Question about workers and proxying to dead upstream


#1

Hey guys…

We have a setup where we serve static files from our nginx servers and
if the file doesn’t exist we proxy to a backend server (that generates
a static file, and we have another app to delete the static files when
they get to old).

The config file looks something like this (on my machine i am testing
with an apache running on port 8888):

worker_processes 1;
events {
worker_connections 5; # 5 for testing. would be much higher in
production
}

upstream dynamic {
server localhost:8888;
}

location / {
ssi on;
try_files $uri $uri/index.html @nothere;
break;
}

location @nothere {
break;

        proxy_redirect on;

        # setting extra header
        proxy_set_header   X-Real-IP        $remote_addr;
        proxy_set_header   X-Forwarded-For 

$proxy_add_x_forwarded_for;

        # setting timeout values for the proxying
        proxy_connect_timeout      90;
        proxy_send_timeout         90;
        proxy_read_timeout         90;

        # setting proxy buffer sizes
        proxy_buffer_size          4k;
        proxy_buffers              4 32k;
        proxy_busy_buffers_size    64k;
        proxy_temp_file_write_size 64k;

        proxy_pass http://dynamic;
}

Anyways my question is: what happens if there are 5 (number of
worker_connection*number_worker_processes) connections to a non
existing file (it has to proxy) and the backend server times out (i
have a sleep in my php for testing purpose)?
Can nginx still serve static files (file that exist)?
Will it allow 5 connections to the upstream?

I can’t find the answer on the wiki anywhere and my own test’s with ab
and curl show that it won’t allow for 5 connections to upstream
servers if it’s hanging on one of them (it will show a “The page you
are looking for is temporarily unavailable.
Please try again later.”) - is this correct?

best,
Adrian


#2

On Mon, May 04, 2009 at 11:49:45PM +0200, Adrian Bak wrote:

worker_processes 1;
location / {
# setting extra header
proxy_buffers 4 32k;
Can nginx still serve static files (file that exist)?
Will it allow 5 connections to the upstream?

I can?t find the answer on the wiki anywhere and my own test?s with ab
and curl show that it won?t allow for 5 connections to upstream
servers if it?s hanging on one of them (it will show a ?The page you
are looking for is temporarily unavailable.
Please try again later.?) - is this correct?

Yes. Note also, that one connection is required for client side,
and one connection is required for proxy/fastcgi side. Therefore
for each proxied request you need 2 connections.


#3

Thanks… That’s what I wanted to hear.
Now I go on and try to sell it to the “big man upstairs” :slight_smile:

best,
Adrian

2009/5/5 Igor S. removed_email_address@domain.invalid: