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Nginx(七):location的使用以及nginx优雅停机原理

  上一篇中,我们了解了如何nginx的配置原则及解析框架,以及解析location配置的具体实现,相信大家对该部分已经有了比较深刻的认识。

  本篇,我们进一步来了解下,解析之后的配置,如何应用到实际中的吧。当然,我们只讲解 location 的查找过程。

1. location的接入流程

  在nginx的前几篇中,我们已经了解了,nginx对于网络的请求接入过程,是一个基于事件的io模型,这是其高性能的根本。io接入之后,再通过 accept -> read -> init_http -> wait_request -> process_request_line -> process_request_header -> process_request ... 的过程,然后就是具体的处理实现。

  而对于location的处理,则是在 ngx_http_handler() 接入之后的分发工作。

// http/ngx_http_core_module.c    
void
ngx_http_handler(ngx_http_request_t *r)
{
    ngx_http_core_main_conf_t  *cmcf;

    r->connection->log->action = NULL;

    if (!r->internal) {
        switch (r->headers_in.connection_type) {
        case 0:
            r->keepalive = (r->http_version > NGX_HTTP_VERSION_10);
            break;

        case NGX_HTTP_CONNECTION_CLOSE:
            r->keepalive = 0;
            break;

        case NGX_HTTP_CONNECTION_KEEP_ALIVE:
            r->keepalive = 1;
            break;
        }

        r->lingering_close = (r->headers_in.content_length_n > 0
                              || r->headers_in.chunked);
        r->phase_handler = 0;

    } else {
        cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
        r->phase_handler = cmcf->phase_engine.server_rewrite_index;
    }

    r->valid_location = 1;
#if (NGX_HTTP_GZIP)
    r->gzip_tested = 0;
    r->gzip_ok = 0;
    r->gzip_vary = 0;
#endif

    r->write_event_handler = ngx_http_core_run_phases;
    ngx_http_core_run_phases(r);
}

// http/ngx_http_core_module.c
void
ngx_http_core_run_phases(ngx_http_request_t *r)
{
    ngx_int_t                   rc;
    ngx_http_phase_handler_t   *ph;
    ngx_http_core_main_conf_t  *cmcf;

    cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);

    ph = cmcf->phase_engine.handlers;
    // 依次遍历各checker, 直到有一个可以处理
    while (ph[r->phase_handler].checker) {

        rc = ph[r->phase_handler].checker(r, &ph[r->phase_handler]);

        if (rc == NGX_OK) {
            return;
        }
    }
}

ngx_int_t
ngx_http_core_find_config_phase(ngx_http_request_t *r,
    ngx_http_phase_handler_t *ph)
{
    u_char                    *p;
    size_t                     len;
    ngx_int_t                  rc;
    ngx_http_core_loc_conf_t  *clcf;

    r->content_handler = NULL;
    r->uri_changed = 0;
    // 查找location的实现,接入查找流程
    rc = ngx_http_core_find_location(r);

    if (rc == NGX_ERROR) {
        ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
        return NGX_OK;
    }

    clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);

    if (!r->internal && clcf->internal) {
        ngx_http_finalize_request(r, NGX_HTTP_NOT_FOUND);
        return NGX_OK;
    }

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "using configuration \"%s%V\"",
                   (clcf->noname ? "*" : (clcf->exact_match ? "=" : "")),
                   &clcf->name);
    // 将查找到的信息,更新到当前会话中
    ngx_http_update_location_config(r);

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "http cl:%O max:%O",
                   r->headers_in.content_length_n, clcf->client_max_body_size);

    if (r->headers_in.content_length_n != -1
        && !r->discard_body
        && clcf->client_max_body_size
        && clcf->client_max_body_size < r->headers_in.content_length_n)
    {
        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                      "client intended to send too large body: %O bytes",
                      r->headers_in.content_length_n);

        r->expect_tested = 1;
        (void) ngx_http_discard_request_body(r);
        ngx_http_finalize_request(r, NGX_HTTP_REQUEST_ENTITY_TOO_LARGE);
        return NGX_OK;
    }

    if (rc == NGX_DONE) {
        ngx_http_clear_location(r);

        r->headers_out.location = ngx_list_push(&r->headers_out.headers);
        if (r->headers_out.location == NULL) {
            ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
            return NGX_OK;
        }

        r->headers_out.location->hash = 1;
        ngx_str_set(&r->headers_out.location->key, "Location");

        if (r->args.len == 0) {
            r->headers_out.location->value = clcf->name;

        } else {
            len = clcf->name.len + 1 + r->args.len;
            p = ngx_pnalloc(r->pool, len);

            if (p == NULL) {
                ngx_http_clear_location(r);
                ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
                return NGX_OK;
            }

            r->headers_out.location->value.len = len;
            r->headers_out.location->value.data = p;

            p = ngx_cpymem(p, clcf->name.data, clcf->name.len);
            *p++ = '?';
            ngx_memcpy(p, r->args.data, r->args.len);
        }

        ngx_http_finalize_request(r, NGX_HTTP_MOVED_PERMANENTLY);
        return NGX_OK;
    }

    r->phase_handler++;
    return NGX_AGAIN;
}      

  以上就是location的接入过程,主要就是接受http_handler的分配处理,具体如何进行查找.即 location 的处理是在nginx读取完所有的请求体之后,依次处理的其中一个步骤。我们下节再看。

2. location的查找过程

  上节看到,http模块在处理location时,使用一个ngx_http_core_find_location()封装好了其查找过程。想想其实现,应该差不多就是依次匹配原来解析出的信息,当然这里面应该是有各种优先级的体现。

// http/ngx_http_core_module.c
static ngx_int_t
ngx_http_core_find_location(ngx_http_request_t *r)
{
    ngx_int_t                  rc;
    ngx_http_core_loc_conf_t  *pclcf;
#if (NGX_PCRE)
    ngx_int_t                  n;
    ngx_uint_t                 noregex;
    ngx_http_core_loc_conf_t  *clcf, **clcfp;

    noregex = 0;
#endif

    pclcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
    // 委托给 static_location 查找
    rc = ngx_http_core_find_static_location(r, pclcf->static_locations);

    if (rc == NGX_AGAIN) {

#if (NGX_PCRE)
        clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);

        noregex = clcf->noregex;
#endif

        /* look up nested locations */
        // NGX_AGAIN, 则进行多次嵌套查找,以保证最佳匹配
        rc = ngx_http_core_find_location(r);
    }
    // 匹配成功,则返回,主要是针对'='的匹配
    if (rc == NGX_OK || rc == NGX_DONE) {
        return rc;
    }

    /* rc == NGX_DECLINED or rc == NGX_AGAIN in nested location */

#if (NGX_PCRE)

    if (noregex == 0 && pclcf->regex_locations) {
        // 正则匹配, 只要存在正则配置,那么正则匹配都会运行
        // 相比于字符匹配,正则匹配性能更差
        // 所以,当你的正则配置越多,则查找效率则必然越差,没必要配置正则就不要配了
        for (clcfp = pclcf->regex_locations; *clcfp; clcfp++) {

            ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                           "test location: ~ \"%V\"", &(*clcfp)->name);
            // 只要有一个正则匹配,则返回该配置
            n = ngx_http_regex_exec(r, (*clcfp)->regex, &r->uri);

            if (n == NGX_OK) {
                // 符合正则表达式,则loc_conf应用上去
                r->loc_conf = (*clcfp)->loc_conf;

                /* look up nested locations */
                // 与正常匹配相反,正则匹配是在一个匹配成功后,再进入嵌套查询
                rc = ngx_http_core_find_location(r);

                return (rc == NGX_ERROR) ? rc : NGX_OK;
            }

            if (n == NGX_DECLINED) {
                continue;
            }

            return NGX_ERROR;
        }
    }
#endif

    return rc;
}

// 非正则location 匹配查找过程
/*
 * NGX_OK       - exact match
 * NGX_DONE     - auto redirect
 * NGX_AGAIN    - inclusive match
 * NGX_DECLINED - no match
 */

static ngx_int_t
ngx_http_core_find_static_location(ngx_http_request_t *r,
    ngx_http_location_tree_node_t *node)
{
    u_char     *uri;
    size_t      len, n;
    ngx_int_t   rc, rv;

    len = r->uri.len;
    uri = r->uri.data;

    rv = NGX_DECLINED;

    for ( ;; ) {

        if (node == NULL) {
            // node为null时,代表匹配完成,此时将返回之前最匹配的一个 loc_conf
            return rv;
        }

        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                       "test location: \"%*s\"",
                       (size_t) node->len, node->name);
        // 取小值进行比较
        n = (len <= (size_t) node->len) ? len : node->len;
        // 包含性检查
        rc = ngx_filename_cmp(uri, node->name, n);

        if (rc != 0) {
            // 二叉树查找过程, 小于0在左,大于0在右
            node = (rc < 0) ? node->left : node->right;

            continue;
        }
        // 相等的情况有两种,第1种是本次uri 长于当前配置的location
        // 第2种是本次uri 短于当前配置的location
        // 针对第1种情况,是属于一种完全匹配的
        if (len > (size_t) node->len) {

            if (node->inclusive) {

                r->loc_conf = node->inclusive->loc_conf;
                rv = NGX_AGAIN;
                // 向前迭代匹配
                node = node->tree;
                uri += n;
                len -= n;

                continue;
            }

            /* exact only */

            node = node->right;

            continue;
        }
        // 此为 uri >= location配置的情况
        if (len == (size_t) node->len) {

            if (node->exact) {
                r->loc_conf = node->exact->loc_conf;
                return NGX_OK;

            } else {
                // 包含性匹配成功
                r->loc_conf = node->inclusive->loc_conf;
                return NGX_AGAIN;
            }
        }

        /* len < node->len */
        // 以'/'结尾的配置, 比uri 多一个值
        if (len + 1 == (size_t) node->len && node->auto_redirect) {

            r->loc_conf = (node->exact) ? node->exact->loc_conf:
                                          node->inclusive->loc_conf;
            rv = NGX_DONE;
        }

        node = node->left;
    }
}
// 正则location查找
// http/ngx_http_variable.c
ngx_int_t
ngx_http_regex_exec(ngx_http_request_t *r, ngx_http_regex_t *re, ngx_str_t *s)
{
    ngx_int_t                   rc, index;
    ngx_uint_t                  i, n, len;
    ngx_http_variable_value_t  *vv;
    ngx_http_core_main_conf_t  *cmcf;

    cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);

    if (re->ncaptures) {
        len = cmcf->ncaptures;

        if (r->captures == NULL || r->realloc_captures) {
            r->realloc_captures = 0;

            r->captures = ngx_palloc(r->pool, len * sizeof(int));
            if (r->captures == NULL) {
                return NGX_ERROR;
            }
        }

    } else {
        len = 0;
    }
    // 正则匹配, pcre_exec
    rc = ngx_regex_exec(re->regex, s, r->captures, len);
    // 无匹配返回 NGX_DECLINED
    if (rc == NGX_REGEX_NO_MATCHED) {
        return NGX_DECLINED;
    }

    if (rc < 0) {
        ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
                      ngx_regex_exec_n " failed: %i on \"%V\" using \"%V\"",
                      rc, s, &re->name);
        return NGX_ERROR;
    }

    for (i = 0; i < re->nvariables; i++) {

        n = re->variables[i].capture;
        index = re->variables[i].index;
        vv = &r->variables[index];

        vv->len = r->captures[n + 1] - r->captures[n];
        vv->valid = 1;
        vv->no_cacheable = 0;
        vv->not_found = 0;
        vv->data = &s->data[r->captures[n]];

#if (NGX_DEBUG)
        {
        ngx_http_variable_t  *v;

        v = cmcf->variables.elts;

        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                       "http regex set $%V to \"%v\"", &v[index].name, vv);
        }
#endif
    }

    r->ncaptures = rc * 2;
    r->captures_data = s->data;

    return NGX_OK;
}      

  以上就是整个nginx非正则的location的匹配过程,可以看到其核心是使用一个有序二叉树,进行的快速查找过程,以尽可能多的匹配为准。即 /api/a/b, /api/a 这两个同时匹配的情况,则会选择匹配最多的 /api/a/b 配置。借助于二叉树的高效数据结构,其复杂度非常常低,O(lgn). 当然,这个快速查找是依赖于其在解析配置时的良好数据维护。

// http/ngx_http_core_module.c    
ngx_int_t
ngx_http_add_location(ngx_conf_t *cf, ngx_queue_t **locations,
    ngx_http_core_loc_conf_t *clcf)
{
    ngx_http_location_queue_t  *lq;

    if (*locations == NULL) {
        *locations = ngx_palloc(cf->temp_pool,
                                sizeof(ngx_http_location_queue_t));
        if (*locations == NULL) {
            return NGX_ERROR;
        }

        ngx_queue_init(*locations);
    }

    lq = ngx_palloc(cf->temp_pool, sizeof(ngx_http_location_queue_t));
    if (lq == NULL) {
        return NGX_ERROR;
    }

    if (clcf->exact_match
#if (NGX_PCRE)
        || clcf->regex
#endif
        || clcf->named || clcf->noname)
    {
        lq->exact = clcf;
        lq->inclusive = NULL;

    } else {
        lq->exact = NULL;
        lq->inclusive = clcf;
    }

    lq->name = &clcf->name;
    lq->file_name = cf->conf_file->file.name.data;
    lq->line = cf->conf_file->line;
    // 虽然看不懂在做什么,但是感觉很厉害的样子
    ngx_queue_init(&lq->list);

    ngx_queue_insert_tail(*locations, &lq->queue);

    return NGX_OK;
}      

  查找过程分解完毕,和nginx的官方文档描述自然是一致的。优先匹配 '=' 类的配置,其次会按照最长配置为原则查找,但正则配置的优先级高于字符的匹配,没必要不要随意配置正则,因为正则会每次都全量查找。

  不过,因为这些所有的操作都是直接基于内存的,并没有io类的重量级操作,即使配置了几百上千个location规则,性能也并不会有太大影响。但我们应该要其根本原因。

  以上所说,仅是location的最外部匹配过程,但location本身是一个块级的配置,它的内部又有非常多的配置规则,这又要细化到其内部解析了。

3. nginx优雅停机原理

  nginx进程的控制与前面location使用有什么关系?? 当然没有关系了,只是想着也简单,顺便就一起讲讲了。

  一般的应用进程管理,只需使用系统提供的相关命令即可完成,比如 kill -9 <pid> 。 而nginx专门提供了一些用于控制其进程的方法,原因是其需要更优雅地处理各种意外情况,如果直接使用系统的控制命令,会导致非常多的边界问题,从而使得nginx本身不再完美。大家需要为这一个个的边界问题,伤透了脑筋,这样也许它就不再那么流行了。

      要实现优雅停机,最本质的工作是要实现资源的优雅管理工作,但还有很重要的点是如何实现这管理工作的调用。来看看nginx如何处理:

// core/ngx_cycle.c
ngx_int_t
ngx_signal_process(ngx_cycle_t *cycle, char *sig)
{
    ssize_t           n;
    ngx_pid_t         pid;
    ngx_file_t        file;
    ngx_core_conf_t  *ccf;
    u_char            buf[NGX_INT64_LEN + 2];

    ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "signal process started");

    ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);

    ngx_memzero(&file, sizeof(ngx_file_t));

    file.name = ccf->pid;
    file.log = cycle->log;

    file.fd = ngx_open_file(file.name.data, NGX_FILE_RDONLY,
                            NGX_FILE_OPEN, NGX_FILE_DEFAULT_ACCESS);

    if (file.fd == NGX_INVALID_FILE) {
        ngx_log_error(NGX_LOG_ERR, cycle->log, ngx_errno,
                      ngx_open_file_n " \"%s\" failed", file.name.data);
        return 1;
    }

    n = ngx_read_file(&file, buf, NGX_INT64_LEN + 2, 0);

    if (ngx_close_file(file.fd) == NGX_FILE_ERROR) {
        ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                      ngx_close_file_n " \"%s\" failed", file.name.data);
    }

    if (n == NGX_ERROR) {
        return 1;
    }

    while (n-- && (buf[n] == CR || buf[n] == LF)) { /* void */ }

    pid = ngx_atoi(buf, ++n);

    if (pid == (ngx_pid_t) NGX_ERROR) {
        ngx_log_error(NGX_LOG_ERR, cycle->log, 0,
                      "invalid PID number \"%*s\" in \"%s\"",
                      n, buf, file.name.data);
        return 1;
    }
    // 以上解析pid, 验证有效性, 下面进行实际进程管控
    return ngx_os_signal_process(cycle, sig, pid);

}

// os/unix/ngx_process.c
ngx_int_t
ngx_os_signal_process(ngx_cycle_t *cycle, char *name, ngx_pid_t pid)
{
    ngx_signal_t  *sig;
    // 遍历所有控制指令,转换成系统的控制标识
    for (sig = signals; sig->signo != 0; sig++) {
        if (ngx_strcmp(name, sig->name) == 0) {
            if (kill(pid, sig->signo) != -1) {
                return 0;
            }

            ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                          "kill(%P, %d) failed", pid, sig->signo);
        }
    }

    return 1;
}
// 控制命令配置表
ngx_signal_t  signals[] = {
    { ngx_signal_value(NGX_RECONFIGURE_SIGNAL),    // SIG##1
      "SIG" ngx_value(NGX_RECONFIGURE_SIGNAL),    // SIG#HUP
      "reload",
      ngx_signal_handler },

    { ngx_signal_value(NGX_REOPEN_SIGNAL),        // SIG##30
      "SIG" ngx_value(NGX_REOPEN_SIGNAL),        // SIG#USR1
      "reopen",
      ngx_signal_handler },

    { ngx_signal_value(NGX_NOACCEPT_SIGNAL),    // SIG##28
      "SIG" ngx_value(NGX_NOACCEPT_SIGNAL),        // SIG#WINCH
      "",
      ngx_signal_handler },

    { ngx_signal_value(NGX_TERMINATE_SIGNAL),    // SIG##15
      "SIG" ngx_value(NGX_TERMINATE_SIGNAL),    // SIG#TERM
      "stop",
      ngx_signal_handler },

    { ngx_signal_value(NGX_SHUTDOWN_SIGNAL),    // SIG##3
      "SIG" ngx_value(NGX_SHUTDOWN_SIGNAL),        // SIG#QUIT
      "quit",
      ngx_signal_handler },

    { ngx_signal_value(NGX_CHANGEBIN_SIGNAL),    // ##31
      "SIG" ngx_value(NGX_CHANGEBIN_SIGNAL),    // USR2
      "",
      ngx_signal_handler },

    { SIGALRM, "SIGALRM", "", ngx_signal_handler },

    { SIGINT, "SIGINT", "", ngx_signal_handler },

    { SIGIO, "SIGIO", "", ngx_signal_handler },

    { SIGCHLD, "SIGCHLD", "", ngx_signal_handler },

    { SIGSYS, "SIGSYS, SIG_IGN", "", NULL },

    { SIGPIPE, "SIGPIPE, SIG_IGN", "", NULL },

    { 0, NULL, "", NULL }
};
// 以上命令的注册过程如下, 以便在响应时可处理
ngx_int_t
ngx_init_signals(ngx_log_t *log)
{
    ngx_signal_t      *sig;
    struct sigaction   sa;

    for (sig = signals; sig->signo != 0; sig++) {
        ngx_memzero(&sa, sizeof(struct sigaction));

        if (sig->handler) {
            sa.sa_sigaction = sig->handler;
            sa.sa_flags = SA_SIGINFO;

        } else {
            sa.sa_handler = SIG_IGN;
        }

        sigemptyset(&sa.sa_mask);
        if (sigaction(sig->signo, &sa, NULL) == -1) {
#if (NGX_VALGRIND)
            ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                          "sigaction(%s) failed, ignored", sig->signame);
#else
            ngx_log_error(NGX_LOG_EMERG, log, ngx_errno,
                          "sigaction(%s) failed", sig->signame);
            return NGX_ERROR;
#endif
        }
    }

    return NGX_OK;
}      

  以上控制指定的处理器,几乎都被设置为 ngx_signal_handler,即当nginx进程收到控制信号,将会该用该方法进行响应。

// 其处理逻辑如下: (主要就是根据当前进程的不同角色和控制信号,设置相应标识)
static void
ngx_signal_handler(int signo, siginfo_t *siginfo, void *ucontext)
{
    char            *action;
    ngx_int_t        ignore;
    ngx_err_t        err;
    ngx_signal_t    *sig;

    ignore = 0;

    err = ngx_errno;

    for (sig = signals; sig->signo != 0; sig++) {
        if (sig->signo == signo) {
            break;
        }
    }

    ngx_time_sigsafe_update();

    action = "";
    // 根据当前进程的类型,做不一样的处理逻辑
    switch (ngx_process) {
    // master进程处理
    case NGX_PROCESS_MASTER:
    case NGX_PROCESS_SINGLE:
        // 根据控制标识,设置相应变量
        // 该变量将被主循环服务读取到
        switch (signo) {
        case ngx_signal_value(NGX_SHUTDOWN_SIGNAL):
            ngx_quit = 1;
            action = ", shutting down";
            break;

        case ngx_signal_value(NGX_TERMINATE_SIGNAL):
        case SIGINT:
            ngx_terminate = 1;
            action = ", exiting";
            break;

        case ngx_signal_value(NGX_NOACCEPT_SIGNAL):
            if (ngx_daemonized) {
                ngx_noaccept = 1;
                action = ", stop accepting connections";
            }
            break;

        case ngx_signal_value(NGX_RECONFIGURE_SIGNAL):
            ngx_reconfigure = 1;
            action = ", reconfiguring";
            break;

        case ngx_signal_value(NGX_REOPEN_SIGNAL):
            ngx_reopen = 1;
            action = ", reopening logs";
            break;

        case ngx_signal_value(NGX_CHANGEBIN_SIGNAL):
            if (ngx_getppid() == ngx_parent || ngx_new_binary > 0) {

                /*
                 * Ignore the signal in the new binary if its parent is
                 * not changed, i.e. the old binary's process is still
                 * running.  Or ignore the signal in the old binary's
                 * process if the new binary's process is already running.
                 */

                action = ", ignoring";
                ignore = 1;
                break;
            }

            ngx_change_binary = 1;
            action = ", changing binary";
            break;

        case SIGALRM:
            ngx_sigalrm = 1;
            break;

        case SIGIO:
            ngx_sigio = 1;
            break;

        case SIGCHLD:
            ngx_reap = 1;
            break;
        }

        break;
    // worker 收到控制请求
    case NGX_PROCESS_WORKER:
    case NGX_PROCESS_HELPER:
        // 同样设置相当标识变量,在主循环中进行处理响应
        switch (signo) {
        case ngx_signal_value(NGX_NOACCEPT_SIGNAL):
            if (!ngx_daemonized) {
                break;
            }
            ngx_debug_quit = 1;
            /* fall through */
        case ngx_signal_value(NGX_SHUTDOWN_SIGNAL):
            ngx_quit = 1;
            action = ", shutting down";
            break;

        case ngx_signal_value(NGX_TERMINATE_SIGNAL):
        case SIGINT:
            ngx_terminate = 1;
            action = ", exiting";
            break;

        case ngx_signal_value(NGX_REOPEN_SIGNAL):
            ngx_reopen = 1;
            action = ", reopening logs";
            break;

        case ngx_signal_value(NGX_RECONFIGURE_SIGNAL):
        case ngx_signal_value(NGX_CHANGEBIN_SIGNAL):
        case SIGIO:
            action = ", ignoring";
            break;
        }

        break;
    }

    if (siginfo && siginfo->si_pid) {
        ngx_log_error(NGX_LOG_NOTICE, ngx_cycle->log, 0,
                      "signal %d (%s) received from %P%s",
                      signo, sig->signame, siginfo->si_pid, action);

    } else {
        ngx_log_error(NGX_LOG_NOTICE, ngx_cycle->log, 0,
                      "signal %d (%s) received%s",
                      signo, sig->signame, action);
    }

    if (ignore) {
        ngx_log_error(NGX_LOG_CRIT, ngx_cycle->log, 0,
                      "the changing binary signal is ignored: "
                      "you should shutdown or terminate "
                      "before either old or new binary's process");
    }
    // 等待子进程完成
    if (signo == SIGCHLD) {
        ngx_process_get_status();
    }

    ngx_set_errno(err);
}

static void
ngx_process_get_status(void)
{
    int              status;
    char            *process;
    ngx_pid_t        pid;
    ngx_err_t        err;
    ngx_int_t        i;
    ngx_uint_t       one;

    one = 0;

    for ( ;; ) {
        pid = waitpid(-1, &status, WNOHANG);

        if (pid == 0) {
            return;
        }

        if (pid == -1) {
            err = ngx_errno;

            if (err == NGX_EINTR) {
                continue;
            }

            if (err == NGX_ECHILD && one) {
                return;
            }

            /*
             * Solaris always calls the signal handler for each exited process
             * despite waitpid() may be already called for this process.
             *
             * When several processes exit at the same time FreeBSD may
             * erroneously call the signal handler for exited process
             * despite waitpid() may be already called for this process.
             */

            if (err == NGX_ECHILD) {
                ngx_log_error(NGX_LOG_INFO, ngx_cycle->log, err,
                              "waitpid() failed");
                return;
            }

            ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, err,
                          "waitpid() failed");
            return;
        }


        one = 1;
        process = "unknown process";

        for (i = 0; i < ngx_last_process; i++) {
            if (ngx_processes[i].pid == pid) {
                ngx_processes[i].status = status;
                ngx_processes[i].exited = 1;
                process = ngx_processes[i].name;
                break;
            }
        }

        if (WTERMSIG(status)) {
#ifdef WCOREDUMP
            ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0,
                          "%s %P exited on signal %d%s",
                          process, pid, WTERMSIG(status),
                          WCOREDUMP(status) ? " (core dumped)" : "");
#else
            ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0,
                          "%s %P exited on signal %d",
                          process, pid, WTERMSIG(status));
#endif

        } else {
            ngx_log_error(NGX_LOG_NOTICE, ngx_cycle->log, 0,
                          "%s %P exited with code %d",
                          process, pid, WEXITSTATUS(status));
        }

        if (WEXITSTATUS(status) == 2 && ngx_processes[i].respawn) {
            ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0,
                          "%s %P exited with fatal code %d "
                          "and cannot be respawned",
                          process, pid, WEXITSTATUS(status));
            ngx_processes[i].respawn = 0;
        }

        ngx_unlock_mutexes(pid);
    }
}      

  ngx_signal_handler 主要处理了各标识字段的设置,那么设置之后并没有做更多的事,即没有进行exit()操作,它又是如何达到响应控制的呢。实际上,当进程的标识变量被设置之后,会被其主循环服务稍后处理。每一次处理任务时,都会去检查相关标识,比如如果标识是退出,则主循环服务将结束自身的循环服务,从而达到响应退出命令的目的。

  实际上,我们在做操作命令时,只是读取了一个nginx的pid即master进程的pid, 所以控制实际上只向master发送了命令。只不过master接收到该命令后,会在必要的时候将其传达给到所有的worker。从而完成整体的控制。

// master循环服务实现
// os/unix/ngx_process_cycle.c
void
ngx_master_process_cycle(ngx_cycle_t *cycle)
{
    char              *title;
    u_char            *p;
    size_t             size;
    ngx_int_t          i;
    ngx_uint_t         sigio;
    sigset_t           set;
    struct itimerval   itv;
    ngx_uint_t         live;
    ngx_msec_t         delay;
    ngx_core_conf_t   *ccf;

    sigemptyset(&set);
    sigaddset(&set, SIGCHLD);
    sigaddset(&set, SIGALRM);
    sigaddset(&set, SIGIO);
    sigaddset(&set, SIGINT);
    sigaddset(&set, ngx_signal_value(NGX_RECONFIGURE_SIGNAL));
    sigaddset(&set, ngx_signal_value(NGX_REOPEN_SIGNAL));
    sigaddset(&set, ngx_signal_value(NGX_NOACCEPT_SIGNAL));
    sigaddset(&set, ngx_signal_value(NGX_TERMINATE_SIGNAL));
    sigaddset(&set, ngx_signal_value(NGX_SHUTDOWN_SIGNAL));
    sigaddset(&set, ngx_signal_value(NGX_CHANGEBIN_SIGNAL));

    if (sigprocmask(SIG_BLOCK, &set, NULL) == -1) {
        ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                      "sigprocmask() failed");
    }

    sigemptyset(&set);


    size = sizeof(master_process);

    for (i = 0; i < ngx_argc; i++) {
        size += ngx_strlen(ngx_argv[i]) + 1;
    }

    title = ngx_pnalloc(cycle->pool, size);
    if (title == NULL) {
        /* fatal */
        exit(2);
    }

    p = ngx_cpymem(title, master_process, sizeof(master_process) - 1);
    for (i = 0; i < ngx_argc; i++) {
        *p++ = ' ';
        p = ngx_cpystrn(p, (u_char *) ngx_argv[i], size);
    }

    ngx_setproctitle(title);


    ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);

    ngx_start_worker_processes(cycle, ccf->worker_processes,
                               NGX_PROCESS_RESPAWN);
    ngx_start_cache_manager_processes(cycle, 0);

    ngx_new_binary = 0;
    delay = 0;
    sigio = 0;
    live = 1;

    for ( ;; ) {
        if (delay) {
            if (ngx_sigalrm) {
                sigio = 0;
                delay *= 2;
                ngx_sigalrm = 0;
            }

            ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
                           "termination cycle: %M", delay);

            itv.it_interval.tv_sec = 0;
            itv.it_interval.tv_usec = 0;
            itv.it_value.tv_sec = delay / 1000;
            itv.it_value.tv_usec = (delay % 1000 ) * 1000;

            if (setitimer(ITIMER_REAL, &itv, NULL) == -1) {
                ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                              "setitimer() failed");
            }
        }

        ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "sigsuspend");

        sigsuspend(&set);

        ngx_time_update();

        ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
                       "wake up, sigio %i", sigio);

        // 只管读取相应标识即可
        if (ngx_reap) {
            ngx_reap = 0;
            ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "reap children");
            // 清理worker
            live = ngx_reap_children(cycle);
        }

        if (!live && (ngx_terminate || ngx_quit)) {
            // woker退出后,master再退出
            ngx_master_process_exit(cycle);
        }

        if (ngx_terminate) {
            if (delay == 0) {
                delay = 50;
            }

            if (sigio) {
                sigio--;
                continue;
            }

            sigio = ccf->worker_processes + 2 /* cache processes */;

            if (delay > 1000) {
                ngx_signal_worker_processes(cycle, SIGKILL);
            } else {
                ngx_signal_worker_processes(cycle,
                                       ngx_signal_value(NGX_TERMINATE_SIGNAL));
            }

            continue;
        }

        if (ngx_quit) {
            ngx_signal_worker_processes(cycle,
                                        ngx_signal_value(NGX_SHUTDOWN_SIGNAL));
            ngx_close_listening_sockets(cycle);

            continue;
        }

        if (ngx_reconfigure) {
            ngx_reconfigure = 0;

            if (ngx_new_binary) {
                ngx_start_worker_processes(cycle, ccf->worker_processes,
                                           NGX_PROCESS_RESPAWN);
                ngx_start_cache_manager_processes(cycle, 0);
                ngx_noaccepting = 0;

                continue;
            }

            ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reconfiguring");

            cycle = ngx_init_cycle(cycle);
            if (cycle == NULL) {
                cycle = (ngx_cycle_t *) ngx_cycle;
                continue;
            }

            ngx_cycle = cycle;
            ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx,
                                                   ngx_core_module);
            ngx_start_worker_processes(cycle, ccf->worker_processes,
                                       NGX_PROCESS_JUST_RESPAWN);
            ngx_start_cache_manager_processes(cycle, 1);

            /* allow new processes to start */
            ngx_msleep(100);

            live = 1;
            ngx_signal_worker_processes(cycle,
                                        ngx_signal_value(NGX_SHUTDOWN_SIGNAL));
        }

        if (ngx_restart) {
            ngx_restart = 0;
            ngx_start_worker_processes(cycle, ccf->worker_processes,
                                       NGX_PROCESS_RESPAWN);
            ngx_start_cache_manager_processes(cycle, 0);
            live = 1;
        }

        if (ngx_reopen) {
            ngx_reopen = 0;
            ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reopening logs");
            ngx_reopen_files(cycle, ccf->user);
            ngx_signal_worker_processes(cycle,
                                        ngx_signal_value(NGX_REOPEN_SIGNAL));
        }

        if (ngx_change_binary) {
            ngx_change_binary = 0;
            ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "changing binary");
            ngx_new_binary = ngx_exec_new_binary(cycle, ngx_argv);
        }

        if (ngx_noaccept) {
            ngx_noaccept = 0;
            ngx_noaccepting = 1;
            ngx_signal_worker_processes(cycle,
                                        ngx_signal_value(NGX_SHUTDOWN_SIGNAL));
        }
    }
}      

  master进程的主要作用,实际也是管理worker,所以控制命令发送到master, 剩余工作就由master完成。总体来说,就是master先将命令发送给worker,然后自身最后再响应命令,保证命令的正确执行。

  woker进程则主要负责真正的业务处理,以及接收master发达过来的控制命令。与master各有分工,其对应控制指令只需自身响应即可。

// worker主循环的实现
static void
ngx_worker_process_cycle(ngx_cycle_t *cycle, void *data)
{
    ngx_int_t worker = (intptr_t) data;

    ngx_process = NGX_PROCESS_WORKER;
    ngx_worker = worker;

    ngx_worker_process_init(cycle, worker);

    ngx_setproctitle("worker process");

    for ( ;; ) {
        // 只管读取相应标识即可
        if (ngx_exiting) {
            if (ngx_event_no_timers_left() == NGX_OK) {
                ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exiting");
                ngx_worker_process_exit(cycle);
            }
        }

        ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "worker cycle");
        // 业务处理
        ngx_process_events_and_timers(cycle);

        if (ngx_terminate) {
            ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exiting");
            ngx_worker_process_exit(cycle);
        }

        if (ngx_quit) {
            ngx_quit = 0;
            ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0,
                          "gracefully shutting down");
            ngx_setproctitle("worker process is shutting down");

            if (!ngx_exiting) {
                ngx_exiting = 1;
                ngx_set_shutdown_timer(cycle);
                ngx_close_listening_sockets(cycle);
                ngx_close_idle_connections(cycle);
            }
        }

        if (ngx_reopen) {
            ngx_reopen = 0;
            ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reopening logs");
            ngx_reopen_files(cycle, -1);
        }
    }
}      

  可以看到,worker的主体循环工作,大多是在响应master的控制指定,也就是前面看到的接收到控制指令后,设置好相应的标识,在该主循环中进行响应。

  最后,我们来思考几个问题:

    1. 如果我直接kill -9 掉master, 那么nginx将会如何?

    2. 如果直接kill -9 掉woker, 那么nginx又将如何?

    3. 如何优雅的关闭nginx?

    4. 如果不使用nginx的控制命令,能否实现ngnix的优雅关闭?(shell实现)

  相信通过上面的理解,这些问题不在话下!

不要害怕今日的苦,你要相信明天,更苦!

继续阅读