nginx源码阅读点滴

ngx_add_inherited_sockets

这个函数的目的是为了实现nginx平滑升级时获取原来的监听fd, 通过环境变量NGINX完成socket的继承，继承来的socket将会放到init_cycle的listening数组中。在NGINX环境变量中，每个socket中间用冒号或分号隔开。完成继承同时设置全局变量ngx_inherited为1。 相关代码：

• src/core/nginx.c

  static ngx_int_t
  ngx_add_inherited_sockets(ngx_cycle_t *cycle)
  {
  u_char           *p, *v, *inherited;
  ngx_int_t         s;
  ngx_listening_t  *ls;
  
  inherited = (u_char *) getenv(NGINX_VAR);
  
  if (inherited == NULL) {
      return NGX_OK;
  }
  
  ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0,
                "using inherited sockets from \"%s\"", inherited);
  
  if (ngx_array_init(&cycle->listening, cycle->pool, 10,
                     sizeof(ngx_listening_t))
      != NGX_OK)
  {
      return NGX_ERROR;
  }
  
  for (p = inherited, v = p; *p; p++) {
      if (*p == ':' || *p == ';') {
          s = ngx_atoi(v, p - v);
          if (s == NGX_ERROR) {
              ngx_log_error(NGX_LOG_EMERG, cycle->log, 0,
                            "invalid socket number \"%s\" in " NGINX_VAR
                            " environment variable, ignoring the rest"
                            " of the variable", v);
              break;
          }
  
          v = p + 1;
  
          ls = ngx_array_push(&cycle->listening);
          if (ls == NULL) {
              return NGX_ERROR;
          }
  
          ngx_memzero(ls, sizeof(ngx_listening_t));
  
          ls->fd = (ngx_socket_t) s;
      }
  }
  
  ngx_inherited = 1;
  
  return ngx_set_inherited_sockets(cycle);
  }
  

• src/core/nginx.c:ngx_exec_new_binary

  p = ngx_cpymem(var, NGINX_VAR "=", sizeof(NGINX_VAR));
  ls = cycle->listening.elts;
  for (i = 0; i < cycle->listening.nelts; i++) {
  p = ngx_sprintf(p, "%ud;", ls[i].fd);
  }
  *p = '\0';
  env[n++] = var;