Archive for August, 2009

Nginx Internals Talk in Guangzhou, China

nginx map

nginx map (click to view large image)

I’m going to give a free talk on nginx’s internals next month (September 19), in Guangzhou, China.

I’ve been reading the source code of nginx for a few days. Digging into this charming code is really a pleasant experience, though at first glance it appeared a little bit difficult to understand. Nginx becomes more and more popular, but unfortunately there is not enough documentation on its architecture and implementation. Now that I have spent a considerable amount of time reading the source code and have gained some knowledge, why not share it with those who want to know things under the hood?

So, if you are interested in this talk and you can be in Guangzhou that day, feel free to join in. Please comment on this post or drop me an email to let me know which parts you are interested in (see the mind map above, draft version though).

There might be a thousand Hamlets in a thousand people’s eyes. Note that I’m not Igor, and the only way I try to understand the nuts and bolts is by reverse engineering it, hence I can’t guarantee you no mistakes or misunderstandings in my talk. And frankly, it is not a trivial topic after all, not only because of the size of nginx’s code base, but also its elaborate design.

The speech will be in Chinese while slides will be in English. Specifics of time and location are coming soon. Stay tuned.

Time: 14:30-17:30, September 19, 2009
Location: Netease Building Tower E, Guangzhou Information Port #16 Keyun RD. Tianhe District, Guangzhou

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A Handy Strace Option

I didn’t notice the ‘-ff’ option of strace until I came across it today. By turning it on, not only fork(2)s can be followed, but also each process’s trace will be written to, where pid is the process id of each process. Typical usage might look like this:

# strace -o tracelog.txt -ff -T command

This option can be quite handy, when debugging programs that spawn child processes.

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Creating a Hello World! Nginx Module

Some of my friends think nginx modules are very difficult to write. Sure it’s not so easy but it’s not that hard either. The only problem is that the documentation is not enough. But don’t let this scare yourself away, the situation is improving.

So I write a hello world nginx module here. It’s pretty short and with enough comments. If you’re a new nginx module developer, feel free to take it as an example and replace hello with whatever your module name is, then start your happy nginx module hacking journey. And I’ll write more topics on nginx soon. Look for it!  :D


 * Copyright (C) Joshua Zhu,
#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>
static char *ngx_http_hello(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);
static ngx_command_t ngx_http_hello_commands[] = {
    { ngx_string("hello"),
      NULL },
static u_char ngx_hello_string[] = "Hello, world!";
static ngx_http_module_t ngx_http_hello_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_module = {
    &ngx_http_hello_module_ctx,    /* module context */
    ngx_http_hello_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 */
static ngx_int_t
ngx_http_hello_handler(ngx_http_request_t *r)
    ngx_int_t    rc;
    ngx_buf_t   *b;
    ngx_chain_t  out;
    /* we response to 'GET' and 'HEAD' requests only */
    if (!(r->method & (NGX_HTTP_GET|NGX_HTTP_HEAD))) {
        return NGX_HTTP_NOT_ALLOWED;
    /* discard request body, since we don't need it here */
    rc = ngx_http_discard_request_body(r);
    if (rc != NGX_OK) {
        return rc;
    /* set the 'Content-type' header */
    r->headers_out.content_type_len = sizeof("text/html") - 1;
    r->headers_out.content_type.len = sizeof("text/html") - 1;
    r-> = (u_char *) "text/html";
    /* send the header only, if the request type is http 'HEAD' */
    if (r->method == NGX_HTTP_HEAD) {
        r->headers_out.status = NGX_HTTP_OK;
        r->headers_out.content_length_n = sizeof(ngx_hello_string) - 1;
        return ngx_http_send_header(r);
    /* allocate a buffer for your response body */
    b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));
    if (b == NULL) {
    /* attach this buffer to the buffer chain */
    out.buf = b; = NULL;
    /* adjust the pointers of the buffer */
    b->pos = ngx_hello_string;
    b->last = ngx_hello_string + sizeof(ngx_hello_string) - 1;
    b->memory = 1;    /* this buffer is in memory */
    b->last_buf = 1;  /* this is the last buffer in the buffer chain */
    /* set the status line */
    r->headers_out.status = NGX_HTTP_OK;
    r->headers_out.content_length_n = sizeof(ngx_hello_string) - 1;
    /* send the headers of your response */
    rc = ngx_http_send_header(r);
    if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {
        return rc;
    /* send the buffer chain of your response */
    return ngx_http_output_filter(r, &out);
static char *
ngx_http_hello(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_handler; /* handler to process the 'hello' directive */
    return NGX_CONF_OK;


HTTP_MODULES="$HTTP_MODULES ngx_http_hello_module"
NGX_ADDON_SRCS="$NGX_ADDON_SRCS $ngx_addon_dir/ngx_http_hello_module.c"


# hello
worker_processes 1;
events {
       worker_connections 1024;
http {
     server {
     	    listen 8080;
	    server_name localhost;
	    location / {

If you want more detailed information, please consult Evan Miller’s Guide To Nginx Module Development.

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