mod_proxy - Apache HTTP Server Version 2.5
Modules
Directives
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Glossary
Apache HTTP Server Version 2.5
Apache
HTTP Server
Documentation
Version 2.5
Modules
Apache Module mod_proxy
Available Languages:
en
fr
ja
Description:
Multi-protocol proxy/gateway server
Status:
Extension
Module Identifier:
proxy_module
Source File:
mod_proxy.c
Summary
Warning
Do not enable proxying with
ProxyRequests
until you have
secured your server
. Open proxy servers are dangerous both to your
network and to the Internet at large.
mod_proxy
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.
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
LoadModule
directive).
The set must include:
mod_proxy
, which provides basic proxy
capabilities
mod_proxy_balancer
and one or more
balancer modules if load balancing is required. (See
mod_proxy_balancer
for more information.)
one or more proxy scheme, or protocol, modules:
Protocol
Module
AJP13 (Apache JServe Protocol version
1.3)
mod_proxy_ajp
CONNECT (for
SSL)
mod_proxy_connect
FastCGI
mod_proxy_fcgi
ftp
mod_proxy_ftp
HTTP/0.9, HTTP/1.0, and
HTTP/1.1
mod_proxy_http
HTTP/2.0
mod_proxy_http2
SCGI
mod_proxy_scgi
UWSGI
mod_proxy_uwsgi
WS and WSS (Web-sockets)
mod_proxy_wstunnel
In addition, extended features are provided by other modules.
Caching is provided by
mod_cache
and related
modules. The ability to contact remote servers using the SSL/TLS
protocol is provided by the
SSLProxy*
directives of
mod_ssl
. These additional modules will need
to be loaded and configured to take advantage of these features.
Topics
Forward Proxies and Reverse
Proxies/Gateways
Basic Examples
Access via Handler
Workers
Controlling Access to Your Proxy
Slow Startup
Intranet Proxy
Protocol Adjustments
Request Bodies
Reverse Proxy Request Headers
Directives
BalancerGrowth
BalancerInherit
BalancerMember
BalancerPersist
NoProxy
Proxy100Continue
ProxyAddHeaders
ProxyBadHeader
ProxyBlock
ProxyDomain
ProxyErrorOverride
ProxyIOBufferSize
ProxyMaxForwards
ProxyPass
ProxyPassInherit
ProxyPassInterpolateEnv
ProxyPassMatch
ProxyPassReverse
ProxyPassReverseCookieDomain
ProxyPassReverseCookiePath
ProxyPreserveHost
ProxyReceiveBufferSize
ProxyRemote
ProxyRemoteMatch
ProxyRequests
ProxySet
ProxySourceAddress
ProxyStatus
ProxyTimeout
ProxyVia
Bugfix checklist
httpd changelog
Known issues
Report a bug
See also
mod_cache
mod_proxy_ajp
mod_proxy_balancer
mod_proxy_connect
mod_proxy_fcgi
mod_proxy_ftp
mod_proxy_hcheck
mod_proxy_http
mod_proxy_scgi
mod_proxy_wstunnel
mod_ssl
Comments
Forward Proxies and Reverse
Proxies/Gateways
Apache HTTP Server can be configured in both a
forward
and
reverse
proxy (also known as
gateway
) mode.
An ordinary
forward proxy
is an intermediate
server that sits between the client and the
origin
server
. 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.
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
mod_cache
) to reduce network usage.
The forward proxy is activated using the
ProxyRequests
directive. Because
forward proxies allow clients to access arbitrary sites through
your server and to hide their true origin, it is essential that
you
secure your server
so that only
authorized clients can access the proxy before activating a
forward proxy.
reverse proxy
(or
gateway
), 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.
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.
A reverse proxy is activated using the
ProxyPass
directive or the
[P]
flag to the
RewriteRule
directive. It is
not
necessary to turn
ProxyRequests
on in order to
configure a reverse proxy.
Basic Examples
The examples below are only a very basic idea to help you
get started. Please read the documentation on the individual
directives.
In addition, if you wish to have caching enabled, consult
the documentation from
mod_cache
Reverse Proxy
ProxyPass "/foo" "http://foo.example.com/bar"
ProxyPassReverse "/foo" "http://foo.example.com/bar"
Forward Proxy
ProxyRequests On
ProxyVia On
Require host internal.example.com
Websocket Upgrade (2.4.47 and later)
ProxyPass "/some/ws/capable/path/" "http://example.com/some/ws/capable/path/" upgrade=websocket
Access via Handler
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:
Reverse Proxy PHP scripts
SetHandler "proxy:unix:/path/to/app.sock|fcgi://localhost"
This feature is available in Apache HTTP Server 2.4.10 and later.
Workers
The proxy manages the configuration of origin servers and their
communication parameters in objects called
workers
There are two built-in workers: the default forward proxy worker and the
default reverse proxy worker. Additional workers can be configured
explicitly.
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.
Explicitly configured workers are identified by their URL.
They are usually created and configured using
ProxyPass
or
ProxyPassMatch
when used
for a reverse proxy:
ProxyPass "/example" "http://backend.example.com" connectiontimeout=5 timeout=30
This will create a worker associated with the origin server URL
that will use the given timeout
values. All timeouts use the
time-interval
directive syntax. When used in a forward proxy, workers are usually defined
via the
ProxySet
directive:
ProxySet http://backend.example.com connectiontimeout=5 timeout=30
or alternatively using
Proxy
and
ProxySet
ProxySet connectiontimeout=5 timeout=30
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
ProxyPass
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.
The URL identifying a direct worker is the URL of its
origin server including any path components given:
ProxyPass "/examples" "http://backend.example.com/examples"
ProxyPass "/docs" "http://backend.example.com/docs"
This example defines two different workers, each using a separate
connection pool and configuration.
Worker Sharing
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
ProxyPass "/apps" "http://backend.example.com/" timeout=60
ProxyPass "/examples" "http://backend.example.com/examples" timeout=10
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
/examples
will be
60
instead
of
10
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
ProxyPass
directives.
Host part in the URL
The host part needs to start with a letter [a-z]. For example:
ProxyPass "/apps" "http://127"
is not valid and will cause an error while processing a request that
maps the path.
Explicitly configured workers come in two flavors:
direct workers
and
(load) balancer workers
They support many important configuration attributes which are
described below in the
ProxyPass
directive. The same attributes can also be set using
ProxySet
The set of options available for a direct worker
depends on the protocol which is specified in the origin server URL.
Available protocols include
ajp
fcgi
ftp
http
and
scgi
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.
A balancer worker is created if its worker URL uses
balancer
as the protocol scheme.
The balancer URL uniquely identifies the balancer worker.
Members are added to a balancer using
BalancerMember
DNS resolution for origin domains
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
ProxyPass
parameters for more details about connection reuse.
Controlling Access to Your Proxy
You can control who can access your proxy via the
control block as in
the following example:
Require ip 192.168.0
For more information on access control directives, see
mod_authz_host
Strictly limiting access is essential if you are using a
forward proxy (using the
ProxyRequests
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
ProxyPass
directive with
ProxyRequests Off
), access control is less
critical because clients can only contact the hosts that you
have specifically configured.
See Also
the
Proxy-Chain-Auth
environment variable.
Slow Startup
If you're using the
ProxyBlock
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.
Intranet Proxy
An Apache httpd proxy server situated in an intranet needs to forward
external requests through the company's firewall (for this, configure
the
ProxyRemote
directive
to forward the respective
scheme
to the firewall proxy).
However, when it has to
access resources within the intranet, it can bypass the firewall when
accessing hosts. The
NoProxy
directive is useful for specifying which hosts belong to the intranet and
should be accessed directly.
Users within an intranet tend to omit the local domain name from their
WWW requests, thus requesting "http://somehost/" instead of
. Some commercial proxy servers
let them get away with this and simply serve the request, implying a
configured local domain. When the
ProxyDomain
directive is used and the server is
configured for proxy service
, 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.
Protocol Adjustments
For circumstances where
mod_proxy
is sending
requests to an origin server that doesn't properly implement
keepalives or HTTP/1.1, there are two
environment variables
that can force the
request to use HTTP/1.0 with no keepalive. These are set via the
SetEnv
directive.
These are the
force-proxy-request-1.0
and
proxy-nokeepalive
notes.
ProxyPass "http://buggyappserver:7001/foo/"
SetEnv force-proxy-request-1.0 1
SetEnv proxy-nokeepalive 1
In 2.4.26 and later, the "no-proxy" environment variable can be set to disable
mod_proxy
processing the current request.
This variable should be set with
SetEnvIf
, as
SetEnv
is not evaluated early enough.
Request Bodies
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
Content-Length
request header. When passing these
requests on to the origin server,
mod_proxy_http
will always attempt to send the
Content-Length
. 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
environment variables
. Setting
proxy-sendcl
ensures maximum compatibility with
upstream servers by always sending the
Content-Length
, while setting
proxy-sendchunked
minimizes resource usage by using
chunked encoding.
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.
Reverse Proxy Request Headers
When acting in a reverse-proxy mode (using the
ProxyPass
directive, for example),
mod_proxy_http
adds several request headers in
order to pass information to the origin server. These headers
are:
X-Forwarded-For
The IP address of the client.
X-Forwarded-Host
The original host requested by the client in the
Host
HTTP request header.
X-Forwarded-Server
The hostname of the proxy server.
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
%{X-Forwarded-For}i
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.
See also the
ProxyPreserveHost
and
ProxyVia
directives, which control
other request headers.
Note: If you need to specify custom request headers to be
added to the forwarded request, use the
RequestHeader
directive.
BalancerGrowth
Directive
Description:
Number of additional Balancers that can be added Post-configuration
Syntax:
BalancerGrowth
Default:
BalancerGrowth 5
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
Compatibility:
BalancerGrowth is only available in Apache HTTP Server 2.3.13
and later.
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.
BalancerInherit
Directive
Description:
Inherit proxy Balancers/Workers defined from the main server
Syntax:
BalancerInherit On|Off
Default:
BalancerInherit On
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
Compatibility:
BalancerInherit is only available in Apache HTTP Server 2.4.5 and later.
This directive will cause the current server/vhost to "inherit"
Balancers and Workers defined in the main server. This can cause issues and
inconsistent behavior if using the Balancer Manager for dynamic changes
and so should be disabled if using that feature.
The setting in the global server defines the default for all vhosts.
Disabling
ProxyPassInherit
also disables BalancerInherit.
BalancerMember
Directive
Description:
Add a member to a load balancing group
Syntax:
BalancerMember [
balancerurl
url
key=value [key=value ...]]
Context:
directory
Status:
Extension
Module:
mod_proxy
This directive adds a member to a load balancing group. It can be used
within a
...>
container
directive and can take any of the key value pair parameters available to
ProxyPass
directives.
One additional parameter is available only to
BalancerMember
directives:
loadfactor
. This is the member load factor - a decimal between 1.0
(default) and 100.0, which defines the weighted load to be applied to the
member in question.
The
balancerurl
is only needed when not within a
...>
container directive. It corresponds to the url of a balancer defined in
ProxyPass
directive.
The path component of the balancer URL in any
...>
container directive
is ignored.
Trailing slashes should typically be removed from the URL of a
BalancerMember
BalancerPersist
Directive
Description:
Attempt to persist changes made by the Balancer Manager across restarts.
Syntax:
BalancerPersist On|Off
Default:
BalancerPersist Off
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
Compatibility:
BalancerPersist is only available in Apache HTTP Server 2.4.4 and later.
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.
NoProxy
Directive
Description:
Hosts, domains, or networks that will be connected to
directly
Syntax:
NoProxy
host
host
] ...
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
This directive is only useful for Apache httpd proxy servers within
intranets. The
NoProxy
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
ProxyRemote
proxy server(s).
Example
ProxyRemote * http://firewall.example.com:81
NoProxy .example.com 192.168.112.0/21
The
host
arguments to the
NoProxy
directive are one of the following type list:
Domain
Domain
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 (
i.e.
, the suffixes of the hostnames are
all ending in
Domain
).
Examples
.com .example.org.
To distinguish
Domain
s from
Hostname
s (both syntactically and semantically; a DNS domain can
have a DNS A record, too!),
Domain
s are always written with a
leading period.
Note
Domain name comparisons are done without regard to the case, and
Domain
s are always assumed to be anchored in the root of the
DNS tree; therefore, the two domains
.ExAmple.com
and
.example.com.
(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.
SubNet
SubNet
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
SubNet
. 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:
192.168
or
192.168.0.0
the subnet 192.168.0.0 with an implied netmask of 16 valid bits
(sometimes used in the netmask form
255.255.0.0
192.168.112.0/21
the subnet
192.168.112.0/21
with a netmask of 21
valid bits (also used in the form
255.255.248.0
As a degenerate case, a
SubNet
with 32 valid bits is the
equivalent to an
IPAddr
, while a
SubNet
with zero
valid bits (
e.g.
, 0.0.0.0/0) is the same as the constant
_Default_
, matching any IP address.
IPAddr
IPAddr
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.
Example
192.168.123.7
Note
An
IPAddr
does not need to be resolved by the DNS system, so
it can result in more effective apache performance.
Hostname
Hostname
is a fully qualified DNS domain name which can
be resolved to one or more
IPAddrs
via the
DNS domain name service. It represents a logical host (in contrast to
Domain
s, see above) and must be resolvable
to at least one
IPAddr
(or often to a list
of hosts with different
IPAddr
s).
Examples
prep.ai.example.edu
www.example.org
Note
In many situations, it is more effective to specify an
IPAddr
in place of a
Hostname
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.
Hostname
comparisons are done without regard to the case,
and
Hostname
s are always assumed to be anchored in the root
of the DNS tree; therefore, the two hosts
WWW.ExAmple.com
and
www.example.com.
(note the trailing period) are
considered equal.
See also
DNS Issues
Directive
Description:
Container for directives applied to proxied resources
Syntax:
> ...
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
Directives placed in
sections apply only to matching proxied content. Shell-style wildcards are
allowed.
For example, the following will allow only hosts in
yournetwork.example.com
to access content via your proxy
server:
Require host yournetwork.example.com
The following example will process all files in the
foo
directory of
example.com
through the
INCLUDES
filter when they are sent through the proxy server:
SetOutputFilter INCLUDES
The next example will allow web clients from the specified IP
addresses to issue
CONNECT
requests to access the
SSL server if
mod_proxy_connect
is enabled.
Require ip 192.168.0.0/16
Differences from the Location configuration section
A backend URL matches the configuration section if it begins with the
the
wildcard-url
string, even if the last path segment in the
directive only matches a prefix of the backend URL. For example,
from the behavior of the
section, which for purposes of this note
treats the final path component as if it ended in a slash.
For more control over the matching, see
See also
Proxy100Continue
Directive
Description:
Forward 100-continue expectation to the origin server
Syntax:
Proxy100Continue Off|On
Default:
Proxy100Continue On
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
Compatibility:
Available in version 2.4.40 and later
This directive determines whether the proxy should forward 100-continue
Expect:
ation to the origin server and thus let it decide when/if
the HTTP request body should be read, or when
Off
the proxy
should generate
100 Continue
intermediate response by itself before
forwarding the request body.
Effectiveness
This option is of use only for HTTP proxying, as handled by
mod_proxy_http
ProxyAddHeaders
Directive
Description:
Add proxy information in X-Forwarded-* headers
Syntax:
ProxyAddHeaders Off|On
Default:
ProxyAddHeaders On
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
Compatibility:
Available in version 2.3.10 and later
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.
Effectiveness
This option is of use only for HTTP proxying, as handled by
mod_proxy_http
ProxyBadHeader
Directive
Description:
Determines how to handle bad header lines in a
response
Syntax:
ProxyBadHeader IsError|Ignore|StartBody
Default:
ProxyBadHeader IsError
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
The
ProxyBadHeader
directive determines the
behavior of
mod_proxy
if it receives syntactically invalid
response header lines (
i.e.
containing no colon) from the origin
server. The following arguments are possible:
IsError
Abort the request and end up with a 502 (Bad Gateway) response. This is
the default behavior.
Ignore
Treat bad header lines as if they weren't sent.
StartBody
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.
ProxyBlock
Directive
Description:
Disallow proxy requests to certain hosts
Syntax:
ProxyBlock *|
hostname
partial-hostname
hostname
partial-hostname
]...
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
The
ProxyBlock
directive can be used to
block FTP or HTTP access to certain hosts via the proxy, based on
a full or partial hostname match, or, if applicable, an IP address
comparison.
Each of the arguments to the
ProxyBlock
directive can be either
or a alphanumeric string.
At startup, the module will attempt to resolve every alphanumeric
string from a DNS name to a set of IP addresses, but any DNS errors
are ignored.
If an asterisk "
" argument is specified,
mod_proxy
will deny access to all FTP or HTTP
sites.
Otherwise, for any request for an HTTP or FTP resource via the
proxy,
mod_proxy
will check the hostname of the
request URI against each specified string. If a partial string
match is found, access is denied. If no matches against hostnames
are found, and a remote (forward) proxy is configured using
ProxyRemote
or
ProxyRemoteMatch
, access is allowed. If no
remote (forward) proxy is configured, the IP address of the
hostname from the URI is compared against all resolved IP
addresses determined at startup. Access is denied if any match is
found.
Note that the DNS lookups may slow down the startup time of the
server.
Example
ProxyBlock news.example.com auctions.example.com friends.example.com
Note that
example
would also be sufficient to match any
of these sites.
Hosts would also be matched if referenced by IP address.
Note also that
ProxyBlock *
blocks connections to all sites.
ProxyDomain
Directive
Description:
Default domain name for proxied requests
Syntax:
ProxyDomain
Domain
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
This directive is only useful for Apache httpd proxy servers within
intranets. The
ProxyDomain
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
Domain
appended
will be generated. The domain name must start with a dot.
Example
ProxyRemote "*" "http://firewall.example.com:81"
NoProxy ".example.com" "192.168.112.0/21"
ProxyDomain ".example.com"
ProxyErrorOverride
Directive
Description:
Override error pages for proxied content
Syntax:
ProxyErrorOverride Off|On [
code
...]
Default:
ProxyErrorOverride Off
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
Compatibility:
The list of status codes was added in 2.5.1
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
mod_include
'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.)
This directive does not affect the processing of informational (1xx),
normal success (2xx), or redirect (3xx) responses.
By default
ProxyErrorOverride
affects all responses with codes between 400 (including)
and 600 (excluding).
Example for default behavior
ProxyErrorOverride On
To change the default behavior, you can specify the status codes to consider, separated by spaces.
If you do so, all other status codes will be ignored.
You can only specify status codes, that are considered error codes: between 400 (including)
and 600 (excluding).
Example for custom status codes
ProxyErrorOverride On 403 405 500 501 502 503 504
ProxyIOBufferSize
Directive
Description:
Determine size of internal data throughput buffer
Syntax:
ProxyIOBufferSize
bytes
Default:
ProxyIOBufferSize 8192
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
The
ProxyIOBufferSize
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
512
, or set
to
to indicate that the system's default buffer size
should be used.
In almost every case, there's no reason to change that value.
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
packetSize
attribute of
your AJP connector on the Tomcat side! The attribute
packetSize
is only available in Tomcat
5.5.20+
and
6.0.2+
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.
Directive
Description:
Container for directives applied to regular-expression-matched
proxied resources
Syntax:
> ...
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
The
directive is
identical to the
directive, except that it matches URLs
using
regular expressions
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
expressions
and modules like
mod_rewrite
. In order to prevent confusion, numbered
(unnamed) backreferences are ignored. Use named groups instead.
Require ldap-group cn=%{env:MATCH_SITENAME},ou=combined,o=Example
See also
ProxyMaxForwards
Directive
Description:
Maximum number of proxies that a request can be forwarded
through
Syntax:
ProxyMaxForwards
number
Default:
ProxyMaxForwards -1
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
The
ProxyMaxForwards
directive specifies the
maximum number of proxies through which a request may pass if there's no
Max-Forwards
header supplied with the request. This may
be set to prevent infinite proxy loops or a DoS attack.
Example
ProxyMaxForwards 15
Note that setting
ProxyMaxForwards
is a
violation of the HTTP/1.1 protocol (RFC2616), which forbids a Proxy
setting
Max-Forwards
if the Client didn't set it.
Earlier Apache httpd versions would always set it. A negative
ProxyMaxForwards
value, including the
default -1, gives you protocol-compliant behavior but may
leave you open to loops.
ProxyPass
Directive
Description:
Maps remote servers into the local server URL-space
Syntax:
ProxyPass [
path
] !|
url
key=value
[key=value
...]] [nocanon] [interpolate] [noquery]
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
Compatibility:
Unix Domain Socket (UDS) support added in 2.4.7
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
reverse
proxy
or
gateway
. The
path
is the name of
a local virtual path;
url
is a partial URL for the
remote server and cannot include a query string.
It is strongly suggested to review the concept of a
Worker
before proceeding any further
with this section.
This directive is not supported within
and
containers.
The
ProxyRequests
directive should
usually be set
off
when using
ProxyPass
In 2.4.7 and later, support for using a Unix Domain Socket is available by using a target
which prepends
unix:/path/lis.sock|
. For example, to proxy
HTTP and target the UDS at /home/www.socket, you would use
unix:/home/www.socket|http://localhost/whatever/
. Since
the socket is local, the hostname used (in this case
localhost
is moot, but it is passed as the Host: header value of the request.
Note:
The path associated with the
unix:
URL is
DefaultRuntimeDir
aware.
Note:
RewriteRule
requires
the
[P,NE]
option to prevent the
'|'
character
from being escaped.
When used inside a
section, the first argument is omitted and the local
directory is obtained from the
. The same will occur inside a
section;
however, ProxyPass does not interpret the regexp as such, so it is necessary
to use
ProxyPassMatch
in this situation instead.
Suppose the local server has address
then
ProxyPass "http://backend.example.com/"
will cause a local request for
to be internally converted
into a proxy request to
If you require a more flexible reverse-proxy configuration, see the
RewriteRule
directive with the
[P]
flag.
The following alternative syntax is possible; however, it can carry a
performance penalty when present in very large numbers. The advantage of
the below syntax is that it allows for dynamic control via the
Balancer Manager
interface:
ProxyPass "/mirror/foo/" "http://backend.example.com/"
If the first argument ends with a trailing
, the second
argument should also end with a trailing
, and vice
versa. Otherwise, the resulting requests to the backend may miss some
needed slashes and do not deliver the expected results.
The
directive is useful in situations where you don't want
to reverse-proxy a subdirectory,
e.g.
ProxyPass "http://backend.example.com/"
ProxyPass "!"
ProxyPass "/mirror/foo/i" "!"
ProxyPass "/mirror/foo" "http://backend.example.com"
will proxy all requests to
/mirror/foo
to
backend.example.com
except
requests made to
/mirror/foo/i
Mixing ProxyPass settings in different contexts does not work:
ProxyPass "/mirror/foo/i" "!"
ProxyPass "http://backend.example.com/"
In this case, a request to
/mirror/foo/i
will get proxied,
because the
ProxyPass
directive in the Location block will be evaluated
first. The fact that
ProxyPass
supports both server and directory contexts
does not mean that their scope and position in the configuration file will
guarantee any ordering or override.
Ordering ProxyPass Directives
The configured
ProxyPass
and
ProxyPassMatch
rules are checked in the order of configuration. The first rule that
matches wins. So usually you should sort conflicting
ProxyPass
rules starting with the
longest URLs first. Otherwise, later rules for longer URLS will be hidden
by any earlier rule which uses a leading substring of the URL. Note that
there is some relation with worker sharing.
Ordering ProxyPass Directives in Locations
Only one
ProxyPass
directive
can be placed in a
Location
block,
and the most specific location will take precedence.
Exclusions and the no-proxy environment variable
Exclusions must come
before
the
general
ProxyPass
directives. In 2.4.26 and later, the "no-proxy"
environment variable is an alternative to exclusions, and is the only
way to configure an exclusion of a
ProxyPass
directive in
Location
context.
This variable should be set with
SetEnvIf
, as
SetEnv
is not evaluated early enough.
ProxyPass
key=value
Parameters
In Apache HTTP Server 2.1 and later, mod_proxy supports pooled
connections to a backend server. Connections created on demand
can be retained in a pool for future use. Limits on the pool size
and other settings can be coded on
the
ProxyPass
directive
using
key=value
parameters, described in the tables
below.
Maximum connections to the backend
By default, mod_proxy will allow and retain the maximum number of
connections that could be used simultaneously by that web server child
process. Use the
max
parameter to reduce the number from
the default. The pool of connections is maintained per web server child
process, and
max
and other settings are not coordinated
among all child processes, except when only one child process is allowed
by configuration or MPM design.
Use the
ttl
parameter to set an optional
time to live; connections which have been unused for at least
ttl
seconds will be closed.
ttl
can be used
to avoid using a connection which is subject to closing because of the
backend server's keep-alive timeout.
Example
ProxyPass "/example" "http://backend.example.com" max=20 ttl=120 retry=300
Worker|BalancerMember parameters
Parameter
Default
Description
min
Minimum number of connection pool entries, unrelated to the
actual number of connections. This only needs to be modified from the
default for special circumstances where heap memory associated with the
backend connections should be preallocated or retained.
max
1...n
Maximum number of connections that will be allowed to the
backend server. The default for this limit is the number of threads
per process in the active MPM. In the Prefork MPM, this is always 1;
while with other MPMs, it is controlled by the
ThreadsPerChild
directive.
smax
max
Retained connection pool entries above this limit are freed
during certain operations if they have been unused for longer than
the time to live, controlled by the
ttl
parameter. If
the connection pool entry has an associated connection, it will be
closed. This only needs to be modified from the default for special
circumstances where connection pool entries and any associated
connections which have exceeded the time to live need to be freed or
closed more aggressively.
acquire
If set, this will be the maximum time to wait for a free
connection in the connection pool, in milliseconds. If there are no free
connections in the pool, the Apache httpd will return
SERVER_BUSY
status to the client.
connectiontimeout
timeout
Connect timeout in seconds.
The number of seconds Apache httpd waits for the creation of a connection to
the backend to complete. By adding a postfix of ms, the timeout can be
also set in milliseconds. Uses the
time-interval
directive syntax
disablereuse
Off
This parameter should be used when you want to force mod_proxy
to immediately close a connection to the backend after being used, and
thus, disable its persistent connection and pool for that backend.
This helps in various situations where a firewall between Apache
httpd and
the backend server (regardless of protocol) tends to silently
drop connections or when backends themselves may be under round-
robin DNS.
When connection reuse is enabled each backend domain is resolved
(with a DNS query) only once per child process and cached for all further
connections until the child is recycled. To disable connection reuse,
set this property value to
On
enablereuse
On
This is the inverse of 'disablereuse' above, provided as a
convenience for scheme handlers that require opt-in for connection
reuse (such as
mod_proxy_fcgi
).
flushpackets
off
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
'auto' means poll/wait for a period of time and flush if
no input has been received for 'flushwait' milliseconds.
Currently, this is in effect only for mod_proxy_ajp and mod_proxy_fcgi.
flushwait
10
The time to wait for additional input, in milliseconds, before
flushing the output brigade if 'flushpackets' is 'auto'.
Uses
time-interval
directive syntax.
iobuffersize
8192
Adjusts the size of the internal scratchpad IO buffer. This allows you
to override the
ProxyIOBufferSize
for a specific worker.
This must be at least 512 or set to 0 for the system default of 8192.
responsefieldsize
8192
Adjust the size of the proxy response field buffer. The buffer size
should be at least the size of the largest expected header size from
a proxied response. Setting the value to 0 will use the system
default of 8192 bytes.
Available in Apache HTTP Server 2.4.34 and later.
keepalive
Off
This parameter should be used when you have a firewall between your
Apache httpd and the backend server, which tends to drop inactive connections.
This flag will tell the Operating System to send
KEEP_ALIVE
messages on inactive connections and thus prevent the firewall
from dropping the connection.
To enable keepalive, set this property value to
On
The frequency of initial and subsequent TCP keepalive probes
depends on global OS settings, and may be as high as 2 hours. To be useful,
the frequency configured in the OS must be smaller than the threshold used
by the firewall. Uses the
time-interval
directive syntax.
lbset
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.
ping
Ping property tells the webserver to "test" the connection to
the backend before forwarding the request. For negative values,
the test is a simple socket check; for positive values, it's
a more functional check, dependent upon the protocol. For AJP, it causes
mod_proxy_ajp
to send a
CPING
request on the ajp13 connection (implemented on Tomcat 3.3.2+, 4.1.28+
and 5.0.13+). For HTTP, it causes
mod_proxy_http
to send a
100-Continue
to the backend (only valid for
HTTP/1.1 - for non HTTP/1.1 backends, this property has no
effect). In both cases, the parameter is the delay in seconds to wait
for the reply.
This feature has been added to avoid problems with hung and
busy backends.
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.
By adding a postfix of ms, the delay can be also set in
milliseconds. Uses the
time-interval
directive syntax.
receivebuffersize
Adjusts the size of the explicit (TCP/IP) network buffer size for
proxied connections. This allows you to override the
ProxyReceiveBufferSize
for a specific worker.
This must be at least 512 or set to 0 for the system default.
redirect
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 parameter
equal to this value.
retry
60
Connection pool worker retry timeout in seconds.
If the connection pool worker to the backend server is in the error state,
Apache httpd 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.
Uses the
time-interval
directive syntax.
route
Route of the worker when used inside load balancer.
The route is a value appended to session id.
status
Single letter value defining the initial status of
this worker.
Worker is disabled and will not accept any requests; will be
automatically retried.
Worker is administratively stopped; will not accept requests
and will not be automatically retried.
Worker is in ignore-errors mode and will always be considered available.
Worker is a hot spare. For each worker in a given lbset that is unusable
(draining, stopped, in error, etc.), a usable hot spare with the same lbset will be used in
its place. Hot spares can help ensure that a specific number of workers are always available
for use by a balancer.
Worker is in hot-standby mode and will only be used if no other
viable workers or spares are available in the balancer set.
Worker is in an error state.
Worker is in drain mode and will only accept existing sticky sessions
destined for itself and ignore all other requests.
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.
timeout
ProxyTimeout
Socket timeout in seconds.
The number of seconds Apache httpd waits for data sent by / to the backend.
Uses the
time-interval
directive syntax.
ttl
Time to live for inactive connections and associated connection
pool entries, in seconds. Once reaching this limit, a
connection will not be used again; it will be closed at some
later time. Uses the
time-interval
directive syntax.
flusher
flush
Name of the provider used by
mod_proxy_fdpass
See the documentation of this module for more details.
secret
Value of secret used by
mod_proxy_ajp
See the documentation of this module for more details.
upgrade
Protocol accepted by
mod_proxy_http
or
mod_proxy_wstunnel
for the HTTP Upgrade mechanism
upon negotiation by the HTTP client/browser (per
RFC 9110 - Upgrade
).
See the
Protocol Upgrade
note below
mapping
Type of mapping between the
path
and the
url
This determines the normalization and/or (non-)decoding that
mod_proxy
will apply to the requested
uri-path
before matching the
path
. If
a mapping matches, it's committed to the
uri-path
such that all the directory
contexts that use a path (like
) will be matched using the
same mapping.
mapping=encoded
prevents the %-decoding of the
uri-path
so
that one can use for instance configurations like:
ProxyPass "/special%3Fsegment" "https://example.com/special%3Fsegment" mapping=encoded
Require ip 172.17.2.0/24
mapping=servlet
refers to the normalization defined by the Servlet
specification, which is for instance applied by Apache Tomcat for servlet containers
(notably the path parameters are ignored for the mapping). An
uri-path
like
/some;foo/path
is then mapped as
/some/path
hence matches any
of the below regardless of the requested path parameters:
ProxyPass "/some/path" "https://servlet.example.com/some/path" mapping=servlet
Require valid-user
Note
It is recommended to use the same mapping on the Apache httpd side than the one
used on the backend side. For instance when configuring authorizations in
blocks for paths that are mapped by
mod_proxy
to some servlet containers (like applications running on Apache Tomcat), one should
use the
mapping=servlet
setting to prevent path parameters and alike from
interfering with the authorizations that are to be enforced in by the Apache httpd.
addressttl
-1
TTL in seconds for how long DNS resolutions of the backend address are cached.
-1 means until restart of Apache httpd.
multipathtcp
Off
Enable/disable the use of
Multipath TCP (MPTCP)
If the Proxy directive scheme starts with the
balancer://
(eg:
balancer://cluster
any path information is ignored), 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 added to this virtual worker. See
mod_proxy_balancer
for more information about how the balancer works.
Balancer parameters
Parameter
Default
Description
lbmethod
byrequests
Balancer load-balance method. Select the load-balancing scheduler
method to use. Either
byrequests
, to perform weighted
request counting;
bytraffic
, to perform weighted
traffic byte count balancing; or
bybusyness
, to perform
pending request balancing. The default is
byrequests
maxattempts
One less than the number of workers, or 1 with a single worker.
Maximum number of failover attempts before giving up.
nofailover
Off
If set to
On
, 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.
stickysession
Balancer sticky session name. The value is usually set to something
like
JSESSIONID
or
PHPSESSIONID
and it depends on the backend application server that support sessions.
If the backend application server uses different names for cookies
and url encoded id (like servlet containers), use | to separate them.
The first part is for the cookie; the second is for the path.
Available in Apache HTTP Server 2.4.4 and later.
stickysessionsep
"."
Sets the separation symbol in the session cookie. Some backend application servers
do not use the '.' as the symbol. For example, the Oracle Weblogic server uses
'!'. The correct symbol can be set using this option. The setting of 'Off'
signifies that no symbol is used.
scolonpathdelim
Off
If set to
On
, the semi-colon character ';' will be
used as an additional sticky session path delimiter/separator. This
is mainly used to emulate mod_jk's behavior when dealing with paths such
as
JSESSIONID=6736bcf34;foo=aabfa
timeout
Balancer timeout in seconds. If set, this will be the maximum time
to wait for a free worker. The default is to not wait.
Uses the
time-interval
directive syntax.
failonstatus
A single or comma-separated list of HTTP status codes. If set, this will
force the worker into error state when the backend returns any status code
in the list. Worker recovery behaves the same as other worker errors.
failontimeout
Off
If set, an IO read timeout after a request is sent to the backend will
force the worker into error state. Worker recovery behaves the same as other
worker errors.
Available in Apache HTTP Server 2.4.5 and later.
nonce
The protective nonce used in the
balancer-manager
application page.
The default is to use an automatically determined UUID-based
nonce, to provide for further protection for the page. If set,
then the nonce is set to that value. A setting of
None
disables all nonce checking.
Note
In addition to the nonce, the
balancer-manager
page
should be protected via an ACL.
growth
Number of additional BalancerMembers to allow to be added
to this balancer in addition to those defined at configuration.
forcerecovery
On
Force the immediate recovery of all workers without considering the
retry parameter of the workers if all workers of a balancer are
in error state. There might be cases where an already overloaded backend
can get into deeper trouble if the recovery of all workers is enforced
without considering the retry parameter of each worker. In this case,
set to
Off
Available in Apache HTTP Server 2.4.2 and later.
A sample balancer setup:
ProxyPass "/special-area" "http://special.example.com" smax=5 max=10
ProxyPass "/" "balancer://mycluster/" stickysession=JSESSIONID|jsessionid nofailover=On
BalancerMember ajp://1.2.3.4:8009
BalancerMember ajp://1.2.3.5:8009 loadfactor=20
# Less powerful server, don't send as many requests there,
BalancerMember ajp://1.2.3.6:8009 loadfactor=5
Configuring hot spares can help ensure that a certain number of
workers are always available for use per load balancer set:
ProxyPass "/" "balancer://sparecluster/"
BalancerMember ajp://1.2.3.4:8009
BalancerMember ajp://1.2.3.5:8009
# The servers below are hot spares. For each server above that is unusable
# (draining, stopped, unreachable, in error state, etc.), one of these spares
# will be used in its place. Two servers will always be available for a request
# unless one or more of the spares is also unusable.
BalancerMember ajp://1.2.3.6:8009 status=+R
BalancerMember ajp://1.2.3.7:8009 status=+R
Setting up a hot-standby that will only be used if no other
members (or spares) are available in the load balancer set:
ProxyPass "/" "balancer://hotcluster/"
BalancerMember ajp://1.2.3.4:8009 loadfactor=1
BalancerMember ajp://1.2.3.5:8009 loadfactor=2.25
# The server below is on hot standby
BalancerMember ajp://1.2.3.6:8009 status=+H
ProxySet lbmethod=bytraffic
Additional ProxyPass Keywords
Normally, mod_proxy will canonicalise ProxyPassed URLs.
But this may be incompatible with some backends, particularly those
that make use of
PATH_INFO
. The optional
nocanon
keyword suppresses this and passes the URL path "raw" to the
backend. Note that this keyword may affect the security of your backend,
as it removes the normal limited protection against URL-based attacks
provided by the proxy.
Normally, mod_proxy will include the query string when
generating the
SCRIPT_FILENAME
environment variable.
The optional
noquery
keyword (available in
httpd 2.4.1 and later) prevents this.
The optional
interpolate
keyword, in combination with
ProxyPassInterpolateEnv
, causes the ProxyPass
to interpolate environment variables, using the syntax
${VARNAME}
. Note that many of the standard CGI-derived
environment variables will not exist when this interpolation happens,
so you may still have to resort to
mod_rewrite
for complex rules. Also note that interpolation is supported
within the scheme/hostname/port portion of a URL only for variables that
are available when the directive is parsed
(like
Define
). Dynamic determination of
those fields can be accomplished with
mod_rewrite
The following example describes how to use
mod_rewrite
to dynamically set the scheme to http or https:
RewriteEngine On
RewriteCond %{HTTPS} =off
RewriteRule . - [E=protocol:http]
RewriteCond %{HTTPS} =on
RewriteRule . - [E=protocol:https]
RewriteRule ^/mirror/foo/(.*) %{ENV:protocol}://backend.example.com/$1 [P]
ProxyPassReverse "/mirror/foo/" "http://backend.example.com/"
ProxyPassReverse "/mirror/foo/" "https://backend.example.com/"
Protocol Upgrade
Since Apache HTTP Server 2.4.47, protocol Upgrade (tunneling) can be handled
end-to-end by
mod_proxy_http
using the
ProxyPass
parameter
upgrade
End-to-end means that the HTTP Upgrade request from the client/browser is first
forwarded by
mod_proxy_http
to the origin server and the connection
will be upgraded (and tunneled by
mod_proxy_http
) only if the origin
server accepts/initiates the upgrade (HTTP response
101 Switching Protocols
).
If the origin server responds with anything else
mod_proxy_http
will continue forwarding (and enforcing) the HTTP protocol as usual for this
connection.
See
Websocket Upgrade (2.4.47 and later)
for an example of
configuration using
mod_proxy_http
For Apache HTTP Server 2.4.46 and earlier (or if
ProxyWebsocketFallbackToProxyHttp
from 2.4.48 and later disables
mod_proxy_http
handling), see the
documentation of
mod_proxy_wstunnel
for how to proxy the WebSocket
protocol.
ProxyPassInherit
Directive
Description:
Inherit ProxyPass directives defined from the main server
Syntax:
ProxyPassInherit On|Off
Default:
ProxyPassInherit On
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
Compatibility:
ProxyPassInherit is only available in Apache HTTP Server 2.4.5 and later.
This directive will cause the current server/vhost to "inherit"
ProxyPass
directives defined in the main server. This can cause issues and
inconsistent behavior if using the Balancer Manager for dynamic changes
and so should be disabled if using that feature.
The setting in the global server defines the default for all vhosts.
Disabling ProxyPassInherit also disables
BalancerInherit
ProxyPassInterpolateEnv
Directive
Description:
Enable Environment Variable interpolation in Reverse Proxy configurations
Syntax:
ProxyPassInterpolateEnv On|Off
Default:
ProxyPassInterpolateEnv Off
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
This directive, together with the
interpolate
argument to
ProxyPass
ProxyPassReverse
ProxyPassReverseCookieDomain
, and
ProxyPassReverseCookiePath
enables reverse proxies to be dynamically
configured using environment variables which may be set by
another module such as
mod_rewrite
It affects the
ProxyPass
ProxyPassReverse
ProxyPassReverseCookieDomain
, and
ProxyPassReverseCookiePath
directives
and causes them to substitute the value of an environment
variable
varname
for the string
${varname}
in configuration directives if the
interpolate
option is set.
The scheme/hostname/port portion of
ProxyPass
may
contain variables, but only the ones available when the directive is parsed
(for example, using
Define
).
For all the other use cases, please consider using
mod_rewrite
instead.
Performance warning
Keep this turned off unless you need it!
Adding variables to
ProxyPass
for example may lead to
the use of the default mod_proxy's workers configured (that don't allow any fine
tuning like connections reuse, etc..).
ProxyPassMatch
Directive
Description:
Maps remote servers into the local server URL-space using regular expressions
Syntax:
ProxyPassMatch [
regex
] !|
url
key=value
[key=value
...]]
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
Compatibility:
Since 2.4.47 the
key=value
Parameters are honored
when the
url
parameter contains backreference(s) (see note below).
This directive is equivalent to
ProxyPass
but makes use of regular expressions instead of simple prefix matching. The
supplied regular expression is matched against the
url
, and if it
matches, the server will substitute any parenthesized matches into the given
string and use it as a new
url
Note:
This directive cannot be used within a
context.
Suppose the local server has address
then
ProxyPassMatch "^/(.*\.gif)$" "http://backend.example.com/$1"
will cause a local request for
to be internally converted
into a proxy request to
The
directive is useful in situations where you don't want
to reverse-proxy a subdirectory.
When used inside a
section, the first argument is omitted and the
regexp is obtained from the
If you require a more flexible reverse-proxy configuration, see the
RewriteRule
directive with the
[P]
flag.
Default Substitution
When the URL parameter doesn't use any backreferences into the regular
expression, the original URL will be appended to the URL parameter.
key=value
Parameters versus
url
with backreference(s)
Since Apache HTTP Server 2.4.47, the
key=value
Parameters
are no longer ignored in a
ProxyPassMatch
using
an
url
with backreference(s). However to keep the existing
behavior regarding reuse/keepalive of backend connections (which were
never reused before for these URLs), the parameter
enablereuse
(or
disablereuse
) default to
off
(resp.
on
in this case. Setting
enablereuse=on
explicitely allows to
reuse connections
unless
some backreference(s) belong in
the
authority
part (hostname and/or port) of the
url
(this condition is enforced since Apache HTTP Server 2.4.55, and produces
a warning at startup because these URLs are not reusable per se).
Security Warning
Take care when constructing the target URL of the rule, considering
the security impact from allowing the client influence over the set of
URLs to which your server will act as a proxy. Ensure that the scheme
and hostname part of the URL is either fixed or does not allow the
client undue influence.
ProxyPassReverse
Directive
Description:
Adjusts the URL in HTTP response headers sent from a reverse
proxied server
Syntax:
ProxyPassReverse [
path
url
[interpolate]
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
This directive lets Apache httpd adjust the URL in the
Location
Content-Location
and
URI
headers on HTTP
redirect responses. This is essential when Apache httpd is used as a
reverse proxy (or gateway) to avoid bypassing the reverse proxy
because of HTTP redirects on the backend servers which stay behind
the reverse proxy.
Only the HTTP response headers specifically mentioned above
will be rewritten. Apache httpd will not rewrite other response
headers, nor will it by default rewrite URL references inside HTML pages.
This means that if the proxied content contains absolute URL
references, they will bypass the proxy. To rewrite HTML content to
match the proxy, you must load and enable
mod_proxy_html
path
is the name of a local virtual path. It is combined
with the requests scheme, host, and port to form the replacement
prefix of the affected response header.
This parameter is usually the same as the first parameter of the
ProxyPass
directive.
url
is a partial URL for the remote server. When the remote
server sends the specifically mentioned headers beginning with this partial
URL, the prefix from the remote server is replaced with a prefix that
points to the reverse proxy.
This parameter is usually the same as the second parameter of the
ProxyPass
directive, but it may
differ if the remote server uses a different scheme, host, port, or path
in the affected headers. In configurations with
ProxyPreserveHost
, the hostname
in the partial URL may already be the hostname of the reverse proxy, which
will prevent the matching and replacement done by this directive.
For example, suppose the local server has address
; then
ProxyPass "/mirror/foo/" "http://backend.example.com/"
ProxyPassReverse "/mirror/foo/" "http://backend.example.com/"
ProxyPassReverseCookieDomain backend.example.com public.example.com
ProxyPassReverseCookiePath "/" "/mirror/foo/"
will not only cause a local request for the
to be internally converted
into a proxy request to
(the functionality which
ProxyPass
provides here).
It also takes care of redirects which the server
backend.example.com
sends
when redirecting
to
. Apache httpd adjusts this to
before forwarding the HTTP
redirect response to the client. Note that the hostname used for
constructing the URL is chosen in respect to the setting of the
UseCanonicalName
directive.
Note that this
ProxyPassReverse
directive can
also be used in conjunction with the proxy feature
RewriteRule ... [P]
) from
mod_rewrite
because it doesn't depend on a corresponding
ProxyPass
directive.
The optional
interpolate
keyword, used together with
ProxyPassInterpolateEnv
, enables interpolation
of environment variables specified using the format
${VARNAME}
Note that interpolation is not supported within the scheme portion of a
URL.
When used inside a
section, the first argument is omitted and the local
directory is obtained from the
. The same occurs inside a
section, but will probably not work as
intended, as ProxyPassReverse will interpret the regexp literally as a
path; if needed in this situation, specify the ProxyPassReverse outside
the section or in a separate
section.
This directive is not supported in
or
sections.
ProxyPassReverseCookieDomain
Directive
Description:
Adjusts the Domain string in Set-Cookie headers from a reverse-
proxied server
Syntax:
ProxyPassReverseCookieDomain
internal-domain
public-domain
[interpolate]
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
Usage is basically similar to
ProxyPassReverse
, but instead of
rewriting headers that are a URL, this rewrites the
domain
string in
Set-Cookie
headers.
ProxyPassReverseCookiePath
Directive
Description:
Adjusts the Path string in Set-Cookie headers from a reverse-
proxied server
Syntax:
ProxyPassReverseCookiePath
internal-path
public-path
[interpolate]
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
Useful in conjunction with
ProxyPassReverse
in situations where backend URL paths are mapped to public paths on the
reverse proxy. This directive rewrites the
path
string in
Set-Cookie
headers. If the beginning of the cookie path matches
internal-path
, the cookie path will be replaced with
public-path
In the example given with
ProxyPassReverse
, the directive:
ProxyPassReverseCookiePath "/" "/mirror/foo/"
will rewrite a cookie with backend path
(or
/example
or, in fact, anything) to
/mirror/foo/
ProxyPreserveHost
Directive
Description:
Use incoming Host HTTP request header for proxy
request
Syntax:
ProxyPreserveHost On|Off
Default:
ProxyPreserveHost Off
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
Compatibility:
Usable in directory
context in 2.3.3 and later.
When enabled, this option will pass the
Host:
line from the incoming
request to the proxied host, instead of the hostname specified in the
ProxyPass
line.
This option should normally be turned
Off
. 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.
ProxyReceiveBufferSize
Directive
Description:
Network buffer size for proxied HTTP and FTP
connections
Syntax:
ProxyReceiveBufferSize
bytes
Default:
ProxyReceiveBufferSize 0
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
The
ProxyReceiveBufferSize
directive specifies an
explicit (TCP/IP) network buffer size for proxied HTTP and FTP connections,
for increased throughput. It has to be greater than
512
or set
to
to indicate that the system's default buffer size should
be used.
Example
ProxyReceiveBufferSize 2048
ProxyRemote
Directive
Description:
Remote proxy used to handle certain requests
Syntax:
ProxyRemote
match
remote-server
username:password
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
Compatibility:
The optional third argument is usable only in httpd 2.5.1 and later.
This defines remote proxies to this proxy.
match
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
to indicate
the server should be contacted for all requests.
remote-server
is
a partial URL for the remote server. Syntax:
remote-server
scheme
://
hostname
[:
port
scheme
is effectively the protocol that should be used to
communicate with the remote server; only
http
and
https
are supported by this module. When using
https
, the requests
are forwarded through the remote proxy using the HTTP CONNECT method.
Example
ProxyRemote http://goodguys.example.com/ http://mirrorguys.example.com:8000
ProxyRemote * http://cleverproxy.localdomain
ProxyRemote ftp http://ftpproxy.mydomain:8080
In the last example, the proxy will forward FTP requests, encapsulated
as yet another HTTP proxy request, to another proxy which can handle
them.
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.
An optional third argument
username:password
may be
given, which defines the Basic authentication credentials to pass
to the configured remote proxy. The credentials will always be
sent without first waiting for the remote proxy to send a Basic
authentication challenge. The
Proxy-Chain-Auth
environment
variable has no effect if this argument is used.
ProxyRemoteMatch
Directive
Description:
Remote proxy used to handle requests matched by regular
expressions
Syntax:
ProxyRemoteMatch
regex
remote-server
username:password
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
Compatibility:
The optional third argument is usable only in httpd 2.5.1 and later.
The
ProxyRemoteMatch
is identical to the
ProxyRemote
directive, except that
the first argument is a
regular expression
match against the requested URL.
ProxyRequests
Directive
Description:
Enables forward (standard) proxy requests
Syntax:
ProxyRequests On|Off
Default:
ProxyRequests Off
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
This allows or prevents Apache httpd from functioning as a forward proxy
server. (Setting ProxyRequests to
Off
does not disable use of
the
ProxyPass
directive.)
In a typical reverse proxy or gateway configuration, this
option should be set to
Off
In order to get the functionality of proxying HTTP or FTP sites, you
need also
mod_proxy_http
or
mod_proxy_ftp
(or both) present in the server.
In order to get the functionality of (forward) proxying HTTPS sites, you
need
mod_proxy_connect
enabled in the server.
Warning
Do not enable proxying with
ProxyRequests
until you have
secured your server
. Open proxy servers are dangerous
both to your network and to the Internet at large.
See also
Forward and Reverse Proxies/Gateways
ProxySet
Directive
Description:
Set various Proxy balancer or member parameters
Syntax:
ProxySet
url
key=value [key=value ...]
Context:
server config, virtual host, directory
Status:
Extension
Module:
mod_proxy
This directive is used as an alternate method of setting any of the
parameters available to Proxy balancers and workers normally done via the
ProxyPass
directive. If used
within a
container directive, the
url
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
RewriteRule
instead of a
ProxyPass
directive.
BalancerMember http://www2.example.com:8080 loadfactor=1
BalancerMember http://www3.example.com:8080 loadfactor=2
ProxySet lbmethod=bytraffic
ProxySet keepalive=On
ProxySet balancer://foo lbmethod=bytraffic timeout=15
ProxySet ajp://backend:7001 timeout=15
Warning
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.
ProxySourceAddress
Directive
Description:
Set local IP address for outgoing proxy connections
Syntax:
ProxySourceAddress
address
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
Compatibility:
Available in version 2.3.9 and later
This directive allows to set a specific local address to bind to when connecting
to a backend server.
ProxyStatus
Directive
Description:
Show Proxy LoadBalancer status in mod_status
Syntax:
ProxyStatus Off|On|Full
Default:
ProxyStatus Off
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
This directive determines whether or not proxy
loadbalancer status data is displayed via the
mod_status
server-status page.
Note
Full
is synonymous with
On
ProxyTimeout
Directive
Description:
Network timeout for proxied requests
Syntax:
ProxyTimeout
time-interval
[s]
Default:
Value of
Timeout
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
This directive allows a user to specify a timeout on proxy requests.
This is useful when you have a slow/buggy appserver which hangs, and you
would rather just return a timeout and fail gracefully instead of waiting
however long it takes the server to return.
ProxyVia
Directive
Description:
Information provided in the
Via
HTTP response
header for proxied requests
Syntax:
ProxyVia On|Off|Full|Block
Default:
ProxyVia Off
Context:
server config, virtual host
Status:
Extension
Module:
mod_proxy
This directive controls the use of the
Via:
HTTP
header by the proxy. Its intended use is to control the flow of
proxy requests along a chain of proxy servers. See
RFC 2616
(HTTP/1.1), section
14.45 for an explanation of
Via:
header lines.
If set to
Off
, which is the default, no special processing
is performed. If a request or reply contains a
Via:
header,
it is passed through unchanged.
If set to
On
, each request and reply will get a
Via:
header line added for the current host.
If set to
Full
, each generated
Via:
header
line will additionally have the Apache httpd server version shown as a
Via:
comment field.
If set to
Block
, every proxy request will have all its
Via:
header lines removed. No new
Via:
header will
be generated.
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Licensed under the
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