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<?xml version="1.0" encoding="ISO-8859-1"?>
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.4</a> > <a href="./">Modules</a></div>
<div id="page-content">
<div id="preamble"><h1>Apache Module mod_proxy</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/mod/mod_proxy.html" title="English"> en </a> |
<a href="../fr/mod/mod_proxy.html" hreflang="fr" rel="alternate" title="Franais"> fr </a> |
<a href="../ja/mod/mod_proxy.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Multi-protocol proxy/gateway server</td></tr>
<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">ModuleIdentifier:</a></th><td>proxy_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">SourceFile:</a></th><td>mod_proxy.c</td></tr></table>
<h3>Summary</h3>
<div class="warning"><h3>Warning</h3>
<p>Do not enable proxying with <code class="directive"><a href="#proxyrequests">ProxyRequests</a></code> until you have <a href="#access">secured your server</a>. Open proxy servers are dangerous both to your
network and to the Internet at large.</p>
</div>
<p><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> and related modules implement a
proxy/gateway for Apache HTTP Server, supporting a number of popular
protocols as well as several different load balancing algorithms.
Third-party modules can add support for additional protocols and
load balancing algorithms.</p>
<p>A set of modules must be loaded into the server to provide the
necessary features. These modules can be included statically at
build time or dynamically via the
<code class="directive"><a href="../mod/mod_so.html#loadmodule">LoadModule</a></code> directive).
The set must include:</p>
<ul>
<li><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>, which provides basic proxy
capabilities</li>
<li><code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code> and one or more
balancer modules if load balancing is required. (See
<code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code> for more information.)</li>
<li>one or more proxy scheme, or protocol, modules:
<table class="bordered">
<tr><th>Protocol</th><th>Module</th></tr>
<tr><td>AJP13 (Apache JServe Protocol version
1.3)</td><td><code class="module"><a href="../mod/mod_proxy_ajp.html">mod_proxy_ajp</a></code></td></tr>
<tr><td>CONNECT (for
SSL)</td><td><code class="module"><a href="../mod/mod_proxy_connect.html">mod_proxy_connect</a></code></td></tr>
<tr><td>FastCGI</td><td><code class="module"><a href="../mod/mod_proxy_fcgi.html">mod_proxy_fcgi</a></code></td></tr>
<tr><td>ftp</td><td><code class="module"><a href="../mod/mod_proxy_ftp.html">mod_proxy_ftp</a></code></td></tr>
<tr><td>HTTP/0.9, HTTP/1.0, and
HTTP/1.1</td><td><code class="module"><a href="../mod/mod_proxy_http.html">mod_proxy_http</a></code></td></tr>
<tr><td>SCGI</td><td><code class="module"><a href="../mod/mod_proxy_scgi.html">mod_proxy_scgi</a></code></td></tr>
<tr><td>WS and WSS (Web-sockets)</td><td><code class="module"><a href="../mod/mod_proxy_wstunnel.html">mod_proxy_wstunnel</a></code></td></tr>
</table>
</li>
</ul>
<p>In addition, extended features are provided by other modules.
Caching is provided by <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code> and related
modules. The ability to contact remote servers using the SSL/TLS
protocol is provided by the <code>SSLProxy*</code> directives of
<code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code>. These additional modules will need
to be loaded and configured to take advantage of these features.</p>
</div>
<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3>Topics</h3>
<ul id="topics">
<li><img alt="" src="../images/down.gif" /> <a href="#forwardreverse">Forward Proxies and Reverse
Proxies/Gateways</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#examples">Basic Examples</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#handler">Access via Handler</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#workers">Workers</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#access">Controlling Access to Your Proxy</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#startup">Slow Startup</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#intranet">Intranet Proxy</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#envsettings">Protocol Adjustments</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#request-bodies">Request Bodies</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#x-headers">Reverse Proxy Request Headers</a></li>
</ul><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="../images/down.gif" /> <a href="#balancergrowth">BalancerGrowth</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#balancerinherit">BalancerInherit</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#balancermember">BalancerMember</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#balancerpersist">BalancerPersist</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#noproxy">NoProxy</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxy"><Proxy></a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxyaddheaders">ProxyAddHeaders</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxybadheader">ProxyBadHeader</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxyblock">ProxyBlock</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxydomain">ProxyDomain</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxyerroroverride">ProxyErrorOverride</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxyiobuffersize">ProxyIOBufferSize</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxymatch"><ProxyMatch></a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxymaxforwards">ProxyMaxForwards</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxypass">ProxyPass</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxypassinherit">ProxyPassInherit</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxypassinterpolateenv">ProxyPassInterpolateEnv</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxypassmatch">ProxyPassMatch</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxypassreverse">ProxyPassReverse</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxypassreversecookiedomain">ProxyPassReverseCookieDomain</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxypassreversecookiepath">ProxyPassReverseCookiePath</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxypreservehost">ProxyPreserveHost</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxyreceivebuffersize">ProxyReceiveBufferSize</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxyremote">ProxyRemote</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxyremotematch">ProxyRemoteMatch</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxyrequests">ProxyRequests</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxyset">ProxySet</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxysourceaddress">ProxySourceAddress</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxystatus">ProxyStatus</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxytimeout">ProxyTimeout</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxyvia">ProxyVia</a></li>
</ul>
<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_proxy">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_proxy">Report a bug</a></li></ul><h3>See also</h3>
<ul class="seealso">
<li><code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code></li>
<li><code class="module"><a href="../mod/mod_proxy_ajp.html">mod_proxy_ajp</a></code></li>
<li><code class="module"><a href="../mod/mod_proxy_connect.html">mod_proxy_connect</a></code></li>
<li><code class="module"><a href="../mod/mod_proxy_fcgi.html">mod_proxy_fcgi</a></code></li>
<li><code class="module"><a href="../mod/mod_proxy_ftp.html">mod_proxy_ftp</a></code></li>
<li><code class="module"><a href="../mod/mod_proxy_http.html">mod_proxy_http</a></code></li>
<li><code class="module"><a href="../mod/mod_proxy_scgi.html">mod_proxy_scgi</a></code></li>
<li><code class="module"><a href="../mod/mod_proxy_wstunnel.html">mod_proxy_wstunnel</a></code></li>
<li><code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></li>
<li><code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code></li>
<li><a href="#comments_section">Comments</a></li></ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="forwardreverse" id="forwardreverse">Forward Proxies and Reverse
Proxies/Gateways</a></h2>
<p>Apache HTTP Server can be configured in both a <dfn>forward</dfn> and
<dfn>reverse</dfn> proxy (also known as <dfn>gateway</dfn>) mode.</p>
<p>An ordinary <dfn>forward proxy</dfn> is an intermediate
server that sits between the client and the <em>origin
server</em>. In order to get content from the origin server,
the client sends a request to the proxy naming the origin server
as the target. The proxy then requests the content from the
origin server and returns it to the client. The client must be
specially configured to use the forward proxy to access other
sites.</p>
<p>A typical usage of a forward proxy is to provide Internet
access to internal clients that are otherwise restricted by a
firewall. The forward proxy can also use caching (as provided
by <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>) to reduce network usage.</p>
<p>The forward proxy is activated using the <code class="directive"><a href="#proxyrequests">ProxyRequests</a></code> directive. Because
forward proxies allow clients to access arbitrary sites through
your server and to hide their true origin, it is essential that
you <a href="#access">secure your server</a> so that only
authorized clients can access the proxy before activating a
forward proxy.</p>
<p>A <dfn>reverse proxy</dfn> (or <dfn>gateway</dfn>), by
contrast, appears to the client just like an ordinary web
server. No special configuration on the client is necessary.
The client makes ordinary requests for content in the namespace
of the reverse proxy. The reverse proxy then decides where to
send those requests and returns the content as if it were itself
the origin.</p>
<p>A typical usage of a reverse proxy is to provide Internet
users access to a server that is behind a firewall. Reverse
proxies can also be used to balance load among several back-end
servers or to provide caching for a slower back-end server.
In addition, reverse proxies can be used simply to bring
several servers into the same URL space.</p>
<p>A reverse proxy is activated using the <code class="directive"><a href="#proxypass">ProxyPass</a></code> directive or the
<code>[P]</code> flag to the <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> directive. It is
<strong>not</strong> necessary to turn <code class="directive"><a href="#proxyrequests">ProxyRequests</a></code> on in order to
configure a reverse proxy.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="examples" id="examples">Basic Examples</a></h2>
<p>The examples below are only a very basic idea to help you
get started. Please read the documentation on the individual
directives.</p>
<p>In addition, if you wish to have caching enabled, consult
the documentation from <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>.</p>
<div class="example"><h3>Reverse Proxy</h3><pre class="prettyprint lang-config">ProxyPass "/foo" "http://foo.example.com/bar"
ProxyPassReverse "/foo" "http://foo.example.com/bar"</pre>
</div>
<div class="example"><h3>Forward Proxy</h3><pre class="prettyprint lang-config">ProxyRequests On
ProxyVia On
<Proxy "*">
Require host internal.example.com
</Proxy></pre>
</div>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="handler" id="handler">Access via Handler</a></h2>
<p>You can also force a request to be handled as a reverse-proxy
request, by creating a suitable Handler pass-through. The example
configuration below will pass all requests for PHP scripts to the
specified FastCGI server using reverse proxy:
</p>
<div class="example"><h3>Reverse Proxy PHP scripts</h3><pre class="prettyprint lang-config"><FilesMatch "\.php$">
# Unix sockets require 2.4.7 or later
SetHandler "proxy:unix:/path/to/app.sock|fcgi://localhost/"
</FilesMatch></pre>
</div>
<p>This feature is available in Apache HTTP Server 2.4.10 and later.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="workers" id="workers">Workers</a></h2>
<p>The proxy manages the configuration of origin servers and their
communication parameters in objects called <dfn>workers</dfn>.
There are two built-in workers: the default forward proxy worker and the
default reverse proxy worker. Additional workers can be configured
explicitly.</p>
<p>The two default workers have a fixed configuration
and will be used if no other worker matches the request.
They do not use HTTP Keep-Alive or connection reuse.
The TCP connections to the origin server will instead be
opened and closed for each request.</p>
<p>Explicitly configured workers are identified by their URL.
They are usually created and configured using
<code class="directive"><a href="#proxypass">ProxyPass</a></code> or
<code class="directive"><a href="#proxypassmatch">ProxyPassMatch</a></code> when used
for a reverse proxy:</p>
<pre class="prettyprint lang-config">ProxyPass "/example" "http://backend.example.com" connectiontimeout=5 timeout=30</pre>
<p>This will create a worker associated with the origin server URL
<code>http://backend.example.com</code> that will use the given timeout
values. When used in a forward proxy, workers are usually defined
via the <code class="directive"><a href="#proxyset">ProxySet</a></code> directive:</p>
<pre class="prettyprint lang-config">ProxySet "http://backend.example.com" connectiontimeout=5 timeout=30</pre>
<p>or alternatively using <code class="directive"><a href="#proxy">Proxy</a></code>
and <code class="directive"><a href="#proxyset">ProxySet</a></code>:</p>
<pre class="prettyprint lang-config"><Proxy "http://backend.example.com">
ProxySet connectiontimeout=5 timeout=30
</Proxy></pre>
<p>Using explicitly configured workers in the forward mode is
not very common, because forward proxies usually communicate with many
different origin servers. Creating explicit workers for some of the
origin servers can still be useful if they are used very often.
Explicitly configured workers have no concept of forward or reverse
proxying by themselves. They encapsulate a common concept of
communication with origin servers. A worker created by
<code class="directive"><a href="#proxypass">ProxyPass</a></code> for use in a
reverse proxy will also be used for forward proxy requests whenever
the URL to the origin server matches the worker URL, and vice versa.</p>
<p>The URL identifying a direct worker is the URL of its
origin server including any path components given:</p>
<pre class="prettyprint lang-config">ProxyPass "/examples" "http://backend.example.com/examples"
ProxyPass "/docs" "http://backend.example.com/docs"</pre>
<p>This example defines two different workers, each using a separate
connection pool and configuration.</p>
<div class="warning"><h3>Worker Sharing</h3>
<p>Worker sharing happens if the worker URLs overlap, which occurs when
the URL of some worker is a leading substring of the URL of another
worker defined later in the configuration file. In the following example</p>
<pre class="prettyprint lang-config">ProxyPass "/apps" "http://backend.example.com/" timeout=60
ProxyPass "/examples" "http://backend.example.com/examples" timeout=10</pre>
<p>the second worker isn't actually created. Instead the first
worker is used. The benefit is, that there is only one connection pool,
so connections are more often reused. Note that all configuration attributes
given explicitly for the later worker will be ignored. This will be logged
as a warning. In the above example, the resulting timeout value
for the URL <code>/examples</code> will be <code>60</code> instead
of <code>10</code>!</p>
<p>If you want to avoid worker sharing, sort your worker definitions
by URL length, starting with the longest worker URLs. If you want to maximize
worker sharing, use the reverse sort order. See also the related warning about
ordering <code class="directive"><a href="#proxypass">ProxyPass</a></code> directives.</p>
</div>
<p>Explicitly configured workers come in two flavors:
<dfn>direct workers</dfn> and <dfn>(load) balancer workers</dfn>.
They support many important configuration attributes which are
described below in the <code class="directive"><a href="#proxypass">ProxyPass</a></code>
directive. The same attributes can also be set using
<code class="directive"><a href="#proxyset">ProxySet</a></code>.</p>
<p>The set of options available for a direct worker
depends on the protocol which is specified in the origin server URL.
Available protocols include <code>ajp</code>, <code>fcgi</code>,
<code>ftp</code>, <code>http</code> and <code>scgi</code>.</p>
<p>Balancer workers are virtual workers that use direct workers known
as their members to actually handle the requests. Each balancer can
have multiple members. When it handles a request, it chooses a member
based on the configured load balancing algorithm.</p>
<p>A balancer worker is created if its worker URL uses
<code>balancer</code> as the protocol scheme.
The balancer URL uniquely identifies the balancer worker.
Members are added to a balancer using
<code class="directive"><a href="#balancermember">BalancerMember</a></code>.</p>
<div class="note"><h3>DNS resolution for origin domains</h3>
<p>DNS resolution happens when the socket to
the origin domain is created for the first time.
When connection reuse is enabled, each backend domain is resolved
only once per child process, and cached for all further connections
until the child is recycled. This information should to be considered
while planning DNS maintenance tasks involving backend domains.
Please also check <code class="directive"><a href="#proxypass">ProxyPass</a></code>
parameters for more details about connection reuse.
</p>
</div>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="access" id="access">Controlling Access to Your Proxy</a></h2>
<p>You can control who can access your proxy via the <code class="directive"><a href="#proxy"><Proxy></a></code> control block as in
the following example:</p>
<pre class="prettyprint lang-config"><Proxy "*">
Require ip 192.168.0
</Proxy></pre>
<p>For more information on access control directives, see
<code class="module"><a href="../mod/mod_authz_host.html">mod_authz_host</a></code>.</p>
<p>Strictly limiting access is essential if you are using a
forward proxy (using the <code class="directive"><a href="#proxyrequests">ProxyRequests</a></code> directive).
Otherwise, your server can be used by any client to access
arbitrary hosts while hiding his or her true identity. This is
dangerous both for your network and for the Internet at large.
When using a reverse proxy (using the <code class="directive"><a href="#proxypass">ProxyPass</a></code> directive with
<code>ProxyRequests Off</code>), access control is less
critical because clients can only contact the hosts that you
have specifically configured.</p>
<p><strong>See Also</strong> the <a href="mod_proxy_http.html#env">Proxy-Chain-Auth</a> environment variable.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="startup" id="startup">Slow Startup</a></h2>
<p>If you're using the <code class="directive"><a href="#proxyblock">ProxyBlock</a></code> directive, hostnames' IP addresses are looked up
and cached during startup for later match test. This may take a few
seconds (or more) depending on the speed with which the hostname lookups
occur.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="intranet" id="intranet">Intranet Proxy</a></h2>
<p>An Apache httpd proxy server situated in an intranet needs to forward
external requests through the company's firewall (for this, configure
the <code class="directive"><a href="#proxyremote">ProxyRemote</a></code> directive
to forward the respective <var>scheme</var> to the firewall proxy).
However, when it has to
access resources within the intranet, it can bypass the firewall when
accessing hosts. The <code class="directive"><a href="#noproxy">NoProxy</a></code>
directive is useful for specifying which hosts belong to the intranet and
should be accessed directly.</p>
<p>Users within an intranet tend to omit the local domain name from their
WWW requests, thus requesting "http://somehost/" instead of
<code>http://somehost.example.com/</code>. Some commercial proxy servers
let them get away with this and simply serve the request, implying a
configured local domain. When the <code class="directive"><a href="#proxydomain">ProxyDomain</a></code> directive is used and the server is <a href="#proxyrequests">configured for proxy service</a>, Apache httpd can return
a redirect response and send the client to the correct, fully qualified,
server address. This is the preferred method since the user's bookmark
files will then contain fully qualified hosts.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="envsettings" id="envsettings">Protocol Adjustments</a></h2>
<p>For circumstances where <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> is sending
requests to an origin server that doesn't properly implement
keepalives or HTTP/1.1, there are two <a href="../env.html">environment variables</a> that can force the
request to use HTTP/1.0 with no keepalive. These are set via the
<code class="directive"><a href="../mod/mod_env.html#setenv">SetEnv</a></code> directive.</p>
<p>These are the <code>force-proxy-request-1.0</code> and
<code>proxy-nokeepalive</code> notes.</p>
<pre class="prettyprint lang-config"><Location "/buggyappserver/">
ProxyPass "http://buggyappserver:7001/foo/"
SetEnv force-proxy-request-1.0 1
SetEnv proxy-nokeepalive 1
</Location></pre>
<p> In 2.4.26 and later, the "no-proxy" environment variable can be set to disable
<code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> processing the current request.
This variable should be set with <code class="directive"><a href="../mod/mod_setenvif.html#setenvif">SetEnvIf</a></code>, as <code class="directive"><a href="../mod/mod_env.html#setenv">SetEnv</a></code>
is not evaluated early enough.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="request-bodies" id="request-bodies">Request Bodies</a></h2>
<p>Some request methods such as POST include a request body.
The HTTP protocol requires that requests which include a body
either use chunked transfer encoding or send a
<code>Content-Length</code> request header. When passing these
requests on to the origin server, <code class="module"><a href="../mod/mod_proxy_http.html">mod_proxy_http</a></code>
will always attempt to send the <code>Content-Length</code>. But
if the body is large and the original request used chunked
encoding, then chunked encoding may also be used in the upstream
request. You can control this selection using <a href="../env.html">environment variables</a>. Setting
<code>proxy-sendcl</code> ensures maximum compatibility with
upstream servers by always sending the
<code>Content-Length</code>, while setting
<code>proxy-sendchunked</code> minimizes resource usage by using
chunked encoding.</p>
<p>Under some circumstances, the server must spool request bodies
to disk to satisfy the requested handling of request bodies. For
example, this spooling will occur if the original body was sent with
chunked encoding (and is large), but the administrator has
asked for backend requests to be sent with Content-Length or as HTTP/1.0.
This spooling can also occur if the request body already has a
Content-Length header, but the server is configured to filter incoming
request bodies.</p>
<p><code class="directive"><a href="../mod/core.html#limitrequestbody">LimitRequestBody</a></code> only applies to
request bodies that the server will spool to disk</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="x-headers" id="x-headers">Reverse Proxy Request Headers</a></h2>
<p>When acting in a reverse-proxy mode (using the <code class="directive"><a href="#proxypass">ProxyPass</a></code> directive, for example),
<code class="module"><a href="../mod/mod_proxy_http.html">mod_proxy_http</a></code> adds several request headers in
order to pass information to the origin server. These headers
are:</p>
<dl>
<dt><code>X-Forwarded-For</code></dt>
<dd>The IP address of the client.</dd>
<dt><code>X-Forwarded-Host</code></dt>
<dd>The original host requested by the client in the <code>Host</code>
HTTP request header.</dd>
<dt><code>X-Forwarded-Server</code></dt>
<dd>The hostname of the proxy server.</dd>
</dl>
<p>Be careful when using these headers on the origin server, since
they will contain more than one (comma-separated) value if the
original request already contained one of these headers. For
example, you can use <code>%{X-Forwarded-For}i</code> in the log
format string of the origin server to log the original clients IP
address, but you may get more than one address if the request
passes through several proxies.</p>
<p>See also the <code class="directive"><a href="#proxypreservehost">ProxyPreserveHost</a></code> and <code class="directive"><a href="#proxyvia">ProxyVia</a></code> directives, which control
other request headers.</p>
<p>Note: If you need to specify custom request headers to be
added to the forwarded request, use the
<code class="directive"><a href="../mod/mod_headers.html#requestheader">RequestHeader</a></code>
directive.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="BalancerGrowth" id="BalancerGrowth">BalancerGrowth</a> <a name="balancergrowth" id="balancergrowth">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of additional Balancers that can be added Post-configuration</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>BalancerGrowth <var>#</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>BalancerGrowth 5</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>BalancerGrowth is only available in Apache HTTP Server 2.3.13
and later.</td></tr>
</table>
<p>This directive allows for growth potential in the number of
Balancers available for a virtualhost in addition to the
number pre-configured. It only takes effect if there is at
least one pre-configured Balancer.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="BalancerInherit" id="BalancerInherit">BalancerInherit</a> <a name="balancerinherit" id="balancerinherit">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Inherit ProxyPassed Balancers/Workers from the main server</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>BalancerInherit On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>BalancerInherit On</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>BalancerInherit is only available in Apache HTTP Server 2.4.5 and later.</td></tr>
</table>
<p>This directive will cause the current server/vhost to "inherit" ProxyPass
Balancers and Workers defined in the main server. This can cause issues and
inconsistent behavior if using the Balancer Manager and so should be disabled
if using that feature.</p>
<p>The setting in the global server defines the default for all vhosts.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="BalancerMember" id="BalancerMember">BalancerMember</a> <a name="balancermember" id="balancermember">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Add a member to a load balancing group</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>BalancerMember [<var>balancerurl</var>] <var>url</var> [<var>key=value [key=value ...]]</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>BalancerMember is only available in Apache HTTP Server 2.2
and later.</td></tr>
</table>
<p>This directive adds a member to a load balancing group. It can be used
within a <code><Proxy <var>balancer://</var>...></code> container
directive and can take any of the key value pair parameters available to
<code class="directive"><a href="#proxypass">ProxyPass</a></code> directives.</p>
<p>One additional parameter is available only to <code class="directive">BalancerMember</code> directives:
<var>loadfactor</var>. This is the member load factor - a decimal number between 1.0
(default) and 100.0, which defines the weighted load to be applied to the
member in question.</p>
<p>The <var>balancerurl</var> is only needed when not within a
<code><Proxy <var>balancer://</var>...></code>
container directive. It corresponds to the url of a balancer defined in
<code class="directive"><a href="#proxypass">ProxyPass</a></code> directive.</p>
<p>The path component of the balancer URL in any
<code><Proxy <var>balancer://</var>...></code> container directive
is ignored.</p>
<p>Trailing slashes should typically be removed from the URL of a
<code class="directive">BalancerMember</code>.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="BalancerPersist" id="BalancerPersist">BalancerPersist</a> <a name="balancerpersist" id="balancerpersist">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Attempt to persist changes made by the Balancer Manager across restarts.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>BalancerPersist On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>BalancerPersist Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>BalancerPersist is only available in Apache HTTP Server 2.4.4 and later.</td></tr>
</table>
<p>This directive will cause the shared memory storage associated
with the balancers and balancer members to be persisted across
restarts. This allows these local changes to not be lost during the
normal restart/graceful state transitions.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="NoProxy" id="NoProxy">NoProxy</a> <a name="noproxy" id="noproxy">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Hosts, domains, or networks that will be connected to
directly</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>NoProxy <var>host</var> [<var>host</var>] ...</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
</table>
<p>This directive is only useful for Apache httpd proxy servers within
intranets. The <code class="directive">NoProxy</code> directive specifies a
list of subnets, IP addresses, hosts and/or domains, separated by
spaces. A request to a host which matches one or more of these is
always served directly, without forwarding to the configured
<code class="directive"><a href="#proxyremote">ProxyRemote</a></code> proxy server(s).</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">ProxyRemote "*" "http://firewall.example.com:81"
NoProxy ".example.com" "192.168.112.0/21"</pre>
</div>
<p>The <var>host</var> arguments to the <code class="directive">NoProxy</code>
directive are one of the following type list:</p>
<dl>
<dt><var><a name="domain" id="domain">Domain</a></var></dt>
<dd>
<p>A <dfn>Domain</dfn> is a partially qualified DNS domain name, preceded
by a period. It represents a list of hosts which logically belong to the
same DNS domain or zone (<em>i.e.</em>, the suffixes of the hostnames are
all ending in <var>Domain</var>).</p>
<div class="example"><h3>Examples</h3><p><code>
.com .example.org.
</code></p></div>
<p>To distinguish <var>Domain</var>s from <var><a href="#hostname">Hostname</a></var>s (both syntactically and semantically; a DNS domain can
have a DNS A record, too!), <var>Domain</var>s are always written with a
leading period.</p>
<div class="note"><h3>Note</h3>
<p>Domain name comparisons are done without regard to the case, and
<var>Domain</var>s are always assumed to be anchored in the root of the
DNS tree; therefore, the two domains <code>.ExAmple.com</code> and
<code>.example.com.</code> (note the trailing period) are considered
equal. Since a domain comparison does not involve a DNS lookup, it is much
more efficient than subnet comparison.</p>
</div></dd>
<dt><var><a name="subnet" id="subnet">SubNet</a></var></dt>
<dd>
<p>A <dfn>SubNet</dfn> is a partially qualified internet address in
numeric (dotted quad) form, optionally followed by a slash and the netmask,
specified as the number of significant bits in the <var>SubNet</var>. It is
used to represent a subnet of hosts which can be reached over a common
network interface. In the absence of the explicit net mask it is assumed
that omitted (or zero valued) trailing digits specify the mask. (In this
case, the netmask can only be multiples of 8 bits wide.) Examples:</p>
<dl>
<dt><code>192.168</code> or <code>192.168.0.0</code></dt>
<dd>the subnet 192.168.0.0 with an implied netmask of 16 valid bits
(sometimes used in the netmask form <code>255.255.0.0</code>)</dd>
<dt><code>192.168.112.0/21</code></dt>
<dd>the subnet <code>192.168.112.0/21</code> with a netmask of 21
valid bits (also used in the form <code>255.255.248.0</code>)</dd>
</dl>
<p>As a degenerate case, a <em>SubNet</em> with 32 valid bits is the
equivalent to an <var><a href="#ipaddr">IPAddr</a></var>, while a <var>SubNet</var> with zero
valid bits (<em>e.g.</em>, 0.0.0.0/0) is the same as the constant
<var>_Default_</var>, matching any IP address.</p></dd>
<dt><var><a name="ipaddr" id="ipaddr">IPAddr</a></var></dt>
<dd>
<p>A <dfn>IPAddr</dfn> represents a fully qualified internet address in
numeric (dotted quad) form. Usually, this address represents a host, but
there need not necessarily be a DNS domain name connected with the
address.</p>
<div class="example"><h3>Example</h3><p><code>
192.168.123.7
</code></p></div>
<div class="note"><h3>Note</h3>
<p>An <var>IPAddr</var> does not need to be resolved by the DNS system, so
it can result in more effective apache performance.</p>
</div></dd>
<dt><var><a name="hostname" id="hostname">Hostname</a></var></dt>
<dd>
<p>A <dfn>Hostname</dfn> is a fully qualified DNS domain name which can
be resolved to one or more <var><a href="#ipaddr">IPAddrs</a></var> via the
DNS domain name service. It represents a logical host (in contrast to
<var><a href="#domain">Domain</a></var>s, see above) and must be resolvable
to at least one <var><a href="#ipaddr">IPAddr</a></var> (or often to a list
of hosts with different <var><a href="#ipaddr">IPAddr</a></var>s).</p>
<div class="example"><h3>Examples</h3><p><code>
prep.ai.example.edu<br />
www.example.org
</code></p></div>
<div class="note"><h3>Note</h3>
<p>In many situations, it is more effective to specify an <var><a href="#ipaddr">IPAddr</a></var> in place of a <var>Hostname</var> since a
DNS lookup can be avoided. Name resolution in Apache httpd can take a remarkable
deal of time when the connection to the name server uses a slow PPP
link.</p>
<p><var>Hostname</var> comparisons are done without regard to the case,
and <var>Hostname</var>s are always assumed to be anchored in the root
of the DNS tree; therefore, the two hosts <code>WWW.ExAmple.com</code>
and <code>www.example.com.</code> (note the trailing period) are
considered equal.</p>
</div></dd>
</dl>
<h3>See also</h3>
<ul>
<li><a href="../dns-caveats.html">DNS Issues</a></li>
</ul>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="Proxy" id="Proxy"><Proxy></a> <a name="proxy" id="proxy">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Container for directives applied to proxied resources</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><Proxy <var>wildcard-url</var>> ...</Proxy></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
</table>
<p>Directives placed in <code class="directive"><Proxy></code>
sections apply only to matching proxied content. Shell-style wildcards are
allowed.</p>
<p>For example, the following will allow only hosts in
<code>yournetwork.example.com</code> to access content via your proxy
server:</p>
<pre class="prettyprint lang-config"><Proxy "*">
Require host yournetwork.example.com
</Proxy></pre>
<p>The following example will process all files in the <code>foo</code>
directory of <code>example.com</code> through the <code>INCLUDES</code>
filter when they are sent through the proxy server:</p>
<pre class="prettyprint lang-config"><Proxy "http://example.com/foo/*">
SetOutputFilter INCLUDES
</Proxy></pre>
<div class="note"><h3>Differences from the Location configuration section</h3>
<p>A backend URL matches the configuration section if it begins with the
the <var>wildcard-url</var> string, even if the last path segment in the
directive only matches a prefix of the backend URL. For example,
<Proxy "http://example.com/foo"> matches all of
http://example.com/foo, http://example.com/foo/bar, and
http://example.com/foobar. The matching of the final URL differs
from the behavior of the <code class="directive"><a href="../mod/core.html#location"><Location></a></code> section, which for purposes of this note
treats the final path component as if it ended in a slash.</p>
<p>For more control over the matching, see <code class="directive"><ProxyMatch></code>.</p>
</div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#proxymatch"><ProxyMatch></a></code></li>
</ul>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ProxyAddHeaders" id="ProxyAddHeaders">ProxyAddHeaders</a> <a name="proxyaddheaders" id="proxyaddheaders">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Add proxy information in X-Forwarded-* headers</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyAddHeaders Off|On</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ProxyAddHeaders On</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.3.10 and later</td></tr>
</table>
<p>This directive determines whether or not proxy related information should be passed to the
backend server through X-Forwarded-For, X-Forwarded-Host and X-Forwarded-Server HTTP headers.</p>
<div class="note"><h3>Effectiveness</h3>
<p>This option is of use only for HTTP proxying, as handled by <code class="module"><a href="../mod/mod_proxy_http.html">mod_proxy_http</a></code>.</p>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ProxyBadHeader" id="ProxyBadHeader">ProxyBadHeader</a> <a name="proxybadheader" id="proxybadheader">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determines how to handle bad header lines in a
response</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyBadHeader IsError|Ignore|StartBody</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ProxyBadHeader IsError</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
</table>
<p>The <code class="directive">ProxyBadHeader</code> directive determines the
behavior of <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> if it receives syntactically invalid
response header lines (<em>i.e.</em> containing no colon) from the origin
server. The following arguments are possible:</p>
<dl>
<dt><code>IsError</code></dt>
<dd>Abort the request and end up with a 502 (Bad Gateway) response. This is
the default behavior.</dd>
<dt><code>Ignore</code></dt>
<dd>Treat bad header lines as if they weren't sent.</dd>
<dt><code>StartBody</code></dt>
<dd>When receiving the first bad header line, finish reading the headers and
treat the remainder as body. This helps to work around buggy backend servers
which forget to insert an empty line between the headers and the body.</dd>
</dl>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ProxyBlock" id="ProxyBlock">ProxyBlock</a> <a name="proxyblock" id="proxyblock">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Words, hosts, or domains that are banned from being
proxied</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyBlock *|<var>word</var>|<var>host</var>|<var>domain</var>
[<var>word</var>|<var>host</var>|<var>domain</var>] ...</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
</table>
<p>The <code class="directive">ProxyBlock</code> directive specifies a list of
words, hosts and/or domains, separated by spaces. HTTP, HTTPS, and
FTP document requests to sites whose names contain matched words,
hosts or domains are <em>blocked</em> by the proxy server. The proxy
module will also attempt to determine IP addresses of list items which
may be hostnames during startup, and cache them for match test as
well. That may slow down the startup time of the server.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">ProxyBlock "news.example.com" "auctions.example.com" "friends.example.com"</pre>
</div>
<p>Note that <code>example</code> would also be sufficient to match any
of these sites.</p>
<p>Hosts would also be matched if referenced by IP address.</p>
<p>Note also that</p>
<pre class="prettyprint lang-config">ProxyBlock "*"</pre>
<p>blocks connections to all sites.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ProxyDomain" id="ProxyDomain">ProxyDomain</a> <a name="proxydomain" id="proxydomain">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Default domain name for proxied requests</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyDomain <var>Domain</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
</table>
<p>This directive is only useful for Apache httpd proxy servers within
intranets. The <code class="directive">ProxyDomain</code> directive specifies
the default domain which the apache proxy server will belong to. If a
request to a host without a domain name is encountered, a redirection
response to the same host with the configured <var>Domain</var> appended
will be generated.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">ProxyRemote "*" "http://firewall.example.com:81"
NoProxy ".example.com" "192.168.112.0/21"
ProxyDomain ".example.com"</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ProxyErrorOverride" id="ProxyErrorOverride">ProxyErrorOverride</a> <a name="proxyerroroverride" id="proxyerroroverride">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Override error pages for proxied content</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyErrorOverride On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ProxyErrorOverride Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
</table>
<p>This directive is useful for reverse-proxy setups where you want to
have a common look and feel on the error pages seen by the end user.
This also allows for included files (via
<code class="module"><a href="../mod/mod_include.html">mod_include</a></code>'s SSI) to get
the error code and act accordingly. (Default behavior would display
the error page of the proxied server. Turning this on shows the SSI
Error message.)</p>
<p>This directive does not affect the processing of informational (1xx),
normal success (2xx), or redirect (3xx) responses.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ProxyIOBufferSize" id="ProxyIOBufferSize">ProxyIOBufferSize</a> <a name="proxyiobuffersize" id="proxyiobuffersize">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determine size of internal data throughput buffer</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyIOBufferSize <var>bytes</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ProxyIOBufferSize 8192</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
</table>
<p>The <code class="directive">ProxyIOBufferSize</code> directive adjusts the size
of the internal buffer which is used as a scratchpad for the data between
input and output. The size must be at least <code>512</code>.</p>
<p>In almost every case, there's no reason to change that value.</p>
<p>If used with AJP, this directive sets the maximum AJP packet size in
bytes. Values larger than 65536 are set to 65536. If you change it from
the default, you must also change the <code>packetSize</code> attribute of
your AJP connector on the Tomcat side! The attribute
<code>packetSize</code> is only available in Tomcat <code>5.5.20+</code>
and <code>6.0.2+</code></p>
<p>Normally it is not necessary to change the maximum packet size.
Problems with the default value have been reported when sending
certificates or certificate chains.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ProxyMatch" id="ProxyMatch"><ProxyMatch></a> <a name="proxymatch" id="proxymatch">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Container for directives applied to regular-expression-matched
proxied resources</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><ProxyMatch <var>regex</var>> ...</ProxyMatch></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
</table>
<p>The <code class="directive"><ProxyMatch></code> directive is
identical to the <code class="directive"><a href="#proxy"><Proxy></a></code> directive, except that it matches URLs
using <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expressions</a>.</p>
<p>From 2.4.8 onwards, named groups and backreferences are captured and
written to the environment with the corresponding name prefixed with
"MATCH_" and in upper case. This allows elements of URLs to be referenced
from within <a href="../expr.html">expressions</a> and modules like
<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>. In order to prevent confusion, numbered
(unnamed) backreferences are ignored. Use named groups instead.</p>
<pre class="prettyprint lang-config"><ProxyMatch "^http://(?<sitename>[^/]+)">
Require ldap-group cn=%{env:MATCH_SITENAME},ou=combined,o=Example
</ProxyMatch></pre>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#proxy"><Proxy></a></code></li>
</ul>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ProxyMaxForwards" id="ProxyMaxForwards">ProxyMaxForwards</a> <a name="proxymaxforwards" id="proxymaxforwards">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximium number of proxies that a request can be forwarded
through</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyMaxForwards <var>number</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ProxyMaxForwards -1</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Default behaviour changed in 2.2.7</td></tr>
</table>
<p>The <code class="directive">ProxyMaxForwards</code> directive specifies the
maximum number of proxies through which a request may pass if there's no
<code>Max-Forwards</code> header supplied with the request. This may
be set to prevent infinite proxy loops or a DoS attack.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">ProxyMaxForwards 15</pre>
</div>
<p>Note that setting <code class="directive">ProxyMaxForwards</code> is a
violation of the HTTP/1.1 protocol (RFC2616), which forbids a Proxy
setting <code>Max-Forwards</code> if the Client didn't set it.
Earlier Apache httpd versions would always set it. A negative
<code class="directive">ProxyMaxForwards</code> value, including the
default -1, gives you protocol-compliant behavior but may
leave you open to loops.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ProxyPass" id="ProxyPass">ProxyPass</a> <a name="proxypass" id="proxypass">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maps remote servers into the local server URL-space</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyPass [<var>path</var>] !|<var>url</var> [<var>key=value</var>
<var>[key=value</var> ...]] [nocanon] [interpolate] [noquery]</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Unix Domain Socket (UDS) support added in 2.4.7</td></tr>
</table>
<p>This directive allows remote servers to be mapped into the
space of the local server. The local server does not act as a
proxy in the conventional sense but appears to be a mirror of the
remote server. The local server is often called a <dfn>reverse
proxy</dfn> or <dfn>gateway</dfn>. The <var>path</var> is the name of
a local virtual path; <var>url</var> is a partial URL for the
remote server and cannot include a query string.</p>
<div class="note">It is strongly suggested to review the concept of a
<a href="#workers">Worker</a> before proceeding any further
with this section.</div>
<div class="note">This directive is not supported within
<code class="directive"><a href="../mod/core.html#directory"><Directory></a></code> and
<code class="directive"><a href="../mod/core.html#files"><Files></a></code> containers.</div>