Function clause error in cowboy_simple_bridge_anchor.erl

[Ramkrishna Kulkarni]

Hello,

After refreshing a page several times, I click on a button and start seeing these errors in the console continuously. Almost one every second.

Instead of refresh, if I redirect to this page (wf:redirect/1) this error goes away.

Could you please help me understand what this is?

Thanks.

...

          <<>>],

         [{file,"src/cow_qs.erl"},{line,34}]},

 {sbw,cache_post_params,1,[{file,"src/sbw.erl"},{line,138}]},

 {simple_bridge,inner_make,2,[{file,"src/simple_bridge.erl"},{line,86}]},

 {cowboy_simple_bridge_anchor,handle,2,

                              [{file,"src/cowboy_bridge_modules/cowboy_simple_bridge_anchor.erl"},

                               {line,33}]},

 {cowboy_handler,handler_handle,4,

                 [{file,"src/cowboy_handler.erl"},{line,111}]},

 {cowboy_protocol,execute,4,[{file,"src/cowboy_protocol.erl"},{line,442}]}]

=ERROR REPORT==== 11-Aug-2015::11:11:50 ===

Error in process <0.10105.0> on node 'my...@127.0.0.1' with exit value: {[{reason,function_clause},{mfa,{cowboy_simple_bridge_anchor,handle,2}},{stacktrace,[{cowboy_simple_bridge_anchor,handle,2,[{file,"src/cowboy_bridge_modules/cowboy_simple_bridge_anchor.erl"},{line,33}]},{cowboy_handler...

[Ramkrishna Kulkarni]

Hello,

I've pasted full log on Gist https://gist.github.com/rkulkarni/b2df413fb0aa12445970

Error status with parsing query params.

Error in simple_bridge:make/2 - error - function_clause

[{cow_qs,parse_qs_name,

         [<<"=&args=g2wAAA ...

Thanks.

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[Jesse Gumm]

Interesting. Based on the error, I'd guess cow_qs is choking on the empty key-value in the submitted post string (=&).

Weird that that's being submitted at all like that and that using wf:redirect solves it. I'll have to see if I can reproduce.

[Ramkrishna Kulkarni]

Hi Jesse,

Do you have any more inputs on this issue? I'm facing this issue quite often now. You can see the full error log here https://gist.github.com/rkulkarni/85c0adb982ce5b469d14.

Thanks.

[Ramkrishna Kulkarni]

Another strange thing I've noticed is that client keeps on making AJAX request when this error occurs.

Request URL:https://x/oetest?mode=search

Request Method:POST

Status Code:500 Internal Server Error

Remote Address:x.x.x.x:443

https://gist.github.com/rkulkarni/13dae0142833beaaac83

Ram

[Ramkrishna Kulkarni]

Hi Jesse,

Could this be due to failed websocket connection establishment? I've seen this error in browser console few times when this happens.

WebSocket connection to 'wss://x/oetest?mode=search' failed: Error in connection establishment: net::ERR_CONNECTION_TIMED_OUT

Also, wondering if there is a way to disable websockets. 

Thanks for the help.

Ram

[Jesse Gumm]

Hey Ram,

Thanks for the gists.

I'm looking into this deeper right now. It's definitely cow_qs choking
on the "&= produced by line 33 of the "POST" gist.

Do you have a textbox (or other form element) on the page that isn't a
Nitrogen element?

I'm spitballing here, but I was able to at least reproduce it myself,
and fixed it with this commit. Give this a shot and let me know. If
it works for you, I'll merge it into mainline as is:
https://github.com/choptastic/nitrogen_core/commit/0a43407c3dc4fd9fcf025d79978d64a0813c5c55


On Tue, Dec 8, 2015 at 1:52 AM, Ramkrishna Kulkarni

--
Jesse Gumm
Owner, Sigma Star Systems
414.940.4866 || sigma-star.com || @jessegumm

[Jesse Gumm]

Oh, and as for disabling websockets, this particular error only seemed
to occur on fallback to using POSTs rather than websockets, hence why
you might think it was indeed related to websockets.

BUT, you can indeed disable websockets. In your template, stick the
following code snippet near the top (preferably before loading
nitrogen.js), and WebSockets will be unavailable in your app.

<script>WebSocket = undefined;</script>

-Jesse

[Ramkrishna Kulkarni]

Thanks a lot for the fix! That did fix the problem. Also, this problem is always reproducible for me when I disable websockets.

I don't think there are any non-nitrogen elements but now I'll take a deeper look as your fix worked.

Thanks again!

[Ramkrishna Kulkarni]

Hi Jesse,

I did find couple of non-nitrogen elements on the page. But it's strange it worked most of the times but broke some times. However, it broke always with websockets disabled.

Ram

[Jesse Gumm]

Yeah, very strange that it worked most of the time.

Without seeing the code, I don't have an explanation why it was
intermittent, but at the very least, it's fixed and merged into
master.

Thanks for your patience!

On Thu, Dec 10, 2015 at 12:31 AM, Ramkrishna Kulkarni