Hello Super Heroes.

I want to limit connections in a service. So I used max_conns directive in upstream.

But it allows twice connections as many as I've set.

So, I suspected myself. Maybe… Am I used the direction in wrong way.

And I found some descriptions about “max_conns” exception rules.

http://nginx.org/en/docs/http/ngx_http_upstream_module.html#server

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If idle keepalive connections, multiple workers, and the shared memory are enabled, the total number of active and idle connections to the proxied server may exceed the max_conns value.
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And I’ve tried change configuration of “keepalive”, “worker numbers” and “shared memory”. But it still the same. It allowed twice connections as many as I expected.


My config file is blow.

#
# max_conns Test Server
#

proxy_cache_path /etc/nginx/cache levels=1:2 keys_zone=my_cache:10m max_size=10g inactive=60s use_temp_path=off;

proxy_cache_key "$scheme$request_method$host$request_uri";

upstream t10 {
zone t1_z 1M;
server localhost:8080 max_conns=5 max_fails=0 fail_timeout=1s;
}

server {
listen 8000 ;
location /test/1 {
proxy_pass http://t10; # it takes 1 seconds
}
}

And I run a shell script blow.

for v in {1..40}
do
curl 'localhost:8000/test/1' -i -l >> 30_2.log &
sleep 0.01
done

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The url ‘localhost:8080/test/1’ takes 1 seconds.

I expected 5 succeed and 35 fail. But it always 10 succeed, 30 failed.