Hi,
I use nginx 0.8.54 together with latest keepalive module and ajp module to build proxy for java runtime, and notice when "accept mutax" is on, the number of upstream connections is 10 to 20 times of that when "accept mutax" is off.
The test environment is 2 CPU cores, 4G RAM.
Nginx conf:
worker_processes 2;
http {
upstream java_server {
server 127.0.0.1:8009 srun_id=jvm1;
keepalive 500 single;
}
server {
listen 80 default;
server_name xxx.xxx.xxx
location /index.jsp {
ajp_intercept_errors on;
ajp_hide_header X-Powered-By;
ajp_buffers 16 8k;
ajp_buffer_size 8k;
ajp_read_timeout 30;
ajp_connect_timeout 20;
ajp_pass java_server;
}
}
}
I use ab -c 100 -n 50000 XXXX to simulate visit, and netstat -an | grep 8009 -c to see how many connections to upstream is built.
when "accept mutax" is on, there is 28473 connections to upstream, but only 1674 connections when "accept mutax" is off.
If there is only on work process, the result is similar to "accept mutax" is off.
Captures packets:
When "accept mutax" is off, It is clear that it is upstream server who closes the connection:
2169 0.215060 127.0.0.1 127.0.0.1 TCP 41621 > 8009 [ACK] Seq=1333 Ack=4654 Win=42496 Len=0 TSV=1513155905 TSER=1513155905
12474 15.216063 127.0.0.1 127.0.0.1 TCP 8009 > 41621 [FIN, ACK] Seq=4654 Ack=1333 Win=42496 Len=0 TSV=1513159655 TSER=1513155905
12499 15.223667 127.0.0.1 127.0.0.1 TCP 41621 > 8009 [FIN, ACK] Seq=1333 Ack=4655 Win=42496 Len=0 TSV=1513159657 TSER=1513159655
12500 15.223672 127.0.0.1 127.0.0.1 TCP 8009 > 41621 [ACK] Seq=4655 Ack=1334 Win=42496 Len=0 TSV=1513159657 TSER=1513159657
When "accept mutax" is on, it comes to nginx:
5966 1.479476 127.0.0.1 127.0.0.1 TCP 54788 > 8009 [ACK] Seq=297 Ack=1035 Win=34944 Len=0 TSV=1513225689 TSER=1513225689
6008 1.483907 127.0.0.1 127.0.0.1 TCP 54788 > 8009 [FIN, ACK] Seq=297 Ack=1035 Win=34944 Len=0 TSV=1513225690 TSER=1513225689
6012 1.484331 127.0.0.1 127.0.0.1 TCP 8009 > 54788 [FIN, ACK] Seq=1035 Ack=298 Win=34944 Len=0 TSV=1513225690 TSER=1513225690
6013 1.484342 127.0.0.1 127.0.0.1 TCP 54788 > 8009 [ACK] Seq=298 Ack=1036 Win=34944 Len=0 TSV=1513225690 TSER=1513225690
I fix this by simply adding a test in the ngx_http_upstream_keepalive_close_handler
static void
ngx_http_upstream_keepalive_close_handler(ngx_event_t *ev)
{
ngx_http_upstream_keepalive_srv_conf_t *conf;
ngx_http_upstream_keepalive_cache_t *item;
int n;
u_char buf;
ngx_connection_t *c;
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ev->log, 0,
"keepalive close handler");
c = ev->data;
item = c->data;
conf = item->conf;
if ((n = c->recv(c, &buf, 1)) == 0) {
ngx_queue_remove(&item->queue);
ngx_close_connection(item->connection);
ngx_queue_insert_head(&conf->free, &item->queue);
}
}
However, I never understand why it fires the event handler.
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