Update: I just got around to trying webupload.arc, and like you said it can't handle that 800KB bzip2 upload from localhost. Files larger than 99339 bytes only render the first 99339 bytes.

I modified /upload to not print the entire file. Somewhere just before 400k the upload dies, again like you said. I experimented with various file sizes. At 392080 bytes, it always succeeds, at 392100 bytes it always fails. At 392090 bytes it fails around half the time. At 392085 bytes it fails around a third of the time.

Very weird.

I think the next step is to build an upload form in pure racket, and see if it suffers from the same problem. I'm not sure when I'll be able to get around to it; it'll require some reading of racket docs.

Update 2: curl indicates both commands behave the same way.

  $ curl -i -F "name=@x.100k" "http://localhost:8080/x?fnid=7Uakm57k8V"
  HTTP/1.1 200 OK
  Content-Type: text/html; charset=utf-8
  Connection: close

   ... headers ...
  <br>Content-Type: multipart/form-data; boundary=----------------------------fd366e3dc6eb
  <br>Content-Length: 100198
  <br> ... more headers ...
  <br><br>
  100198

  $ curl -i -F "name=@x.392100" "http://localhost:8080/x?fnid=7Uakm57k8V"
  HTTP/1.1 200 OK
  Content-Type: text/html; charset=utf-8
  Connection: close

   ... headers ...
  <br>Content-Type: multipart/form-data; boundary=----------------------------c97bd48c8631
  <br>Content-Length: 392300
  <br> ... more headers ...
  <br><br>
  392300

Looks like this has come up before, 2.5 years ago: http://arclanguage.org/item?id=10462 [1]. Rocketnia's recent comment also turned out to be a surprisingly relevant clue, with its reference to make-limited-input-port: http://arclanguage.org/item?id=16202.

(readc req!in) seems to get stuck before reading the whole thing. Here's the source:

  (w/outfile o f
     (whilet c (and (> n 0) (readc req!in))
               (-- n)
               (pr "n now is " n)
               (disp c o)))

  (mac form-multi (n . body)
    (w/uniq ga
      `(tag (form method 'post
                  enctype "multipart/form-data"
                  action ,n)
         ,@body)))

  arc> (= i 0)
  arc> (w/infile in "x" (whilet c readb.in ++.i))
  arc> i
  400000

Can you read the file that was POSTed and save it? Ignore parsing out the multipart stuff. Just save what came in through the request.

Here's the test at /upload_is_broken

  (mac form-multi (n . body)
    (w/uniq ga
      `(tag (form method 'post
                  enctype "multipart/form-data"
                  action ,n)
         ,@body)))

  (defop upload_is_broken req
    (form-multi "upload_static"                           
      (gentag input type 'file name 'name)
      (submit "upload")))

  (defop upload_static req
     (withs (n req!clen
               f (string "/dev/shm/" (uniq)))
            (pr "saving multipart data\n")
            (pr "clen is " n "\n")
            (w/outfile o f
                       (whilet c (and (> n 0) (readb req!in))
                               (-- n)
                               ;;(pr "n now is " n)                                                                         
                               (writeb c o)))
            (pr "SAVED multipart data. Success!!!\n")))

  saving multipart data clen is 1591333 SAVED multipart data. Success!!!

http://tyche.pu-toyama.ac.jp/~a-urasim/lsvl/data/bzip2_1.0.5...

  $ md5sum bzip2_1.0.5.orig.tar.gz 
  3c15a0c8d1d3ee1c46a1634d00617b1a  bzip2_1.0.5.orig.tar.gz

  saving multipart data clen is 841607 SAVED multipart data. Success!!!

  server {
    listen 80;
    server_name  somewebsite.com;
    access_log /var/log/nginx/somewebsite.com.access.log;

    location / {
      proxy_pass        http://somewebsite.com:2012;
      proxy_set_header  X-Real-IP  $remote_addr;
    }
  }

I tried setting the following in /etc/nginx/sites-available/somewebsite.com:

  server {
  # ... various vars as in http://arclanguage.org/item?id=16317 plus the following:
  client_max_body_size 10m;
  }

In both cases uploading the bzip2 file hangs.

I also tried setting client_max_body_size in /etc/nginx/nginx.conf but there get a different error:

  Restarting nginx: [emerg]: unknown directive "client_max_body_size" in /etc/nginx/nginx.conf:31