📅 最后修改于: 2021-01-07 06:07:23 🧑 作者: Mango
变量是编程语言的自然组成部分。这些只是使用命令性语言(例如Perl，C / C++，Bourne shell，Perl)保存各种值的容器。值可以是诸如“ hello world”之类的字符串，诸如“ 3.14”之类的数字，甚至可以是复杂的事物，例如以这些语言引用数组或哈希表。
但是，对于Nginx配置语言，变量只能保存一种类型的值，即字符串。但有一个有趣的例外：ngx_array_var延伸的Nginx变量包含数组的第三方模块，但它是由编码C指针作为幕后的二进制字符串值来实现。
考虑我们的nginx.conf配置文件，其中包含以下行：
set $a "hello world";
在这里，我们通过set配置指令为变量“ $ a”赋值，该配置指令来自标准的nginx_rewrite模块。在这里，我们将字符串值“ hello world”分配给“ $ a”。
从上面的示例中，我们可以看到Nginx变量名称在其前面带有一个美元符号($)。因此，可以说，每当要在配置文件中添加对nginx变量的引用时，都必须添加美元($)前缀。
我们来看另一个简单的例子
set $a hello;
set $b "$a, $a";
从上面的示例中，我们可以看到变量$ a用于构造变量$ b的值。因此，在完成这两个指令后，$ a的值为“ hello”，$ b的值为“ hello，hello”。此技术称为“变量插值”。
我们来看一下Nginx中的变量列表：
| Variable | Description |
|---|---|
| $ancient_browser | This variable is used to equal the value set by the ancient_browser_value directive, if a browser was identified as ancient. |
| $arg_name | Name of the argument in the request line. |
| $args | List of arguments on the request line. |
| $binary_remote_addr (ngx_http_core_module) | Client address in the form of binary. Length of value is always 4 bytes for IP4 addresses or 16 bytes for IPv6 addresses. |
| $binary_remote_addr (ngx_stream_core_module) | Client address in the form of binary. Length of value is always 4 bytes for IP4 addresses or 16 bytes for IPv6 addresses. |
| $body_bytes_sent | Number of bytes sent to the client, not counts the response header. |
| $bytes_received | Number of bytes received from a client. |
| $bytes_sent (ngx_http_core_module) | Number of bytes sent to a client. |
| $bytes_sent (ngx_http_log_module) | Number of bytes sent to a client. |
| $bytes_sent (ngx_stream_core_module) | Number of bytes sent to a client. |
| $connection (ngx_http_core_module) | connection serial number |
| $connection (ngx_http_log_module) | connection serial number |
| $connection (ngx_stream_core_module) | connection serial number |
| $connection_requests (ngx_http_core_module) | Current number of requests made via connection. |
| $connection_requests (ngx_http_log_module) | Current number of requests made via connection. |
| $connections_active | Same as Active connections value |
| $connections_reading | Same as Reading value |
| $connections_waiting | Same as the Waiting value |
| $connections_writing | Same as the writing value. |
| $content_length | “Content length” request header field. |
| $content_type | “Content type” request header field |
| $cookie_name | The name of cookie |
| $date_gmt | Current time in GMT (Greenwich Mean Time). To set the format, use the config command with timefmt parameter. |
| $date_local | Current time in the local time zone. To set the format, use the config command with timefmt parameter. |
| $document_root | Value of root or alias directive for the current request. |
| $document_uri | It is same as $uri. |
| $fastcgi_path_info | When using the fastcgi_split_path_info directive, the $fastcgi_script_name variable equals the value of the first capture set by the directive. And the value of second capture set by the fastcgi_split_path_info directive. This variable is used to set the PATH_INFO parameter. |
| $fastcgi_script_name | Request URI (Uniform Resource Identifier) or, if a URI ends with a slash, request URI with an index file name configured by the fastcgi_index directive appended to it. |
| $geoip_area_code (ngx_http_geoip_module) | Telephone area code (US only). This variable may contain some information which is outdated since the corresponding database field is deprecated. |
| $geoip_area_code (ngx_stream_geoip_module) | Telephone area code (US only). This variable may contain outdated information since the corresponding database field is deprecated. |
| $geoip_city (ngx_http_geoip_module) | City name, e.g. “Washinton”, “Moscow”. |
| $geoip_city (ngx_stream_geoip_module) | City name, e.g. “Washinton”, “Moscow”. |
| $geoip_city_continent_code (ngx_http_geoip_module) | Continent code in two letters. For example, “NA”, “EU”. |
| $geoip_city_continent_code (ngx_stream_geoip_module) | Continent code in two letters. For example, “NA”, “EU”. |
| $geoip_city_country_code (ngx_http_geoip_module) | Continent code in two letters. For example, “NA”, “EU”. |
| $geoip_city_country_code (ngx_http_geoip_module) | Country code in two letters. For example, “RU”, “US”. |
| $geoip_city_country_code (ngx_stream_geoip_module) | Country code in two letters. For example, “RU”, “US”. |
| $geoip_city_country_code3 (ngx_http_geoip_module) | Country code in three letters. For example, “RUS”, “USA”. |
| $geoip_city_country_code3 (ngx_stream_geoip_module) | Country code in three letters. For example, “RUS”, “USA”. |
| $geoip_city_country_name (ngx_http_geoip_module) | Name of the country. For example, “India”, “United States”. |
| $geoip_city_country_name (ngx_stream_geoip_module) | Name of the country. For example, “India”, “United States”. |
| $geoip_country_code (ngx_http_geoip_module) | Country code in two letters. For example, “RU”, “US”. |
| $geoip_country_code (ngx_stream_geoip_module) | Country code in two letters. For example, “RU”, “US”. |
| $geoip_country_code3 (ngx_http_geoip_module) | Country code in three letters. For example, “RUS”, “USA”. |
| $geoip_country_code3 (ngx_stream_geoip_module) | Country code in three letters. For example, “RUS”, “USA”. |
| $geoip_country_name (ngx_http_geoip_module) | Name of the country. For example, “India”, “United States”. |
| $geoip_country_name (ngx_stream_geoip_module) | Name of the country. For example, “India”, “United States”. |
| $geoip_dma_code (ngx_http_geoip_module) | It is the DMA (Designated Market Area) code or metro code in US, according to the geo-targeting in Google AdWords API. |
| $geoip_dma_code (ngx_stream_geoip_module) | It is the DMA (Designated Market Area) code or metro code in US, according to the geo-targeting in Google AdWords API. |
| $geoip_latitude (ngx_http_geoip_module) | Latitude. |
| $geoip_latitude (ngx_stream_geoip_module) | Latitude. |
| $geoip_longitude (ngx_http_geoip_module) | Longitude |
| $geoip_longitude (ngx_stream_geoip_module) | Longitude |
| $geoip_org (ngx_http_geoip_module) | Name of the organization. For example “University of California”. |
| $geoip_org (ngx_stream_geoip_module) | Name of the organization. For example “University of California”. |
| $geoip_postal_code (ngx_http_geoip_module) | Postal code. |
| $geoip_postal_code (ngx_stream_geoip_module) | Postal code. |
| $geoip_region (ngx_http_geoip_module) | The name of the region (Province, region, state, federal land, territory) for example, for Moscow City, DC. |
| $geoip_region (ngx_stream_geoip_module) | The name of the region (Province, region, state, federal land, territory) for example, for Moscow City, DC. |
| $geoip_region_name (ngx_http_geoip_module) | Country region name ((Province, region, state, federal land, territory), for example “Moscow City”, “District of Columbia”. |
| $geoip_region_name (ngx_stream_geoip_module) | Country region name ((Province, region, state, federal land, territory), for example “Moscow City”, “District of Columbia”. |
| $gzip_ratio | It is the achieved compression ratio, computed as the ratio between the original and compressed response sizes. |
| $host | Host name from the request line, host name form the Host request header field, or the server name matching a request. |
| $hostname (ngx_http_core_module) | Host name. |
| $hostname (ngx_stream_core_module) | Host name. |
| $http2 | Negotiated protocol identifier: h2 for HTTP/2 over TLS, h2c for HTTP/2 over clear text TCP, or an empty string otherwise. |
| $http_name | It is the arbitrary request header field: the last part of a variable name is the field name which is converted to lower case with dashes replaced by underscores. |
| $https | If connection operates in SSL mode then it is “on”, or an empty string otherwise. |
| $invalid_referer | If the “Referer” request header field value is considered valid, then the string is empty, otherwise 1. |
| $is_args | “?” if a request line has arguments, or an empty string otherwise. |
| $jwt_claim_name | It returns the value of a specified JWT (JSON Web Token) claim. |
| $jwt_header_name | Returns the value of a specified JOSE (JavaScript Object Signing and Encryption) header. |
| $limit_rate | Setting this variable enables response rate limiting. |
| $memcached_key | Defines a key for obtaining response from a memcached server. |
| $modern_browser | Equals the value set by the modern_browser_value directive, if a browser was identified as modern. |
| $msec (ngx_http_core_module) | Current time in seconds with the ms (milliseconds) resolution. |
| $msec (ngx_http_log_module) | Time in seconds with a milliseconds resolution at the time of the log write. |
| $msec (ngx_stream_core_module) | Current time in seconds with the ms (milliseconds) resolution. |
| $msie | Equals 1 if a browser was identified as MSIE (Microsoft Internet Explorer) of any version. |
| $nginx_version (ngx_http_core_module) | Shows the nginx version |
| $nginx_version (ngx_stream_core_module) | Nginx version. |
| $pid (ngx_http_core_module) | PID (Process ID) of the worker process. |
| $pid (ngx_stream_core_module) | PID (Process ID) of the worker process. |
| $pipe (ngx_http_core_module) | “p” if request was pipelined, “.” Otherwise. |
| $pipe (ngx_http_log_module) | “p” if request was pipelined, “.” Otherwise. |
| $protocol | Protocol used to communicate with the client: UDP or TCP. |
| $proxy_add_x_forwarded_for | the “X-Forwarded-For” client request header field with the $remote_addr variable appended to it, separated by a comma. If the “X-Forwarded-For” field is not present in the client request header, the $proxy_add_x_forwarded_for variable is equal to the $remote_addr variable. |
| $proxy_host | Name and port of the proxied server as specified in the proxy_pass directive. |
| $proxy_port | Port of the proxied server as specified in the proxy_pass directive, or the default port of the protocol. |
| $proxy_protocol_addr (ngx_http_core_module) | Client address from the PROXY protocol header, or an empty string otherwise. The PROXY protocol must be enabled before. This can be done by setting the proxy protocol parameter in the listen directive. |
| $proxy_protocol_addr (ngx_stream_core_module) | Client address from the PROXY protocol header, or an empty string otherwise. The PROXY protocol must be enabled before. This can be done by setting the proxy protocol parameter in the listen directive. |
| $proxy_protocol_port (ngx_http_core_module) | Client address from the PROXY protocol header, or an empty string otherwise. The PROXY protocol must be enabled before. This can be done by setting the proxy protocol parameter in the listen directive. |
| $proxy_protocol_port (ngx_stream_core_module) | Client address from the PROXY protocol header, or an empty string otherwise. The PROXY protocol must be enabled before. This can be done by setting the proxy protocol parameter in the listen directive. |
| $query_string | Same as $args |
| $realip_remote_addr (ngx_http_realip_module) | It is used to keep the original client address. |
| $realip_remote_addr (ngx_stream_realip_module) | It is used to keep the original client address. |
| $realip_remote_port (ngx_http_realip_module) | It is used to keep the original client address. |
| $realip_remote_port (ngx_stream_realip_module) | It is used to keep the original client address. |
| $realpath_root | An absolute path name corresponding to the alias or root directive’s value for the current request, with all symbolic links resolved to real paths. |
| $remote_addr (ngx_http_core_module) | Client Address |
| $remote_addr (ngx_stream_core_module) | Client Address |
| $remote_port (ngx_http_core_module) | Client Port |
| $remote_port (ngx_stream_core_module) | Client port |
| $remote_user | User name supplied with the Basic authentication. |
| $request | Full original request line. |
| $request_body | The variable’s value is made available in locations processed by the proxy_pass, and scgi_pass directive when the request body was read to a memory_buffer. |
| $request_body_file | Name of a temporary file with the request body. |
| $request_completion | Value is “OK” if a request has completed, or an empty string otherwise. |
| $request_filename | File path for the current request, based on the root or alias directives, and the request URI. |
| $request_id | Unique request identifier generated from 16 random bytes, in hexadecimal. |
| $request_length (ngx_http_core_module) | Request length (request line, request body, and header). |
| $request_length (ngx_http_log_module) | Request length (request line, request body, and header). |
| $request_method | Request method. Usually “GET” or “POST”. |
| $request_time (ngx_http_core_module) | Request processing time in seconds with a milliseconds resolution; time elapsed since the first bytes were read from the client. |
| $request_time (ngx_http_log_module) | Request processing time in seconds with a milliseconds resolution; time elapsed between the first bytes were read from the client and the log write after the last bytes were sent to the client. |
| $request_uri | Full original request URI (Uniform Resource Identifier) with arguments. |
| $scheme | Request scheme which may be http or https |
| $secure_link | Shows the status a link check and the value depends on the selected operation mode. |
| $secure_link_expires | The lifetime of a link passed in a request; |
| $sent_http_name | It is the arbitrary response header field; the last part of a variable name is the name of the field converted to lower case with dashes replaced by underscores. |
| $sent_trailer_name | Arbitrary field sent at the end of the response; the last part of a variable name is the name of the field converted to lower case with dashes replaced by underscores. |
| $server_addr (ngx_http_core_module) | Server’s address which accepted a request. To compute the value of this variable requires a system call. |
| $server_addr (ngx_stream_core_module) | Server’s address which accepted a request. To compute the value of this variable requires a system call. |
| $server_name | Server’s name which accepted a request. |
| $server_port (ngx_http_core_module) | Server’s port which accepted a request. |
| $server_port (ngx_stream_core_module) | Server’s port which accepted a connection. |
| $server_protocol | It is a request protocol, usually HTTP/1.0, HTTP/1.1 or HTTP/2.0. |
| $session_log_binary_id | Current session ID in the form of binary. |
| $session_log_id | Current session ID. |
| $session_time | Session duration in seconds with a milliseconds resolution. |
| $slice_range | The current slice range in HTTP byte range format. E.g. bytes=0-1048575 |
| $spdy | SPDY protocol version for SPDY(pronounced as speedy) connections, or an empty string otherwise. |
| $spdy_request_priority | Request priority for SPDY (pronounced as speedy) connections or an empty string otherwise. |
| $ssl_cipher (ngx_http_ssl_module) | Returns the string of ciphers used for an established SSL (Secure Sockets Layer) connection. |
| $ssl_cipher (ngx_stream_ssl_module) | Returns the string of ciphers used for an established SSL (Secure Sockets Layer) connection. |
| $ssl_ciphers (ngx_http_ssl_module) | It will return the list of ciphers supported by the client. Here, known ciphers are listed by names and unknown are shown in hexadecimal, for example, AES128-SHA:AES256-SHA:0x00ff |
| $ssl_ciphers (ngx_stream_ssl_module) | It will return the list of ciphers supported by the client. Here, known ciphers are listed by names and unknown are shown in hexadecimal, for example, AES128-SHA:AES256-SHA:0x00ff |
| $ssl_client_cert (ngx_http_ssl_module) | It will return the client certificate in the PEM (Privacy Enhanced Mail) for an established SSL connection, with each line except the 1st prepended with the tab character. |
| $ssl_client_cert (ngx_stream_ssl_module) | It will return the client certificate in the PEM (Privacy Enhanced Mail) for an established SSL connection, with each line except the 1st prepended with the tab character. |
| $ssl_client_escaped_cert | It will return the client certificate in the PEM (Privacy Enhanced Mail) for an established SSL connection |
| $ssl_client_fingerprint (ngx_http_ssl_module) | It will return the SHA1 (Secure Hash Algorithm) fingerprint of the client certificate for an established SSL connection. |
| $ssl_client_fingerprint (ngx_stream_ssl_module) | It will return the SHA1 (Secure Hash Algorithm) fingerprint of the client certificate for an established SSL connection. |
| $ssl_client_i_dn (ngx_http_ssl_module) | Returns the “issuer DN” (where DN is Distinguished name) string of the client certificate for an established SSL connection according to RFC 2253. |
| $ssl_client_i_dn (ngx_stream_ssl_module) | Returns the “issuer DN” (where DN is Distinguished name) string of the client certificate for an established SSL connection according to RFC 2253. |
| $ssl_client_i_dn_legacy | Returns the “issuer DN” (where DN is Distinguished name) string of the client certificate for an established SSL connection. |
| $ssl_client_raw_cert (ngx_http_ssl_module) | It will return the client certificate in the PEM (Privacy Enhanced Mail) format for an established SSL connection. |
| $ssl_client_raw_cert (ngx_stream_ssl_module) | It will return the client certificate in the PEM (Privacy Enhanced Mail) format for an established SSL connection. |
| $ssl_client_s_dn (ngx_http_ssl_module) | Returns the “subject DN” (where DN is Distinguished name) string of the client certificate for an established SSL connection according to RFC2253. |
| $ssl_client_s_dn (ngx_stream_ssl_module) | Returns the “subject DN” (where DN is Distinguished name) string of the client certificate for an established SSL connection according to RFC2253. |
| $ssl_client_s_dn_legacy | Returns the “subject DN” (where DN is Distinguished name) string of the client certificate for an established SSL connection. |
| $ssl_client_serial (ngx_http_ssl_module) | It will return the serial number of the client certificate for an established SSL connection. |
| $ssl_client_serial (ngx_stream_ssl_module) | It will return the serial number of the client certificate for an established SSL connection. |
| $ssl_client_v_end (ngx_http_ssl_module) | It will return the end date of the client certificate. |
| $ssl_client_v_end (ngx_stream_ssl_module) | It will return the end date of the client certificate. |
| $ssl_client_v_remain (ngx_http_ssl_module) | It will return the number of days until the client certificate expires. |
| $ssl_client_v_remain (ngx_stream_ssl_module) | It will return the number of days until the client certificate expires. |
| $ssl_client_v_start (ngx_http_ssl_module) | It will return the start date of the client certificate. |
| $ssl_client_v_start (ngx_stream_ssl_module) | It will return the start date of the client certificate. |
| $ssl_client_verify (ngx_http_ssl_module) | It will return the result of client certificate verification: “SUCCESS”, “FAILD:reason”, and “NONE” if a certificate was not present. |
| $ssl_client_verify (ngx_stream_ssl_module) | It will return the result of client certificate verification: “SUCCESS”, “FAILD:reason”, and “NONE” if a certificate was not present. |
| $ssl_curves (ngx_http_ssl_module) | Returns the list of curves supported by the client. All known curves are listed by names, and unknown are shown in hexadecimal, for example: 0x001d:prime256v1:secp521r1:secp384r1 |
| $ssl_curves (ngx_stream_ssl_module) | Returns the list of curves supported by the client. All known curves are listed by names, and unknown are shown in hexadecimal, for example: 0x001d:prime256v1:secp521r1:secp384r1 |
| $ssl_early_data | It will return 1 if TLS 1.3 early data is used and the handshake is not complete otherwise return empty. |
| $ssl_preread_alpn_protocols | It returns the list of protocols advertised by the client through ALPN and the values are separated by commas. |
| $ssl_preread_protocol | The highest SSL (Secure Sockets layer) protocol version supported by the client. |
| $ssl_preread_server_name | Returns the name of the server requested through SNI (Sever Name Indication). |
| $ssl_protocol (ngx_http_ssl_module) | It will return the protocol of an established SSL connection. |
| $ssl_protocol (ngx_stream_ssl_module) | It will return the protocol of an established SSL connection. |
| $ssl_server_name (ngx_http_ssl_module) | Returns the name of the server requested through SNI (Server Name Indication). |
| $ssl_server_name (ngx_stream_ssl_module) | Returns the name of the server requested through SNI (Server Name Indication). |
| $ssl_session_id (ngx_http_ssl_module) | It will return the session identifier of an established SSL connection. |
| $ssl_session_id (ngx_stream_ssl_module) | It will return the session identifier of an established SSL connection. |
| $ssl_session_reused (ngx_http_ssl_module) | Returns “r” if an SSL session was reused or “.” Otherwise. |
| $ssl_session_reused (ngx_stream_ssl_module) | Returns “r” if an SSL session was reused or “.” Otherwise. |
| $status (ngx_http_core_module) | Response status. |
| $status (ngx_http_log_module) | Response status. |
| $status (ngx_stream_core_module) | Session status, which can be one of the following: 200: Session completed successfully. 400: Data of client could not be parsed. 403: access forbidden. 500: internal server error. 502: bad gateway. 503: service unavailable. |
| $tcpinfo_rtt | Displays the information about the client TCP connection, available on systems that support the TCP_INFO socket option. |
| $tcpinfo_rttvar | Displays the information about the client TCP connection, available on systems that support the TCP_INFO socket option. |
| $tcpinfo_snd_cwnd | Displays the information about the client TCP connection, available on systems that support the TCP_INFO socket option. |
| $tcpinfo_rcv_space | Displays the information about the client TCP connection, available on systems that support the TCP_INFO socket option. |
| $time_iso8601 (ngx_http_core_module) | Shows the Local time in the standard format of ISO 8601. |
| $time_iso8601 (ngx_http_log_module) | Shows the Local time in the standard format of ISO 8601. |
| $time_iso8601 (ngx_stream_core_module) | Shows the Local time in the standard format of ISO 8601. |
| $time_local (ngx_http_core_module) | Shows the Local time in the format of common log |
| $time_local (ngx_http_log_module) | Shows the local time in the format of common log. |
| $time_local (ngx_stream_core_module) | Shows the local time in the format of common log. |
| $uid_got | The name of the cookie and received client identifier. |
| $uid_reset | If the variable is set to a ?non-empty’ string means that is not ?0′, then the client identifier are reset. The special value log additionally leads to the output of messages about the reset identifiers to the error_log. |
| $uid_set | The name of the cookie and sent the client identifier. |
| $upstream_addr (ngx_http_upstream_module) | It will keep the IP address and port, or the path to the UNIX-domain socket of the upstream server. If several servers were contacted during request processing, then their addresses are separated by commas. |
| $upstream_addr (ngx_stream_upstream_module) | It will keep the IP address and port, or the path to the UNIX-domain socket of the upstream server. If several servers were contacted during request processing, then their addresses are separated by commas. |
| $upstream_bytes_received (ngx_http_upstream_module) | Number of bytes received from an upstream stream server. Values from several connections are separated by commas (,) and colons (:) like addresses in the $upstream_addr variable. |
| $upstream_bytes_received (ngx_stream_upstream_module) | Number of bytes received from an upstream stream server. Values from several connections are separated by commas (,) and colons (:) like addresses in the $upstream_addr variable. |
| $upstream_bytes_sent (ngx_http_upstream_module) | Number of bytes sent to an upstream stream server. Values from several connections are separated by commas (,) and colons (:) like addresses in the $upstream_addr variable. |
| $upstream_bytes_sent (ngx_stream_upstream_module) | Number of bytes sent to an upstream stream server. Values from several connections are separated by commas (,) and colons (:) like addresses in the $upstream_addr variable. |
| $upstream_cache_status | It will keep the status of accessing a response cache. The status can be either “BYPASS”, “MISS”, “EXPIRED”, “STALE”, “REVALIDATED”, “UPDATING” or “HIT”. |
| $upstream_connect_time (ngx_http_upstream_module) | It is used to keep the time spent on establishing a connection with the upstream server (1.9.1); the time is kept in seconds with millisecond resolution. In case of SSL, adds time spent on handshake. Times of several connections are separated by commas (,) and colons (:) like addresses in the $upstream_addr variable. |
| $upstream_connect_time (ngx_stream_upstream_module) | Keeps the time to connect to the upstream server; the time is kept in seconds with milliseconds resolution. Times of several connections are separated by commas (,) like addresses in the $upstream_addr variable. |
| $upstream_cookie_name | Cookie with the defined name sent by the upstream server in the Set-Cookie response header field. Only the cookies from the response of the last server are saved. |
| $upstream_first_byte_time | Time to receive the first byte of data. The time is kept in seconds with millisecond resolution. Times of multiple connections are separated by commas (,) like addresses in the $upstream_addr variable. |
| $upstream_header_time | It is used to keep the time spent on receiving header from the upstream server. Times of multiple connections are separated by commas (,) and colons (:) like addresses in the $upstream_addr variable. |
| $upstream_http_name | Keep the server response header fields. |
| $upstream_queue_time | It is used to keep time the request spent in the upstream queue; the time is kept in seconds with milliseconds resolution. Times of multiple connections are separated by commas (,) and colons (:) like addresses in the $upstream_addr variable. |
| $upstream_response_length | It is used to keep the length of the response obtained from the upstream server. The length is kept in bytes. Lengths of multiple responses are separated by commas (,) and colons (:) like addresses in the $upstream_addr variable. |
| $upstream_response_time | It is used to keep time spent on receiving the response from the upstream server; the time is kept in seconds with milliseconds resolution. Times of several connections are separated by commas (,) and colons (:) like addresses in the $upstream_addr variable. |
| $upstream_session_time | Session duration in seconds with milliseconds resolution. Times of several connections are separated by commas (,) like addresses in the $upstream_addr variable. |
| $upstream_status | It is used to keep the status code of the response obtained from the upstream server. Status codes of the several responses are separated by commas (,) and colons (:) like addresses in the $upstream_addr variable. If the server can’t be selected, the variable keeps the 502 (Bad Gateway) status code. |
| $upstream_trailer_name | It is used to keep the field from the end of the response obtained from the upstream server. |
| $uri | Current URI in request, normalized. We can change the value of the $uri during request processing, e.g. when doing internal redirects, or when using index files. |