Re: sendfile() failed (9: Bad file descriptor) while sending request to upstream

[papajoe]

Hey Maxim!

Thank you very much for your suggestion. Unfortunately our "project" still
uses 1.13.3 (as of today only 1.13.3 is available via stretch-backports), so
the mirror module (>= 1.13.4) is not yet available for here.

I hope I will find the time to eventually report back on your config
suggestion this as soon as I have the option to run your configuration with
"live conditions".

I very much appreciate there is an official implementation for "replaying
requests" now. Keep on rocking!

Best
Benny

Posted at Nginx Forum: 
https://forum.nginx.org/read.php?21,118976,278743#msg-278743

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Re: sendfile() failed (9: Bad file descriptor) while sending request to upstream

[Maxim Dounin]

Hello!

On Thu, Feb 22, 2018 at 08:12:25AM -0500, papajoe wrote:

> Hey everybody,
> 
> I experienced this issue using nginx version 1.10.x and 1.13.x
> 
> 
> given a basic configuration like:
> 
> upstream myupstream {
> server internal01:80;
> server internal02:80 backup;
> }
> 
> server {
> listen 81 default_server;
> listen [::]:81 default_server;
> 
> server_name _;
> 
> location / {
> proxy_pass http://myupstream;
> post_action @hot_standby;
> }
> 
> location @hot_standby {
> proxy_pass http://internal02:80;
> }
> }
> 
> 
> I receive the "sendfile() failed (9: Bad file descriptor) while sending
> request to upstream"  error when trying to POST data exceeding 16k body
> size. The error does not occur for requests with less than 16k data.
> As far as I can understand the code / documentation, 16k by default (for
> 64bit systems) is the limit when nginx starts to use a tempfile instead of a
> memory buffer.
> http://nginx.org/en/docs/http/ngx_http_core_module.html#client_body_buffer_size
> 
> This makes me believe that the problem only kicks in when nginx decides to
> use a tempfile instead of an inmemory buffer.
> 
> 
> For my setup I was able to fix the issue by an alignment between
> client_body_buffer_size and client_max_body_size.
> 
> client_max_body_size1m;
> client_body_buffer_size   1m;
> 
> 
> Hope this can help anybody.

Just in case you are interested in details, this is a result in 
optimization in the proxy module, which removes the request body 
file as soon as a response is received.  Additional details can be 
found here:

http://hg.nginx.org/nginx/rev/f583559aadc7
https://trac.nginx.org/nginx/ticket/585

To fix this, consider using mirror instead of the [intentionally 
undocumented] post_action directive, see 
http://nginx.org/en/docs/http/ngx_http_mirror_module.html.

-- 
Maxim Dounin
http://mdounin.ru/
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Re: sendfile() failed (9: Bad file descriptor) while sending request to upstream

[papajoe]

Hey everybody,

I experienced this issue using nginx version 1.10.x and 1.13.x


given a basic configuration like:

upstream myupstream {
server internal01:80;
server internal02:80 backup;
}

server {
listen 81 default_server;
listen [::]:81 default_server;

server_name _;

location / {
proxy_pass http://myupstream;
post_action @hot_standby;
}

location @hot_standby {
proxy_pass http://internal02:80;
}
}


I receive the "sendfile() failed (9: Bad file descriptor) while sending
request to upstream"  error when trying to POST data exceeding 16k body
size. The error does not occur for requests with less than 16k data.
As far as I can understand the code / documentation, 16k by default (for
64bit systems) is the limit when nginx starts to use a tempfile instead of a
memory buffer.
http://nginx.org/en/docs/http/ngx_http_core_module.html#client_body_buffer_size

This makes me believe that the problem only kicks in when nginx decides to
use a tempfile instead of an inmemory buffer.


For my setup I was able to fix the issue by an alignment between
client_body_buffer_size and client_max_body_size.

client_max_body_size1m;
client_body_buffer_size   1m;


Hope this can help anybody.

Best
Benny

Posted at Nginx Forum: 
https://forum.nginx.org/read.php?21,118976,278721#msg-278721

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