ngx_backtrace_module.c

/////
#include "backtrace.h"
#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>

typedef struct { ngx_str_t output_words; } ngx_backtrace_loc_conf_t;

// To process HelloWorld command arguments
static char *ngx_backtrace(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);

// Allocate memory for HelloWorld command
static void *ngx_backtrace_create_loc_conf(ngx_conf_t *cf);

// Copy HelloWorld argument to another place
static char *ngx_backtrace_merge_loc_conf(ngx_conf_t *cf, void *parent,
                                          void *child);

// Structure for the HelloWorld command
static ngx_command_t ngx_backtrace_commands[] = {
    {ngx_string("hello_world"), // The command name
     NGX_HTTP_LOC_CONF | NGX_CONF_TAKE1,
     ngx_backtrace, // The command handler
     NGX_HTTP_LOC_CONF_OFFSET, offsetof(ngx_backtrace_loc_conf_t, output_words),
     NULL},
    ngx_null_command};

// Structure for the HelloWorld context
static ngx_http_module_t ngx_backtrace_module_ctx = {
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    ngx_backtrace_create_loc_conf,
    ngx_backtrace_merge_loc_conf};

static ngx_int_t ngx_backtrace_init_process(ngx_cycle_t *cycle);

// Structure for the HelloWorld module, the most important thing
ngx_module_t ngx_backtrace_module = {
    ///
    NGX_MODULE_V1,              /* module version */
    &ngx_backtrace_module_ctx,  /* config */
    ngx_backtrace_commands,     /* command */
    NGX_HTTP_MODULE,            /* module type */
    NULL,                       /* init  master */
    NULL,                       /* init module */
    ngx_backtrace_init_process, /* init process */
    NULL,
    NULL,
    NULL,
    NULL,
    NGX_MODULE_V1_PADDING //
};

static ngx_int_t ngx_backtrace_init_process(ngx_cycle_t *cycle) {
  if (!cycle)
    return NGX_ERROR;
  backtraceinit();
  return NGX_OK;
}

static ngx_int_t ngx_backtrace_handler(ngx_http_request_t *r) {
  ngx_int_t rc;
  ngx_buf_t *b;
  ngx_chain_t out[2];

  ngx_backtrace_loc_conf_t *hlcf;
  hlcf = ngx_http_get_module_loc_conf(r, ngx_backtrace_module);

  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[0].buf = b;
  out[0].next = &out[1];

  b->pos = (u_char *)"hello_world, ";
  b->last = b->pos + sizeof("hello_world, ") - 1;
  b->memory = 1;

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

  out[1].buf = b;
  out[1].next = NULL;

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

  r->headers_out.status = NGX_HTTP_OK;
  r->headers_out.content_length_n =
      hlcf->output_words.len + sizeof("hello_world, ") - 1;
  rc = ngx_http_send_header(r);
  if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {
    return rc;
  }

  return ngx_http_output_filter(r, &out[0]);
}

static void *ngx_backtrace_create_loc_conf(ngx_conf_t *cf) {
  ngx_backtrace_loc_conf_t *conf;

  conf = ngx_pcalloc(cf->pool, sizeof(ngx_backtrace_loc_conf_t));
  if (conf == NULL) {
    return NGX_CONF_ERROR;
  }
  conf->output_words.len = 0;
  conf->output_words.data = NULL;

  return conf;
}

static char *ngx_backtrace_merge_loc_conf(ngx_conf_t *cf, void *parent,
                                          void *child) {
  ngx_backtrace_loc_conf_t *prev = parent;
  ngx_backtrace_loc_conf_t *conf = child;
  ngx_conf_merge_str_value(conf->output_words, prev->output_words, "Nginx");
  return NGX_CONF_OK;
}

static char *ngx_backtrace(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_backtrace_handler;
  ngx_conf_set_str_slot(cf, cmd, conf);
  return NGX_CONF_OK;
}