hello world nginx module

ngx_hello_world

/*
 * Hello world NGINX template for the blog
 *
 * For nginx data types refer -
 * http://antoine.bonavita.free.fr/nginx_mod_dev_en.html
 * @author: sunil mallya
 *

*/


#include <ngx_core.h>
#include <ngx_http.h>
#include <pthread.h>
#include <stdlib.h>
#include <time.h>

/*
 *  These function install request handlers
 */
static char *ngx_http_test_healthcheck_hook(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
static ngx_int_t ngx_http_test_handler_healthcheck(ngx_http_request_t *r);

// config handlers
static ngx_conf_post_handler_pt ngx_http_test_my_test_variable_p = ngx_http_test_my_test_variable;

// Module Hook Methods
ngx_int_t test_init_process(ngx_cycle_t *cycle);
void test_exit_process(ngx_cycle_t *cycle);
ngx_int_t test_init_module(ngx_cycle_t *cycle);

/*
 * specific configuration structure
 *
 * */
typedef struct {
    time_t my_test_variable;
    // Add more variables to the struct here
} ngx_http_test_loc_conf_t;

static ngx_http_test_loc_conf_t ngx_http_test_loc_conf;

/*
 *  config vars 
 */
static ngx_command_t  ngx_http_test_commands[] = {

    { ngx_string("variable_name_in_config"),
        NGX_HTTP_MAIN_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
        ngx_conf_set_sec_slot,
        NGX_HTTP_LOC_CONF_OFFSET,
        offsetof(ngx_http_test_loc_conf_t, my_test_variable),
        &ngx_http_test_my_test_variable_p},
    
    ngx_null_command
};


/* Create loc conf to be used by the module
 * It takes a directive struct (ngx_conf_t) and returns a newly 
 * created module configuration struct
 */
static void *
ngx_http_test_create_loc_conf(ngx_conf_t * cf)
{
    ngx_http_test_loc_conf_t * conf;
    
    conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_test_loc_conf_t));
    
    if(conf == NULL) {
        return NGX_CONF_ERROR;
    }
    
    conf->my_test_variable = NGX_CONF_UNSET_UINT;
    return conf;
}


static char *
ngx_http_test_merge_loc_conf(ngx_conf_t * cf, void * parent, void * child)
{
    
    return NGX_CONF_OK;
}

static char *
ngx_http_test_my_test_variable(ngx_conf_t *cf, void *post, void *data){
    time_t *name = data; // i.e., first field of var
   
    if(name == NULL){
        return NGX_CONF_ERROR;
    }    
    
    ngx_http_test_loc_conf.my_test_variable = *name; 
    return NGX_CONF_OK;
}

/* Module Context
 *
 * This is a static ngx_http_module_t struct, which just has a bunch of function
 * references for creating the three configurations and merging them together. 
 * Its name is ngx_http_<module name>_module_ctx. In order, the function references are:
 *
 * preconfiguration
 * postconfiguration
 * creating the main conf (i.e., do a malloc and set defaults)
 * initializing the main conf (i.e., override the defaults with what's in nginx.conf)
 * creating the server conf
 * merging it with the main conf
 * creating the location conf
 * merging it with the server conf
 */

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

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

    ngx_http_test_create_loc_conf, /* create server configuration */
    ngx_http_test_merge_loc_conf,  /* merge server configuration */
    ngx_http_test_create_loc_conf, /* create location configuration */
    ngx_http_test_merge_loc_conf   /* merge location configuration */
};



/* Module Definition
 * This is one more layer of indirection, the ngx_module_t struct. 
 * The variable is called ngx_http_<module name>_module. 
 * This is where references to the context and directives go, as well as the 
 * remaining callbacks (exit thread, exit process, etc.). 
 * The module definition is sometimes used as a key to look up data associated with a particular module
 *
 */
ngx_module_t ngx_http_test_module = {
  NGX_MODULE_V1,
  &ngx_http_test_module_ctx,  /* module context */
  ngx_http_test_commands,     /* module directives */
  NGX_HTTP_MODULE,            /* module type */
  NULL,                       /* init master */
  test_init_module,           /* init module */
  &test_init_process,         /* init process */
  NULL,                       /* init thread */
  NULL,                       /* exit thread */
  &test_exit_process,         /* exit process */
  NULL,                       /* exit master */
  NGX_MODULE_V1_PADDING
};

ngx_int_t test_init_process(ngx_cycle_t *cycle){
    
    // Call any init functions that you have to
    // Place to start background threads, watchdogs etc...
    //
    return 0;
}


void
test_exit_process(ngx_cycle_t *cycle){
    test_terminate_updater();
}

ngx_int_t
test_init_module(ngx_cycle_t *cycle){
    return 0;
}


static ngx_int_t ngx_http_test_handler_healthcheck(ngx_http_request_t *r)
{
    ngx_buf_t    *b;
    ngx_chain_t   out;
    
    r->headers_out.content_type.len = sizeof("text/plain") - 1;
    r->headers_out.content_type.data = (u_char *) "text/plain";
    
    b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));
    
    out.buf = b;
    out.next = NULL;
    
    char * body = "some msg";
    b->pos = (unsigned char*)body;
    b->last = (unsigned char*)body + strlen((char*)body);
    
    b->memory = 1;
    b->last_buf = 1;
    
    r->headers_out.content_length_n = strlen((char*)body);
    ngx_http_send_header(r);
    
    return ngx_http_output_filter(r, &out);
}


// Handlers installers : Hooks for each of the Interface handlers
static char *ngx_http_test_healthcheck_hook(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_test_handler_healthcheck;
    
    return NGX_CONF_OK;
}