nginx websocket源码优化 – 作者:stan1y

websocket协议简介

websocket是基于TCP的应用层协议,用于在C/S架构的应用中实现双向通信,rfc文档说明rfc6455
websocket在建立连接时会使用HTTP协议,所以websocket协议是基于HTTP协议实现的。

目前很多卡牌类的游戏选择使用websocket协议进行通信。

websocket具备如下特点:

1.可以进行双向通信,会话通信实时性强。

2.建立起websocket连接,可以一直保持连接,在此期间可以源源不断的发送消息,直到关闭请求。避免了HTTP的非状态性(连接时总开销减少)。和http相比连接创建后,客户端服务端进行数据交换时,协议控制的数据包头部较小(通信量减少)。

3.web服务器与客户端之间建立起连接后,所有的通信都依靠这个专用协议进行。通信过程中可互相发送JSON、XML、HTML或图片等任意格式的数据。不论服务器还是客户端,任意一方都可直接向对方发送数据。

4.更好的二进制支持,支持扩展。

websocket协议格式:

0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-------+-+-------------+-------------------------------+
|F|R|R|R| opcode|M| Payload len |    Extended payload length    |
|I|S|S|S|  (4)  |A|     (7)     |             (16/64)           |
|N|V|V|V|       |S|             |   (if payload len==126/127)   |
| |1|2|3|       |K|             |                               |
+-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
|     Extended payload length continued, if payload len == 127  |
+ - - - - - - - - - - - - - - - +-------------------------------+
|                               |Masking-key, if MASK set to 1  |
+-------------------------------+-------------------------------+
| Masking-key (continued)       |          Payload Data         |
+-------------------------------- - - - - - - - - - - - - - - - +
:                     Payload Data continued ...                :
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
|                     Payload Data continued ...                |
+---------------------------------------------------------------+

nginx支持websocket说明

在使用nginx开启websocket配置时,可以通过在server{}块中配置websocket配置。

server {
      listen   80;
      server_name www.domain.com;
      location / {
         proxy_pass   http://127.0.0.1:8080/; //回源地址
     proxy_http_version 1.1;
         proxy_read_timeout   600s; //超时设置
         //启用支持websocket
         proxy_set_header Upgrade $http_upgrade;
         proxy_set_header Connection "upgrade";
      }
}

如上配置它表明websocket请求连接的时候,升级连接将http连接变成websocket连接。

但这里会有一个问题,这样在server{}块中配置websocket,该server{}必须处理websocket流量,所有发往后端的流量都带上upgrade和connection头。

proxy_set_header  Upgrade $http_upgrade;

proxy_set_header  Connection $connection_upgrade;

nginx websocket源码优化

在server{}中配置websocket时,所有发往后端upstream的流量会添加websocket头。

假如发往后端upstream的请求,有的需要添加websocket头升级为websocket,有的请求不需要,如果继续使用原生的nginx配置,会导致该场景该配置,出现问题。

所以该场景下需改动和优化nginx源码,来区分client的流量是否是websocket。

ngx_http_proxy_websocket_headers:区别在于connection和upgrade

static ngx_keyval_t  ngx_http_proxy_websocket_headers[] = {

{ ngx_string("Host"), ngx_string("$proxy_host") },

{ ngx_string("Connection"), ngx_string("Upgrade") },

{ ngx_string("Content-Length"), ngx_string("$proxy_internal_body_length") },

{ ngx_string("Transfer-Encoding"), ngx_string("$proxy_internal_chunked") },

{ ngx_string("TE"), ngx_string("") },

{ ngx_string("Keep-Alive"), ngx_string("") },

{ ngx_string("Expect"), ngx_string("") },

{ ngx_string("Upgrade"), ngx_string("websocket") },

{ ngx_null_string, ngx_null_string }

};

#ifdef NGX_WEBSOCKET_INNER

// 通过headers来init

rc = ngx_http_proxy_init_headers(cf, conf, &conf->websocket_headers,

ngx_http_proxy_websocket_headers);

if (rc != NGX_OK) {

return NGX_CONF_ERROR;

}

#endif

static ngx_int_t

ngx_http_process_connection(ngx_http_request_t *r, ngx_table_elt_t *h,

ngx_uint_t offset)

{

...

// 获取upgrade标志

if (ngx_strcasestrn(h->value.data, "Upgrade", 7 - 1)) {

r->is_websocket_request |= NGX_WEBSOCKET_HEADER_CONNECTION;

}

...

}


if (r->headers_in.upgrade == NULL) {

goto not_websocket_request;

} else if ((r->is_websocket_request & NGX_WEBSOCKET_HEADER_CONNECTION) == 0) {

goto not_websocket_request;

// } else if (ngx_strncasecmp(r->headers_in.upgrade->value.data, (u_char *)"websocket", 9) == 0) {

// 判断是否含有websocket,添加标志

} else if (ngx_strcasestrn(r->headers_in.upgrade->value.data, "websocket", 9 - 1)) {

r->is_websocket_request |= NGX_WEBSOCKET_HEADER_UPGRADE;

}

// 两种标志都有,r->websocket_request 标志位置位

if (r->is_websocket_request == (NGX_WEBSOCKET_HEADER_UPGRADE | NGX_WEBSOCKET_HEADER_CONNECTION)) {

r->websocket_request = 1;

r->http_version = NGX_HTTP_VERSION_11;

} else {

r->websocket_request = 0;

}

ngx_http_proxy_process_header配置upstream的标志位

static ngx_int_t

ngx_http_proxy_process_header(ngx_http_request_t *r)

{

...

if (u->headers_in.status_n == NGX_HTTP_SWITCHING_PROTOCOLS) {

u->keepalive = 0;

if (r->headers_in.upgrade) {

u->upgrade = 1;

}

}

...

}

在ngx_http_upstream_send_response种使用该标志位

static void

ngx_http_upstream_send_response(ngx_http_request_t *r, ngx_http_upstream_t *u)

{

...

if (u->upgrade) {

ngx_http_upstream_upgrade(r, u);

return;

}

...

}

ngx_http_upstream_upgrade给上下游设置读写事件

static void

ngx_http_upstream_upgrade(ngx_http_request_t *r, ngx_http_upstream_t *u)

{

...

u->read_event_handler = ngx_http_upstream_upgraded_read_upstream;

u->write_event_handler = ngx_http_upstream_upgraded_write_upstream;

r->read_event_handler = ngx_http_upstream_upgraded_read_downstream;

r->write_event_handler = ngx_http_upstream_upgraded_write_downstream;

...

}

每个读写时间所用的函数都是一样的,入参不同:from_upstream代表是否是后端,do_write代表是否是写事件

下面以upstream的读事件为例

static void

ngx_http_upstream_process_upgraded(ngx_http_request_t *r,

ngx_uint_t from_upstream, ngx_uint_t do_write)

{

...

// from_upstream为1,src为upstream(上游),dst为downstream(下游)

if (from_upstream) {

src = upstream;

dst = downstream;

b = &u->buffer;




}

for ( ;; ) {

// do_write为0忽略。

if (do_write) {}

if (size && src->read->ready) {

// src为upstream,用来读

n = src->recv(src, b->last, size);

// n >0 接收大于0的字节数,do_write置为1,continue进行写入

if (n > 0) {

do_write = 1;

b->last += n;




if (from_upstream) {

u->state->bytes_received += n;

}

continue;

}

// 加入三个计时器,upstream读写都加,downstream只加写入,相当于除了client的接收没加计时器,都加了

if (upstream->write->active && !upstream->write->ready) {

ngx_add_timer(upstream->write, u->conf->send_timeout);

} else if (upstream->write->timer_set) {

ngx_del_timer(upstream->write);

}

if (upstream->read->active && !upstream->read->ready) {

ngx_add_timer(upstream->read, u->conf->read_timeout);

} else if (upstream->read->timer_set) {

ngx_del_timer(upstream->read);

}


if (downstream->write->active && !downstream->write->ready) {

ngx_add_timer(downstream->write, clcf->send_timeout);

} else if (downstream->write->timer_set) {

ngx_del_timer(downstream->write);

}

...

}

来源:freebuf.com 2020-11-29 13:57:23 by: stan1y

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