nginx的keepalive相关参数使用源码解读
作者：codecraft
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本文主要研究一下nginx的keepalive相关参数
keepalive_timeout
Syntax: keepalive_timeout timeout [header_timeout]; Default: keepalive_timeout 75s; Context: http, server, location
默认是75s，客户端的一个keep-alive连接在服务端保持open的时间，为0表示禁用keep-alive，可选指定header_timeout，若有指定则response header会有Keep-Alive: timeout=time，该header能被Mozilla和Konqueror浏览器识别，MSIE浏览器大概在60s会关闭keep-alive连接
keepalive_requests
Syntax: keepalive_requests number; Default: keepalive_requests 1000; Context: http, server, location
keepalive_requests用于指定一个keep-alive连接最大处理的请求数，超过此值则连接被关闭
ngx_http_core_module
nginx/src/http/ngx_http_core_module.c
void
ngx_http_update_location_config(ngx_http_request_t *r)
{
ngx_http_core_loc_conf_t *clcf;
clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
if (r->method & clcf->limit_except) {
r->loc_conf = clcf->limit_except_loc_conf;
clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
}
if (r == r->main) {
ngx_set_connection_log(r->connection, clcf->error_log);
}
if ((ngx_io.flags & NGX_IO_SENDFILE) && clcf->sendfile) {
r->connection->sendfile = 1;
} else {
r->connection->sendfile = 0;
}
if (clcf->client_body_in_file_only) {
r->request_body_in_file_only = 1;
r->request_body_in_persistent_file = 1;
r->request_body_in_clean_file =
clcf->client_body_in_file_only == NGX_HTTP_REQUEST_BODY_FILE_CLEAN;
r->request_body_file_log_level = NGX_LOG_NOTICE;
} else {
r->request_body_file_log_level = NGX_LOG_WARN;
}
r->request_body_in_single_buf = clcf->client_body_in_single_buffer;
if (r->keepalive) {
if (clcf->keepalive_timeout == 0) {
r->keepalive = 0;
} else if (r->connection->requests >= clcf->keepalive_requests) {
r->keepalive = 0;
} else if (ngx_current_msec - r->connection->start_time
> clcf->keepalive_time)
{
r->keepalive = 0;
} else if (r->headers_in.msie6
&& r->method == NGX_HTTP_POST
&& (clcf->keepalive_disable
& NGX_HTTP_KEEPALIVE_DISABLE_MSIE6))
{
/*
* MSIE may wait for some time if an response for
* a POST request was sent over a keepalive connection
*/
r->keepalive = 0;
} else if (r->headers_in.safari
&& (clcf->keepalive_disable
& NGX_HTTP_KEEPALIVE_DISABLE_SAFARI))
{
/*
* Safari may send a POST request to a closed keepalive
* connection and may stall for some time, see
* https://bugs.webkit.org/show_bug.cgi?id=5760
*/
r->keepalive = 0;
}
}
if (!clcf->tcp_nopush) {
/* disable TCP_NOPUSH/TCP_CORK use */
r->connection->tcp_nopush = NGX_TCP_NOPUSH_DISABLED;
}
if (clcf->handler) {
r->content_handler = clcf->handler;
}
}ngx_http_core_module的ngx_http_update_location_config(ngx_http_request_t *r)方法在keepalive为true时，若connection的requests的requests大于等于配置的keepalive_requests，则设置keepalive为0；若ngx_current_msec减去connection的start_time等于keepalive_time则设置keepalive为0
ngx_http_header_filter
nginx/src/http/ngx_http_header_filter_module.c
static ngx_int_t
ngx_http_header_filter(ngx_http_request_t *r)
{
u_char *p;
size_t len;
ngx_str_t host, *status_line;
ngx_buf_t *b;
ngx_uint_t status, i, port;
ngx_chain_t out;
ngx_list_part_t *part;
ngx_table_elt_t *header;
ngx_connection_t *c;
ngx_http_core_loc_conf_t *clcf;
ngx_http_core_srv_conf_t *cscf;
u_char addr[NGX_SOCKADDR_STRLEN];
if (r->header_sent) {
return NGX_OK;
}
r->header_sent = 1;
if (r != r->main) {
return NGX_OK;
}
//......
if (r->keepalive && (ngx_terminate || ngx_exiting)) {
r->keepalive = 0;
}
//......
if (r->headers_out.status == NGX_HTTP_SWITCHING_PROTOCOLS) {
len += sizeof("Connection: upgrade" CRLF) - 1;
} else if (r->keepalive) {
len += sizeof("Connection: keep-alive" CRLF) - 1;
/*
* MSIE and Opera ignore the "Keep-Alive: timeout=<N>" header.
* MSIE keeps the connection alive for about 60-65 seconds.
* Opera keeps the connection alive very long.
* Mozilla keeps the connection alive for N plus about 1-10 seconds.
* Konqueror keeps the connection alive for about N seconds.
*/
if (clcf->keepalive_header) {
len += sizeof("Keep-Alive: timeout=") - 1 + NGX_TIME_T_LEN + 2;
}
} else {
len += sizeof("Connection: close" CRLF) - 1;
}
//......
if (r->headers_out.status == NGX_HTTP_SWITCHING_PROTOCOLS) {
b->last = ngx_cpymem(b->last, "Connection: upgrade" CRLF,
sizeof("Connection: upgrade" CRLF) - 1);
} else if (r->keepalive) {
b->last = ngx_cpymem(b->last, "Connection: keep-alive" CRLF,
sizeof("Connection: keep-alive" CRLF) - 1);
if (clcf->keepalive_header) {
b->last = ngx_sprintf(b->last, "Keep-Alive: timeout=%T" CRLF,
clcf->keepalive_header);
}
} else {
b->last = ngx_cpymem(b->last, "Connection: close" CRLF,
sizeof("Connection: close" CRLF) - 1);
}
} ngx_http_header_filter_module的ngx_http_header_filter方法，在keepalive为1时会添加Connection: keep-alive，若开启keepalive_header，则添加Keep-Alive: timeout=%T"；若keepalive为0时，则添加Connection: close到response的header
小结
nginx提供了keepalive_timeout(一个keep-alive连接在服务端保持open的时间)及keepalive_requests(一个keep-alive连接最大处理的请求数)参数，其中ngx_http_core_module的ngx_http_update_location_config(ngx_http_request_t *r)方法在keepalive为true时，若connection的requests的requests大于等于配置的keepalive_requests，则设置keepalive为0；若ngx_current_msec减去connection的start_time等于keepalive_time则设置keepalive为0；而ngx_http_header_filter_module的ngx_http_header_filter方法，在keepalive为1时会添加Connection: keep-alive，若开启keepalive_header，则添加Keep-Alive: timeout=%T"；若keepalive为0时，则添加Connection: close到response的header。
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