nginx模块开发：ngx_xqw_backtrace_module

模块介绍

当nginx运行过程中收到异常退出信号SIGINT，会将当前函数调用堆栈输出到日志文件当中。除了处理SIGINT之外，还可以在模块中添加相应信号。

模块开发流程

1. 创建配置结构体

<code><span>typedef</span><span>struct</span> ngx_xqw_backtrace_conf_s{
    ngx_log_t *<span>log</span>; <span>// 日志</span>
    ngx_int_t size; <span>// 栈最大深度</span>
}ngx_xqw_backtrace_conf_t;</code>

每个模块都有相应的配置结构体。
2. 实现create_conf为配置结构体分配内存，并返回相应的指针

<code><span>// 初始化配置结构体</span><span>static</span><span>void</span> *
ngx_http_xqw_backtrace_create_conf(ngx_cycle_t *cycle)
{
    ngx_xqw_backtrace_conf_t *bcf = <span>NULL</span>;
    bcf = ngx_palloc(cycle->pool, <span>sizeof</span>(ngx_xqw_backtrace_conf_t));

    <span>if</span> (bcf == <span>NULL</span>)
        <span>return</span><span>NULL</span>;

    bcf->size = NGX_CONF_UNSET;
    <span>return</span> bcf;
}</code>

以上是创建结构体流程。
3. 为每个配置项设置set回调函数。如果配置项参数是数字，可以将set设置为ngx_conf_set_num_slot，否则需要自己实现。

<code><span>// a、用ngx_get_conf得到该模块的结构体</span><span>// b、获取配置项中的参数 cf->cycle->elts</span><span>// c、由参数构造模块结构体中的成员</span>
static char*
ngx_xqw_backtrace_log(ngx_conf_t <span>*cf</span>, ngx_command_t <span>*cmd</span>, void <span>*conf</span>)
{
    ngx_str_t <span>file</span>, <span>*value</span>;
    ngx_log_t <span>*log</span>;
    ngx_xqw_backtrace_conf_t <span>*bcf</span>;

    bcf = (ngx_xqw_backtrace_conf_t <span>*)</span> ngx_get_conf(cf->cycle->conf_ctx, 
        ngx_xqw_backtrace_module);

    value = cf->args->elts;

    <span>file</span> = value[<span>1</span>];

    <span>// 解析配置文件出错返回 NGX_CONF_ERROR</span><span>if</span> (ngx_conf_full_name(cf->cycle, &<span>file</span>, <span>1</span>) != NGX_OK)
        <span>return</span> NGX_CONF_ERROR;

    <span>log</span> = ngx_log_create(cf->cycle, &<span>file</span>);
    <span>if</span> (<span>log</span> == NULL)
        <span>return</span> NGX_CONF_ERROR;

    bcf-><span>log</span> = <span>log</span>;
    bcf-><span>log</span>->log_level = NGX_LOG_ERR; <span>// 每个LOGFILE都有相应的级别,</span><span>// 需要设置好级别后才能输出到自定义的LOGFILE</span><span>return</span> NGX_CONF_OK;
}
</code>

以上是 解析配置项的流程
4. 初始化信号的处理函数

<code><span>static</span> ngx_int_t
ngx_init_error_signal(ngx_log_t *log)
{
    ngx_backtrace_signal_t *sigs;
    <span>struct</span> sigaction sa;

    <span>// 不需要用index的循环方法</span><span>for</span> (sigs = ngx_backtrace_signals; sigs->name != <span>NULL</span>; sigs ++)
    {
        ngx_memzero(&sa, <span>sizeof</span>(<span>struct</span> sigaction));
        sa<span>.sa_handler</span> = sigs->handler;
        sigemptyset(&sa<span>.sa_mask</span>);
        <span>if</span> (sigaction(sigs->value, &sa, <span>NULL</span>) == -<span>1</span>)
        {
            perror(<span>"sigaction"</span>);
            <span>return</span> NGX_ERROR;
        }
    }

    <span>return</span> NGX_OK;
}</code>

围绕sigaction实现
5. 编写异常处理函数

<code>static <span>void</span>
ngx_backtrace_signal_handler(int sig)
{
    ngx_backtrace_signal_t <span>*</span>sigs;
    ngx_xqw_backtrace_conf_t <span>*</span>bcf;
    <span>void</span><span>*</span>buff;
    size_t size;

    bcf <span>=</span> (ngx_xqw_backtrace_conf_t<span>*</span>) ngx_get_conf(ngx_cycle<span>-></span>conf_ctx, 
        ngx_xqw_backtrace_module);

    ngx_log_error(NGX_LOG_ERR, bcf<span>-></span><span>log</span>, <span>0</span>, <span>"hello error\n"</span>);

    <span>if</span> (bcf <span>==</span><span>NULL</span>)
        fprintf(stderr, <span>"ngx_get_conf error\n"</span>);

    for (sigs <span>=</span> ngx_backtrace_signals; sigs<span>-></span>name <span>!=</span><span>NULL</span>; <span>++</span> sigs)
        <span>if</span> (sigs<span>-></span>value <span>==</span> sig)
            break;

    <span>// 要退出了，故将信号设置为默认处理方式</span>
    struct sigaction sa;
    ngx_memzero(<span>&</span>sa, sizeof(struct sigaction));
    sigemptyset(<span>&</span>sa<span>.</span>sa_mask);
    sa<span>.</span>sa_handler <span>=</span> SIG_DFL;
    <span>if</span> (sigaction(sigs<span>-></span>value, <span>&</span>sa, <span>NULL</span>) <span>==</span><span>-</span><span>1</span>)
        perror(<span>"signal handler sigaction:"</span>);

    <span>if</span> (bcf<span>-></span>size <span>==</span> NGX_CONF_UNSET)
        bcf<span>-></span>size <span>=</span> MAX_STACK_SIZE;

    buff <span>=</span> (<span>void</span><span>*</span>)ngx_palloc(ngx_cycle<span>-></span>pool, 
        bcf<span>-></span>size <span>*</span> sizeof (<span>void</span><span>*</span>));

    <span>if</span> (buff <span>==</span><span>NULL</span>)
        fprintf(stderr, <span>"ngx_palloc error\n"</span>);

    size <span>=</span> backtrace(buff, bcf<span>-></span>size);
    backtrace_symbols_fd(buff, size, bcf<span>-></span><span>log</span><span>-></span>file<span>-></span>fd);

    kill(ngx_getpid(), sig);    
}</code>

需要将信号的处理函数恢复为默认处理情况，处理完成后并再次发送该信号。

参考资料

淘宝发布的ngx_backtrace_module模块

ngx_xqw_backtrace_module下载链接

http://download.csdn.net/detail/wxq714586001/8719535

以上就介绍了nginx模块开发：ngx_xqw_backtrace_module，包括了方面的内容，希望对PHP教程有兴趣的朋友有所帮助。