sunet/scheme/httpd/surflets/surflet-handler.scm

480 lines
16 KiB
Scheme

;; the servlet handler
;; Copyright Andreas Bernauer, 2002
(define *debug* #t)
;;; instance-table: entry for every new request on a servlet page
(define-record-type instance :instance
(make-instance servlet-name memo
continuation-table continuation-table-lock
continuation-counter)
instance?
(servlet-name instance-servlet-name)
(memo instance-memo set-instance-memo!)
(continuation-table instance-continuation-table)
(continuation-table-lock instance-continuation-table-lock)
(continuation-counter instance-continuation-counter))
(define-record memo
(message 'kill) ;kill, killed, adjust-timeout
(value #f)
(new-memo #f))
;; caller must do locking stuff
(define (memo-killed! memo)
(set-memo:message memo 'killed))
(define-record-type session :session
(make-session instance-id return-continuation)
session?
(instance-id really-session-instance-id
set-session-instance-id!)
(return-continuation really-session-return-continuation
set-session-return-continuation!))
(define-record options
(cache-plugins? #t)
(instance-lifetime 600)) ; in seconds
(define *options* (make-options))
;(define *options-lock* (make-lock)) ; currently unused
(define *instance-table* (make-integer-table)) ; instance-id is index
(define *instance-table-lock* (make-lock))
(define random
(let* ((source (make-random-source))
(random-integer (begin
(random-source-randomize! source)
(random-source-make-integers source))))
(lambda ()
(random-integer 1073741824)))) ; I hope, 1+ billion is enough....
;; servlet-prefix gives virtual prefixed path to servlets
(define (servlet-handler servlet-path servlet-prefix)
(lambda (path req)
(if (pair? path) ; need at least one element
(let ((request-method (request:method req))
(path-string (uri-path-list->path path)))
(cond
; ((string=? path-string "profile") ; triggers profiling
; (http-syslog (syslog-level debug)
; "profiling: triggered in servlet-handler [~a]"
; (profile-space)) ; PROFILE
; (make-http-error-response http-status/accepted req "profiled"))
; ((string=? path-string "reset") ; triggers cache clearing
; (http-syslog (syslog-level debug)
; "servlet-handler: clearing plugin cache")
; (reset-plugin-cache!)
; (http-syslog (syslog-level debug)
; "servlet-handler: clearing instance table")
; (reset-instance-table!)
; (make-http-error-response http-status/accepted req "plugin cache cleared"))
((or (string=? request-method "GET")
; (string=? request-method "POST")) ; do this at later time
)
(let ((response
(if (resume-url? path-string)
(resume-url path-string servlet-path req)
(launch-new-instance path-string servlet-path req))))
(if (redirect-body? (response-body response))
;; prefix with servlet-path
(make-redirect-response
(string-join (file-name-as-directory servlet-prefix)
(redirect-body-location (response-body response))))
response)))
(else
(make-http-error-response http-status/method-not-allowed req
request-method))))
(make-http-error-response http-status/bad-request req
(format #f "Bad path: ~s" path)))))
(define (launch-new-instance path-string servlet-path req)
(if (file-not-exists? (absolute-file-name path-string servlet-path))
(make-http-error-response http-status/not-found req path-string)
(begin
(obtain-lock *instance-table-lock*)
;; no access to instance table until new instance-id is saved
(let ((instance-id (generate-new-table-id *instance-table*))
(memo (make-memo)))
(table-set! *instance-table* instance-id
(make-instance path-string ; used to make
; redirections to origin
memo
(make-integer-table) ; continuation table
(make-lock) ; continuation table lock
(make-thread-safe-counter))) ; continuation counter
(release-lock *instance-table-lock*)
(register-session! instance-id 'no-return)
(let ((plugin (with-fatal-error-handler*
(lambda (condition decline)
(instance-delete! instance-id)
(decline))
(lambda ()
(get-plugin-rt-structure path-string servlet-path)))))
(fork-thread (instance-surveillance instance-id
(+ (time)
(options:instance-lifetime *options*))
memo))
(reset
(begin
(with-cwd
servlet-path
(with-names-from-rt-structure
plugin plugin-interface
(main req))))))))))
(define (instance-surveillance instance-id time-to-die memo)
(lambda ()
(let loop ((time-to-die time-to-die)
(memo memo))
(debug "instance-surveillance[~s]: going to sleep until ~a"
instance-id (format-date "~c" (date time-to-die)))
(let ((seconds-to-sleep (- time-to-die (time))))
(if (positive? seconds-to-sleep)
(sleep (* 1000 seconds-to-sleep))))
;; check state of the world
(case (memo:message memo)
((killed) ; too late
(debug "instance-surveillance[~s]: instance already killed, dieing"
instance-id)
)
((adjust-timeout) ; new timeout
(debug "instance-surveillance[~s]: adjusting timeout" instance-id)
(loop (memo:value memo)
(memo:new-memo memo)))
((kill) ; kill instance
(debug "instance-surveillance[~s]: killing"
instance-id)
(obtain-lock *instance-table-lock*)
(table-set! *instance-table* instance-id #f)
(release-lock *instance-table-lock*))
(else
(format (current-error-port)
"instance-surveillance[~s]: unknown message ~s; dieing"
instance-id (memo:message memo)))))))
;; try to get continuation-table and then the continuation
(define resume-url
(let ((bad-request
(lambda (path-string req)
(make-http-error-response
http-status/bad-request req
(format #f
"<br>
<p>There may be several reasons, why your request was denied:
<ul>
<li>The servlet does not accept any requests any more.</li>
<li>The servlet URL has timed out.</li>
<li>You URL is illformed.</li>
</ul>
</p>
<p>In any case, you may try to restart the servlet from the <a href=\"~a\">beginning</a></p>"
(resume-url-servlet-name path-string)))))
(lookup-continuation-table
(lambda (instance continuation-table continuation-id)
(let ((continuation-table-lock (instance-continuation-table-lock instance)))
(obtain-lock continuation-table-lock)
(let ((result (table-ref continuation-table continuation-id)))
(release-lock continuation-table-lock)
result)))))
(lambda (path-string servlet-path req)
(receive (instance-id continuation-id)
(resume-url-ids path-string)
(let ((instance (instance-lookup instance-id)))
(if instance
(let* ((continuation-table (instance-continuation-table instance))
(resume (lookup-continuation-table instance continuation-table
continuation-id)))
(if resume
(with-cwd
servlet-path
(reset
(begin
(register-session! instance-id 'no-return)
(resume req))))
(bad-request path-string req)))
(bad-request path-string req)))
))))
(define (send/suspend response-maker)
(shift return
(let* ((instance-id (session-instance-id))
(instance (instance-lookup instance-id)))
;; the session might be deleted in the meanwhile
(if instance
(begin
(instance-adjust-timeout! instance-id)
(let ((continuations-table (instance-continuation-table instance))
(continuation-table-lock (instance-continuation-table-lock instance))
(continuation-counter (instance-next-continuation-counter instance)))
(obtain-lock continuation-table-lock)
(let ((continuation-id (generate-new-table-id continuations-table)))
(table-set! continuations-table continuation-id return)
(release-lock continuation-table-lock)
(let ((new-url (make-resume-url (instance-servlet-name instance)
instance-id
continuation-counter
continuation-id)))
(response-maker new-url)))))
(make-http-error-response http-status/not-found #f
"The URL refers to a servlet, whose instance is no longer alive.")))))
(define (send/finish response)
(instance-delete! (session-instance-id))
(shift unused response))
(define (send response)
(shift unsused response))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; access to instance-table
(define (instance-lookup instance-id)
(obtain-lock *instance-table-lock*)
(let ((result (table-ref *instance-table* instance-id)))
(release-lock *instance-table-lock*)
result))
(define (instance-next-continuation-counter instance)
(thread-safe-counter-next!
(instance-continuation-counter instance)))
(define (instance-delete! instance-id)
(obtain-lock *instance-table-lock*)
;; notify surveillance of instance being alread killed (prevents
;; surveillance of killing new instance that has the same number by
;; accident)
(let ((instance (table-ref *instance-table* instance-id)))
(memo-killed! (instance-memo instance)))
;; why can't table entries be deleted correctly?
(table-set! *instance-table* instance-id #f)
(release-lock *instance-table-lock*))
(define (instance-adjust-timeout! instance-id)
(obtain-lock *instance-table-lock*)
(let* ((instance (table-ref *instance-table* instance-id))
(memo (instance-memo instance))
(new-memo (make-memo)))
;; Do it this way: new values and then new message
(set-memo:value memo
(+ (time)
(options:instance-lifetime *options*)))
(set-memo:new-memo memo new-memo)
;; I don't think we need locking here. Do you agree?
(set-instance-memo! instance new-memo)
(set-memo:message memo 'adjust-timeout))
(release-lock *instance-table-lock*))
(define (reset-instance-table!)
(with-fatal-error-handler
(lambda (condtion decline)
(release-lock *instance-table-lock*)
(decline))
(lambda ()
(obtain-lock *instance-table-lock*)
;; notify instance killing
(table-walk
(lambda (instance-id instance)
(memo-killed! (instance-memo instance)))
*instance-table*)
(set! *instance-table* (make-integer-table))
(release-lock *instance-table*))))
(define (get-instances)
(obtain-lock *instance-table-lock*)
(let ((instances '()))
(table-walk
(lambda (instance-id instance-entry)
(set! instances (cons (cons instance-id instance-entry) instances)))
*instance-table*)
(release-lock *instance-table-lock*)
instances))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ID generation
;; locking must be done by caller
;; FIXME?: this may loop forever, if the table is full (can this happen?)
(define (generate-new-table-id table)
(let loop ((id (random)))
(if (table-ref table id)
(loop (random))
id)))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; PLUGINs CACHE
(define *plugin-table* (make-string-table)) ; path-string is index
(define *plugin-table-lock* (make-lock))
;; PLUGIN-NAME is like "news-dir/latest-news.scm"
(define (get-plugin-rt-structure plugin-name directory)
(let* ((full-plugin-name (absolute-file-name plugin-name directory))
(load-plugin
(lambda (cached?)
(with-fatal-error-handler*
(lambda (condition decline)
(if cached? (release-lock *plugin-table-lock*))
(decline))
(lambda ()
;; load-config-file does not care about cwd(?)
;; --> absolute file name needed
(load-config-file full-plugin-name)
;; plugin-structure to load must be named "plugin"
(let ((plugin-structure (reify-structure 'plugin)))
(load-structure plugin-structure)
(if cached?
(begin
(table-set! *plugin-table* full-plugin-name
(cons plugin-structure
(file-last-mod full-plugin-name)))
;; only now the lock may be released
(release-lock *plugin-table-lock*)))
plugin-structure))))))
(if (options:cache-plugins? *options*)
(begin
;; The lock is only obtained and released, if plugins are
;; cached. LOAD-PLUGIN gets the CACHED? parameter, so
;; nothing may happen, if in the meanwhile caching is turned
;; off.
(obtain-lock *plugin-table-lock*)
(let ((plugin (table-ref *plugin-table* full-plugin-name)))
(if plugin
(if (equal? (file-last-mod full-plugin-name)
(cdr plugin))
(begin
(release-lock *plugin-table-lock*)
(car plugin))
(load-plugin #t))
(load-plugin #t))))
(load-plugin #f))))
(define (get-loaded-plugins)
(obtain-lock *plugin-table-lock*)
(let ((loaded-plugins '()))
(table-walk
(lambda (plugin-path rt-structure)
(set! loaded-plugins (cons plugin-path loaded-plugins)))
*plugin-table*)
(release-lock *plugin-table-lock*)
loaded-plugins))
(define (unload-plugin plugin-name)
(obtain-lock *plugin-table-lock*)
(if (table-ref *plugin-table* plugin-name)
(table-set! *plugin-table* plugin-name #f))
(release-lock *plugin-table-lock*))
(define (reset-plugin-cache!)
(with-fatal-error-handler*
(lambda (condition decline)
(release-lock *plugin-table-lock*)
(decline))
(lambda ()
(obtain-lock *plugin-table-lock*)
(set! *plugin-table* (make-string-table))
(release-lock *plugin-table-lock*))))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; SESSION
(define *session* (make-thread-cell #f))
(define (register-session! instance-id return-continuation)
(thread-cell-set! *session*
(make-session instance-id return-continuation)))
;(define (save-session-return-continuation! return-continuation)
; (set-session-instance-id! (thread-cell-ref *session*)
; return-continuation))
(define (session-instance-id)
(really-session-instance-id (thread-cell-ref *session*)))
(define (session-return-continuation)
(really-session-return-continuation (thread-cell-ref *session*)))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; RESUME-URL
(define *resume-url-regexp* (rx (submatch (* (- printing ";")))
";k" (submatch (* digit)) ; Instance-ID
";c" (+ digit) "-" (submatch (* digit)))) ; Continuation-ID
(define (make-resume-url path-string instance-id continuation-counter continuation-id)
(string-append path-string
";k" (number->string (session-instance-id))
";c" (number->string continuation-counter)
"-" (number->string continuation-id)))
(define (resume-url-instance-id id-url)
(receive (instance-id continuation-id)
(resume-url-ids id-url)
instance-id))
(define (resume-url-continuation-id id-url)
(receive (instance-id continuation-id)
(resume-url-ids id-url)
continuation-id))
(define (resume-url-ids id-url)
(let ((match (regexp-search *resume-url-regexp* id-url)))
(if match
(values (string->number (match:substring match 2))
(string->number (match:substring match 3)))
(error "resume-url-ids: no instance/continuation id" id-url))))
(define (resume-url-servlet-name id-url)
(let ((match (regexp-search *resume-url-regexp* id-url)))
(if match
(match:substring match 1)
(error "resume-url-servlet-name: no servlet-name found"))))
(define (resume-url? id-url)
(regexp-search? *resume-url-regexp* id-url))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; access to options
(define (set-instance-lifetime! new-lifetime)
(set-options:instance-lifetime *options* new-lifetime))
(define (get-instance-lifetime)
(options:instance-lifetime *options*))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; thread-safe counter
(define-record-type counter :counter
(really-make-counter counter lock)
(counter counter-counter set-counter-counter!)
(lock counter-lock))
(define (make-thread-safe-counter)
(really-make-counter 0 (make-lock)))
;;; read current value
(define (thread-safe-counter counter)
(obtain-lock (counter-lock counter))
(let ((result (counter-counter counter)))
(release-lock (counter-lock counter))
result))
;;; make next value and return it
(define (thread-safe-counter-next! counter)
(obtain-lock (counter-lock counter))
(let ((result (+ 1 (counter-counter counter))))
(set-counter-counter! counter result)
(release-lock (counter-lock counter))
result))
(define (debug fmt . args)
(if *debug*
(format #t "DEBUG: ~?~%" fmt args)
(force-output)))