((argv0 (= string->number client) _ ...)
+                      (let ((files (process-open-files process)))
+                        (daemon-session process
+                                        (lookup-process client)
+                                        (lookup-children (process-id process))
+                                        (filter lock-file? files))))))
+                 children)
+            master)))
+
+(define (daemon-session->recutils session port)
+  "Display SESSION information in recutils format on PORT."
+  (format port "SessionPID: ~a~%"
+          (process-id (daemon-session-process session)))
+  (format port "ClientPID: ~a~%"
+          (process-id (daemon-session-client session)))
+  (format port "ClientCommand:~{ ~a~}~%"
+          (process-command (daemon-session-client session)))
+  (for-each (lambda (lock)
+              (format port "LockHeld: ~a~%" lock))
+            (daemon-session-locks-held session))
+  (for-each (lambda (process)
+              (format port "ChildProcess: ~a:~{ ~a~}~%"
+                      (process-id process)
+                      (process-command process)))
+            (daemon-session-children session)))
+
+
+;;;
+;;; Options.
+;;;
+
+(define %options
+  (list (option '(#\h "help") #f #f
+                (lambda args
+                  (show-help)
+                  (exit 0)))
+        (option '(#\V "version") #f #f
+                (lambda args
+                  (show-version-and-exit "guix processes")))))
+
+(define (show-help)
+  (display (G_ "Usage: guix processes
+List the current Guix sessions and their processes."))
+  (newline)
+  (display (G_ "
+  -h, --help             display this help and exit"))
+  (display (G_ "
+  -V, --version          display version information and exit"))
+  (newline)
+  (show-bug-report-information))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-processes . args)
+  (define options
+    (args-fold* args %options
+                (lambda (opt name arg result)
+                  (leave (G_ "~A: unrecognized option~%") name))
+                cons
+                '()))
+
+  (for-each (lambda (session)
+              (daemon-session->recutils session (current-output-port))
+              (newline))
+            (daemon-sessions)))