[Ur] fastCGI backend and POST /.msgs HTTP/1.1 requests

[Adam Chlipala]

Thanks for that patch.  It doesn't compile on Mac OS, but it seems 
likely that there is some simple fix.

As for the original problem, it sounds like it's definitely a bug in 
Ur/Web, but I don't anticipate having the time to debug it in detail 
myself for another few weeks.  It seems likely that your theory is 
right, that your library's unusual (for Ur/Web) use of process spawning 
has triggered some pathology.

On 04/15/2017 03:05 PM, Sergey Mironov wrote:
> I've carried out more experiments to find out the source of the zero
> request_id problem, without success. There is an important detail: I
> use FFI library (urweb-callback) to spawn async jobs from custom
> worker threads. Those threads do run uw_begin/uw_commit/uw_rollback
> (and eventually call [send] on stored channels), but they don't handle
> normal http requests and AFAIK should never trigger calls to
> fastcgi_write method. Please tell me if I am wrong and  uw_begin may
> actually result in call to fastcgi_write.
>
> Besides that, I tracked another issue regarding socket inheritance by
> child processes due to missing CLOEXEC flag.
>
> Here is the pull request  https://github.com/urweb/urweb/pull/75
>
> Regards,
> Sergey
>
>
> 2017-04-15 1:46 GMT+03:00 Sergey Mironov <grrwlf at gmail.com>:
>> Yes, I am able to reproduce the error with the latest Ur/Web. I've
>> checked the related code and didn't find any obvious errors. But, if I
>> replace the following assignment
>>    o->r.requestIdB0 = current_request_id & 0x000000ff;
>> with the assignment to 1, the error disappears.
>>
>> Very strange.
>>
>> Regards,
>> Sergey
>>
>>
>> 2017-04-14 18:28 GMT+03:00 Benjamin Barenblat <benjamin at barenblat.name>:
>>> On Thu, Apr 13, 2017 at 6:35 PM, Sergey Mironov <grrwlf at gmail.com> wrote:
>>>> I am facing a problem running the application compiled in FastCGI mode
>>>> with nginx. The error on server says
>>>>
>>>> 2017/04/14 01:19:13 [error] 11847#0: *2 upstream sent unexpected
>>>> FastCGI request id low byte: 0 while reading response header from
>>>> upstream, client: 127.0.0.1, server: , request: "POST /.msgs
>>>> HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host:
>>>> "127.0.0.1:8081", referrer: "http://127.0.0.1:8081/App/convertFile/48"
>>> That sounds suspiciously like
>>> <https://github.com/urweb/urweb/issues/57>. Are you running the latest
>>> version of Ur/Web?
>>>
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