# How come nginx is only accepting 1 connection?

**URL:** <https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949>\
**Category:** NGINX\
**Created:** [January 18, 2011, 3:45pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949 "2011-01-18T15:45:31Z")\
**Posts on this page:** 13\
**Page:** 1

<div class="post-metadata">

**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\
**Post date:** [January 18, 2011, 3:45pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/1 "2011-01-18T15:45:31Z")

</div>

Dear Nginx Community,

I’m trying to setup nginx with the pylons framework via uwsgi.  
Nginx-0.8.54 is compiled using:

./configure --add-module=…/nginx-upload-progress-module/  
–prefix=/mynginx-bin --with-http\_ssl\_module  
–add-module=…/nginx\_accept\_language\_module

And nginx.conf is:

worker\_processes 1;  
daemon off;  
events {  
worker\_connections 1024;  
}  
http {  
include mime.types;  
default\_type application/octet-stream;  
upload\_progress proxied 512m;  
server {  
listen 5002;  
server\_name localhost;  
charset utf-8;  
root /myproj/public;  
index index.html;  
client\_max\_body\_size 2048m;  
location / {  
uwsgi\_pass unix:/myproj/uwsgi.socket;  
include uwsgi\_params;  
uwsgi\_param SCRIPT\_NAME /;  
track\_uploads proxied 30s;  
}  
location ^~ /upload\_progress {  
report\_uploads proxied;  
}  
}  
}

You can see there I’m trying to create the ajax file uploader. UWSGI  
and pylons are the latest. UWSGI is using --paste parameter. I have to  
put in “daemon off;” because this is meant for development, and I’ll  
have console interruption control.

I discovered that my nginx can only accept 1 connection at a time.  
When a large file is uploading, all ajax calls to /upload\_progress are  
blocked. The requests are only answered after the upload is finished.  
Opening another tab for the file upload form will also be blocked  
until the upload finishes. It appears that nginx is throttling to  
process only 1 request at a time.

Why does this happen? Did I somehow touched some settings to cause this?

## Thanks!

Best regards,  
He Shiming

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 4:02pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/2 "2011-01-18T16:02:29Z")

</div>

Il giorno 18/gen/2011, alle ore 15.44, He Shiming ha scritto:

> ```
> listen 5002;
> }
> 
> ```
> 
> I discovered that my nginx can only accept 1 connection at a time.  
> When a large file is uploading, all ajax calls to /upload\_progress are  
> blocked. The requests are only answered after the upload is finished.  
> Opening another tab for the file upload form will also be blocked  
> until the upload finishes. It appears that nginx is throttling to  
> process only 1 request at a time.
> 
> Why does this happen? Did I somehow touched some settings to cause this?
> 
> T

How many processes/workers have you setup in uWSGI ?

It look like you are running uWSGI with only one process (or thread, or  
async core)  
add -p and you should solve it

–  
Roberto De Ioris

> **[unbit - Overview](https://github.com/unbit)**
>
> makers of uWSGI and many more open source projects - unbit

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 4:08pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/3 "2011-01-18T16:08:46Z")

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On Tue, Jan 18, 2011 at 11:00 PM, Roberto De Ioris [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> 

Thanks but it didn’t make any difference. I’ve seen 10 worker spawned,  
however, nginx isn’t dispatching requests to these uwsgi workers, if  
opening more than 1 tab at a time.

Any other ideas?

–  
Best regards,  
He Shiming

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 4:19pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/4 "2011-01-18T16:19:29Z")

</div>

Hello!

On Tue, Jan 18, 2011 at 11:07:20PM +0800, He Shiming wrote:

> > 
> 
> Thanks but it didn’t make any difference. I’ve seen 10 worker spawned,  
> however, nginx isn’t dispatching requests to these uwsgi workers, if  
> opening more than 1 tab at a time.
> 
> Any other ideas?

Other ideas: don’t test with browser, test with telnet/netcat. Or  
at least make sure you’re monitoring what’s happening on the wire  
(with tcpdump/wireshark) while doing so.

For this particular case - most likly it’s your browser which  
limits connections.

Maxim D.

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 4:26pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/5 "2011-01-18T16:26:23Z")

</div>

On Tue, Jan 18, 2011 at 11:18 PM, Maxim D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> Other ideas: don’t test with browser, test with telnet/netcat. Or  
> at least make sure you’re monitoring what’s happening on the wire  
> (with tcpdump/wireshark) while doing so.
> 
> For this particular case - most likly it’s your browser which  
> limits connections.
> 
> Maxim D.

Unfortunately telnet showed the same behavior. I really couldn’t  
understand what settings could cause this behavior?

–  
Best regards,  
He Shiming

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 4:43pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/6 "2011-01-18T16:43:58Z")

</div>

On Tue, Jan 18, 2011 at 11:30 PM, Sven ‘Darkman’ Michels  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Hi,
> 
> I’m not familar with UWSGI but i think this could be the problem. If you  
> do not run demonized it may only be able to handle one request per time.  
> So for testing i would recommend to start it in deamon mode, check if  
> the problem still exist and if not you know whats wrong.
> 
> Regards,  
> Sven

Hmm… I tried daemon on. But the behavior is still the same. I start  
to think I didn’t compile it right. This is really weird…

I’ve got another instance of nginx running fine, it’s the ubuntu  
software repo version.

I compiled and configured exactly as my first message. I just don’t  
see any reason that the number of connections is limited to 1.

–  
Best regards,  
He Shiming

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 4:52pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/7 "2011-01-18T16:52:45Z")

</div>

Il giorno 18/gen/2011, alle ore 16.42, He Shiming ha scritto:

> > Sven
> 
> Hmm… I tried daemon on. But the behavior is still the same. I start  
> to think I didn’t compile it right. This is really weird…

Daemon mode is not related to this kind of problems. For example  
if you start uWSGI from upstart or supervisor you do not daemonize it  
and so on.

Can you post the full uWSGI command line ?

–  
Roberto De Ioris

> **[unbit - Overview](https://github.com/unbit)**
>
> makers of uWSGI and many more open source projects - unbit

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 4:56pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/8 "2011-01-18T16:56:31Z")

</div>

Hello!

On Tue, Jan 18, 2011 at 11:24:46PM +0800, He Shiming wrote:

> Unfortunately telnet showed the same behavior. I really couldn’t  
> understand what settings could cause this behavior?

There are no settings in nginx which may cause such behaviour  
(well, problems may happen with “sendfile on;” without  
sendfile\_max\_chunk set while sending huge files over fast links -  
due to blocking in sendfile() syscall, but it’s not your case).

This may be problem in track\_uploads module though, it’s third party  
one and I have no idea about it’s bugs.

You may test the following:

1. If requesting normal static file (or just sending an invalid  
request) works.

2. If doing the same with track\_uploads disabled works.

Maxim D.

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 5:24pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/9 "2011-01-18T17:24:11Z")

</div>

2011/1/18 Maxim D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> You may test the following:
> 
> 1. If requesting normal static file (or just sending an invalid  
> request) works.
> 
> 2. If doing the same with track\_uploads disabled works.
> 
> Maxim D.

UWSGI is like this: uwsgi --paste  
config:/pylonsenv/ajaxupload/production.ini --socket  
/pylonsenv/ajaxupload/uwsgi.socket -H /pylonsenv -p 10

I tried disabling the upload progress module. I even tried upgrading  
to nginx 0.9.3, disabling all modules during compiling. Nothing works.

–  
Best regards,  
He Shiming

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 4:31pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/10 "2011-01-18T16:31:24Z")

</div>

Hi,

Am 18.01.2011 15:44, schrieb He Shiming:

> You can see there I’m trying to create the ajax file uploader. UWSGI  
> and pylons are the latest. UWSGI is using --paste parameter. I have to  
> put in “daemon off;” because this is meant for development, and I’ll  
> have console interruption control.

I’m not familar with UWSGI but i think this could be the problem. If you  
do not run demonized it may only be able to handle one request per time.  
So for testing i would recommend to start it in deamon mode, check if  
the problem still exist and if not you know whats wrong.

Regards,  
Sven

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 5:34pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/11 "2011-01-18T17:34:14Z")

</div>

Il giorno 18/gen/2011, alle ore 17.23, He Shiming ha scritto:

> > 
> 
> UWSGI is like this: uwsgi --paste  
> config:/pylonsenv/ajaxupload/production.ini --socket  
> /pylonsenv/ajaxupload/uwsgi.socket -H /pylonsenv -p 10
> 
> I tried disabling the upload progress module. I even tried upgrading  
> to nginx 0.9.3, disabling all modules during compiling. Nothing works.
> 
> -

Are you sure you are not running pylons with debug enabled ?

It can cause some problems with multiprocess apps

–  
Roberto De Ioris

> **[unbit - Overview](https://github.com/unbit)**
>
> makers of uWSGI and many more open source projects - unbit

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 5:41pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/12 "2011-01-18T17:41:46Z")

</div>

On Wed, Jan 19, 2011 at 12:33 AM, Roberto De Ioris [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> Are you sure you are not running pylons with debug enabled ?
> 
> It can cause some problems with multiprocess apps
> 
> –  
> Roberto De Ioris  
> [http://unbit.it](http://unbit.it)

Hi, thank you all for your help. Eventually I came to the conclusion  
that during the uploading, nginx gets so busy with disk i/o, it can’t  
process any other requests.

It’s a local testing so I’m uploading fairly large files to simulate  
the waiting. So it looks like there’s no problem after all. I just  
have to figure out how to throttle upload speed to really simulate  
this.

–  
Best regards,  
He Shiming

---

<div class="post-metadata">

**Author:** ![He\_Shiming](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a9a28c/32.png) [@He\_Shiming](https://www.ruby-forum.com/u/He_Shiming)\
**Post date:** [January 18, 2011, 7:22pm UTC](https://www.ruby-forum.com/t/how-come-nginx-is-only-accepting-1-connection/201949/13 "2011-01-18T19:22:57Z")

</div>

Hello!

On Wed, Jan 19, 2011 at 12:39:56AM +0800, He Shiming wrote:

> > 
> 
> Hi, thank you all for your help. Eventually I came to the conclusion  
> that during the uploading, nginx gets so busy with disk i/o, it can’t  
> process any other requests.
> 
> It’s a local testing so I’m uploading fairly large files to simulate  
> the waiting. So it looks like there’s no problem after all. I just  
> have to figure out how to throttle upload speed to really simulate  
> this.

Yep, indeed, you’re right. While reading request body nginx  
doesn’t return to event loop until it’s read all the data from  
socket recv buffer. This may cause it keep calling recv() if  
uploading over fast link and client\_body\_buffer\_size is smaller  
than socket’s recv buffer.

Using bigger client\_body\_buffer\_size (bigger than recv buffers  
used) should help.

Maxim D.