services: Add rshiny service.

* gnu/services/science.scm: New file.
(<rshiny-configuration>): New record.
(rshiny-shepherd-service-type): New variable.
* doc/guix.texi (Miscellaneous Services): Document it.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.

doc/guix.texi

@@ -26612,6 +26612,55 @@ setuid-root (@pxref{Setuid Programs}) such that unprivileged users can invoke
 @command{singularity run} and similar commands.
 @end defvr
 
+@cindex rshiny
+@subsubheading R-Shiny service
+
+The @code{(gnu services science)} module provides the following service.
+
+@defvr {Scheme Variable} rshiny-service-type
+
+This is a type of service which is used to run a webapp created with
+@code{r-shiny}.  This service sets the @code{R_LIBS_USER} environment
+variable and runs the provided script to call @code{runApp}.
+
+@deftp {Data Type} rshiny-configuration
+This is the data type representing the configuration of rshiny.
+
+@table @asis
+
+@item @code{package} (default: @code{r-shiny})
+The package to use.
+
+@item @code{binary} (defaunlt @code{"rshiny"})
+The name of the binary or shell script located at @code{package/bin/} to
+run when the service is run.
+
+The common way to create this file is as follows:
+
+@lisp
+@dots{}
+(let* ((out       (assoc-ref %outputs "out"))
+       (targetdir (string-append out "/share/" ,name))
+       (app       (string-append out "/bin/" ,name))
+       (Rbin      (string-append (assoc-ref %build-inputs "r-min")
+                                 "/bin/Rscript")))
+@dots{}
+  (mkdir-p (string-append out "/bin"))
+  (call-with-output-file app
+    (lambda (port)
+      (format port
+"#!~a
+library(shiny)
+setwd(\"~a\")
+runApp(launch.browser=0, port=4202)~%\n"
+      Rbin targetdir)))
+@dots{}
+@end lisp
+
+@end table
+@end deftp
+@end defvr
+
 @cindex Nix
 @subsubheading Nix service
 

gnu/local.mk

@@ -599,6 +599,7 @@ GNU_SYSTEM_MODULES =				\
   %D%/services/nix.scm				\
   %D%/services/nfs.scm			\
   %D%/services/pam-mount.scm			\
+  %D%/services/science.scm			\
   %D%/services/security-token.scm		\
   %D%/services/shepherd.scm			\
   %D%/services/sound.scm			\

gnu/services/science.scm

@@ -0,0 +1,57 @@
+(define-module (gnu services science)
+  #:export (<rshiny-configuration>
+            rshiny-configuration
+            rshiny-configuration?
+            rshiny-configuration-package
+            rshiny-configuration-binary
+            rshiny-shepherd-service
+            rshiny-service-type))
+
+(use-modules (gnu)
+             (guix records)
+             (ice-9 match))
+(use-service-modules shepherd)
+(use-package-modules cran)
+
+(define-record-type* <rshiny-configuration>
+  rshiny-configuration
+  make-rshiny-configuration
+  rshiny-configuration?
+  (package          rshiny-configuration-package    ; package
+                    (default r-shiny))
+  (binary           rshiny-configuration-binary     ; string
+                    (default "rshiny")))
+
+(define rshiny-shepherd-service
+  (match-lambda
+    (($ <rshiny-configuration> package binary)
+     (list
+       (shepherd-service
+         (documentation (string-append "R-Shiny service for " binary))
+         (provision (list (symbol-append 'rshiny- (string->symbol
+                                                    (string-take binary 9)))))
+         (requirement '(networking))
+         (start
+           #~(exec-command
+               (list
+                 #$(string-append "/run/current-system/profile/bin/" binary))
+               ;#:log-file #$(string-append "/var/log/" binary ".log") ; kills shepherd
+               #:environment-variables
+               (list "R_LIBS_USER=/run/current-system/profile/site-library/")))
+         (stop #~(make-kill-destructor)))))))
+
+(define rshiny-service-type
+  (service-type
+    (name 'rshiny)
+    (extensions
+      (list
+        (service-extension shepherd-root-service-type
+                           rshiny-shepherd-service)
+        (service-extension profile-service-type
+                           ;; We want the package installed so that it
+                           ;; pulls in the propagated inputs as well.
+                           (lambda (config)
+                             (list
+                               (rshiny-configuration-package config))))))
+    (description
+     "Run an R-Shiny webapp as a Guix Service.")))