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view xml/en/docs/http/ngx_http_limit_conn_module.xml @ 3069:d4639ff91e10
Documented max_commands in mail module.
author | Maxim Dounin <mdounin@mdounin.ru> |
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date | Mon, 01 Apr 2024 04:08:07 +0300 |
parents | 9eadb98ec770 |
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<?xml version="1.0"?> <!-- Copyright (C) Igor Sysoev Copyright (C) Nginx, Inc. --> <!DOCTYPE module SYSTEM "../../../../dtd/module.dtd"> <module name="Module ngx_http_limit_conn_module" link="/en/docs/http/ngx_http_limit_conn_module.html" lang="en" rev="15"> <section id="summary"> <para> The <literal>ngx_http_limit_conn_module</literal> module is used to limit the number of connections per the defined key, in particular, the number of connections from a single IP address. </para> <para> Not all connections are counted. A connection is counted only if it has a request being processed by the server and the whole request header has already been read. </para> </section> <section id="example" name="Example Configuration"> <para> <example> http { limit_conn_zone $binary_remote_addr zone=addr:10m; ... server { ... location /download/ { limit_conn addr 1; } </example> </para> </section> <section id="directives" name="Directives"> <directive name="limit_conn"> <syntax><value>zone</value> <value>number</value></syntax> <default/> <context>http</context> <context>server</context> <context>location</context> <para> Sets the shared memory zone and the maximum allowed number of connections for a given key value. When this limit is exceeded, the server will return the <link id="limit_conn_status">error</link> in reply to a request. For example, the directives <example> limit_conn_zone $binary_remote_addr zone=addr:10m; server { location /download/ { limit_conn addr 1; } </example> allow only one connection per an IP address at a time. <note> In HTTP/2 and HTTP/3, each concurrent request is considered a separate connection. </note> </para> <para> There could be several <literal>limit_conn</literal> directives. For example, the following configuration will limit the number of connections to the server per a client IP and, at the same time, the total number of connections to the virtual server: <example> limit_conn_zone $binary_remote_addr zone=perip:10m; limit_conn_zone $server_name zone=perserver:10m; server { ... limit_conn perip 10; limit_conn perserver 100; } </example> </para> <para> These directives are inherited from the previous configuration level if and only if there are no <literal>limit_conn</literal> directives defined on the current level. </para> </directive> <directive name="limit_conn_dry_run"> <syntax><literal>on</literal> | <literal>off</literal></syntax> <default>off</default> <context>http</context> <context>server</context> <context>location</context> <appeared-in>1.17.6</appeared-in> <para> Enables the dry run mode. In this mode, the number of connections is not limited, however, in the shared memory zone, the number of excessive connections is accounted as usual. </para> </directive> <directive name="limit_conn_log_level"> <syntax> <literal>info</literal> | <literal>notice</literal> | <literal>warn</literal> | <literal>error</literal></syntax> <default>error</default> <context>http</context> <context>server</context> <context>location</context> <appeared-in>0.8.18</appeared-in> <para> Sets the desired logging level for cases when the server limits the number of connections. </para> </directive> <directive name="limit_conn_status"> <syntax><value>code</value></syntax> <default>503</default> <context>http</context> <context>server</context> <context>location</context> <appeared-in>1.3.15</appeared-in> <para> Sets the status code to return in response to rejected requests. </para> </directive> <directive name="limit_conn_zone"> <syntax> <value>key</value> <literal>zone</literal>=<value>name</value>:<value>size</value></syntax> <default/> <context>http</context> <para> Sets parameters for a shared memory zone that will keep states for various keys. In particular, the state includes the current number of connections. The <value>key</value> can contain text, variables, and their combination. Requests with an empty key value are not accounted. <note> Prior to version 1.7.6, a <value>key</value> could contain exactly one variable. </note> Usage example: <example> limit_conn_zone $binary_remote_addr zone=addr:10m; </example> Here, a client IP address serves as a key. Note that instead of <var>$remote_addr</var>, the <var>$binary_remote_addr</var> variable is used here. The <var>$remote_addr</var> variable’s size can vary from 7 to 15 bytes. The stored state occupies either 32 or 64 bytes of memory on 32-bit platforms and always 64 bytes on 64-bit platforms. The <var>$binary_remote_addr</var> variable’s size is always 4 bytes for IPv4 addresses or 16 bytes for IPv6 addresses. The stored state always occupies 32 or 64 bytes on 32-bit platforms and 64 bytes on 64-bit platforms. One megabyte zone can keep about 32 thousand 32-byte states or about 16 thousand 64-byte states. If the zone storage is exhausted, the server will return the <link id="limit_conn_status">error</link> to all further requests. </para> </directive> <directive name="limit_zone"> <syntax> <value>name</value> <value>$variable</value> <value>size</value></syntax> <default/> <context>http</context> <para> This directive was made obsolete in version 1.1.8 and was removed in version 1.7.6. An equivalent <link id="limit_conn_zone"/> directive with a changed syntax should be used instead: <note> <literal>limit_conn_zone</literal> <value>$variable</value> <literal>zone</literal>=<value>name</value>:<value>size</value>; </note> </para> </directive> </section> <section id="variables" name="Embedded Variables"> <para> <list type="tag"> <tag-name id="var_limit_conn_status"><var>$limit_conn_status</var></tag-name> <tag-desc> keeps the result of limiting the number of connections (1.17.6): <literal>PASSED</literal>, <literal>REJECTED</literal>, or <literal>REJECTED_DRY_RUN</literal> </tag-desc> </list> </para> </section> </module>