services: Add Varnish service.

* gnu/services/web.scm (<varnish-configuration>): New record type.
(%varnish-accounts, %varnish-service-type): New variables.
(varnish-shepherd-service): New procedure.
* gnu/tests/web.scm (%varnish-vcl, %varnish-os): New variables.
(%test-varnish): New test.
* doc/guix.texi (Web Services): Document it.

doc/guix.texi

@@ -16888,6 +16888,86 @@ body of a named location block cannot contain location blocks.
 @end table
 @end deftp
 
+@subsubheading Varnish Cache
+@cindex Varnish
+Varnish is a fast cache server that sits in between web applications
+and end users.  It proxies requests from clients and caches the
+accessed URLs such that multiple requests for the same resource only
+creates one request to the back-end.
+
+@defvr {Scheme Variable} varnish-service-type
+Service type for the Varnish daemon.
+@end defvr
+
+@deftp {Data Type} varnish-configuration
+Data type representing the @code{varnish} service configuration.
+This type has the following parameters:
+
+@table @asis
+@item @code{package} (default: @code{varnish})
+The Varnish package to use.
+
+@item @code{name} (default: @code{"default"})
+A name for this Varnish instance.  Varnish will create a directory in
+@file{/var/varnish/} with this name and keep temporary files there.  If
+the name starts with a forward slash, it is interpreted as an absolute
+directory name.
+
+Pass the @code{-n} argument to other Varnish programs to connect to the
+named instance, e.g. @command{varnishncsa -n default}.
+
+@item @code{backend} (default: @code{"localhost:8080"})
+The backend to use.  This option has no effect if @code{vcl} is set.
+
+@item @code{vcl} (default: #f)
+The @dfn{VCL} (Varnish Configuration Language) program to run.  If this
+is @code{#f}, Varnish will proxy @code{backend} using the default
+configuration.  Otherwise this must be a file-like object with valid
+VCL syntax.
+
+@c Varnish does not support HTTPS, so keep this URL to avoid confusion.
+For example, to mirror @url{http://www.gnu.org,www.gnu.org} with VCL you
+can do something along these lines:
+
+@example
+(define %gnu-mirror
+  (plain-file
+   "gnu.vcl"
+   "vcl 4.1;
+backend gnu @{ .host = "www.gnu.org"; @}"))
+
+(operating-system
+  ...
+  (services (cons (service varnish-service-type
+                           (varnish-configuration
+                            (listen '(":80"))
+                            (vcl %gnu-mirror)))
+                  %base-services)))
+@end example
+
+The configuration of an already running Varnish instance can be inspected
+and changed using the @command{varnishadm} program.
+
+Consult the @url{https://varnish-cache.org/docs/,Varnish User Guide} and
+@url{https://book.varnish-software.com/4.0/,Varnish Book} for
+comprehensive documentation on Varnish and its configuration language.
+
+@item @code{listen} (default: @code{'("localhost:80")})
+List of addresses Varnish will listen on.
+
+@item @code{storage} (default: @code{'("malloc,128m")})
+List of storage backends that will be available in VCL.
+
+@item @code{parameters} (default: @code{'()})
+List of run-time parameters in the form @code{'(("parameter" . "value"))}.
+
+@item @code{extra-options} (default: @code{'()})
+Additional arguments to pass to the @command{varnishd} process.
+
+@end table
+@end deftp
+
+@subsubheading FastCGI
 @cindex fastcgi
 @cindex fcgiwrap
 FastCGI is an interface between the front-end and the back-end of a web

gnu/services/web.scm

@@ -8,6 +8,7 @@
 ;;; Copyright © 2017, 2018 Clément Lassieur <clement@lassieur.org>
 ;;; Copyright © 2018 Pierre-Antoine Rouby <pierre-antoine.rouby@inria.fr>
 ;;; Copyright © 2017 Christopher Baines <mail@cbaines.net>
+;;; Copyright © 2018 Marius Bakke <mbakke@fastmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -190,7 +191,21 @@
             tailon-configuration-config-file
             tailon-configuration-package
 
-            tailon-service-type))
+            tailon-service-type
+
+            <varnish-configuration>
+            varnish-configuration
+            varnish-configuration?
+            varnish-configuration-package
+            varnish-configuration-name
+            varnish-configuration-backend
+            varnish-configuration-vcl
+            varnish-configuration-listen
+            varnish-configuration-storage
+            varnish-configuration-parameters
+            varnish-configuration-extra-options
+
+            varnish-service-type))
 
 ;;; Commentary:
 ;;;
@@ -1162,3 +1177,82 @@ files.")
                   (files (append (tailon-configuration-file-files old-config-file)
                                  files))))))))
    (default-value (tailon-configuration))))
+
+
+;;;
+;;; Varnish
+;;;
+
+(define-record-type* <varnish-configuration>
+  varnish-configuration make-varnish-configuration
+  varnish-configuration?
+  (package             varnish-configuration-package          ;<package>
+                       (default varnish))
+  (name                varnish-configuration-name             ;string
+                       (default "default"))
+  (backend             varnish-configuration-backend          ;string
+                       (default "localhost:8080"))
+  (vcl                 varnish-configuration-vcl              ;#f | <file-like>
+                       (default #f))
+  (listen              varnish-configuration-listen           ;list of strings
+                       (default '("localhost:80")))
+  (storage             varnish-configuration-storage          ;list of strings
+                       (default '("malloc,128m")))
+  (parameters          varnish-configuration-parameters       ;list of string pairs
+                       (default '()))
+  (extra-options       varnish-configuration-extra-options    ;list of strings
+                       (default '())))
+
+(define %varnish-accounts
+  (list (user-group
+         (name "varnish")
+         (system? #t))
+        (user-account
+         (name "varnish")
+         (group "varnish")
+         (system? #t)
+         (comment "Varnish Cache User")
+         (home-directory "/var/varnish")
+         (shell (file-append shadow "/sbin/nologin")))))
+
+(define varnish-shepherd-service
+  (match-lambda
+    (($ <varnish-configuration> package name backend vcl listen storage
+                                parameters extra-options)
+     (list (shepherd-service
+            (provision (list (symbol-append 'varnish- (string->symbol name))))
+            (documentation (string-append "The Varnish Web Accelerator"
+                                          " (" name ")"))
+            (requirement '(networking))
+            (start #~(make-forkexec-constructor
+                      (list #$(file-append package "/sbin/varnishd")
+                            "-n" #$name
+                            #$@(if vcl
+                                   #~("-f" #$vcl)
+                                   #~("-b" #$backend))
+                            #$@(append-map (lambda (a) (list "-a" a)) listen)
+                            #$@(append-map (lambda (s) (list "-s" s)) storage)
+                            #$@(append-map (lambda (p)
+                                             (list "-p" (format #f "~a=~a"
+                                                                (car p) (cdr p))))
+                                           parameters)
+                            #$@extra-options)
+                      ;; Varnish will drop privileges to the "varnish" user when
+                      ;; it exists.  Not passing #:user here allows the service
+                      ;; to bind to ports < 1024.
+                      #:pid-file (if (string-prefix? "/" #$name)
+                                     (string-append #$name "/_.pid")
+                                     (string-append "/var/varnish/" #$name "/_.pid"))))
+            (stop #~(make-kill-destructor)))))))
+
+(define varnish-service-type
+  (service-type
+   (name 'varnish)
+   (description "Run the Varnish cache server.")
+   (extensions
+    (list (service-extension account-service-type
+                             (const %varnish-accounts))
+          (service-extension shepherd-root-service-type
+                             varnish-shepherd-service)))
+   (default-value
+     (varnish-configuration))))

gnu/tests/web.scm

@@ -32,6 +32,7 @@
   #:use-module (guix store)
   #:export (%test-httpd
             %test-nginx
+            %test-varnish
             %test-php-fpm
             %test-hpcguix-web
             %test-tailon))
@@ -167,6 +168,46 @@ HTTP-PORT."
    (value (run-webserver-test name %nginx-os
                               #:log-file "/var/log/nginx/access.log"))))
 
+
+;;;
+;;; Varnish
+;;;
+
+(define %varnish-vcl
+  (mixed-text-file
+   "varnish-test.vcl"
+   "vcl 4.0;
+backend dummy { .host = \"127.1.1.1\"; }
+sub vcl_recv { return(synth(200, \"OK\")); }
+sub vcl_synth {
+  synthetic(\"" %index.html-contents "\");
+  set resp.http.Content-Type = \"text/plain\";
+  return(deliver);
+}"))
+
+(define %varnish-os
+  (simple-operating-system
+   (dhcp-client-service)
+   ;; Pretend to be a web server that serves %index.html-contents.
+   (service varnish-service-type
+            (varnish-configuration
+             (name "/tmp/server")
+             ;; Use a small VSL buffer to fit in the test VM.
+             (parameters '(("vsl_space" . "4M")))
+             (vcl %varnish-vcl)))
+   ;; Proxy the "server" using the builtin configuration.
+   (service varnish-service-type
+            (varnish-configuration
+             (parameters '(("vsl_space" . "4M")))
+             (backend "localhost:80")
+             (listen '(":8080"))))))
+
+(define %test-varnish
+  (system-test
+   (name "varnish")
+   (description "Test the Varnish Cache server.")
+   (value (run-webserver-test "varnish-default" %varnish-os))))
+
 
 ;;;
 ;;; PHP-FPM