Nginx(三)：http模块的处理流程解析之正向代理
无疑，在nginx的核心服务中，http服务占据了相当大的份量。那么，要想多了解nginx多一点，则必须要了解其http模块的工作机制。
而在上一篇文章中，我们已完全了解了nginx的worker工作机制，以及它是如何接入http服务的，但很明显那很粗，我们需要更深入点理解http模块的工作原理。
而本身nginx对模块的支持又是复杂的，至少我们认为有两个大方向，正向代理和反向代理。正向代理实际上就是一个http服务器，明显简单些，所以，我们本篇就来说说nginx的正向代理实现吧。
0. 整体时序图
如果你对nginx的http模块工作原理有过深入理解，相信只需要这一张时序图就够。为了节省大家宝贵时，可以先一览宏图。
1.异步io事件的交接
我们知道，nginx的核心是事件io机制的使用，当外部网络io就绪时，内核会回应nginx, 而nginx则会通过accept(), receive(), fd_set 等方法，将事件接入进来，从而转交到http服务模块。其中select模块我们上一篇中已经讲过，此时再简单回顾下：（需要的话）
// event/modules/ngx_select_module.c
// io 事件监听
static ngx_int_t
ngx_select_process_events(ngx_cycle_t *cycle, ngx_msec_t timer,
ngx_uint_t flags) {
int ready, nready;
ngx_err_t err;
ngx_uint_t i, found;
ngx_event_t *ev;
ngx_queue_t *queue;
struct timeval tv, *tp;
ngx_connection_t *c;
// 获取 max_fd, 系统传值需要
if (max_fd == -1) {
for (i = 0; i < nevents; i++) {
c = event_index[i]->data;
if (max_fd < c->fd) {
max_fd = c->fd;
}
}
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
"change max_fd: %i", max_fd);
}
#if (NGX_DEBUG)
if (cycle->log->log_level & NGX_LOG_DEBUG_ALL) {
for (i = 0; i < nevents; i++) {
ev = event_index[i];
c = ev->data;
ngx_log_debug2(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
"select event: fd:%d wr:%d", c->fd, ev->write);
}
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
"max_fd: %i", max_fd);
}
#endif
if (timer == NGX_TIMER_INFINITE) {
tp = NULL;
} else {
tv.tv_sec = (long) (timer / 1000);
tv.tv_usec = (long) ((timer % 1000) * 1000);
tp = &tv;
}
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
"select timer: %M", timer);
work_read_fd_set = master_read_fd_set;
work_write_fd_set = master_write_fd_set;
// 在此处交由内核进行处理网络事件，epoll 机制，至少有一个事件到来时返回
// tp 代表是否要超时退出
ready = select(max_fd + 1, &work_read_fd_set, &work_write_fd_set, NULL, tp);
err = (ready == -1) ? ngx_errno : 0;
if (flags & NGX_UPDATE_TIME || ngx_event_timer_alarm) {
// 事件结束后，先尝试更新gmtTime 时间信息
ngx_time_update();
}
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
"select ready %d", ready);
if (err) {
ngx_uint_t level;
if (err == NGX_EINTR) {
if (ngx_event_timer_alarm) {
ngx_event_timer_alarm = 0;
return NGX_OK;
}
level = NGX_LOG_INFO;
} else {
level = NGX_LOG_ALERT;
}
ngx_log_error(level, cycle->log, err, "select() failed");
if (err == NGX_EBADF) {
ngx_select_repair_fd_sets(cycle);
}
return NGX_ERROR;
}
if (ready == 0) {
if (timer != NGX_TIMER_INFINITE) {
return NGX_OK;
}
ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
"select() returned no events without timeout");
return NGX_ERROR;
}
nready = 0;
// 遍历所有事件
for (i = 0; i < nevents; i++) {
ev = event_index[i];
c = ev->data;
found = 0;
// 写事件处理
if (ev->write) {
if (FD_ISSET(c->fd, &work_write_fd_set)) {
found = 1;
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
"select write %d", c->fd);
}
}
// 读或accept事件
else {
if (FD_ISSET(c->fd, &work_read_fd_set)) {
found = 1;
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
"select read %d", c->fd);
}
}
// 读写就绪事件 found 都为1
if (found) {
ev->ready = 1;
ev->available = -1;
// 如果是 accept 事件则取 ngx_posted_accept_events 队列
// 否则取 ngx_posted_events 队列
queue = ev->accept ? &ngx_posted_accept_events
: &ngx_posted_events;
// 将事件插入到相应队列尾部
ngx_post_event(ev, queue);
// 有效就绪事件+1
nready++;
}
}
// 如果两个值不相等，则需要修正下
if (ready != nready) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
"select ready != events: %d:%d", ready, nready);
ngx_select_repair_fd_sets(cycle);
}
return NGX_OK;
}反正大概意思就是会调用内核级别的select/poll或epoll等io机制，等待io事件的发生，然后返回到用户态。当然，为了保证系统例外情况，都会进行超时设置，避免系统事件检测的偶发异常，可以在超时机制帮助下正常工作。
此处接收到的事件可能写入两个队列: 即是否是 accept 队列之分。最开始建立连接时，自然是放入accept队列的，后续则一般放ngx_posted_events队列中。这两个队列，后续将被分开处理。accept 队列会将socket接入，并注册read监听。而 posted_events 则是需要进行正式处理的队列，将会读取数据，写入客户端等更多工作。
其中，ngx_http_init_connection 的初始化过程，如需要请点击查看.
// http/ngx_http_request.c
// 初始化socket连接, 接入 http模块
void
ngx_http_init_connection(ngx_connection_t *c)
{
ngx_uint_t i;
ngx_event_t *rev;
struct sockaddr_in *sin;
ngx_http_port_t *port;
ngx_http_in_addr_t *addr;
ngx_http_log_ctx_t *ctx;
ngx_http_connection_t *hc;
#if (NGX_HAVE_INET6)
struct sockaddr_in6 *sin6;
ngx_http_in6_addr_t *addr6;
#endif
// 分配数据内存
hc = ngx_pcalloc(c->pool, sizeof(ngx_http_connection_t));
if (hc == NULL) {
ngx_http_close_connection(c);
return;
}
c->data = hc;
/* find the server configuration for the address:port */
port = c->listening->servers;
if (port->naddrs > 1) {
/*
* there are several addresses on this port and one of them
* is an "*:port" wildcard so getsockname() in ngx_http_server_addr()
* is required to determine a server address
*/
if (ngx_connection_local_sockaddr(c, NULL, 0) != NGX_OK) {
ngx_http_close_connection(c);
return;
}
// 根据网络类型处理
switch (c->local_sockaddr->sa_family) {
#if (NGX_HAVE_INET6)
case AF_INET6:
sin6 = (struct sockaddr_in6 *) c->local_sockaddr;
addr6 = port->addrs;
/* the last address is "*" */
for (i = 0; i < port->naddrs - 1; i++) {
if (ngx_memcmp(&addr6[i].addr6, &sin6->sin6_addr, 16) == 0) {
break;
}
}
hc->addr_conf = &addr6[i].conf;
break;
#endif
default: /* AF_INET */
sin = (struct sockaddr_in *) c->local_sockaddr;
addr = port->addrs;
/* the last address is "*" */
for (i = 0; i < port->naddrs - 1; i++) {
if (addr[i].addr == sin->sin_addr.s_addr) {
break;
}
}
hc->addr_conf = &addr[i].conf;
break;
}
} else {
switch (c->local_sockaddr->sa_family) {
#if (NGX_HAVE_INET6)
case AF_INET6:
addr6 = port->addrs;
hc->addr_conf = &addr6[0].conf;
break;
#endif
default: /* AF_INET */
addr = port->addrs;
hc->addr_conf = &addr[0].conf;
break;
}
}
/* the default server configuration for the address:port */
hc->conf_ctx = hc->addr_conf->default_server->ctx;
ctx = ngx_palloc(c->pool, sizeof(ngx_http_log_ctx_t));
if (ctx == NULL) {
ngx_http_close_connection(c);
return;
}
ctx->connection = c;
ctx->request = NULL;
ctx->current_request = NULL;
c->log->connection = c->number;
// 每个http server 都有自己的日志记录控制
c->log->handler = ngx_http_log_error;
c->log->data = ctx;
c->log->action = "waiting for request";
c->log_error = NGX_ERROR_INFO;
rev = c->read;
// 设置接收数据处理器为 ngx_http_wait_request_handler
rev->handler = ngx_http_wait_request_handler;
c->write->handler = ngx_http_empty_handler;
#if (NGX_HTTP_V2)
if (hc->addr_conf->http2) {
rev->handler = ngx_http_v2_init;
}
#endif
#if (NGX_HTTP_SSL)
{
ngx_http_ssl_srv_conf_t *sscf;
sscf = ngx_http_get_module_srv_conf(hc->conf_ctx, ngx_http_ssl_module);
if (sscf->enable || hc->addr_conf->ssl) {
hc->ssl = 1;
c->log->action = "SSL handshaking";
rev->handler = ngx_http_ssl_handshake;
}
}
#endif
if (hc->addr_conf->proxy_protocol) {
hc->proxy_protocol = 1;
c->log->action = "reading PROXY protocol";
}
if (rev->ready) {
/* the deferred accept(), iocp */
if (ngx_use_accept_mutex) {
ngx_post_event(rev, &ngx_posted_events);
return;
}
rev->handler(rev);
return;
}
// 将rev 放入到 ngx_event_timer_rbtree 队列中, 红黑树实现
ngx_add_timer(rev, c->listening->post_accept_timeout);
// 重用 connection
ngx_reusable_connection(c, 1);
// 处理 读就绪事件，注册 read 监听
if (ngx_handle_read_event(rev, 0) != NGX_OK) {
ngx_http_close_connection(c);
return;
}
}经过 ngx_http_init_connection 之后,就注册了read事件, 该事件基本已就绪, 所以将会在下一次进行select操作时返回该事件, 即下一次worker巡检时触发 read. 而此时的handler则被设置为 ngx_http_wait_request_handler.
// http/ngx_http_request.c
// 处理socket读事件
static void
ngx_http_wait_request_handler(ngx_event_t *rev)
{
u_char *p;
size_t size;
ssize_t n;
ngx_buf_t *b;
ngx_connection_t *c;
ngx_http_connection_t *hc;
ngx_http_core_srv_conf_t *cscf;
c = rev->data;
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http wait request handler");
if (rev->timedout) {
ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT, "client timed out");
ngx_http_close_connection(c);
return;
}
if (c->close) {
ngx_http_close_connection(c);
return;
}
hc = c->data;
cscf = ngx_http_get_module_srv_conf(hc->conf_ctx, ngx_http_core_module);
// 默认1024 缓冲大小
size = cscf->client_header_buffer_size;
b = c->buffer;
// 首次接入时，创建初始空间
if (b == NULL) {
// 创建缓冲区接收http传过来的数据
b = ngx_create_temp_buf(c->pool, size);
if (b == NULL) {
ngx_http_close_connection(c);
return;
}
c->buffer = b;
} else if (b->start == NULL) {
// 缓冲冲填满，需要另外增加空间？
b->start = ngx_palloc(c->pool, size);
if (b->start == NULL) {
ngx_http_close_connection(c);
return;
}
b->pos = b->start;
b->last = b->start;
b->end = b->last + size;
}
// 接收数据
n = c->recv(c, b->last, size);
if (n == NGX_AGAIN) {
if (!rev->timer_set) {
ngx_add_timer(rev, c->listening->post_accept_timeout);
ngx_reusable_connection(c, 1);
}
if (ngx_handle_read_event(rev, 0) != NGX_OK) {
ngx_http_close_connection(c);
return;
}
/*
* We are trying to not hold c->buffer's memory for an idle connection.
*/
// 如果还要等待更多数据，释放占有空间
if (ngx_pfree(c->pool, b->start) == NGX_OK) {
b->start = NULL;
}
return;
}
if (n == NGX_ERROR) {
ngx_http_close_connection(c);
return;
}
if (n == 0) {
ngx_log_error(NGX_LOG_INFO, c->log, 0,
"client closed connection");
ngx_http_close_connection(c);
return;
}
b->last += n;
// 如果配置了 proxy_pass （且匹配了模式）, 则走代理逻辑
if (hc->proxy_protocol) {
hc->proxy_protocol = 0;
p = ngx_proxy_protocol_read(c, b->pos, b->last);
if (p == NULL) {
ngx_http_close_connection(c);
return;
}
b->pos = p;
if (b->pos == b->last) {
c->log->action = "waiting for request";
b->pos = b->start;
b->last = b->start;
ngx_post_event(rev, &ngx_posted_events);
return;
}
}
c->log->action = "reading client request line";
// 设置不可重用连接
ngx_reusable_connection(c, 0);
// 创建 http 连接请求, 分配内存空, 设置下一个 handler 等等
c->data = ngx_http_create_request(c);
if (c->data == NULL) {
ngx_http_close_connection(c);
return;
}
// 设置读取数据的处理器为 ngx_http_process_request_line, 以便下次使用
rev->handler = ngx_http_process_request_line;
ngx_http_process_request_line(rev);
}ngx_http_wait_request_handler 非常重要的一个任务就是接收客户端的传送数据,即调用 recv 方法处理数据, 使用缓冲区的方式进行读取, 默认缓冲区大小为 1024, 即实际是处理不了太多数据的. 最多读取1024字节, 然后正常情况下就进入到 ngx_http_process_request_line() 逻辑了. 也就是说, 剩下的数据会在接下再被读取, 而非一次性被读取完成. 其中, ngx_http_create_request 主要是为 body体分配内存空间.
// http/ngx_http_request.c
ngx_http_request_t *
ngx_http_create_request(ngx_connection_t *c)
{
ngx_http_request_t *r;
ngx_http_log_ctx_t *ctx;
ngx_http_core_loc_conf_t *clcf;
// 重要: 分配请求的上下文信息
r = ngx_http_alloc_request(c);
if (r == NULL) {
return NULL;
}
c->requests++;
clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
ngx_set_connection_log(c, clcf->error_log);
ctx = c->log->data;
ctx->request = r;
ctx->current_request = r;
#if (NGX_STAT_STUB)
(void) ngx_atomic_fetch_add(ngx_stat_reading, 1);
r->stat_reading = 1;
(void) ngx_atomic_fetch_add(ngx_stat_requests, 1);
#endif
return r;
}// http/ngx_http_request.c
static ngx_http_request_t *
ngx_http_alloc_request(ngx_connection_t *c)
{
ngx_pool_t *pool;
ngx_time_t *tp;
ngx_http_request_t *r;
ngx_http_connection_t *hc;
ngx_http_core_srv_conf_t *cscf;
ngx_http_core_main_conf_t *cmcf;
hc = c->data;
cscf = ngx_http_get_module_srv_conf(hc->conf_ctx, ngx_http_core_module);
pool = ngx_create_pool(cscf->request_pool_size, c->log);
if (pool == NULL) {
return NULL;
}
r = ngx_pcalloc(pool, sizeof(ngx_http_request_t));
if (r == NULL) {
ngx_destroy_pool(pool);
return NULL;
}
r->pool = pool;
r->http_connection = hc;
r->signature = NGX_HTTP_MODULE;
r->connection = c;
// 设置配置信息备用
r->main_conf = hc->conf_ctx->main_conf;
r->srv_conf = hc->conf_ctx->srv_conf;
r->loc_conf = hc->conf_ctx->loc_conf;
// 可能使用读取方式为 blocking, 如果是异步读取, 则无需blocking
r->read_event_handler = ngx_http_block_reading;
// 将刚刚读取出的数据引用给到header指针, 以便重新读取
r->header_in = hc->busy ? hc->busy->buf : c->buffer;
if (ngx_list_init(&r->headers_out.headers, r->pool, 20,
sizeof(ngx_table_elt_t))
!= NGX_OK)
{
ngx_destroy_pool(r->pool);
return NULL;
}
if (ngx_list_init(&r->headers_out.trailers, r->pool, 4,
sizeof(ngx_table_elt_t))
!= NGX_OK)
{
ngx_destroy_pool(r->pool);
return NULL;
}
r->ctx = ngx_pcalloc(r->pool, sizeof(void *) * ngx_http_max_module);
if (r->ctx == NULL) {
ngx_destroy_pool(r->pool);
return NULL;
}
cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
r->variables = ngx_pcalloc(r->pool, cmcf->variables.nelts
* sizeof(ngx_http_variable_value_t));
if (r->variables == NULL) {
ngx_destroy_pool(r->pool);
return NULL;
}
#if (NGX_HTTP_SSL)
if (c->ssl) {
r->main_filter_need_in_memory = 1;
}
#endif
r->main = r;
r->count = 1;
// 分配系统默认值
tp = ngx_timeofday();
r->start_sec = tp->sec;
r->start_msec = tp->msec;
r->method = NGX_HTTP_UNKNOWN;
r->http_version = NGX_HTTP_VERSION_10;
r->headers_in.content_length_n = -1;
r->headers_in.keep_alive_n = -1;
r->headers_out.content_length_n = -1;
r->headers_out.last_modified_time = -1;
r->uri_changes = NGX_HTTP_MAX_URI_CHANGES + 1;
r->subrequests = NGX_HTTP_MAX_SUBREQUESTS + 1;
r->http_state = NGX_HTTP_READING_REQUEST_STATE;
r->log_handler = ngx_http_log_error_handler;
return r;
}而接下来的handler被设置为了 ngx_http_process_request_line , 则会进一步读取数据, 处理事件, 也是处理的核心任务.
2. 核心数据读取解析
前面我们看到, nginx 通过调用系统级recv() 接收部分客户端数据过来, 但那里仅有一个缓冲区的大小, 有可能取到的数据是不完整的. 那么, 自然需要进一步处理, 即: ngx_http_process_request_line . 它会在第一次接到数据时就进行调用, 但如果存在多数据段, 则会反复进行该 handler 的调用(这是一个核心的异步io的处理实现, 类似断点续传):
// http/ngx_http_request.c
// 读取body数据，并响应客户端
static void
ngx_http_process_request_line(ngx_event_t *rev)
{
ssize_t n;
ngx_int_t rc, rv;
ngx_str_t host;
ngx_connection_t *c;
ngx_http_request_t *r;
c = rev->data;
r = c->data;
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, rev->log, 0,
"http process request line");
if (rev->timedout) {
ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT, "client timed out");
c->timedout = 1;
ngx_http_close_request(r, NGX_HTTP_REQUEST_TIME_OUT);
return;
}
rc = NGX_AGAIN;
for ( ;; ) {
if (rc == NGX_AGAIN) {
// 读取header, 因为前面已经读取了部分buff, 可能就直接返回
n = ngx_http_read_request_header(r);
if (n == NGX_AGAIN || n == NGX_ERROR) {
break;
}
}
// 读取body 数据, 按照http协议解析，非常长
// 如解析出 GET HTTP1.1...
rc = ngx_http_parse_request_line(r, r->header_in);
if (rc == NGX_OK) {
/* the request line has been parsed successfully */
// 解析成功部分信息, 进行记录处理
r->request_line.len = r->request_end - r->request_start;
r->request_line.data = r->request_start;
r->request_length = r->header_in->pos - r->request_start;
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
"http request line: \"%V\"", &r->request_line);
r->method_name.len = r->method_end - r->request_start + 1;
r->method_name.data = r->request_line.data;
if (r->http_protocol.data) {
r->http_protocol.len = r->request_end - r->http_protocol.data;
}
// 处理 uri, 解析路径, 放入 r->uri.data
if (ngx_http_process_request_uri(r) != NGX_OK) {
break;
}
if (r->schema_end) {
r->schema.len = r->schema_end - r->schema_start;
r->schema.data = r->schema_start;
}
if (r->host_end) {
host.len = r->host_end - r->host_start;
host.data = r->host_start;
rc = ngx_http_validate_host(&host, r->pool, 0);
if (rc == NGX_DECLINED) {
ngx_log_error(NGX_LOG_INFO, c->log, 0,
"client sent invalid host in request line");
ngx_http_finalize_request(r, NGX_HTTP_BAD_REQUEST);
break;
}
if (rc == NGX_ERROR) {
ngx_http_close_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
break;
}
if (ngx_http_set_virtual_server(r, &host) == NGX_ERROR) {
break;
}
r->headers_in.server = host;
}
if (r->http_version < NGX_HTTP_VERSION_10) {
if (r->headers_in.server.len == 0
&& ngx_http_set_virtual_server(r, &r->headers_in.server)
== NGX_ERROR)
{
break;
}
ngx_http_process_request(r);
break;
}
if (ngx_list_init(&r->headers_in.headers, r->pool, 20,
sizeof(ngx_table_elt_t))
!= NGX_OK)
{
ngx_http_close_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
break;
}
c->log->action = "reading client request headers";
// 如果运行到此处, 则意味着header数据未读取完成, 需要下一次io事件继续
// handler 变更为 ngx_http_process_request_headers
rev->handler = ngx_http_process_request_headers;
ngx_http_process_request_headers(rev);
break;
}
if (rc != NGX_AGAIN) {
/* there was error while a request line parsing */
ngx_log_error(NGX_LOG_INFO, c->log, 0,
ngx_http_client_errors[rc - NGX_HTTP_CLIENT_ERROR]);
if (rc == NGX_HTTP_PARSE_INVALID_VERSION) {
ngx_http_finalize_request(r, NGX_HTTP_VERSION_NOT_SUPPORTED);
} else {
ngx_http_finalize_request(r, NGX_HTTP_BAD_REQUEST);
}
break;
}
/* NGX_AGAIN: a request line parsing is still incomplete */
if (r->header_in->pos == r->header_in->end) {
rv = ngx_http_alloc_large_header_buffer(r, 1);
if (rv == NGX_ERROR) {
ngx_http_close_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
break;
}
if (rv == NGX_DECLINED) {
r->request_line.len = r->header_in->end - r->request_start;
r->request_line.data = r->request_start;
ngx_log_error(NGX_LOG_INFO, c->log, 0,
"client sent too long URI");
ngx_http_finalize_request(r, NGX_HTTP_REQUEST_URI_TOO_LARGE);
break;
}
}
}
// 处理请求, 响应客户端
ngx_http_run_posted_requests(c);
}
// http/ngx_http_request.c
// 进一步处理 header 信息
static void
ngx_http_process_request_headers(ngx_event_t *rev)
{
u_char *p;
size_t len;
ssize_t n;
ngx_int_t rc, rv;
ngx_table_elt_t *h;
ngx_connection_t *c;
ngx_http_header_t *hh;
ngx_http_request_t *r;
ngx_http_core_srv_conf_t *cscf;
ngx_http_core_main_conf_t *cmcf;
c = rev->data;
r = c->data;
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, rev->log, 0,
"http process request header line");
if (rev->timedout) {
ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT, "client timed out");
c->timedout = 1;
ngx_http_close_request(r, NGX_HTTP_REQUEST_TIME_OUT);
return;
}
cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
rc = NGX_AGAIN;
for ( ;; ) {
// 依次解析每一行 header 信息
if (rc == NGX_AGAIN) {
// 如果解析到最后还没完, 说明后续还需要读取数据
if (r->header_in->pos == r->header_in->end) {
rv = ngx_http_alloc_large_header_buffer(r, 0);
if (rv == NGX_ERROR) {
ngx_http_close_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
break;
}
if (rv == NGX_DECLINED) {
p = r->header_name_start;
r->lingering_close = 1;
if (p == NULL) {
ngx_log_error(NGX_LOG_INFO, c->log, 0,
"client sent too large request");
ngx_http_finalize_request(r,
NGX_HTTP_REQUEST_HEADER_TOO_LARGE);
break;
}
len = r->header_in->end - p;
if (len > NGX_MAX_ERROR_STR - 300) {
len = NGX_MAX_ERROR_STR - 300;
}
ngx_log_error(NGX_LOG_INFO, c->log, 0,
"client sent too long header line: \"%*s...\"",
len, r->header_name_start);
ngx_http_finalize_request(r,
NGX_HTTP_REQUEST_HEADER_TOO_LARGE);
break;
}
}
// 将会尝试读取更多的 header 数据
n = ngx_http_read_request_header(r);
if (n == NGX_AGAIN || n == NGX_ERROR) {
break;
}
}
/* the host header could change the server configuration context */
cscf = ngx_http_get_module_srv_conf(r, ngx_http_core_module);
// 重新解析 header 信息
rc = ngx_http_parse_header_line(r, r->header_in,
cscf->underscores_in_headers);
if (rc == NGX_OK) {
r->request_length += r->header_in->pos - r->header_name_start;
if (r->invalid_header && cscf->ignore_invalid_headers) {
/* there was error while a header line parsing */
ngx_log_error(NGX_LOG_INFO, c->log, 0,
"client sent invalid header line: \"%*s\"",
r->header_end - r->header_name_start,
r->header_name_start);
continue;
}
/* a header line has been parsed successfully */
h = ngx_list_push(&r->headers_in.headers);
if (h == NULL) {
ngx_http_close_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
break;
}
h->hash = r->header_hash;
h->key.len = r->header_name_end - r->header_name_start;
h->key.data = r->header_name_start;
h->key.data[h->key.len] = '\0';
h->value.len = r->header_end - r->header_start;
h->value.data = r->header_start;
h->value.data[h->value.len] = '\0';
h->lowcase_key = ngx_pnalloc(r->pool, h->key.len);
if (h->lowcase_key == NULL) {
ngx_http_close_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
break;
}
if (h->key.len == r->lowcase_index) {
ngx_memcpy(h->lowcase_key, r->lowcase_header, h->key.len);
} else {
ngx_strlow(h->lowcase_key, h->key.data, h->key.len);
}
hh = ngx_hash_find(&cmcf->headers_in_hash, h->hash,
h->lowcase_key, h->key.len);
// ngx_http_process_host, 处理 host 验证
// ngx_http_process_connection, 处理 keepalive
if (hh && hh->handler(r, h, hh->offset) != NGX_OK) {
break;
}
ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
"http header: \"%V: %V\"",
&h->key, &h->value);
continue;
}
// header 解析完成后, 处理body 数据了
if (rc == NGX_HTTP_PARSE_HEADER_DONE) {
/* a whole header has been parsed successfully */
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
"http header done");
r->request_length += r->header_in->pos - r->header_name_start;
r->http_state = NGX_HTTP_PROCESS_REQUEST_STATE;
rc = ngx_http_process_request_header(r);
if (rc != NGX_OK) {
break;
}
ngx_http_process_request(r);
break;
}
if (rc == NGX_AGAIN) {
/* a header line parsing is still not complete */
continue;
}
/* rc == NGX_HTTP_PARSE_INVALID_HEADER */
ngx_log_error(NGX_LOG_INFO, c->log, 0,
"client sent invalid header line");
ngx_http_finalize_request(r, NGX_HTTP_BAD_REQUEST);
break;
}
ngx_http_run_posted_requests(c);
}以上是整个http的主要流程之一, 主要分为读取 header 处理header, 读取body处理body, 最后 ngx_http_run_posted_requests, 做后置处理. 其中重要的实现方式是, 依次读取每个字节, 进行http协议解析, 按行划分 header, 以及读取部分buffer就处理部分header等优化.
接下来, 我们看看其对 body 部分的处理:
// http/ngx_http_request.c
// 处理 body 部分处理, 并处理响应对应请求
void
ngx_http_process_request(ngx_http_request_t *r)
{
ngx_connection_t *c;
c = r->connection;
#if (NGX_HTTP_SSL)
// https 处理...
#endif
// 删除 timer
if (c->read->timer_set) {
ngx_del_timer(c->read);
}
#if (NGX_STAT_STUB)
(void) ngx_atomic_fetch_add(ngx_stat_reading, -1);
r->stat_reading = 0;
(void) ngx_atomic_fetch_add(ngx_stat_writing, 1);
r->stat_writing = 1;
#endif
// 设置读写 handler 为 ngx_http_request_handler, 以便在必要的时候使用
c->read->handler = ngx_http_request_handler;
c->write->handler = ngx_http_request_handler;
r->read_event_handler = ngx_http_block_reading;
// 由 ngx_http_handler 处理细节, 下节再看
ngx_http_handler(r);
}
// http/ngx_http_request.c
// 读写处理器
static void
ngx_http_request_handler(ngx_event_t *ev)
{
ngx_connection_t *c;
ngx_http_request_t *r;
c = ev->data;
r = c->data;
ngx_http_set_log_request(c->log, r);
ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
"http run request: \"%V?%V\"", &r->uri, &r->args);
if (c->close) {
r->main->count++;
ngx_http_terminate_request(r, 0);
ngx_http_run_posted_requests(c);
return;
}
if (ev->delayed && ev->timedout) {
ev->delayed = 0;
ev->timedout = 0;
}
if (ev->write) {
r->write_event_handler(r);
} else {
r->read_event_handler(r);
}
ngx_http_run_posted_requests(c);
}大体就是如何使用 recv() 读取数据的过程, 看着流程多, 但实际上其时间复杂度基本为 O(1), 所以效率蛮高的.
3. http 请求的处理
经过数据准备, 数据解析后, 就可以进行逻辑处理了. ngx 中支持许多的功能操作, 如配置内容跳转, 反向代理, 负载均衡 等等. 这些都统一归为一类操作.
void
ngx_http_handler(ngx_http_request_t *r)
{
ngx_http_core_main_conf_t *cmcf;
r->connection->log->action = NULL;
// 设置 keepalive 标识
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
// 设置写处理器为 ngx_http_core_run_phases, 即开始响应客户端流程
r->write_event_handler = ngx_http_core_run_phases;
ngx_http_core_run_phases(r);
}
// http/ngx_http_core_module.c
// 响应客户端操作, 多阶段式操作
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;
// 依次调用各 checker, 直到有响应 OK 的checker为止
while (ph[r->phase_handler].checker) {
// 每次调用 checker 之后, 内部都会将 r->phase_handler++, 即迭代下一个
// 此处的 checker 非常之多, 是在各模块启动时, 自动向 ngx_http_core_module.main_conf 中进行注册的
/**
* 定义如下:
typedef enum {
NGX_HTTP_POST_READ_PHASE = 0,
NGX_HTTP_SERVER_REWRITE_PHASE,
NGX_HTTP_FIND_CONFIG_PHASE,
NGX_HTTP_REWRITE_PHASE,
NGX_HTTP_POST_REWRITE_PHASE,
NGX_HTTP_PREACCESS_PHASE,
NGX_HTTP_ACCESS_PHASE,
NGX_HTTP_POST_ACCESS_PHASE,
NGX_HTTP_PRECONTENT_PHASE,
NGX_HTTP_CONTENT_PHASE,
NGX_HTTP_LOG_PHASE
} ngx_http_phases;
// 注册方式
cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);
h = ngx_array_push(&cmcf->phases[NGX_HTTP_ACCESS_PHASE].handlers);
*h = ngx_http_access_handler;
*/
// 将请求信息和 handler 本身传入调用(不是面向, 只能这么做了)
rc = ph[r->phase_handler].checker(r, &ph[r->phase_handler]);
// 只要有一个处理成功, 则后续不再调用
if (rc == NGX_OK) {
return;
}
}
}
// http/modules/ngx_http_rewrite_module.c
// 路径重写模块
ngx_int_t
ngx_http_core_rewrite_phase(ngx_http_request_t *r, ngx_http_phase_handler_t *ph)
{
ngx_int_t rc;
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
"rewrite phase: %ui", r->phase_handler);
rc = ph->handler(r);
if (rc == NGX_DECLINED) {
r->phase_handler++;
return NGX_AGAIN;
}
if (rc == NGX_DONE) {
return NGX_OK;
}
/* NGX_OK, NGX_AGAIN, NGX_ERROR, NGX_HTTP_... */
ngx_http_finalize_request(r, rc);
return NGX_OK;
}
static ngx_int_t
ngx_http_rewrite_handler(ngx_http_request_t *r)
{
ngx_int_t index;
ngx_http_script_code_pt code;
ngx_http_script_engine_t *e;
ngx_http_core_srv_conf_t *cscf;
ngx_http_core_main_conf_t *cmcf;
ngx_http_rewrite_loc_conf_t *rlcf;
cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
cscf = ngx_http_get_module_srv_conf(r, ngx_http_core_module);
index = cmcf->phase_engine.location_rewrite_index;
if (r->phase_handler == index && r->loc_conf == cscf->ctx->loc_conf) {
/* skipping location rewrite phase for server null location */
return NGX_DECLINED;
}
rlcf = ngx_http_get_module_loc_conf(r, ngx_http_rewrite_module);
if (rlcf->codes == NULL) {
return NGX_DECLINED;
}
e = ngx_pcalloc(r->pool, sizeof(ngx_http_script_engine_t));
if (e == NULL) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
e->sp = ngx_pcalloc(r->pool,
rlcf->stack_size * sizeof(ngx_http_variable_value_t));
if (e->sp == NULL) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
e->ip = rlcf->codes->elts;
e->request = r;
e->quote = 1;
e->log = rlcf->log;
e->status = NGX_DECLINED;
while (*(uintptr_t *) e->ip) {
code = *(ngx_http_script_code_pt *) e->ip;
code(e);
}
return e->status;
}
// http/modules/ngx_http_core_module.c
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;
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);
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;
}
// http/ngx_http_core_module.c
ngx_int_t
ngx_http_core_generic_phase(ngx_http_request_t *r, ngx_http_phase_handler_t *ph)
{
ngx_int_t rc;
/*
* generic phase checker,
* used by the post read and pre-access phases
*/
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
"generic phase: %ui", r->phase_handler);
rc = ph->handler(r);
if (rc == NGX_OK) {
r->phase_handler = ph->next;
return NGX_AGAIN;
}
if (rc == NGX_DECLINED) {
r->phase_handler++;
return NGX_AGAIN;
}
if (rc == NGX_AGAIN || rc == NGX_DONE) {
return NGX_OK;
}
/* rc == NGX_ERROR || rc == NGX_HTTP_... */
ngx_http_finalize_request(r, rc);
return NGX_OK;
}
static ngx_int_t
ngx_http_index_handler(ngx_http_request_t *r)
{
u_char *p, *name;
size_t len, root, reserve, allocated;
ngx_int_t rc;
ngx_str_t path, uri;
ngx_uint_t i, dir_tested;
ngx_http_index_t *index;
ngx_open_file_info_t of;
ngx_http_script_code_pt code;
ngx_http_script_engine_t e;
ngx_http_core_loc_conf_t *clcf;
ngx_http_index_loc_conf_t *ilcf;
ngx_http_script_len_code_pt lcode;
if (r->uri.data[r->uri.len - 1] != '/') {
return NGX_DECLINED;
}
if (!(r->method & (NGX_HTTP_GET|NGX_HTTP_HEAD|NGX_HTTP_POST))) {
return NGX_DECLINED;
}
ilcf = ngx_http_get_module_loc_conf(r, ngx_http_index_module);
clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
allocated = 0;
root = 0;
dir_tested = 0;
name = NULL;
/* suppress MSVC warning */
path.data = NULL;
index = ilcf->indices->elts;
for (i = 0; i < ilcf->indices->nelts; i++) {
if (index[i].lengths == NULL) {
if (index[i].name.data[0] == '/') {
return ngx_http_internal_redirect(r, &index[i].name, &r->args);
}
reserve = ilcf->max_index_len;
len = index[i].name.len;
} else {
ngx_memzero(&e, sizeof(ngx_http_script_engine_t));
e.ip = index[i].lengths->elts;
e.request = r;
e.flushed = 1;
/* 1 is for terminating '\0' as in static names */
len = 1;
while (*(uintptr_t *) e.ip) {
lcode = *(ngx_http_script_len_code_pt *) e.ip;
len += lcode(&e);
}
/* 16 bytes are preallocation */
reserve = len + 16;
}
if (reserve > allocated) {
name = ngx_http_map_uri_to_path(r, &path, &root, reserve);
if (name == NULL) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
allocated = path.data + path.len - name;
}
if (index[i].values == NULL) {
/* index[i].name.len includes the terminating '\0' */
ngx_memcpy(name, index[i].name.data, index[i].name.len);
path.len = (name + index[i].name.len - 1) - path.data;
} else {
e.ip = index[i].values->elts;
e.pos = name;
while (*(uintptr_t *) e.ip) {
code = *(ngx_http_script_code_pt *) e.ip;
code((ngx_http_script_engine_t *) &e);
}
if (*name == '/') {
uri.len = len - 1;
uri.data = name;
return ngx_http_internal_redirect(r, &uri, &r->args);
}
path.len = e.pos - path.data;
*e.pos = '\0';
}
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
"open index \"%V\"", &path);
ngx_memzero(&of, sizeof(ngx_open_file_info_t));
of.read_ahead = clcf->read_ahead;
of.directio = clcf->directio;
of.valid = clcf->open_file_cache_valid;
of.min_uses = clcf->open_file_cache_min_uses;
of.test_only = 1;
of.errors = clcf->open_file_cache_errors;
of.events = clcf->open_file_cache_events;
if (ngx_http_set_disable_symlinks(r, clcf, &path, &of) != NGX_OK) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
if (ngx_open_cached_file(clcf->open_file_cache, &path, &of, r->pool)
!= NGX_OK)
{
if (of.err == 0) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, of.err,
"%s \"%s\" failed", of.failed, path.data);
#if (NGX_HAVE_OPENAT)
if (of.err == NGX_EMLINK
|| of.err == NGX_ELOOP)
{
return NGX_HTTP_FORBIDDEN;
}
#endif
if (of.err == NGX_ENOTDIR
|| of.err == NGX_ENAMETOOLONG
|| of.err == NGX_EACCES)
{
return ngx_http_index_error(r, clcf, path.data, of.err);
}
if (!dir_tested) {
rc = ngx_http_index_test_dir(r, clcf, path.data, name - 1);
if (rc != NGX_OK) {
return rc;
}
dir_tested = 1;
}
if (of.err == NGX_ENOENT) {
continue;
}
ngx_log_error(NGX_LOG_CRIT, r->connection->log, of.err,
"%s \"%s\" failed", of.failed, path.data);
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
uri.len = r->uri.len + len - 1;
if (!clcf->alias) {
uri.data = path.data + root;
} else {
uri.data = ngx_pnalloc(r->pool, uri.len);
if (uri.data == NULL) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
p = ngx_copy(uri.data, r->uri.data, r->uri.len);
ngx_memcpy(p, name, len - 1);
}
return ngx_http_internal_redirect(r, &uri, &r->args);
}
return NGX_DECLINED;
}
static ngx_int_t
ngx_http_static_handler(ngx_http_request_t *r)
{
u_char *last, *location;
size_t root, len;
ngx_str_t path;
ngx_int_t rc;
ngx_uint_t level;
ngx_log_t *log;
ngx_buf_t *b;
ngx_chain_t out;
ngx_open_file_info_t of;
ngx_http_core_loc_conf_t *clcf;
if (!(r->method & (NGX_HTTP_GET|NGX_HTTP_HEAD|NGX_HTTP_POST))) {
return NGX_HTTP_NOT_ALLOWED;
}
if (r->uri.data[r->uri.len - 1] == '/') {
return NGX_DECLINED;
}
log = r->connection->log;
/*
* ngx_http_map_uri_to_path() allocates memory for terminating '\0'
* so we do not need to reserve memory for '/' for possible redirect
*/
last = ngx_http_map_uri_to_path(r, &path, &root, 0);
if (last == NULL) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
path.len = last - path.data;
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, log, 0,
"http filename: \"%s\"", path.data);
clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
ngx_memzero(&of, sizeof(ngx_open_file_info_t));
of.read_ahead = clcf->read_ahead;
of.directio = clcf->directio;
of.valid = clcf->open_file_cache_valid;
of.min_uses = clcf->open_file_cache_min_uses;
of.errors = clcf->open_file_cache_errors;
of.events = clcf->open_file_cache_events;
if (ngx_http_set_disable_symlinks(r, clcf, &path, &of) != NGX_OK) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
if (ngx_open_cached_file(clcf->open_file_cache, &path, &of, r->pool)
!= NGX_OK)
{
switch (of.err) {
case 0:
return NGX_HTTP_INTERNAL_SERVER_ERROR;
case NGX_ENOENT:
case NGX_ENOTDIR:
case NGX_ENAMETOOLONG:
level = NGX_LOG_ERR;
rc = NGX_HTTP_NOT_FOUND;
break;
case NGX_EACCES:
#if (NGX_HAVE_OPENAT)
case NGX_EMLINK:
case NGX_ELOOP:
#endif
level = NGX_LOG_ERR;
rc = NGX_HTTP_FORBIDDEN;
break;
default:
level = NGX_LOG_CRIT;
rc = NGX_HTTP_INTERNAL_SERVER_ERROR;
break;
}
if (rc != NGX_HTTP_NOT_FOUND || clcf->log_not_found) {
ngx_log_error(level, log, of.err,
"%s \"%s\" failed", of.failed, path.data);
}
return rc;
}
r->root_tested = !r->error_page;
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, log, 0, "http static fd: %d", of.fd);
if (of.is_dir) {
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, log, 0, "http dir");
ngx_http_clear_location(r);
r->headers_out.location = ngx_list_push(&r->headers_out.headers);
if (r->headers_out.location == NULL) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
len = r->uri.len + 1;
if (!clcf->alias && r->args.len == 0) {
location = path.data + root;
*last = '/';
} else {
if (r->args.len) {
len += r->args.len + 1;
}
location = ngx_pnalloc(r->pool, len);
if (location == NULL) {
ngx_http_clear_location(r);
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
last = ngx_copy(location, r->uri.data, r->uri.len);
*last = '/';
if (r->args.len) {
*++last = '?';
ngx_memcpy(++last, r->args.data, r->args.len);
}
}
r->headers_out.location->hash = 1;
ngx_str_set(&r->headers_out.location->key, "Location");
r->headers_out.location->value.len = len;
r->headers_out.location->value.data = location;
return NGX_HTTP_MOVED_PERMANENTLY;
}
#if !(NGX_WIN32) /* the not regular files are probably Unix specific */
if (!of.is_file) {
ngx_log_error(NGX_LOG_CRIT, log, 0,
"\"%s\" is not a regular file", path.data);
return NGX_HTTP_NOT_FOUND;
}
#endif
if (r->method == NGX_HTTP_POST) {
return NGX_HTTP_NOT_ALLOWED;
}
rc = ngx_http_discard_request_body(r);
if (rc != NGX_OK) {
return rc;
}
log->action = "sending response to client";
r->headers_out.status = NGX_HTTP_OK;
r->headers_out.content_length_n = of.size;
r->headers_out.last_modified_time = of.mtime;
if (ngx_http_set_etag(r) != NGX_OK) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
if (ngx_http_set_content_type(r) != NGX_OK) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
if (r != r->main && of.size == 0) {
return ngx_http_send_header(r);
}
r->allow_ranges = 1;
/* we need to allocate all before the header would be sent */
b = ngx_calloc_buf(r->pool);
if (b == NULL) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
b->file = ngx_pcalloc(r->pool, sizeof(ngx_file_t));
if (b->file == NULL) {
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}
rc = ngx_http_send_header(r);
if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {
return rc;
}
b->file_pos = 0;
b->file_last = of.size;
b->in_file = b->file_last ? 1: 0;
b->last_buf = (r == r->main) ? 1: 0;
b->last_in_chain = 1;
b->file->fd = of.fd;
b->file->name = path;
b->file->log = log;
b->file->directio = of.is_directio;
out.buf = b;
out.next = NULL;
return ngx_http_output_filter(r, &out);
}
// http/ngx_http_request.c
void
ngx_http_finalize_request(ngx_http_request_t *r, ngx_int_t rc)
{
ngx_connection_t *c;
ngx_http_request_t *pr;
ngx_http_core_loc_conf_t *clcf;
c = r->connection;
ngx_log_debug5(NGX_LOG_DEBUG_HTTP, c->log, 0,
"http finalize request: %i, \"%V?%V\" a:%d, c:%d",
rc, &r->uri, &r->args, r == c->data, r->main->count);
if (rc == NGX_DONE) {
ngx_http_finalize_connection(r);
return;
}
if (rc == NGX_OK && r->filter_finalize) {
c->error = 1;
}
if (rc == NGX_DECLINED) {
r->content_handler = NULL;
r->write_event_handler = ngx_http_core_run_phases;
ngx_http_core_run_phases(r);
return;
}
if (r != r->main && r->post_subrequest) {
rc = r->post_subrequest->handler(r, r->post_subrequest->data, rc);
}
if (rc == NGX_ERROR
|| rc == NGX_HTTP_REQUEST_TIME_OUT
|| rc == NGX_HTTP_CLIENT_CLOSED_REQUEST
|| c->error)
{
if (ngx_http_post_action(r) == NGX_OK) {
return;
}
ngx_http_terminate_request(r, rc);
return;
}
if (rc >= NGX_HTTP_SPECIAL_RESPONSE
|| rc == NGX_HTTP_CREATED
|| rc == NGX_HTTP_NO_CONTENT)
{
if (rc == NGX_HTTP_CLOSE) {
c->timedout = 1;
ngx_http_terminate_request(r, rc);
return;
}
if (r == r->main) {
if (c->read->timer_set) {
ngx_del_timer(c->read);
}
if (c->write->timer_set) {
ngx_del_timer(c->write);
}
}
c->read->handler = ngx_http_request_handler;
c->write->handler = ngx_http_request_handler;
ngx_http_finalize_request(r, ngx_http_special_response_handler(r, rc));
return;
}
if (r != r->main) {
if (r->buffered || r->postponed) {
if (ngx_http_set_write_handler(r) != NGX_OK) {
ngx_http_terminate_request(r, 0);
}
return;
}
pr = r->parent;
if (r == c->data || r->background) {
if (!r->logged) {
clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
if (clcf->log_subrequest) {
ngx_http_log_request(r);
}
r->logged = 1;
} else {
ngx_log_error(NGX_LOG_ALERT, c->log, 0,
"subrequest: \"%V?%V\" logged again",
&r->uri, &r->args);
}
r->done = 1;
if (r->background) {
ngx_http_finalize_connection(r);
return;
}
r->main->count--;
if (pr->postponed && pr->postponed->request == r) {
pr->postponed = pr->postponed->next;
}
c->data = pr;
} else {
ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
"http finalize non-active request: \"%V?%V\"",
&r->uri, &r->args);
r->write_event_handler = ngx_http_request_finalizer;
if (r->waited) {
r->done = 1;
}
}
if (ngx_http_post_request(pr, NULL) != NGX_OK) {
r->main->count++;
ngx_http_terminate_request(r, 0);
return;
}
ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
"http wake parent request: \"%V?%V\"",
&pr->uri, &pr->args);
return;
}
if (r->buffered || c->buffered || r->postponed) {
if (ngx_http_set_write_handler(r) != NGX_OK) {
ngx_http_terminate_request(r, 0);
}
return;
}
if (r != c->data) {
ngx_log_error(NGX_LOG_ALERT, c->log, 0,
"http finalize non-active request: \"%V?%V\"",
&r->uri, &r->args);
return;
}
r->done = 1;
r->read_event_handler = ngx_http_block_reading;
r->write_event_handler = ngx_http_request_empty_handler;
if (!r->post_action) {
r->request_complete = 1;
}
if (ngx_http_post_action(r) == NGX_OK) {
return;
}
if (c->read->timer_set) {
ngx_del_timer(c->read);
}
if (c->write->timer_set) {
c->write->delayed = 0;
ngx_del_timer(c->write);
}
if (c->read->eof) {
ngx_http_close_request(r, 0);
return;
}
ngx_http_finalize_connection(r);
}可以看出，nginx处理http流程框架非常简单，即一直遍历执行所有checker，但本身checker数量又比较多，所以给我们的处理带来了复杂度。此处相当于是责任链模式的应用，而且这链是可以被任意注册的，所以也为我们扩展性打开了方便之门。从部分上按一定序执行checker，只要有一个处理完成，即带调用后续checker。
这些checker大体上被分为了几类，body数据读取类，config配置文件读取类，rewrite路径重写类，access权限验证类，content内容处理类，log日志记录类。从总体上是有序的，但对于某类处理，则是任意的。
本文讲解了nginx作为正向代理（http服务器）的处理过程，当然我们可以简单认为是一个文件路径查找的过程。无非就是解析请求头请求体信息，然后查找所有可能的地方，验证可能的权限，然后就输出内容到客户端了。其实和其他的http服务器没啥差别，但nginx的优势在于性能，在于配置的简便性。性能上基于非阻塞io，配置上则已形成自有的一套简洁语法。
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—END—
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原始发表：2021-01-18，如有侵权请联系 cloudcommunity@tencent.com 删除
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