Yes, I think you're right. I originally wrote that because I was
thinking that this code might be involved in evaluating the user's
submission, but I am not pretty sure I was wrong about that. So, yes I
agree that putting this into the production server may be worth a try
(depending on how severe the problem you're having is I suppose).
It may make sense to try it out yourself a little bit between due
dates or something. I did some testing, but more is better.
Also, while I was reading the code again, however, I noticed that my
diff didn't have enough syncronization. Here's an improved one.
Robby
diff --git a/handin-server/private/reloadable.rkt
b/handin-server/private/reloadable.rkt
index 1055822..32de38f 100644
--- a/handin-server/private/reloadable.rkt
+++ b/handin-server/private/reloadable.rkt
@@ -1,8 +1,36 @@
#lang racket/base
(require syntax/moddep "logger.rkt")
+(module mon racket/base
+ (define sema (make-semaphore 1))
+ (define-syntax-rule
+ (provide/monitor (id x ...))
+ (begin
+ (define -id
+ (let ([id (λ (x ...)
+ (call-with-semaphore
+ sema
+ (λ () (id x ...))))])
+ id))
+ (provide (rename-out [-id id]))))
+ (define-syntax-rule
+ (protect e)
+ (call-with-semaphore sema (λ () e)))
+ (provide provide/monitor protect))
+(require (submod "." mon))
-(provide reload-module)
+(module+ test
+ (module m racket/base
+ (require (submod ".." ".." mon))
+ (define (f x) (* 2 (g x)))
+ (define (g x) (+ x 1))
+ (provide/monitor (f x))
+ (provide/monitor (g x)))
+ (require (submod "." m) rackunit)
+ (check-equal? (g 2) 3)
+ (check-equal? (f 11) 24))
+
+(provide/monitor (reload-module modspec path))
(define (reload-module modspec path)
;; the path argument is not needed (could use resolve-module-path here), but
;; its always known when this function is called
@@ -20,7 +48,7 @@
;; pulls out a value from a module, reloading the module if its source file was
;; modified
-(provide auto-reload-value)
+(provide/monitor (auto-reload-value modspec valname))
(define module-times (make-hash))
(define (auto-reload-value modspec valname)
(define path0 (resolve-module-path modspec #f))
@@ -43,7 +71,7 @@
;; pulls out a procedure from a module, and returns a wrapped procedure that
;; automatically reloads the module if the file was changed whenever the
;; procedure is used
-(provide auto-reload-procedure)
+(provide/monitor (auto-reload-procedure x y))
(define (auto-reload-procedure modspec procname)
(let ([path (resolve-module-path modspec #f)] [date #f] [proc #f] [poll #f])
(define (reload)
@@ -55,4 +83,4 @@
(reload-module modspec path)
(set! proc (dynamic-require modspec procname))))))
(reload)
- (lambda xs (reload) (apply proc xs))))
+ (lambda xs (protect (reload)) (apply proc xs))))
diff --git a/info.rkt b/info.rkt
index 00a42f9..a5686d5 100644
--- a/info.rkt
+++ b/info.rkt
@@ -11,6 +11,7 @@
"net-lib"
"pconvert-lib"
"sandbox-lib"
+ "rackunit-lib"
"web-server-lib"))
(define build-deps '("gui-doc"
"racket-doc"
On Thu, Nov 26, 2015 at 6:23 PM, Paolo Giarrusso <p.giarru...@gmail.com> wrote:
> On 25 November 2015 at 14:54, Robby Findler <ro...@eecs.northwestern.edu>
> wrote:
>> I'm still not completely
>> sure, but since you seem to be able to provoke the error, that
>> emboldens me to suggest you apply the diff below and see if it goes
>> away.
>
> I'm doing this. Annoyingly, I can't force the crash at will yet, and
> an automated handin-server stress-tester is not in our plans yet :-|.
>
>> That diff is probably not what we'd want in the end, since it is too
>> much locking (we would want a namespace-specific lock not a global
>> one) but if the error does go away, that means that this is probably
>> the right place to put the lock in.
>
> Makes sense.
>
> But for my production environment, I guess that this patch won't
> overly restrict concurrency: I guess namespaces correspond to checkers
> in the handin-server, right? So, since I only ever open one
> assignment, I should only have one namespace anyway?
>
> Cheers,
> Paolo
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