Add a new `extra-dispatcher-file' configuration option.

This allows handling other requests to implement additional
course-related functionality by the already running server (instead of
adding more servers for whatever's needed).  The documentation needs
more work though: it refers to `dispatcher/c' which needs to be added,
and there is no real sample code for it.  (My use is too specific to be
used.)

Author: elibarzilay

handin-server/private/config.rkt

@@ -79,6 +79,7 @@
     [(port-number)             (values 7979                  id           )]
     [(use-https)               (values #t                    id           )]
     [(hook-file)               (values #f                    path/false   )]
+    [(extra-dispatcher-file)   (values #f                    path/false   )]
     [(session-timeout)         (values 300                   id           )]
     [(session-memory-limit)    (values 40000000              id           )]
     [(default-file-name)       (values "handin.rkt"          id           )]

handin-server/private/hooker.rkt

@@ -2,11 +2,10 @@
 
 (require "config.rkt" "logger.rkt" "reloadable.rkt")
 
-(provide hook)
+(provide hook extra-dispatcher)
 
 (define hook-file #f)
 (define hook-proc #f)
-
 (define (hook what alist)
   (let ([file (get-conf 'hook-file)])
     (when file
@@ -15,3 +14,15 @@
         (set! hook-proc (auto-reload-procedure `(file ,(path->string file))
                                                'hook)))
       (hook-proc what (current-session) alist))))
+
+(define dispatcher-file #f)
+(define dispatcher-proc #f)
+(define ((extra-dispatcher otherwise) connection request)
+  (let ([file (get-conf 'extra-dispatcher-file)])
+    (cond [(not file) (otherwise)]
+          [else (unless (equal? file dispatcher-file)
+                  (set! dispatcher-file file)
+                  (set! dispatcher-proc
+                        (auto-reload-procedure `(file ,(path->string file))
+                                               'dispatcher)))
+                (dispatcher-proc connection request)])))

handin-server/run-servlet.rkt

@@ -13,6 +13,7 @@
          web-server/managers/lru
          (prefix-in sequencer: web-server/dispatchers/dispatch-sequencer)
          (prefix-in log: web-server/dispatchers/dispatch-log)
+         web-server/dispatchers/dispatch
          web-server/http/request-structs
          net/url
          openssl
@@ -67,6 +68,7 @@
 
 (provide run-servlet)
 (define (run-servlet dispatcher
+                     #:extra-dispatcher [extra-dispatcher #f]
                      #:log-file [log-file #f])
   ;; a channel for incoming requests
   (define ach (make-async-channel))
@@ -93,6 +95,7 @@
      (wrap-sequence
       (and log-file (log:make #:format (log:log-format->format 'apache-default)
                               #:log-path log-file))
+      (and extra-dispatcher (extra-dispatcher next-dispatcher))
       (let ([init-path (make-parameter "/")])
         (dispatch/servlet
          (lambda (req)

handin-server/scribblings/server-setup.scrbl

@@ -164,7 +164,7 @@ This directory contains the following files and sub-directories:
     @filepath{users.rktd} file and fill in such information.  (The third
     element for such descriptors is ignored.)}
 
-  @item{@indexed-racket[hook-file] --- a path (relative to handin
+  @item{@indexed-racket[hook-file] --- a path (relative to the handin
     server directory or absolute) that specifies a filename that
     contains a `hook' module.  This is useful as a general device for
     customizing the server through Racket code.  The file is expected
@@ -211,11 +211,29 @@ This directory contains the following files and sub-directories:
              '("[email protected]") '() '()
              (map (lambda (key+val)
                     (apply format "~a: ~s" key+val))
-                  alist))))]}}]
-  
+                  alist))))]}}
+
+  @item{@indexed-racket[extra-dispatcher-file] --- a path (relative to
+    the handin server directory or absolute) that specifies a filename
+    that contains a `dispatcher' module.  When specified, this file will
+    be loaded, and it is expected to provide a @racket[dispatcher]
+    function, which can be used by the web server, i.e., one that
+    satisfies @racket[dispatcher/c].  This dispatcher will get used in
+    the embedded handin server, before the handin servlet.  It can
+    therefore be used to handle additional servlets that implement
+    additional functionality.  Here is a sample skeleton:
+
+      @racketmod[
+        racket/base
+        (require web-server/http web-server/servlet-dispatch)
+        (provide dispatcher)
+        (define (start req)
+          ;; implement the "foo" operation
+          ....)
+        (define dispatcher (dispatch/servlet start #:regexp #rx"^/foo"))]}]
 
   The @secref{grading-utils} uses the following keys:
-  
+
   @itemlist[
 
      @item{@indexed-racket[deadline]: sets a per-assignment deadline for submissions,

handin-server/web-status-server.rkt

@@ -9,10 +9,10 @@
          web-server/servlet
          web-server/compat/0/coerce
          web-server/compat/0/http/response-structs
-         handin-server/private/md5
-         handin-server/private/logger
-         handin-server/private/config
-         handin-server/private/hooker
+         "private/md5.rkt"
+         "private/logger.rkt"
+         "private/config.rkt"
+         "private/hooker.rkt"
          "run-servlet.rkt")
 
 (define (aget alist key)
@@ -343,6 +343,7 @@
     (begin0 (parameterize ([error-print-context-length 0])
               (run-servlet
                dispatcher
+               #:extra-dispatcher extra-dispatcher
                #:log-file (get-conf 'web-log-file)))
       (log-line "*** embedded web server started"))
     ;; simple "server" so it's known that there is no server