mod_proxy.xml revision d40245991835767528e0dcd234f176aef45bc038
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<modulesynopsis metafile="mod_proxy.xml.meta">
<name>mod_proxy</name>
<status>Extension</status>
<identifier>proxy_module</identifier>
<summary>
<note type="warning"><title>Warning</title>
<p>Do not enable proxying with <directive module="mod_proxy"
>ProxyRequests</directive> 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>
</note>
proxying capability for <code>AJP13</code> (Apache JServe Protocol
version 1.3), <code>FTP</code>, <code>CONNECT</code> (for SSL),
The module can be configured to connect to other proxy modules for these
and other protocols.</p>
<p>Apache's proxy features are divided into several modules in
addition to <module>mod_proxy</module>:
<module>mod_proxy_http</module>, <module>mod_proxy_ftp</module>,
<module>mod_proxy_ajp</module>, <module>mod_proxy_balancer</module>,
and <module>mod_proxy_connect</module>. Thus, if you want to use
one or more of the particular proxy functions, load
<module>mod_proxy</module> <em>and</em> the appropriate module(s)
into the server (either statically at compile-time or dynamically
via the <directive module="mod_so">LoadModule</directive>
directive).</p>
<p>In addition, extended features are provided by other modules.
Caching is provided by <module>mod_cache</module> and related
protocol is provided by the <code>SSLProxy*</code> directives of
<module>mod_ssl</module>. These additional modules will need
to be loaded and configured to take advantage of these features.</p>
</summary>
<seealso><module>mod_cache</module></seealso>
<seealso><module>mod_proxy_http</module></seealso>
<seealso><module>mod_proxy_ftp</module></seealso>
<seealso><module>mod_proxy_connect</module></seealso>
<seealso><module>mod_proxy_balancer</module></seealso>
<seealso><module>mod_ssl</module></seealso>
<section id="forwardreverse"><title>Forward and Reverse Proxies</title>
<p>Apache can be configured in both a <dfn>forward</dfn> and
<dfn>reverse</dfn> proxy 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 and 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 <module>mod_cache</module>) to reduce network usage.</p>
<p>The forward proxy is activated using the <directive
module="mod_proxy">ProxyRequests</directive> 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>, 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 name-space of the reverse
proxy. The reverse proxy then decides where to send those
requests, and returns the content as if it was 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 <directive
module="mod_proxy">ProxyPass</directive> directive or the
<code>[P]</code> flag to the <directive
module="mod_rewrite">RewriteRule</directive> directive. It is
<strong>not</strong> necessary to turn <directive
module="mod_proxy">ProxyRequests</directive> on in order to
configure a reverse proxy.</p>
</section> <!-- /forwardreverse -->
<section id="examples"><title>Basic Examples</title>
<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 <module>mod_cache</module>.</p>
<example><title>Forward Proxy</title>
ProxyRequests On<br />
ProxyVia On<br />
<br />
<Proxy *><br />
<indent>
Order deny,allow<br />
Deny from all<br />
Allow from internal.example.com<br />
</indent>
</Proxy>
</example>
<example><title>Reverse Proxy</title>
ProxyRequests Off<br />
<br />
<Proxy *><br />
<indent>
Order deny,allow<br />
Allow from all<br />
</indent>
</Proxy><br />
<br />
ProxyPass /foo http://foo.example.com/bar<br />
ProxyPassReverse /foo http://foo.example.com/bar
</example>
</section> <!-- /examples -->
<section id="access"><title>Controlling access to your proxy</title>
<p>You can control who can access your proxy via the <directive
module="mod_proxy" type="section">Proxy</directive> control block as in
the following example:</p>
<example>
<Proxy *><br />
<indent>
Order Deny,Allow<br />
Deny from all<br />
Allow from 192.168.0<br />
</indent>
</Proxy>
</example>
<p>For more information on access control directives, see
<module>mod_authz_host</module>.</p>
<p>Strictly limiting access is essential if you are using a
forward proxy (using the <directive
module="mod_proxy">ProxyRequests</directive> 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 <directive
module="mod_proxy">ProxyPass</directive> directive with
<code>ProxyRequests Off</code>), access control is less
critical because clients can only contact the hosts that you
have specifically configured.</p>
>Proxy-Chain-Auth</a> environment variable.</p>
</section> <!-- /access -->
<section id="startup"><title>Slow Startup</title>
<p>If you're using the <directive module="mod_proxy"
>ProxyBlock</directive> 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>
</section> <!-- /startup -->
<section id="intranet"><title>Intranet Proxy</title>
<p>An Apache proxy server situated in an intranet needs to forward
external requests through the company's firewall (for this, configure
the <directive module="mod_proxy">ProxyRemote</directive> 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 <directive module="mod_proxy">NoProxy</directive>
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
let them get away with this and simply serve the request, implying a
configured local domain. When the <directive module="mod_proxy"
>ProxyDomain</directive> directive is used and the server is <a
href="#proxyrequests">configured for proxy service</a>, Apache 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>
</section> <!-- /intranet -->
<section id="envsettings"><title>Protocol Adjustments</title>
<p>For circumstances where <module>mod_proxy</module> is sending
requests to an origin server that doesn't properly implement
href="/env.html">environment variables</a> that can force the
<directive module="mod_env">SetEnv</directive> directive.</p>
<p>These are the <code>force-proxy-request-1.0</code> and
<code>proxy-nokeepalive</code> notes.</p>
<example>
<Location /buggyappserver/><br />
<indent>
ProxyPass http://buggyappserver:7001/foo/<br />
SetEnv force-proxy-request-1.0 1<br />
SetEnv proxy-nokeepalive 1<br />
</indent>
</Location>
</example>
</section> <!-- /envsettings -->
<section id="request-bodies"><title>Request Bodys</title>
<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, <module>mod_proxy_http</module>
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>
</section> <!-- /request-bodies -->
<section id="x-headers"><title>Reverse Proxy Request Headers</title>
<p>When acting in a reverse-proxy mode (using the <directive
module="mod_proxy">ProxyPass</directive> directive, for example),
<module>mod_proxy_http</module> 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 <directive
module="mod_proxy">ProxyPreserveHost</directive> and <directive
module="mod_proxy">ProxyVia</directive> directives, which control
other request headers.</p>
</section> <!--/x-headers -->
<directivesynopsis type="section">
<name>Proxy</name>
<description>Container for directives applied to proxied resources</description>
<syntax><Proxy <var>wildcard-url</var>> ...</Proxy></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>Directives placed in <directive type="section">Proxy</directive>
sections apply only to matching proxied content. Shell-style wildcards are
allowed.</p>
<p>For example, the following will allow only hosts in
server:</p>
<example>
<Proxy *><br />
<indent>
Order Deny,Allow<br />
Deny from all<br />
Allow from yournetwork.example.com<br />
</indent>
</Proxy>
</example>
<p>The following example will process all files in the <code>foo</code>
filter when they are sent through the proxy server:</p>
<example>
<Proxy http://example.com/foo/*><br />
<indent>
SetOutputFilter INCLUDES<br />
</indent>
</Proxy>
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyBadHeader</name>
<description>Determines how to handle bad header lines in a
response</description>
<syntax>ProxyBadHeader IsError|Ignore|StartBody</syntax>
<default>ProxyBadHeader IsError</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<compatibility>Available in Apache 2.0.44 and later</compatibility>
<usage>
<p>The <directive>ProxyBadHeader</directive> directive determines the
behaviour of <module>mod_proxy</module> if it receives syntactically invalid
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 behaviour.</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>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>ProxyMatch</name>
<description>Container for directives applied to regular-expression-matched
proxied resources</description>
<syntax><ProxyMatch <var>regex</var>> ...</ProxyMatch></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive type="section">ProxyMatch</directive> directive is
identical to the <directive module="mod_proxy"
type="section">Proxy</directive> directive, except it matches URLs
using <glossary ref="regex">regular expressions</glossary>.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyPreserveHost</name>
<description>Use incoming Host HTTP request header for proxy
request</description>
<syntax>ProxyPreserveHost On|Off</syntax>
<default>ProxyPreserveHost Off</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<compatibility>Available in Apache 2.0.31 and later.</compatibility>
<usage>
<p>When enabled, this option will pass the Host: line from the incoming
request to the proxied host, instead of the hostname specified in the
<directive>ProxyPass</directive> line.</p>
<p>This option should normally be turned <code>Off</code>. It is mostly
useful in special configurations like proxied mass name-based virtual
hosting, where the original Host header needs to be evaluated by the
backend server.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyRequests</name>
<description>Enables forward (standard) proxy requests</description>
<syntax>ProxyRequests On|Off</syntax>
<default>ProxyRequests Off</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>This allows or prevents Apache from functioning as a forward proxy
server. (Setting ProxyRequests to <code>Off</code> does not disable use of
the <directive module="mod_proxy">ProxyPass</directive> directive.)</p>
<p>In a typical reverse proxy configuration, this option should be set to
<code>Off</code>.</p>
<p>In order to get the functionality of proxying HTTP or FTP sites, you
need also <module>mod_proxy_http</module> or <module>mod_proxy_ftp</module>
(or both) present in the server.</p>
<note type="warning"><title>Warning</title>
<p>Do not enable proxying with <directive
module="mod_proxy">ProxyRequests</directive> 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>
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyRemote</name>
<description>Remote proxy used to handle certain requests</description>
<syntax>ProxyRemote <var>match</var> <var>remote-server</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>This defines remote proxies to this proxy. <var>match</var> is either the
name of a URL-scheme that the remote server supports, or a partial URL
for which the remote server should be used, or <code>*</code> to indicate
the server should be contacted for all requests. <var>remote-server</var> is
a partial URL for the remote server. Syntax:</p>
<example>
<dfn>remote-server</dfn> =
<var>scheme</var>://<var>hostname</var>[:<var>port</var>]
</example>
<p><var>scheme</var> is effectively the protocol that should be used to
communicate with the remote server; only <code>http</code> is supported by
this module.</p>
<example><title>Example</title>
ProxyRemote * http://cleversite.com<br />
ProxyRemote ftp http://ftpproxy.mydomain.com:8080
</example>
<p>In the last example, the proxy will forward FTP requests, encapsulated
as yet another HTTP proxy request, to another proxy which can handle
them.</p>
<p>This option also supports reverse proxy configuration - a backend
webserver can be embedded within a virtualhost URL space even if that
server is hidden by another forward proxy.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyRemoteMatch</name>
<description>Remote proxy used to handle requests matched by regular
expressions</description>
<syntax>ProxyRemoteMatch <var>regex</var> <var>remote-server</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>ProxyRemoteMatch</directive> is identical to the
<directive module="mod_proxy">ProxyRemote</directive> directive, except the
first argument is a <glossary ref="regex">regular expression</glossary>
match against the requested URL.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>BalancerMember</name>
<description>Add a member to a load balancing group</description>
<syntax>BalancerMember <var>url</var> [<var
>key=value [key=value ...]]</var></syntax>
<contextlist><context>directory</context>
</contextlist>
<compatibility>BalancerMember is only available in Apache 2.2
and later.</compatibility>
<usage>
<p>This directive adds a member to a load balancing group. It must be used
within a <code><Proxy <var>balancer://</var>...></code> container
directive, and can take any of the parameters available to
<directive module="mod_proxy">ProxyPass</directive> directives.</p>
<p>One additional parameter is available only to <directive
module="mod_proxy">BalancerMember</directive> directives:
<var>loadfactor</var>. This is the member load factor - a number between 1
(default) and 100, which defines the weighted load to be applied to the
member in question.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxySet</name>
<description>Set various Proxy balancer or member parameters</description>
<syntax>ProxySet <var>url</var> <var>key=value [key=value ...]</var></syntax>
<contextlist><context>directory</context>
</contextlist>
<compatibility>ProxySet is only available in Apache 2.2
and later.</compatibility>
<usage>
<p>This directive is used as an alternate method of setting any of the
parameters available to Proxy balancers and workers normally done via the
<directive module="mod_proxy">ProxyPass</directive> directive. If used
within a <code><Proxy <var>balancer url|worker url</var>></code>
container directive, the <var>url</var> argument is not required. As a side
effect the respective balancer or worker gets created. This can be useful
when doing reverse proxying via a
<directive module="mod_rewrite">RewriteRule</directive> instead of a
<directive module="mod_proxy">ProxyPass</directive> directive.</p>
<example>
<Proxy balancer://hotcluster><br />
<indent>
BalancerMember http://www2.example.com:8009 loadfactor=1<br />
BalancerMember http://www3.example.com:8009 loadfactor=2<br />
ProxySet lbmethod=bytraffic<br />
</indent>
</Proxy>
</example>
<example>
<Proxy http://backend><br />
<indent>
ProxySet keepalive=On<br />
</indent>
</Proxy>
</example>
<example>
ProxySet balancer://foo lbmethod=bytraffic timeout=15
</example>
<example>
ProxySet ajp://backend:7001 timeout=15
</example>
<note type="warning"><title>Warning</title>
<p>Keep in mind that the same parameter key can have a different meaning
depending whether it is applied to a balancer or a worker as shown by the two
examples above regarding timeout.</p>
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyPass</name>
<description>Maps remote servers into the local server URL-space</description>
<syntax>ProxyPass [<var>path</var>] !|<var>url</var> [<var>key=value</var>
<var>[key=value</var> ...]]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context>
</contextlist>
<usage>
<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. <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>
<note type="warning">The <directive
module="mod_proxy">ProxyRequests</directive> directive should
usually be set <strong>off</strong> when using
<directive>ProxyPass</directive>.</note>
then</p>
<example>
</example>
<p>will cause a local request for
<note type="warning">
<p>If the first argument ends with a trailing <strong>/</strong>, the second
argument should also end with a trailing <strong>/</strong> and vice
versa. Otherwise the resulting requests to the backend may miss some
needed slashes and do not deliver the expected results.
</p>
</note>
<p>The <code>!</code> directive is useful in situations where you don't want
<example>
</example>
<note><title>Note</title>
<p>Order is important. you need to put the exclusions <em>before</em> the
general <directive>ProxyPass</directive> directive.</p>
</note>
<p>As of Apache 2.1, the ability to use pooled connections to a backend
server is available. Using the <code>key=value</code> parameters it is
possible to tune this connection pooling. The default for a <code>Hard
Maximum</code> for the number of connections is the number of threads per
process in the active MPM. In the Prefork MPM, this is always 1, while with
the Worker MPM it is controlled by the
<directive>ThreadsPerChild</directive>.</p>
<p>Setting <code>min</code> will determine how many connections will always
be open to the backend server. Upto the Soft Maximum or <code>smax</code>
number of connections will be created on demand. Any connections above
<code>smax</code> are subject to a time to live or <code>ttl</code>. Apache
will never create more than the Hard Maximum or <code>max</code> connections
to the backend server.</p>
<example>
ProxyPass /example http://backend.example.com smax=5 max=20 ttl=120 retry=300
</example>
<table>
<tr><th>Parameter</th>
<th>Default</th>
<th>Description</th></tr>
<tr><td>min</td>
<td>0</td>
<td>Minimum number of connections that will always
be open to the backend server.</td></tr>
<tr><td>max</td>
<td>Hard Maximum number of connections that will be
allowed to the backend server. The default for a Hard Maximum
for the number of connections is the number of threads per process in the
active MPM. In the Prefork MPM, this is always 1, while with the Worker MPM
it is controlled by the <directive>ThreadsPerChild</directive>.
Apache will never create more than the Hard Maximum connections
to the backend server.</td></tr>
<tr><td>smax</td>
<td>max</td>
<td>Upto the Soft Maximum
number of connections will be created on demand. Any connections above
<code>smax</code> are subject to a time to live or <code>ttl</code>.
</td></tr>
<tr><td>acquire</td>
<td>-</td>
<td>If set this will be the maximum time to wait for a free
connection in the connection pool. If there are no free connections
in the pool the Apache will return <code>SERVER_BUSY</code> status to
the client.
</td></tr>
<tr><td>flushpackets</td>
<td>off</td>
<td>Determines whether the proxy module will auto-flush the output
brigade after each "chunk" of data. 'off' means that it will flush
only when needed, 'on' means after each chunk is sent and
no input has been received for 'flushwait' milliseconds.
Currently this is in effect only for AJP.
</td></tr>
<tr><td>flushwait</td>
<td>10</td>
<td>The time to wait for additional input, in milliseconds, before
flushing the output brigade if 'flushpackets' is 'auto'.
</td></tr>
<tr><td>keepalive</td>
<td>Off</td>
<td>This parameter should be used when you have a firewall between your
Apache and the backend server, who tend to drop inactive connections.
This flag will tell the Operating System to send <code>KEEP_ALIVE</code>
messages on inactive connections (interval depends on global OS settings,
generally 120ms), and thus prevent the firewall to drop the connection.
To enable keepalive set this property value to <code>On</code>.
</td></tr>
<tr><td>lbset</td>
<td>0</td>
<td>Sets the load balancer cluster set that the worker is a member
of. The load balancer will try all members of a lower numbered
lbset before trying higher numbered ones.
</td></tr>
<tr><td>ping</td>
<td>0</td>
<td>Ping property tells webserver to send a <code>CPING</code>
request on ajp13 connection before forwarding a request.
The parameter is the delay in seconds to wait for the
<code>CPONG</code> reply.
This features has been added to avoid problem with hung and
been implemented on Tomcat 3.3.2+, 4.1.28+ and 5.0.13+.
This will increase the network traffic during the normal operation
which could be an issue, but it will lower the
traffic in case some of the cluster nodes are down or busy.
Currently this has an effect only for AJP.
</td></tr>
<tr><td>redirect</td>
<td>-</td>
<td>Redirection Route of the worker. This value is usually
set dynamically to enable safe removal of the node from
the cluster. If set all requests without session id will be
redirected to the BalancerMember that has route parametar
equal as this value.
</td></tr>
<tr><td>retry</td>
<td>60</td>
<td>Connection pool worker retry timeout in seconds.
If the connection pool worker to the backend server is in the error state,
Apache will not forward any requests to that server until the timeout
expires. This enables to shut down the backend server for maintenance,
and bring it back online later. A value of 0 means always retry workers
in an error state with no timeout.
</td></tr>
<tr><td>route</td>
<td>-</td>
<td>Route of the worker when used inside load balancer.
The route is a value appended to session id.
</td></tr>
<tr><td>status</td>
<td>-</td>
<td>Single letter value defining the initial status of
this worker: 'D' is disabled, 'S' is stopped, 'I' is ignore-errors,
'H' is hot-standby and 'E' is in an error state. Status
can be set (which is the default) by prepending with '+' or
cleared by prepending with '-'.
Thus, a setting of 'S-E' sets this worker to Stopped and
clears the in-error flag.
</td></tr>
<tr><td>timeout</td>
<td><directive>Timeout</directive></td>
<td>Connection timeout in seconds.
If not set the Apache will wait until the free connection
is available. This directive is used for limiting the number
of connections to the backend server together with <code>max</code>
parameter.
</td></tr>
<tr><td>ttl</td>
<td>-</td>
<td>Time To Live for the inactive connections above the
<code>smax</code> connections in seconds. Apache will close all
connections that has not been used inside that time period.
</td></tr>
</table>
<p>If the Proxy directive scheme starts with the
<code>balancer://</code> then a virtual worker that does not really
communicate with the backend server will be created. Instead it is responsible
for the management of several "real" workers. In that case the special set of
parameters can be add to this virtual worker. See <module>mod_proxy_balancer</module>
for more information about how the balancer works.
</p>
<table>
<tr><th>Parameter</th>
<th>Default</th>
<th>Description</th></tr>
<tr><td>lbmethod</td>
<td>byrequests</td>
<td>Balancer load-balance method. Select the load-balancing scheduler
method to use. Either <code>byrequests</code>, to perform weighted
request counting or <code>bytraffic</code>, to perform weighted
traffic byte count balancing. Default is <code>byrequests</code>.
</td></tr>
<tr><td>maxattempts</td>
<td>1</td>
<td>Maximum number of failover attempts before giving up.
</td></tr>
<tr><td>nofailover</td>
<td>Off</td>
<td>If set to <code>On</code> the session will break if the worker is in
error state or disabled. Set this value to On if backend servers do not
support session replication.
</td></tr>
<tr><td>stickysession</td>
<td>-</td>
<td>Balancer sticky session name. The value is usually set to something
like <code>JSESSIONID</code> or <code>PHPSESSIONID</code>,
and it depends on the backend application server that support sessions.
If the backend application server uses different name for cookies
and url encoded id (like servlet containers) use | to to separate them.
The first part is for the cookie the second for the path.
</td></tr>
<tr><td>timeout</td>
<td>0</td>
<td>Balancer timeout in seconds. If set this will be the maximum time
to wait for a free worker. Default is not to wait.
</td></tr>
</table>
<p>A sample balancer setup</p>
<example>
ProxyPass /special-area http://special.example.com/ smax=5 max=10<br />
ProxyPass / balancer://mycluster/ stickysession=JSESSIONID|jsessionid nofailover=On<br />
<Proxy balancer://mycluster><br />
<indent>
BalancerMember http://1.2.3.4:8009<br />
BalancerMember http://1.2.3.5:8009 smax=10<br />
# Less powerful server, don't send as many requests there<br />
BalancerMember http://1.2.3.6:8009 smax=1 loadfactor=20<br />
</indent>
</Proxy>
</example>
<p>Setting up a hot-standby, that will only be used if no other
members are available</p>
<example>
ProxyPass / balancer://hotcluster/ <br />
<Proxy balancer://hotcluster><br />
<indent>
BalancerMember http://1.2.3.4:8009 loadfactor=1<br />
BalancerMember http://1.2.3.5:8009 loadfactor=2<br />
# The below is the hot standby<br />
BalancerMember http://1.2.3.6:8009 status=+H<br />
ProxySet lbmethod=bytraffic
</indent>
</Proxy>
</example>
<p>When used inside a <directive type="section" module="core"
>Location</directive> section, the first argument is omitted and the local
directory is obtained from the <directive type="section" module="core"
>Location</directive>.</p>
<p>If you require a more flexible reverse-proxy configuration, see the
<directive module="mod_rewrite">RewriteRule</directive> directive with the
<code>[P]</code> flag.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyPassMatch</name>
<description>Maps remote servers into the local server URL-space using regular expressions</description>
<syntax>ProxyPassMatch [<var>regex</var>] !|<var>url</var> [<var>key=value</var>
<var>[key=value</var> ...]]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context>
</contextlist>
<usage>
<p>This directive is equivalent to <directive module="mod_proxy">ProxyPass</directive>,
but makes use of regular expressions, instead of simple prefix matching. The
supplied regular expression is matched against the <var>url</var>, and if it
matches, the server will substitute any parenthesized matches into the given
string and use it as a new <var>url</var>.</p>
then</p>
<example>
ProxyPassMatch ^(/.*\.gif)$ http://backend.example.com$1
</example>
<p>will cause a local request for
<p>The <code>!</code> directive is useful in situations where you don't want
to reverse-proxy a subdirectory.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyPassReverse</name>
<description>Adjusts the URL in HTTP response headers sent from a reverse
proxied server</description>
<syntax>ProxyPassReverse [<var>path</var>] <var>url</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context>
</contextlist>
<usage>
<p>This directive lets Apache adjust the URL in the <code>Location</code>,
<code>Content-Location</code> and <code>URI</code> headers on HTTP redirect
responses. This is essential when Apache is used as a reverse proxy to avoid
by-passing the reverse proxy because of HTTP redirects on the backend
servers which stay behind the reverse proxy.</p>
<p>Only the HTTP response headers specifically mentioned above
will be rewritten. Apache will not rewrite other response
headers, nor will it rewrite URL references inside HTML pages.
This means that if the proxied content contains absolute URL
references, they will by-pass the proxy. A third-party module
that will look inside the HTML and rewrite URL references is Nick
Kew's <a href="http://apache.webthing.com/mod_proxy_html/"
>mod_proxy_html</a>.</p>
<p><var>path</var> is the name of a local virtual path. <var>url</var> is a
partial URL for the remote server - the same way they are used for the
<directive module="mod_proxy">ProxyPass</directive> directive.</p>
<p>For example, suppose the local server has address
<example>
</example>
<p>will not only cause a local request for the
(the functionality <code>ProxyPass</code> provides here). It also takes care
redirect response to the client. Note that the hostname used for
constructing the URL is chosen in respect to the setting of the <directive
module="core">UseCanonicalName</directive> directive.</p>
<p>Note that this <directive>ProxyPassReverse</directive> directive can
also be used in conjunction with the proxy pass-through feature
(<code>RewriteRule ... [P]</code>) from <module>mod_rewrite</module>
because it doesn't depend on a corresponding <directive module="mod_proxy"
>ProxyPass</directive> directive.</p>
<p>When used inside a <directive type="section" module="core"
>Location</directive> section, the first argument is omitted and the local
directory is obtained from the <directive type="section" module="core"
>Location</directive>.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyPassReverseCookieDomain</name>
<description>Adjusts the Domain string in Set-Cookie headers from a reverse-
proxied server</description>
<syntax>ProxyPassReverseCookieDomain <var>internal-domain</var> <var>public-domain</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context>
</contextlist>
<usage>
<p>Usage is basically similar to
<directive module="mod_proxy">ProxyPassReverse</directive>, but instead of
rewriting headers that are a URL, this rewrites the <code>domain</code>
string in <code>Set-Cookie</code> headers.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyPassReverseCookiePath</name>
<description>Adjusts the Path string in Set-Cookie headers from a reverse-
proxied server</description>
<syntax>ProxyPassReverseCookiePath <var>internal-path</var> <var>public-path</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context>
</contextlist>
<usage>
<p>Usage is basically similar to
<directive module="mod_proxy">ProxyPassReverse</directive>, but instead of
rewriting headers that are a URL, this rewrites the <code>path</code>
string in <code>Set-Cookie</code> headers.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AllowCONNECT</name>
<description>Ports that are allowed to <code>CONNECT</code> through the
proxy</description>
<syntax>AllowCONNECT <var>port</var> [<var>port</var>] ...</syntax>
<default>AllowCONNECT 443 563</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>AllowCONNECT</directive> directive specifies a list
of port numbers to which the proxy <code>CONNECT</code> method may
connect. Today's browsers use this method when a <code>https</code>
connection is requested and proxy tunneling over HTTP is in effect.</p>
<p>By default, only the default https port (<code>443</code>) and the
default snews port (<code>563</code>) are enabled. Use the
<directive>AllowCONNECT</directive> directive to override this default and
allow connections to the listed ports only.</p>
<p>Note that you'll need to have <module>mod_proxy_connect</module> present
in the server in order to get the support for the <code>CONNECT</code> at
all.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyBlock</name>
<description>Words, hosts, or domains that are banned from being
proxied</description>
<syntax>ProxyBlock *|<var>word</var>|<var>host</var>|<var>domain</var>
[<var>word</var>|<var>host</var>|<var>domain</var>] ...</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>ProxyBlock</directive> directive specifies a list of
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>
<example><title>Example</title>
</example>
IP address.</p>
<p>Note that <code>wotsamattau</code> would also be sufficient to match
<p>Note also that</p>
<example>
ProxyBlock *
</example>
<p>blocks connections to all sites.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyReceiveBufferSize</name>
<description>Network buffer size for proxied HTTP and FTP
connections</description>
<syntax>ProxyReceiveBufferSize <var>bytes</var></syntax>
<default>ProxyReceiveBufferSize 0</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>ProxyReceiveBufferSize</directive> directive specifies an
for increased throughput. It has to be greater than <code>512</code> or set
to <code>0</code> to indicate that the system's default buffer size should
be used.</p>
<example><title>Example</title>
ProxyReceiveBufferSize 2048
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyIOBufferSize</name>
<description>Determine size of internal data throughput buffer</description>
<syntax>ProxyIOBufferSize <var>bytes</var></syntax>
<default>ProxyIOBufferSize 8192</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>ProxyIOBufferSize</directive> 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 less or equal <code>8192</code>.</p>
<p>In almost every case there's no reason to change that value.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyMaxForwards</name>
<description>Maximium number of proxies that a request can be forwarded
through</description>
<syntax>ProxyMaxForwards <var>number</var></syntax>
<default>ProxyMaxForwards -1</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<compatibility>Available in Apache 2.0 and later;
<usage>
<p>The <directive>ProxyMaxForwards</directive> 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>
<example><title>Example</title>
ProxyMaxForwards 15
</example>
<p>Note that setting <directive>ProxyMaxForwards</directive> is a
setting <code>Max-Forwards</code> if the Client didn't set it.
Earlier Apache versions would always set it. A negative
<directive>ProxyMaxForwards</directive> value, including the
default -1, gives you protocol-compliant behaviour, but may
leave you open to loops.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>NoProxy</name>
<description>Hosts, domains, or networks that will be connected to
directly</description>
<syntax>NoProxy <var>host</var> [<var>host</var>] ...</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>This directive is only useful for Apache proxy servers within
intranets. The <directive>NoProxy</directive> directive specifies a
spaces. A request to a host which matches one or more of these is
always served directly, without forwarding to the configured
<directive module="mod_proxy">ProxyRemote</directive> proxy server(s).</p>
<example><title>Example</title>
ProxyRemote * http://firewall.mycompany.com:81<br />
</example>
<p>The <var>host</var> arguments to the <directive>NoProxy</directive>
directive are one of the following type list:</p>
<dl>
<!-- ===================== Domain ======================= -->
<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
all ending in <var>Domain</var>).</p>
<example><title>Examples</title>
.com .apache.org.
</example>
<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>
<note><title>Note</title>
<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
equal. Since a domain comparison does not involve a DNS lookup, it is much
more efficient than subnet comparison.</p>
</note></dd>
<!-- ===================== SubNet ======================= -->
<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>
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="#ipadr">IPAddr</a></var>, while a <var>SubNet</var> with zero
<var>_Default_</var>, matching any IP address.</p></dd>
<!-- ===================== IPAddr ======================= -->
<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>
<example><title>Example</title>
192.168.123.7
</example>
<note><title>Note</title>
<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>
</note></dd>
<!-- ===================== Hostname ======================= -->
<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>
<example><title>Examples</title>
prep.ai.mit.edu<br />
</example>
<note><title>Note</title>
<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 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
considered equal.</p>
</note></dd>
</dl>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyTimeout</name>
<description>Network timeout for proxied requests</description>
<syntax>ProxyTimeout <var>seconds</var></syntax>
<default>ProxyTimeout 300</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<compatibility>Available in Apache 2.0.31 and later</compatibility>
<usage>
<p>This directive allows a user to specifiy a timeout on proxy requests.
would rather just return a timeout and fail gracefully instead of waiting
however long it takes the server to return.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyDomain</name>
<description>Default domain name for proxied requests</description>
<syntax>ProxyDomain <var>Domain</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>This directive is only useful for Apache proxy servers within
intranets. The <directive>ProxyDomain</directive> 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>
<example><title>Example</title>
ProxyRemote * http://firewall.mycompany.com:81<br />
ProxyDomain .mycompany.com
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyVia</name>
<description>Information provided in the <code>Via</code> HTTP response
header for proxied requests</description>
<syntax>ProxyVia On|Off|Full|Block</syntax>
<default>ProxyVia Off</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>This directive controls the use of the <code>Via:</code> HTTP
header by the proxy. Its intended use is to control the flow of
proxy requests along a chain of proxy servers. See <a
14.45 for an explanation of <code>Via:</code> header lines.</p>
<ul>
<li>If set to <code>Off</code>, which is the default, no special processing
is performed. If a request or reply contains a <code>Via:</code> header,
it is passed through unchanged.</li>
<li>If set to <code>On</code>, each request and reply will get a
<code>Via:</code> header line added for the current host.</li>
<li>If set to <code>Full</code>, each generated <code>Via:</code> header
line will additionally have the Apache server version shown as a
<code>Via:</code> comment field.</li>
<li>If set to <code>Block</code>, every proxy request will have all its
<code>Via:</code> header lines removed. No new <code>Via:</code> header will
be generated.</li>
</ul>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyErrorOverride</name>
<description>Override error pages for proxied content</description>
<syntax>ProxyErrorOverride On|Off</syntax>
<default>ProxyErrorOverride Off</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<compatibility>Available in version 2.0 and later</compatibility>
<usage>
<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
<module>mod_include</module>'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>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyPassInterpolateEnv</name>
<description>Enable Environment Variable interpolation in Reverse Proxy configurations</description>
<syntax>ProxyPassInterpolateEnv On|Off</syntax>
<default>ProxyPassInterpolateEnv Off</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
</contextlist>
<compatibility>Available in trunk only</compatibility>
<usage>
<p>This directive enables reverse proxies to be dynamically
configured using environment variables, which may be set by
another module such as <module>mod_rewrite</module>.
It affects the <directive>ProxyPass</directive>,
<directive>ProxyPassReverse</directive>,
<directive>ProxyPassReverseCookieDomain</directive>, and
<directive>ProxyPassReverseCookiePath</directive> directives,
and causes them to substitute the value of an environment
variable <code>varname</code> for the string <code>${varname}</code>
in configuration directives.</p>
<p>Keep this turned off (for server performance) unless you need it!</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ProxyStatus</name>
<description>Show Proxy LoadBalancer status in mod_status</description>
<syntax>ProxyStatus Off|On|Full</syntax>
<default>ProxyStatus Off</default>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>
<compatibility>Available in version 2.2 and later</compatibility>
<usage>
<p>This directive determines whether or not proxy
loadbalancer status data is displayed via the <module>mod_status</module>
server-status page.</p>
<note><title>Note</title>
<p><strong>Full</strong> is synonymous with <strong>On</strong></p>
</note>
</usage>
</directivesynopsis>
</modulesynopsis>