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+++ b/xml/en/docs/http/ngx_http_limit_req_module.xml	Mon Nov 14 18:09:03 2011 +0000
@@ -0,0 +1,162 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<!DOCTYPE module SYSTEM "../../../../dtd/module.dtd">
+
+<module name="Module ngx_http_limit_req_module"
+        link="/en/docs/http/ngx_http_limit_req_module.html"
+        lang="en">
+
+<section id="summary">
+
+<para>
+The module ngx_http_limit_req_module (0.7.21) allow to limit the number
+of requests per defined key, in particular, the number of requests
+from a single IP address.
+The limitation is done using the “leaky bucket” method.
+</para>
+
+</section>
+
+
+<section id="example" name="Example Configuration">
+
+<para>
+<example>
+http {
+    limit_req_zone $binary_remote_addr zone=one:10m rate=1r/s;
+
+    ...
+
+    server {
+
+        ...
+
+        location /search/ {
+            limit_req zone=one burst=5;
+        }
+</example>
+</para>
+
+</section>
+
+
+<section id="directives" name="Directives">
+
+<directive name="limit_req">
+<syntax>
+    <parameter>zone</parameter>=<argument>name</argument>
+    [<parameter>burst</parameter>=<argument>number</argument>]
+    [<parameter>nodelay</parameter>]
+</syntax>
+<default/>
+<context>http</context>
+<context>server</context>
+<context>location</context>
+
+<para>
+Sets a zone and the maximum allowed burst of requests.
+If the rate of requests exceeds the rate configured for a zone,
+request processing is delayed such as that they are processed
+at a defined rate.
+Excessive requests are delayed until their number exceeds the
+defined number of bursts.
+In this case, the request is terminated with an error
+<http-status code="503" text="Service Temporarily Unavailable"/>.
+By default, the number of bursts is equal to zero.
+For example, the directives
+<example>
+limit_req_zone $binary_remote_addr zone=one:10m rate=1r/s;
+
+    server {
+        location /search/ {
+            limit_req zone=one burst=5;
+        }
+
+</example>
+allow not more than 1 request per second at an average,
+with bursts not exceeding 5 requests.
+</para>
+
+<para>
+If delaying of excessive requests while requests are being limited is not
+desired, the parameter <parameter>nodelay</parameter> should be used:
+<example>
+            limit_req zone=one burst=5 nodelay;
+</example>
+</para>
+
+</directive>
+
+
+<directive name="limit_req_log_level">
+<syntax>
+<value>info</value> |
+<value>notice</value> |
+<value>warn</value> |
+<value>error</value>
+</syntax>
+<default>error</default>
+<context>http</context>
+<context>server</context>
+<context>location</context>
+<appeared-in>0.8.18</appeared-in>
+
+<para>
+Sets the desired logging level for cases when the server limits
+the number of requests, or delays request processing. 
+Delays are logged with the level one less than limits; for example,
+if <command>limit_req_log_level notice</command> is specified,
+delays are logged with the <value>info</value> level.
+</para>
+
+</directive>
+
+
+<directive name="limit_req_zone">
+<syntax>
+    <argument>$variable </argument>
+    <parameter>zone</parameter>=<argument>name</argument>:<argument>size </argument>
+    <parameter>rate</parameter>=<argument>rate</argument>
+</syntax>
+<default/>
+<context>http</context>
+
+<para>
+Sets the parameters for a zone that keeps states for various keys.
+This state stores the current number of requests in particular.
+The key is the value of the specified variable.
+Example usage: 
+<example>
+limit_req_zone $binary_remote_addr zone=one:10m rate=1r/s;
+</example>
+</para>
+
+<para>
+Here, the states are kept in a 10 megabyte zone “one”, and an
+average rate of requests for this zone cannot exceed
+1 request per second.
+</para>
+
+<para>
+An IP address of the client serves as a key.
+Note that instead of <var>$remote_addr</var>, the
+<var>$binary_remote_addr</var> variable is used here,
+allowing to lower the size of a state down to 64 bytes.
+One megabyte zone can keep about 16 thousand 64-byte states.
+If the storage for a zone is exhausted, the server will return error
+<http-status code="503" text="Service Temporarily Unavailable"/>
+to all further requests.
+</para>
+
+<para>
+The rate is specified in requests per second (r/s).
+If a rate of less than one request per second is desired,
+it is specified in request per minute (r/m).
+For example, half-request per second is 30r/m.
+</para>
+
+</directive>
+
+</section>
+
+</module>