<a href="../tr/howto/public_html.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p>
</div>
-
<p>In addition to being a "basic" web server, and providing static and
- dynamic content to end-users, Apache httpd (as well as most other web
- servers) can also act as a reverse proxy server, also-known-as a
- "gateway" server.</p>
-
-
<p>In such scenarios, httpd itself does not generate or host the data,
- but rather the content is obtained by one or several backend servers,
- which normally have no direct connection to the external network. As
- httpd receives a request from a client, the request itself is <em>proxied</em>
- to one of these backend servers, which then handles the request, generates
- the content and then sends this content back to httpd, which then
- generates the actual HTTP response back to the client.</p>
-
-
<p>There are numerous reasons for such an implementation, but generally
- the typical rationales are due to security, high-availability, load-balancing
- and centralized authentication/authorization. It is critical in these
- implementations that the layout, design and architecture of the backend
- infrastructure (those servers which actually handle the requests) are
- insulated and protected from the outside; as far as the client is concerned,
- the reverse proxy server <em>is</em> the sole source of all content.</p>
-
-
<p>A typical implementation is below:</p>
-
<p><img src="../images/reverse-proxy-arch.png" alt="reverse-proxy-arch" /></p>
-
- </div>
+ <p>In addition to being a "basic" web server, and providing static and
+ dynamic content to end-users, Apache httpd (as well as most other web
+ servers) can also act as a reverse proxy server, also-known-as a
+ "gateway" server.</p>
+
+ <p>In such scenarios, httpd itself does not generate or host the data,
+ but rather the content is obtained by one or several backend servers,
+ which normally have no direct connection to the external network. As
+ httpd receives a request from a client, the request itself is <em>proxied</em>
+ to one of these backend servers, which then handles the request, generates
+ the content and then sends this content back to httpd, which then
+ generates the actual HTTP response back to the client.</p>
+
+ <p>There are numerous reasons for such an implementation, but generally
+ the typical rationales are due to security, high-availability, load-balancing
+ and centralized authentication/authorization. It is critical in these
+ implementations that the layout, design and architecture of the backend
+ infrastructure (those servers which actually handle the requests) are
+ insulated and protected from the outside; as far as the client is concerned,
+ the reverse proxy server <em>is</em> the sole source of all content.</p>
+
+ <p>A typical implementation is below:</p>
+ <p><img src="../images/reverse-proxy-arch.png" alt="reverse-proxy-arch" /></p>
+
+ </div>
<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#related">Reverse Proxy</a></li>
-<li><img alt="" src="../images/down.gif" /> <a href="#userdir">Simple reverse proxying</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#simple">Simple reverse proxying</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#cluster">Clusters and Balancers</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#config">Balancer and BalancerMember configuration</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#failover">Failover</a></li>
</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="related" id="related">Reverse Proxy</a></h2>
-
-
<table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code></li><li><code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></li><li><code class="module"><a href="../mod/mod_proxy_hcheck.html">mod_proxy_hcheck</a></code></li></ul></td><td><ul><li><code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code></li><li><code class="directive"><a href="../mod/mod_proxy.html#balancermember">BalancerMember</a></code></li></ul></td></tr></table>
-
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+
+ <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code></li><li><code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></li><li><code class="module"><a href="../mod/mod_proxy_hcheck.html">mod_proxy_hcheck</a></code></li></ul></td><td><ul><li><code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code></li><li><code class="directive"><a href="../mod/mod_proxy.html#balancermember">BalancerMember</a></code></li></ul></td></tr></table>
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
-<h2><a name="userdir" id="userdir">Simple reverse proxying</a></h2>
-
+<h2><a name="simple" id="simple">Simple reverse proxying</a></h2>
+
+
+ <p>
+ The <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code>
+ directive specifies the mapping of incoming requests to the backend
+ server (or a cluster of servers known as a <code>Balancer</code>
+ group). The simpliest example proxies all requests (<code>"/"</code>)
+ to a single backend:
+ </p>
+
+ <pre class="prettyprint lang-config">ProxyPass "/" "http://www.example.com"</pre>
+
- <p>The <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code>
- directive specifies the mapping of incoming requests to the backend
- server (or a cluster of servers known as a <code>Balancer</code>
- group). The simpliest example proxies all requests (<code>"/"</code>)
- to a single backend:</p>
+ <p>
+ To ensure that and <code>Location:</code> headers generated from
+ the backend are modified to point to the reverse proxy, instead of
+ back to itself, the <code class="directive"><a href="../mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code>
+ directive is most often required:
+ </p>
- <pre class="prettyprint lang-config">ProxyPass "/" "http://www.example.com"</pre>
+ <pre class="prettyprint lang-config"> ProxyPass "/" "http://www.example.com"
+ ProxyPassReverse "/" "http://www.example.com"</pre>
+
+
+ <p>Only specific URIs can be proxied, as shown in this example:</p>
+
+ <pre class="prettyprint lang-config"> ProxyPass "/images" "http://www.example.com"
+ ProxyPassReverse "/images" "http://www.example.com"</pre>
+
+
+ <p>In the above, any requests which start with the <code>/images</code>
+ path with be proxied to the specified backend, otherwise it will be handled
+ locally.
+ </p>
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="cluster" id="cluster">Clusters and Balancers</a></h2>
+
+ <p>
+ As useful as the above is, it still has the deficiencies that should
+ the (single) backend node go down, or become heavily loaded, that proxying
+ those requests provides no real advantage. What is needed is the ability
+ to define a set or group of backend servers which can handle such
+ requests and for the reverse proxy to load balance and failover among
+ them. This group is sometimes called a <em>cluster</em> but Apache httpd's
+ term is a <em>balancer</em>. One defines a balancer by leveraging the
+ <code class="directive"><a href="../mod/mod_proxy.html#proxy">Proxy</a></code> and
+ <code class="directive"><a href="../mod/mod_proxy.html#balancermember">BalancerMember</a></code> directives as
+ shown:
+ </p>
- <p>To ensure that and <code>Location:</code> headers generated from
- the backend are modified to point to the reverse proxy, instead of
- back to itself, the <code class="directive"><a href="../mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code>
- directive is most often required:</p>
+ <pre class="prettyprint lang-config"> <Proxy balancer://myset>
+ BalancerMember http://www2.example.com:8080
+ BalancerMember http://www3.example.com:8080
+ ProxySet lbmethod=bytraffic
+ </Proxy>
+
+ ProxyPass "/images" "balancer://myset"
+ ProxyPassReverse "/images" "balancer://myset"</pre>
+
+
+ <p>
+ The <code>balancer://</code> scheme is what tells httpd that we are creating
+ a balancer set, with the name <em>myset</em>. It includes 2 backend servers,
+ which httpd calls <em>BalancerMembers</em>. In this case, any requests for
+ <code>/images</code> will be proxied to <em>one</em> of the 2 backends.
+ The <code class="directive"><a href="../mod/mod_proxy.html#proxyset">ProxySet</a></code> directive
+ specifies that the <em>myset</em> Balancer use a load balancing algorithm
+ that balances based on I/O bytes.
+ </p>
+
+ <div class="note"><h3>Hint</h3>
+ <p>
+ <em>BalancerMembers</em> are also sometimes referred to as <em>workers</em>.
+ </p>
+ </div>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="config" id="config">Balancer and BalancerMember configuration</a></h2>
+
+
+ <p>
+ You can adjust numerous configuration details of the <em>balancers</em>
+ and the <em>workers</em> via the various parameters defined in
+ <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code>. For example,
+ assuming we would want <code>http://www3.example.com:8080</code> to
+ handle 3x the traffic with a timeout of 1 second, we would adjust the
+ configuration as follows:
+ </p>
+
+ <pre class="prettyprint lang-config"> <Proxy balancer://myset>
+ BalancerMember http://www2.example.com:8080
+ BalancerMember http://www3.example.com:8080 loadfactor=3 timeout=1
+ ProxySet lbmethod=bytraffic
+ </Proxy>
+
+ ProxyPass "/images" "balancer://myset"
+ ProxyPassReverse "/images" "balancer://myset"</pre>
+
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="failover" id="failover">Failover</a></h2>
+
- <pre class="prettyprint lang-config"> ProxyPass "/" "http://www.example.com"
- ProxyPassReverse "/" "http://www.example.com"</pre>
+ <p>
+ You can also fine-tune various failover scenarios, detailing which
+ workers and even which balancers should accessed in such cases. For
+ example, the below setup implements 2 failover cases: In the first,
+ <code>http://hstandby.example.com:8080</code> is only sent traffic
+ if all other workers in the <em>myset</em> balancer are not available.
+ If that worker itself is not available, only then will the
+ <code>http://bkup1.example.com:8080</code> and <code>http://bkup2.example.com:8080</code>
+ workers be brought into rotation:
+ </p>
+ <pre class="prettyprint lang-config"> <Proxy balancer://myset>
+ BalancerMember http://www2.example.com:8080
+ BalancerMember http://www3.example.com:8080 loadfactor=3 timeout=1
+ BalancerMember http://hstandby.example.com:8080 status=+H
+ BalancerMember http://bkup1.example.com:8080 lbset=1
+ BalancerMember http://bkup2.example.com:8080 lbset=1
+ ProxySet lbmethod=byrequests
+ </Proxy>
- <p>Only specific URIs can be proxied, as shown in this example:</p>
+ ProxyPass "/images" "balancer://myset"
+ ProxyPassReverse "/images" "balancer://myset"</pre>
- <pre class="prettyprint lang-config"> ProxyPass "/images" "http://www.example.com"
- ProxyPassReverse "/images" "http://www.example.com"</pre>
+ <p>
+ The magic of this failover setup is setting <code>http://hstandby.example.com:8080</code>
+ with the <code>+H</code> status flag, which puts it in <em>hot standby</em> mode,
+ and making the 2 <code>bkup#</code> servers part of the #1 load balancer set (the
+ default set is 0); for failover, hot standbys (if they exist) are used 1st, when all regular
+ workers are unavailable; load balancer sets are always tried lowest number first.
+ </p>
- <p>In the above, any requests which start with the <code>/images</code>
- path with be proxied to the specified backend, otherwise it will be handled
- locally.</p>
- </div></div>
+ </div></div>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="../en/howto/public_html.html" title="English"> en </a> |
<a href="../fr/howto/public_html.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
projects / thirdparty / apache / httpd.git / commitdiff
