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diff --git a/docs/manual/howto/reverse_proxy.html.en b/docs/manual/howto/reverse_proxy.html.en new file mode 100644 index 0000000..bd20161 --- /dev/null +++ b/docs/manual/howto/reverse_proxy.html.en @@ -0,0 +1,360 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head> +<meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type" /> +<!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>Reverse Proxy Guide - Apache HTTP Server Version 2.4</title> +<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> +<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> +<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" /> +<script src="../style/scripts/prettify.min.js" type="text/javascript"> +</script> + +<link href="../images/favicon.ico" rel="shortcut icon" /></head> +<body id="manual-page"><div id="page-header"> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> +<p class="apache">Apache HTTP Server Version 2.4</p> +<img alt="" src="../images/feather.png" /></div> +<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div> +<div id="path"> +<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.4</a> > <a href="./">How-To / Tutorials</a></div><div id="page-content"><div id="preamble"><h1>Reverse Proxy Guide</h1> +<div class="toplang"> +<p><span>Available Languages: </span><a href="../en/howto/reverse_proxy.html" title="English"> en </a> | +<a href="../fr/howto/reverse_proxy.html" hreflang="fr" rel="alternate" title="Français"> fr </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 class="centered"><img src="../images/reverse-proxy-arch.png" alt="reverse-proxy-arch" /></p> + + </div> +<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><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="#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> +<li><img alt="" src="../images/down.gif" /> <a href="#manager">Balancer Manager</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#health-check">Dynamic Health Checks</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#status">BalancerMember status flags</a></li> +</ul><h3>See also</h3><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> +<div class="section"> +<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> + 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/" +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> + + <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> + + + <p> + You can also fine-tune various failover scenarios, detailing which workers + and even which balancers should be accessed in such cases. For example, the + below setup implements three failover cases: + </p> + <ol> + <li> + <code>http://spare1.example.com:8080</code> and + <code>http://spare2.example.com:8080</code> are only sent traffic if one + or both of <code>http://www2.example.com:8080</code> or + <code>http://www3.example.com:8080</code> is unavailable. (One spare + will be used to replace one unusable member of the same balancer set.) + </li> + <li> + <code>http://hstandby.example.com:8080</code> is only sent traffic if + all other workers in balancer set <code>0</code> are not available. + </li> + <li> + If all load balancer set <code>0</code> workers, spares, and the standby + are unavailable, only then will the + <code>http://bkup1.example.com:8080</code> and + <code>http://bkup2.example.com:8080</code> workers from balancer set + <code>1</code> be brought into rotation. + </li> + </ol> + <p> + Thus, it is possible to have one or more hot spares and hot standbys for + each load balancer set. + </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://spare1.example.com:8080 status=+R + BalancerMember http://spare2.example.com:8080 status=+R + 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> + +ProxyPass "/images/" "balancer://myset/" +ProxyPassReverse "/images/" "balancer://myset/"</pre> + + + <p> + For failover, hot spares are used as replacements for unusable workers in + the same load balancer set. A worker is considered unusable if it is + draining, stopped, or otherwise in an error/failed state. Hot standbys are + used if all workers and spares in the load balancer set are + unavailable. Load balancer sets (with their respective hot spares and + standbys) are always tried in order from lowest to highest. + </p> + + </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="manager" id="manager">Balancer Manager</a></h2> + + + <p> + One of the most unique and useful features of Apache httpd's reverse proxy is + the embedded <em>balancer-manager</em> application. Similar to + <code class="module"><a href="../mod/mod_status.html">mod_status</a></code>, <em>balancer-manager</em> displays + the current working configuration and status of the enabled + balancers and workers currently in use. However, not only does it + display these parameters, it also allows for dynamic, runtime, on-the-fly + reconfiguration of almost all of them, including adding new <em>BalancerMembers</em> + (workers) to an existing balancer. To enable these capability, the following + needs to be added to your configuration: + </p> + + <pre class="prettyprint lang-config"><Location "/balancer-manager"> + SetHandler balancer-manager + Require host localhost +</Location></pre> + + + <div class="warning"><h3>Warning</h3> + <p>Do not enable the <em>balancer-manager</em> until you have <a href="../mod/mod_proxy.html#access">secured your server</a>. In + particular, ensure that access to the URL is tightly + restricted.</p> + </div> + + <p> + When the reverse proxy server is accessed at that url + (eg: <code>http://rproxy.example.com/balancer-manager/</code>, you will see a + page similar to the below: + </p> + <p class="centered"><img src="../images/bal-man.png" alt="balancer-manager page" /></p> + + <p> + This form allows the devops admin to adjust various parameters, take + workers offline, change load balancing methods and add new works. For + example, clicking on the balancer itself, you will get the following page: + </p> + <p class="centered"><img src="../images/bal-man-b.png" alt="balancer-manager page" /></p> + + <p> + Whereas clicking on a worker, displays this page: + </p> + <p class="centered"><img src="../images/bal-man-w.png" alt="balancer-manager page" /></p> + + <p> + To have these changes persist restarts of the reverse proxy, ensure that + <code class="directive"><a href="../mod/mod_proxy.html#balancerpersist">BalancerPersist</a></code> is enabled. + </p> + + </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="health-check" id="health-check">Dynamic Health Checks</a></h2> + + + <p> + Before httpd proxies a request to a worker, it can <em>"test"</em> if that worker + is available via setting the <code>ping</code> parameter for that worker using + <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code>. Oftentimes it is + more useful to check the health of the workers <em>out of band</em>, in a + dynamic fashion. This is achieved in Apache httpd by the + <code class="module"><a href="../mod/mod_proxy_hcheck.html">mod_proxy_hcheck</a></code> module. + </p> + + </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="status" id="status">BalancerMember status flags</a></h2> + + + <p> + In the <em>balancer-manager</em> the current state, or <em>status</em>, of a worker + is displayed and can be set/reset. The meanings of these statuses are as follows: + </p> + <table class="bordered"> + <tr><th>Flag</th><th>String</th><th>Description</th></tr> + <tr><td> </td><td><em>Ok</em></td><td>Worker is available</td></tr> + <tr><td> </td><td><em>Init</em></td><td>Worker has been initialized</td></tr> + <tr><td><code>D</code></td><td><em>Dis</em></td><td>Worker is disabled and will not accept any requests; will be + automatically retried.</td></tr> + <tr><td><code>S</code></td><td><em>Stop</em></td><td>Worker is administratively stopped; will not accept requests + and will not be automatically retried</td></tr> + <tr><td><code>I</code></td><td><em>Ign</em></td><td>Worker is in ignore-errors mode and will always be considered available.</td></tr> + <tr><td><code>R</code></td><td><em>Spar</em></td><td>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.</td></tr> + <tr><td><code>H</code></td><td><em>Stby</em></td><td>Worker is in hot-standby mode and will only be used if no other + viable workers or spares are available in the balancer set.</td></tr> + <tr><td><code>E</code></td><td><em>Err</em></td><td>Worker is in an error state, usually due to failing pre-request check; + requests will not be proxied to this worker, but it will be retried depending on + the <code>retry</code> setting of the worker.</td></tr> + <tr><td><code>N</code></td><td><em>Drn</em></td><td>Worker is in drain mode and will only accept existing sticky sessions + destined for itself and ignore all other requests.</td></tr> + <tr><td><code>C</code></td><td><em>HcFl</em></td><td>Worker has failed dynamic health check and will not be used until it + passes subsequent health checks.</td></tr> + </table> + </div></div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="../en/howto/reverse_proxy.html" title="English"> en </a> | +<a href="../fr/howto/reverse_proxy.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p> +</div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. 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