Occasionally, clicking on a link in the webapp will hang. When this
happens, which has only been seen in Chromium so far, the tab will spin
forever, without anything loading. Other tabs can be opened with
middle-click on links in the webapp, and work fine. Stopping and reloading
in the tab tends to hang again, although eventually this will clear the
hang up.

-------

My best procedure to replicate this, about 25% of the time:

* have 2 large files and a libreoffice spreadsheet
* start webapp, make repository
* open file browser using button in webapp
* move files into repository
* make media subdir; move media into it
* open spreadsheet, modify, save
* click on New Repository button for the hang

Running recordmydesktop at the same time may also help.. Or giving a
presentation in Australia. :/

-------

Hypotheses:

* Warp's slowloris protection could be triggering. Possibly by the
  repeated hits to update the alerts? I added a settingsOnException handler
  that logs all exceptions, and ThreadKilled is happening several times.
  The only place in Warp that kills threads is due to a timeout installed
  for that. 

  **Verified** Bug filed upstream:  <https://github.com/yesodweb/wai/issues/146>

  ** workaround in place **

* Something deep in git-annex, such as the inotidy code, could be
  preventing a web server thread from running. But then why do other
  tabs and other web browsers work while it's stuck?
  It would have to affect only 1 thread.

-------

I captured a clean protocol dump of this happening. It includes only the
final, hanging http request and subsequent traffic, not the setup.

We can see the web browser send a request. The server ACKs it at the TCP
level, but never sends any reply. The web browser continues sending TCP
keep-alive packets, which are acked by the server. This continued as long
as the browser tab was left open.

Question: Did the browser send a complete & valid request? The last part
sent is a cookie and "\r\n\r\n".. So it seems complete. Unless warp is
expecting a request body?

<pre>
17:22:30.533079 IP localhost.localdomain.53239 > localhost.localdomain.45836: Flags [P.], seq 4237976899:4237977772, ack 2608808926, win 2048, options [nop,nop,TS val 4895706 ecr 4885760], length 873
	0x0000:  4500 039d be84 4000 4006 7ad4 7f00 0001  E.....@.@.z.....
	0x0010:  7f00 0001 cff7 b30c fc9a 6543 9b7f 43de  ..........eC..C.
	0x0020:  8018 0800 0192 0000 0101 080a 004a b3da  .............J..
	0x0030:  004a 8d00 4745 5420 2f63 6f6e 6669 672f  .J..GET./config/
	0x0040:  7265 706f 7369 746f 7279 3f61 7574 683d  repository?auth=
	0x0050:  6437 6266 3037 3438 6663 3863 3031 3965  d7bf0748fc8c019e
	0x0060:  6230 3966 3530 3631 6164 6663 3861 3563  b09f5061adfc8a5c
	0x0070:  3430 3437 3633 6562 3736 6630 6163 3533  404763eb76f0ac53
	0x0080:  3663 3362 6230 3066 3835 6663 6361 3233  6c3bb00f85fcca23
	0x0090:  6235 3639 3764 3332 3464 3737 3930 3063  b5697d324d77900c
	0x00a0:  3739 3532 6430 6165 3235 3166 6331 6337  7952d0ae251fc1c7
	0x00b0:  3532 3632 6330 3233 6265 3936 3066 3563  5262c023be960f5c
	0x00c0:  3364 6135 6532 6262 6234 3639 3863 3035  3da5e2bbb4698c05
	0x00d0:  2048 5454 502f 312e 310d 0a48 6f73 743a  .HTTP/1.1..Host:
	0x00e0:  2031 3237 2e30 2e30 2e31 3a34 3538 3336  .127.0.0.1:45836
	0x00f0:  0d0a 436f 6e6e 6563 7469 6f6e 3a20 6b65  ..Connection:.ke
	0x0100:  6570 2d61 6c69 7665 0d0a 4163 6365 7074  ep-alive..Accept
	0x0110:  3a20 7465 7874 2f68 746d 6c2c 6170 706c  :.text/html,appl
	0x0120:  6963 6174 696f 6e2f 7868 746d 6c2b 786d  ication/xhtml+xm
	0x0130:  6c2c 6170 706c 6963 6174 696f 6e2f 786d  l,application/xm
	0x0140:  6c3b 713d 302e 392c 2a2f 2a3b 713d 302e  l;q=0.9,*/*;q=0.
	0x0150:  380d 0a55 7365 722d 4167 656e 743a 204d  8..User-Agent:.M
	0x0160:  6f7a 696c 6c61 2f35 2e30 2028 5831 313b  ozilla/5.0.(X11;
	0x0170:  204c 696e 7578 2069 3638 3629 2041 7070  .Linux.i686).App
	0x0180:  6c65 5765 624b 6974 2f35 3337 2e31 3720  leWebKit/537.17.
	0x0190:  284b 4854 4d4c 2c20 6c69 6b65 2047 6563  (KHTML,.like.Gec
	0x01a0:  6b6f 2920 4368 726f 6d65 2f32 342e 302e  ko).Chrome/24.0.
	0x01b0:  3133 3132 2e36 3820 5361 6661 7269 2f35  1312.68.Safari/5
	0x01c0:  3337 2e31 370d 0a52 6566 6572 6572 3a20  37.17..Referer:.
	0x01d0:  6874 7470 3a2f 2f31 3237 2e30 2e30 2e31  http://127.0.0.1
	0x01e0:  3a34 3538 3336 2f3f 6175 7468 3d64 3762  :45836/?auth=d7b
	0x01f0:  6630 3734 3866 6338 6330 3139 6562 3039  f0748fc8c019eb09
	0x0200:  6635 3036 3161 6466 6338 6135 6334 3034  f5061adfc8a5c404
	0x0210:  3736 3365 6237 3666 3061 6335 3336 6333  763eb76f0ac536c3
	0x0220:  6262 3030 6638 3566 6363 6132 3362 3536  bb00f85fcca23b56
	0x0230:  3937 6433 3234 6437 3739 3030 6337 3935  97d324d77900c795
	0x0240:  3264 3061 6532 3531 6663 3163 3735 3236  2d0ae251fc1c7526
	0x0250:  3263 3032 3362 6539 3630 6635 6333 6461  2c023be960f5c3da
	0x0260:  3565 3262 6262 3436 3938 6330 350d 0a41  5e2bbb4698c05..A
	0x0270:  6363 6570 742d 456e 636f 6469 6e67 3a20  ccept-Encoding:.
	0x0280:  677a 6970 2c64 6566 6c61 7465 2c73 6463  gzip,deflate,sdc
	0x0290:  680d 0a41 6363 6570 742d 4c61 6e67 7561  h..Accept-Langua
	0x02a0:  6765 3a20 656e 2d55 532c 656e 3b71 3d30  ge:.en-US,en;q=0
	0x02b0:  2e38 0d0a 4163 6365 7074 2d43 6861 7273  .8..Accept-Chars
	0x02c0:  6574 3a20 4953 4f2d 3838 3539 2d31 2c75  et:.ISO-8859-1,u
	0x02d0:  7466 2d38 3b71 3d30 2e37 2c2a 3b71 3d30  tf-8;q=0.7,*;q=0
	0x02e0:  2e33 0d0a 436f 6f6b 6965 3a20 5f53 4553  .3..Cookie:._SES
	0x02f0:  5349 4f4e 3d45 3363 7455 496c 7341 5451  SION=E3ctUIlsATQ
	0x0300:  3631 694c 6d54 6954 7131 6f37 6465 7830  61iLmTiTq1o7dex0
	0x0310:  3361 6f57 3049 4b63 7663 467a 5838 4344  3aoW0IKcvcFzX8CD
	0x0320:  5432 7666 4b31 6c42 416d 6279 3166 764f  T2vfK1lBAmby1fvO
	0x0330:  4643 7952 7863 6f5a 6277 5633 6a4b 4971  FCyRxcoZbwV3jKIq
	0x0340:  6b35 6958 4674 7557 5261 6b48 6944 6132  k5iXFtuWRakHiDa2
	0x0350:  7769 3075 2f53 6430 5a49 7a75 4464 7947  wi0u/Sd0ZIzuDdyG
	0x0360:  774f 6a31 7838 3130 356a 772f 5a2b 355a  wOj1x8105jw/Z+5Z
	0x0370:  6f4b 6f48 396e 6779 6e4b 5366 5839 742f  oKoH9ngynKSfX9t/
	0x0380:  6862 4b79 435a 6966 7739 4148 3053 6d4b  hbKyCZifw9AH0SmK
	0x0390:  436e 4c38 5358 513d 3d0d 0a0d 0a         CnL8SXQ==....
17:22:30.571152 IP localhost.localdomain.45836 > localhost.localdomain.53239: Flags [.], ack 873, win 2048, options [nop,nop,TS val 4895716 ecr 4895706], length 0
	0x0000:  4500 0034 f15b 4000 4006 4b66 7f00 0001  E..4.[@.@.Kf....
	0x0010:  7f00 0001 b30c cff7 9b7f 43de fc9a 68ac  ..........C...h.
	0x0020:  8010 0800 fe28 0000 0101 080a 004a b3e4  .....(.......J..
	0x0030:  004a b3da                                .J..
17:22:35.803152 IP localhost.localdomain.53240 > localhost.localdomain.45836: Flags [.], ack 2157632553, win 2048, options [nop,nop,TS val 4897024 ecr 4885760], length 0
	0x0000:  4500 0034 3a63 4000 4006 025f 7f00 0001  E..4:c@.@.._....
	0x0010:  7f00 0001 cff8 b30c 7533 e963 809a dc29  ........u3.c...)
	0x0020:  8010 0800 fe28 0000 0101 080a 004a b900  .....(.......J..
	0x0030:  004a 8d00                                .J..
17:22:35.803213 IP localhost.localdomain.45836 > localhost.localdomain.53240: Flags [.], ack 1, win 2048, options [nop,nop,TS val 4897024 ecr 4840696], length 0
	0x0000:  4500 0034 10e5 4000 4006 2bdd 7f00 0001  E..4..@.@.+.....
	0x0010:  7f00 0001 b30c cff8 809a dc29 7533 e964  ...........)u3.d
	0x0020:  8010 0800 fe28 0000 0101 080a 004a b900  .....(.......J..
	0x0030:  0049 dcf8                                .I..
17:23:15.611193 IP localhost.localdomain.53239 > localhost.localdomain.45836: Flags [.], ack 1, win 2048, options [nop,nop,TS val 4906976 ecr 4895716], length 0
	0x0000:  4500 0034 be85 4000 4006 7e3c 7f00 0001  E..4..@.@.~<....
	0x0010:  7f00 0001 cff7 b30c fc9a 68ab 9b7f 43de  ..........h...C.
	0x0020:  8010 0800 fe28 0000 0101 080a 004a dfe0  .....(.......J..
	0x0030:  004a b3e4                                .J..
17:23:15.611290 IP localhost.localdomain.45836 > localhost.localdomain.53239: Flags [.], ack 873, win 2048, options [nop,nop,TS val 4906976 ecr 4895706], length 0
	0x0000:  4500 0034 f15c 4000 4006 4b65 7f00 0001  E..4.\@.@.Ke....
	0x0010:  7f00 0001 b30c cff7 9b7f 43de fc9a 68ac  ..........C...h.
	0x0020:  8010 0800 fe28 0000 0101 080a 004a dfe0  .....(.......J..
	0x0030:  004a b3da                                .J..
</pre>

[[!tag /design/assistant]]
[[done]]