Nginx Module Concurrency Query

[Danny Glover]

Hello, 

I have been trying to get a simple nginx_module working. I referred
http://www.evanmiller.org/nginx-modules-guide.html and found it very
useful. 

The module takes "http://10.90.50.31:1257/hello?w=lelj&ljd=22112" and
sleeps for few sec and simply prints the URI. 

Here is the code :-
----
#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>
#include <unistd.h>

static char *ngx_http_hello_world(ngx_conf_t *cf, ngx_command_t *cmd,
void *conf);

static ngx_command_t  ngx_http_hello_world_commands[] = {

  { ngx_string("hello_world"),
    NGX_HTTP_LOC_CONF|NGX_CONF_NOARGS,
    ngx_http_hello_world,
    0,
    0,
    NULL },

    ngx_null_command
};

//static u_char  ngx_hello_world[] = "elcome world";

static ngx_http_module_t  ngx_http_hello_world_module_ctx = {
  NULL,                          /* preconfiguration */
  NULL,                          /* postconfiguration */

  NULL,                          /* create main configuration */
  NULL,                          /* init main configuration */

  NULL,                          /* create server configuration */
  NULL,                          /* merge server configuration */

  NULL,                          /* create location configuration */
  NULL                           /* merge location configuration */
};

ngx_module_t ngx_http_hello_world_module = {
  NGX_MODULE_V1,
  &ngx_http_hello_world_module_ctx, /* module context */
  ngx_http_hello_world_commands,   /* module directives */
  NGX_HTTP_MODULE,               /* module type */
  NULL,                          /* init master */
  NULL,                          /* init module */
  NULL,                          /* init process */
  NULL,                          /* init thread */
  NULL,                          /* exit thread */
  NULL,                          /* exit process */
  NULL,                          /* exit master */
  NGX_MODULE_V1_PADDING
};

int sum(int a, int b)
{
        return a+b;
}

static ngx_int_t ngx_http_hello_world_handler(ngx_http_request_t *r)
{
  ngx_buf_t    *b;
  ngx_chain_t   out;

  r->headers_out.content_type.len = sizeof("text/html") - 1;
  r->headers_out.content_type.data = (u_char *) "text/html";

  b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));

  out.buf = b;
  out.next = NULL;

  b->pos = (r->args).data;
  b->last = (r->args).data + (r->args).len;
  b->memory = 1;
  b->last_buf = 1;

  usleep(1500000);

  r->headers_out.status = NGX_HTTP_OK;
  r->headers_out.content_length_n = (r->args).len;
  ngx_http_send_header(r);

  return ngx_http_output_filter(r, &out);
}

static char *ngx_http_hello_world(ngx_conf_t *cf, ngx_command_t *cmd,
void *conf)
{
  ngx_http_core_loc_conf_t  *clcf;

  clcf = ngx_http_conf_get_module_loc_conf(cf, ngx_http_core_module);
  clcf->handler = ngx_http_hello_world_handler;

  return NGX_CONF_OK;
}
-----

nginx.conf 
###########
worker_processes  4;
events {
    worker_connections  1024;
}
....  # ... # 

                location = /hello {
                        hello_world ;
                }
#########


But I guess, I am missing something here. 


I tried ab (Apache benchmarking) on it, and I found that response time
degrades on increasing concurrency. 

# ab -c 10 -n 100 "http://10.90.50.31:1257/hello?w=lelj&ljd=22112" 
...
Time per request:       3804.810 [ms] (mean)
...

# ab -c 20 -n 100 "http://10.90.50.31:1257/hello?w=lelj&ljd=22112" 
...
Time per request:       7587.228 [ms] (mean)
...

# ab -c 30  -n 100 "http://10.90.50.31:1257/hello?w=lelj&ljd=22112"
...
Time per request:       11376.207 [ms] (mean)
.... 


The response time was 11376ms, 7587ms, 3804ms for 30, 20, 10 concurrency
respectively.  
I am not sure what I am missing. 

Can someone please guide me on how do I make this module scale? 


- Danny

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,211552,211552#msg-211552