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89565ae25f070411b0b32505b798195a9c98a1c2mturk<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="/faq/">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p>
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3f08db06526d6901aa08c110b5bc7dde6bc39905nd<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 2.5</a> > <a href="./">Modules</a></div>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<div id="preamble"><h1>Apache Module mod_proxy_ajp</h1>
412bf2d2fd3ee0608bc0767e2281e47ea317963end<p><span>Available Languages: </span><a href="/en/mod/mod_proxy_ajp.html" title="English"> en </a> |
f086b4b402fa9a2fefc7dda85de2a3cc1cd0a654rjung<a href="/ja/mod/mod_proxy_ajp.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>AJP support module for
89565ae25f070411b0b32505b798195a9c98a1c2mturk<code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code></td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>proxy_ajp_module</td></tr>
e5ce3ac0e9b720c0fa23782e29168a0810697fdetakashi<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>mod_proxy_ajp.c</td></tr>
7aa680104c2f453afc31222656d3ad33fab33ff2nd<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.1 and later</td></tr></table>
9a58dc6a2b26ec128b1270cf48810e705f1a90dbsf <p>This module <em>requires</em> the service of <code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code>. It provides support for the
89565ae25f070411b0b32505b798195a9c98a1c2mturk <code>Apache JServ Protocol version 1.3</code> (hereafter
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Thus, in order to get the ability of handling <code>AJP13</code>
89565ae25f070411b0b32505b798195a9c98a1c2mturk protocol, <code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code> and
89565ae25f070411b0b32505b798195a9c98a1c2mturk <code class="module"><a href="/mod/mod_proxy_ajp.html">mod_proxy_ajp</a></code> have to be present in the server.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Do not enable proxying until you have <a href="mod_proxy.html#access">secured your server</a>. Open proxy
89565ae25f070411b0b32505b798195a9c98a1c2mturk servers are dangerous both to your network and to the Internet at
89565ae25f070411b0b32505b798195a9c98a1c2mturk<div id="quickview"><h3 class="directives">Directives</h3>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<p>This module provides no
89565ae25f070411b0b32505b798195a9c98a1c2mturk directives.</p>
eb8ce30512a5e12d6b74971d9add7176fbee8e23rbowen<li><img alt="" src="/images/down.gif" /> <a href="#usage">Usage</a></li>
b97955fc7710323d2352a6c6f514fec02649e12dcovener<li><img alt="" src="/images/down.gif" /> <a href="#env">Environment Variables</a></li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<li><img alt="" src="/images/down.gif" /> <a href="#overviewprotocol">Overview of the protocol</a></li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<li><img alt="" src="/images/down.gif" /> <a href="#basppacketstruct">Basic Packet Structure</a></li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<li><img alt="" src="/images/down.gif" /> <a href="#rpacetstruct">Request Packet Structure</a></li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<li><img alt="" src="/images/down.gif" /> <a href="#resppacketstruct">Response Packet Structure</a></li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<li><code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code></li>
b97955fc7710323d2352a6c6f514fec02649e12dcovener<li><a href="/env.html">Environment Variable documentation</a></li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
eb8ce30512a5e12d6b74971d9add7176fbee8e23rbowen <p>This module is used to reverse proxy to a backend application server
eb8ce30512a5e12d6b74971d9add7176fbee8e23rbowen (e.g. Apache Tomcat) using the AJP13 protocol. The usage is similar to
995458e5b966bd8d44be7124c88ff6dd4e7a2736nd an HTTP reverse proxy, but uses the <code>ajp://</code> prefix:</p>
e487d6c09669296f94a5190cc34586a98e624a00nd <div class="example"><h3>Simple Reverse Proxy</h3><pre class="prettyprint lang-config">
e487d6c09669296f94a5190cc34586a98e624a00nd <div class="example"><h3>Balancer Reverse Proxy</h3><pre class="prettyprint lang-config">
2d24960fa1e6afc7ad5f1bf58b6b3f5e7a9a3497humbedooh<Proxy balancer://cluster>
2d24960fa1e6afc7ad5f1bf58b6b3f5e7a9a3497humbedooh BalancerMember ajp://app1.example.com:8009 loadfactor=1
2d24960fa1e6afc7ad5f1bf58b6b3f5e7a9a3497humbedooh BalancerMember ajp://app2.example.com:8009 loadfactor=2
2d24960fa1e6afc7ad5f1bf58b6b3f5e7a9a3497humbedooh ProxySet lbmethod=bytraffic
2d24960fa1e6afc7ad5f1bf58b6b3f5e7a9a3497humbedooh</Proxy>
995458e5b966bd8d44be7124c88ff6dd4e7a2736nd <p>Note that usually no
eb8ce30512a5e12d6b74971d9add7176fbee8e23rbowen <code class="directive"><a href="/mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code>
eb8ce30512a5e12d6b74971d9add7176fbee8e23rbowen directive is necessary. The AJP request includes the original host
eb8ce30512a5e12d6b74971d9add7176fbee8e23rbowen header given to the proxy, and the application server can be expected
eb8ce30512a5e12d6b74971d9add7176fbee8e23rbowen to generate self-referential headers relative to this host, so no
995458e5b966bd8d44be7124c88ff6dd4e7a2736nd rewriting is necessary.</p>
995458e5b966bd8d44be7124c88ff6dd4e7a2736nd <p>The main exception is when the URL path on the proxy differs from that
eb8ce30512a5e12d6b74971d9add7176fbee8e23rbowen backend. In this case, a redirect header can be rewritten relative to the
995458e5b966bd8d44be7124c88ff6dd4e7a2736nd original host URL (not the backend <code>ajp://</code> URL), for
995458e5b966bd8d44be7124c88ff6dd4e7a2736nd example:</p>
e487d6c09669296f94a5190cc34586a98e624a00nd <div class="example"><h3>Rewriting Proxied Path</h3><pre class="prettyprint lang-config">
2d24960fa1e6afc7ad5f1bf58b6b3f5e7a9a3497humbedoohProxyPass /apps/foo ajp://backend.example.com:8009/foo
2d24960fa1e6afc7ad5f1bf58b6b3f5e7a9a3497humbedoohProxyPassReverse /apps/foo http://www.example.com/foo
995458e5b966bd8d44be7124c88ff6dd4e7a2736nd <p>However, it is usually better to deploy the application on the backend
eb8ce30512a5e12d6b74971d9add7176fbee8e23rbowen server at the same path as the proxy rather than to take this approach.
eb8ce30512a5e12d6b74971d9add7176fbee8e23rbowen</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
b97955fc7710323d2352a6c6f514fec02649e12dcovener<h2><a name="env" id="env">Environment Variables</a></h2>
9a58dc6a2b26ec128b1270cf48810e705f1a90dbsf <p>Environment variables whose names have the prefix <code>AJP_</code>
9a58dc6a2b26ec128b1270cf48810e705f1a90dbsf are forwarded to the origin server as AJP request attributes
b97955fc7710323d2352a6c6f514fec02649e12dcovener (with the AJP_ prefix removed from the name of the key).</p>
b97955fc7710323d2352a6c6f514fec02649e12dcovener</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<h2><a name="overviewprotocol" id="overviewprotocol">Overview of the protocol</a></h2>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The <code>AJP13</code> protocol is packet-oriented. A binary format
89565ae25f070411b0b32505b798195a9c98a1c2mturk was presumably chosen over the more readable plain text for reasons of
89565ae25f070411b0b32505b798195a9c98a1c2mturk performance. The web server communicates with the servlet container over
89565ae25f070411b0b32505b798195a9c98a1c2mturk TCP connections. To cut down on the expensive process of socket creation,
89565ae25f070411b0b32505b798195a9c98a1c2mturk the web server will attempt to maintain persistent TCP connections to the
89565ae25f070411b0b32505b798195a9c98a1c2mturk servlet container, and to reuse a connection for multiple request/response
89565ae25f070411b0b32505b798195a9c98a1c2mturk cycles.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Once a connection is assigned to a particular request, it will not be
89565ae25f070411b0b32505b798195a9c98a1c2mturk used for any others until the request-handling cycle has terminated. In
89565ae25f070411b0b32505b798195a9c98a1c2mturk other words, requests are not multiplexed over connections. This makes
89565ae25f070411b0b32505b798195a9c98a1c2mturk for much simpler code at either end of the connection, although it does
89565ae25f070411b0b32505b798195a9c98a1c2mturk cause more connections to be open at once.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Once the web server has opened a connection to the servlet container,
89565ae25f070411b0b32505b798195a9c98a1c2mturk the connection can be in one of the following states:</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <li> Idle <br /> No request is being handled over this connection. </li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <li> Assigned <br /> The connecton is handling a specific request.</li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Once a connection is assigned to handle a particular request, the basic
89565ae25f070411b0b32505b798195a9c98a1c2mturk request informaton (e.g. HTTP headers, etc) is sent over the connection in
89565ae25f070411b0b32505b798195a9c98a1c2mturk a highly condensed form (e.g. common strings are encoded as integers).
89565ae25f070411b0b32505b798195a9c98a1c2mturk Details of that format are below in Request Packet Structure. If there is a
89565ae25f070411b0b32505b798195a9c98a1c2mturk body to the request <code>(content-length > 0)</code>, that is sent in a
89565ae25f070411b0b32505b798195a9c98a1c2mturk separate packet immediately after.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>At this point, the servlet container is presumably ready to start
89565ae25f070411b0b32505b798195a9c98a1c2mturk processing the request. As it does so, it can send the
844def494f17cb1ab0983427d5c3939e1a03ff8cnd following messages back to the web server:</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <li>SEND_HEADERS <br />Send a set of headers back to the browser.</li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <li>SEND_BODY_CHUNK <br />Send a chunk of body data back to the browser.
89565ae25f070411b0b32505b798195a9c98a1c2mturk <li>GET_BODY_CHUNK <br />Get further data from the request if it hasn't all
89565ae25f070411b0b32505b798195a9c98a1c2mturk been transferred yet. This is necessary because the packets have a fixed
89565ae25f070411b0b32505b798195a9c98a1c2mturk maximum size and arbitrary amounts of data can be included the body of a
89565ae25f070411b0b32505b798195a9c98a1c2mturk request (for uploaded files, for example). (Note: this is unrelated to
89565ae25f070411b0b32505b798195a9c98a1c2mturk HTTP chunked tranfer).</li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <li>END_RESPONSE <br /> Finish the request-handling cycle.</li>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Each message is accompanied by a differently formatted packet of data.
89565ae25f070411b0b32505b798195a9c98a1c2mturk See Response Packet Structures below for details.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<h2><a name="basppacketstruct" id="basppacketstruct">Basic Packet Structure</a></h2>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>There is a bit of an XDR heritage to this protocol, but it differs
89565ae25f070411b0b32505b798195a9c98a1c2mturk in lots of ways (no 4 byte alignment, for example).</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Byte order: I am not clear about the endian-ness of the individual
89565ae25f070411b0b32505b798195a9c98a1c2mturk bytes. I'm guessing the bytes are little-endian, because that's what
89565ae25f070411b0b32505b798195a9c98a1c2mturk XDR specifies, and I'm guessing that sys/socket library is magically
89565ae25f070411b0b32505b798195a9c98a1c2mturk making that so (on the C side). If anyone with a better knowledge of
89565ae25f070411b0b32505b798195a9c98a1c2mturk socket calls can step in, that would be great.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>There are four data types in the protocol: bytes, booleans,
844def494f17cb1ab0983427d5c3939e1a03ff8cnd integers and strings.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <dd>A single byte, <code>1 = true</code>, <code>0 = false</code>.
89565ae25f070411b0b32505b798195a9c98a1c2mturk Using other non-zero values as true (i.e. C-style) may work in some places,
89565ae25f070411b0b32505b798195a9c98a1c2mturk but it won't in others.</dd>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <dd>A number in the range of <code>0 to 2^16 (32768)</code>. Stored in
89565ae25f070411b0b32505b798195a9c98a1c2mturk 2 bytes with the high-order byte first.</dd>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <dd>A variable-sized string (length bounded by 2^16). Encoded with
89565ae25f070411b0b32505b798195a9c98a1c2mturk the length packed into two bytes first, followed by the string
89565ae25f070411b0b32505b798195a9c98a1c2mturk (including the terminating '\0'). Note that the encoded length does
89565ae25f070411b0b32505b798195a9c98a1c2mturk <strong>not</strong> include the trailing '\0' -- it is like
89565ae25f070411b0b32505b798195a9c98a1c2mturk <code>strlen</code>. This is a touch confusing on the Java side, which
89565ae25f070411b0b32505b798195a9c98a1c2mturk is littered with odd autoincrement statements to skip over these
89565ae25f070411b0b32505b798195a9c98a1c2mturk terminators. I believe the reason this was done was to allow the C
89565ae25f070411b0b32505b798195a9c98a1c2mturk code to be extra efficient when reading strings which the servlet
89565ae25f070411b0b32505b798195a9c98a1c2mturk container is sending back -- with the terminating \0 character, the
89565ae25f070411b0b32505b798195a9c98a1c2mturk C code can pass around references into a single buffer, without copying.
89565ae25f070411b0b32505b798195a9c98a1c2mturk if the \0 was missing, the C code would have to copy things out in order
89565ae25f070411b0b32505b798195a9c98a1c2mturk to get its notion of a string.</dd>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>According to much of the code, the max packet size is <code>
89565ae25f070411b0b32505b798195a9c98a1c2mturk 8 * 1024 bytes (8K)</code>. The actual length of the packet is encoded in
89565ae25f070411b0b32505b798195a9c98a1c2mturk the header.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Packets sent from the server to the container begin with
89565ae25f070411b0b32505b798195a9c98a1c2mturk <code>0x1234</code>. Packets sent from the container to the server
89565ae25f070411b0b32505b798195a9c98a1c2mturk begin with <code>AB</code> (that's the ASCII code for A followed by the
89565ae25f070411b0b32505b798195a9c98a1c2mturk ASCII code for B). After those first two bytes, there is an integer
89565ae25f070411b0b32505b798195a9c98a1c2mturk (encoded as above) with the length of the payload. Although this might
89565ae25f070411b0b32505b798195a9c98a1c2mturk suggest that the maximum payload could be as large as 2^16, in fact, the
844def494f17cb1ab0983427d5c3939e1a03ff8cnd code sets the maximum to be 8K.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <td colspan="6"><em>Packet Format (Server->Container)</em></td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <td colspan="6"><em>Packet Format (Container->Server)</em></td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>For most packets, the first byte of the payload encodes the type of
89565ae25f070411b0b32505b798195a9c98a1c2mturk message. The exception is for request body packets sent from the server to
89565ae25f070411b0b32505b798195a9c98a1c2mturk the container -- they are sent with a standard packet header (<code>
89565ae25f070411b0b32505b798195a9c98a1c2mturk 0x1234</code> and then length of the packet), but without any prefix code
89565ae25f070411b0b32505b798195a9c98a1c2mturk after that.</p>
844def494f17cb1ab0983427d5c3939e1a03ff8cnd <p>The web server can send the following messages to the servlet
844def494f17cb1ab0983427d5c3939e1a03ff8cnd container:</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <td>Begin the request-processing cycle with the following data</td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <td>The web server asks the container to shut itself down.</td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <td>The web server asks the container to take control
89565ae25f070411b0b32505b798195a9c98a1c2mturk (secure login phase).</td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <td>The web server asks the container to respond quickly with a CPong.
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>To ensure some basic security, the container will only actually do the
89565ae25f070411b0b32505b798195a9c98a1c2mturk <code>Shutdown</code> if the request comes from the same machine on which
89565ae25f070411b0b32505b798195a9c98a1c2mturk it's hosted.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The first <code>Data</code> packet is send immediatly after the
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The servlet container can send the following types of messages to the
844def494f17cb1ab0983427d5c3939e1a03ff8cnd webserver:</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <td>Send a chunk of the body from the servlet container to the web
89565ae25f070411b0b32505b798195a9c98a1c2mturk server (and presumably, onto the browser). </td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <td>Send the response headers from the servlet container to the web
89565ae25f070411b0b32505b798195a9c98a1c2mturk server (and presumably, onto the browser).</td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <td>Marks the end of the response (and thus the request-handling cycle).
89565ae25f070411b0b32505b798195a9c98a1c2mturk <td>Get further data from the request if it hasn't all been
89565ae25f070411b0b32505b798195a9c98a1c2mturk transferred yet.</td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Each of the above messages has a different internal structure, detailed
89565ae25f070411b0b32505b798195a9c98a1c2mturk</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<h2><a name="rpacetstruct" id="rpacetstruct">Request Packet Structure</a></h2>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>For messages from the server to the container of type
89565ae25f070411b0b32505b798195a9c98a1c2mturkAJP13_FORWARD_REQUEST :=
89565ae25f070411b0b32505b798195a9c98a1c2mturk prefix_code (byte) 0x02 = JK_AJP13_FORWARD_REQUEST
89565ae25f070411b0b32505b798195a9c98a1c2mturk method (byte)
89565ae25f070411b0b32505b798195a9c98a1c2mturk protocol (string)
89565ae25f070411b0b32505b798195a9c98a1c2mturk req_uri (string)
89565ae25f070411b0b32505b798195a9c98a1c2mturk remote_addr (string)
89565ae25f070411b0b32505b798195a9c98a1c2mturk remote_host (string)
89565ae25f070411b0b32505b798195a9c98a1c2mturk server_name (string)
89565ae25f070411b0b32505b798195a9c98a1c2mturk server_port (integer)
89565ae25f070411b0b32505b798195a9c98a1c2mturk is_ssl (boolean)
89565ae25f070411b0b32505b798195a9c98a1c2mturk num_headers (integer)
89565ae25f070411b0b32505b798195a9c98a1c2mturk request_headers *(req_header_name req_header_value)
89565ae25f070411b0b32505b798195a9c98a1c2mturk attributes *(attribut_name attribute_value)
89565ae25f070411b0b32505b798195a9c98a1c2mturk request_terminator (byte) OxFF
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The <code>request_headers</code> have the following structure:
9a58dc6a2b26ec128b1270cf48810e705f1a90dbsfreq_header_name :=
89565ae25f070411b0b32505b798195a9c98a1c2mturk sc_req_header_name | (string) [see below for how this is parsed]
89565ae25f070411b0b32505b798195a9c98a1c2mturksc_req_header_name := 0xA0xx (integer)
89565ae25f070411b0b32505b798195a9c98a1c2mturkreq_header_value := (string)
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The <code>attributes</code> are optional and have the following
89565ae25f070411b0b32505b798195a9c98a1c2mturk structure:</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturkattribute_name := sc_a_name | (sc_a_req_attribute string)
89565ae25f070411b0b32505b798195a9c98a1c2mturkattribute_value := (string)
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Not that the all-important header is <code>content-length</code>,
89565ae25f070411b0b32505b798195a9c98a1c2mturk because it determines whether or not the container looks for another
89565ae25f070411b0b32505b798195a9c98a1c2mturk packet immediately.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <h3>Detailed description of the elements of Forward Request
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>For all requests, this will be 2. See above for details on other Prefix
9a58dc6a2b26ec128b1270cf48810e705f1a90dbsf <p>Later version of ajp13, will transport
89565ae25f070411b0b32505b798195a9c98a1c2mturk additional methods, even if they are not in this list.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <h3>protocol, req_uri, remote_addr, remote_host, server_name,
89565ae25f070411b0b32505b798195a9c98a1c2mturk server_port, is_ssl</h3>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>These are all fairly self-explanatory. Each of these is required, and
89565ae25f070411b0b32505b798195a9c98a1c2mturk will be sent for every request.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The structure of <code>request_headers</code> is the following:
89565ae25f070411b0b32505b798195a9c98a1c2mturk First, the number of headers <code>num_headers</code> is encoded.
89565ae25f070411b0b32505b798195a9c98a1c2mturk Then, a series of header name <code>req_header_name</code> / value
89565ae25f070411b0b32505b798195a9c98a1c2mturk Common header names are encoded as integers,
89565ae25f070411b0b32505b798195a9c98a1c2mturk to save space. If the header name is not in the list of basic headers,
89565ae25f070411b0b32505b798195a9c98a1c2mturk it is encoded normally (as a string, with prefixed length). The list of
89565ae25f070411b0b32505b798195a9c98a1c2mturk common headers <code>sc_req_header_name</code>and their codes
89565ae25f070411b0b32505b798195a9c98a1c2mturk is as follows (all are case-sensitive):</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>Name</td><td>Code value</td><td>Code name</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>accept</td><td>0xA001</td><td>SC_REQ_ACCEPT</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>accept-charset</td><td>0xA002</td><td>SC_REQ_ACCEPT_CHARSET
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>accept-encoding</td><td>0xA003</td><td>SC_REQ_ACCEPT_ENCODING
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>accept-language</td><td>0xA004</td><td>SC_REQ_ACCEPT_LANGUAGE
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>authorization</td><td>0xA005</td><td>SC_REQ_AUTHORIZATION</td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>connection</td><td>0xA006</td><td>SC_REQ_CONNECTION</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>content-type</td><td>0xA007</td><td>SC_REQ_CONTENT_TYPE</td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>content-length</td><td>0xA008</td><td>SC_REQ_CONTENT_LENGTH</td>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>cookie</td><td>0xA009</td><td>SC_REQ_COOKIE</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>cookie2</td><td>0xA00A</td><td>SC_REQ_COOKIE2</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>host</td><td>0xA00B</td><td>SC_REQ_HOST</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>pragma</td><td>0xA00C</td><td>SC_REQ_PRAGMA</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>referer</td><td>0xA00D</td><td>SC_REQ_REFERER</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <tr><td>user-agent</td><td>0xA00E</td><td>SC_REQ_USER_AGENT</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The Java code that reads this grabs the first two-byte integer and if
89565ae25f070411b0b32505b798195a9c98a1c2mturk it sees an <code>'0xA0'</code> in the most significant
89565ae25f070411b0b32505b798195a9c98a1c2mturk byte, it uses the integer in the second byte as an index into an array of
89565ae25f070411b0b32505b798195a9c98a1c2mturk header names. If the first byte is not <code>0xA0</code>, it assumes that
89565ae25f070411b0b32505b798195a9c98a1c2mturk the two-byte integer is the length of a string, which is then read in.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>This works on the assumption that no header names will have length
89565ae25f070411b0b32505b798195a9c98a1c2mturk greater than <code>0x9999 (==0xA000 - 1)</code>, which is perfectly
89565ae25f070411b0b32505b798195a9c98a1c2mturk reasonable, though somewhat arbitrary.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk important. If it is present and non-zero, the container assumes that
89565ae25f070411b0b32505b798195a9c98a1c2mturk the request has a body (a POST request, for example), and immediately
89565ae25f070411b0b32505b798195a9c98a1c2mturk reads a separate packet off the input stream to get that body.
89565ae25f070411b0b32505b798195a9c98a1c2mturk (e.g. <code>?context</code>) are all optional. For each, there is a
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem single byte code to indicate the type of attribute, and then its value
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem (string or integer). They can be sent in any order (though the C code
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem always sends them in the order listed below). A special terminating code
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem is sent to signal the end of the list of optional attributes. The list of
89565ae25f070411b0b32505b798195a9c98a1c2mturk byte codes is:</p>
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>Information</td><td>Code Value</td><td>Type Of Value</td><td>Note</td></tr>
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?context</td><td>0x01</td><td>-</td><td>Not currently implemented
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?servlet_path</td><td>0x02</td><td>-</td><td>Not currently implemented
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?remote_user</td><td>0x03</td><td>String</td><td /></tr>
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?auth_type</td><td>0x04</td><td>String</td><td /></tr>
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?query_string</td><td>0x05</td><td>String</td><td /></tr>
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?jvm_route</td><td>0x06</td><td>String</td><td /></tr>
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?ssl_cert</td><td>0x07</td><td>String</td><td /></tr>
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?ssl_cipher</td><td>0x08</td><td>String</td><td /></tr>
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?ssl_session</td><td>0x09</td><td>String</td><td /></tr>
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?req_attribute</td><td>0x0A</td><td>String</td><td>Name (the name of the
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>?ssl_key_size</td><td>0x0B</td><td>Integer</td><td /></tr>
12eb0882b553ff0fe7637fccff3fd74da4f7ffd3rpluem <tr><td>are_done</td><td>0xFF</td><td>-</td><td>request_terminator</td></tr>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The <code>context</code> and <code>servlet_path</code> are not
89565ae25f070411b0b32505b798195a9c98a1c2mturk currently set by the C code, and most of the Java code completely ignores
89565ae25f070411b0b32505b798195a9c98a1c2mturk whatever is sent over for those fields (and some of it will actually break
89565ae25f070411b0b32505b798195a9c98a1c2mturk if a string is sent along after one of those codes). I don't know if this
89565ae25f070411b0b32505b798195a9c98a1c2mturk is a bug or an unimplemented feature or just vestigial code, but it's
89565ae25f070411b0b32505b798195a9c98a1c2mturk missing from both sides of the connection.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The <code>remote_user</code> and <code>auth_type</code> presumably
89565ae25f070411b0b32505b798195a9c98a1c2mturk refer to HTTP-level authentication, and communicate the remote user's
89565ae25f070411b0b32505b798195a9c98a1c2mturk username and the type of authentication used to establish their identity
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The <code>query_string</code>, <code>ssl_cert</code>,
89565ae25f070411b0b32505b798195a9c98a1c2mturk <code>ssl_cipher</code>, and <code>ssl_session</code> refer to the
89565ae25f070411b0b32505b798195a9c98a1c2mturk corresponding pieces of HTTP and HTTPS.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The <code>jvm_route</code>, is used to support sticky
89565ae25f070411b0b32505b798195a9c98a1c2mturk sessions -- associating a user's sesson with a particular Tomcat instance
89565ae25f070411b0b32505b798195a9c98a1c2mturk in the presence of multiple, load-balancing servers.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Beyond this list of basic attributes, any number of other attributes
89565ae25f070411b0b32505b798195a9c98a1c2mturk can be sent via the <code>req_attribute</code> code <code>0x0A</code>.
89565ae25f070411b0b32505b798195a9c98a1c2mturk A pair of strings to represent the attribute name and value are sent
89565ae25f070411b0b32505b798195a9c98a1c2mturk immediately after each instance of that code. Environment values are passed
89565ae25f070411b0b32505b798195a9c98a1c2mturk in via this method.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Finally, after all the attributes have been sent, the attribute
89565ae25f070411b0b32505b798195a9c98a1c2mturk terminator, <code>0xFF</code>, is sent. This signals both the end of the
89565ae25f070411b0b32505b798195a9c98a1c2mturk list of attributes and also then end of the Request Packet.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
89565ae25f070411b0b32505b798195a9c98a1c2mturk<h2><a name="resppacketstruct" id="resppacketstruct">Response Packet Structure</a></h2>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>for messages which the container can send back to the server.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturkAJP13_SEND_BODY_CHUNK :=
89565ae25f070411b0b32505b798195a9c98a1c2mturk prefix_code 3
89565ae25f070411b0b32505b798195a9c98a1c2mturk chunk_length (integer)
89565ae25f070411b0b32505b798195a9c98a1c2mturk chunk *(byte)
c32f47bb60db3b2ae0912e881597f7c7de6fdad9pctony chunk_terminator (byte) Ox00
89565ae25f070411b0b32505b798195a9c98a1c2mturkAJP13_SEND_HEADERS :=
89565ae25f070411b0b32505b798195a9c98a1c2mturk prefix_code 4
89565ae25f070411b0b32505b798195a9c98a1c2mturk http_status_code (integer)
89565ae25f070411b0b32505b798195a9c98a1c2mturk http_status_msg (string)
89565ae25f070411b0b32505b798195a9c98a1c2mturk num_headers (integer)
89565ae25f070411b0b32505b798195a9c98a1c2mturk response_headers *(res_header_name header_value)
89565ae25f070411b0b32505b798195a9c98a1c2mturkres_header_name :=
89565ae25f070411b0b32505b798195a9c98a1c2mturk sc_res_header_name | (string) [see below for how this is parsed]
89565ae25f070411b0b32505b798195a9c98a1c2mturksc_res_header_name := 0xA0 (byte)
89565ae25f070411b0b32505b798195a9c98a1c2mturkheader_value := (string)
89565ae25f070411b0b32505b798195a9c98a1c2mturkAJP13_END_RESPONSE :=
89565ae25f070411b0b32505b798195a9c98a1c2mturk prefix_code 5
89565ae25f070411b0b32505b798195a9c98a1c2mturk reuse (boolean)
89565ae25f070411b0b32505b798195a9c98a1c2mturkAJP13_GET_BODY_CHUNK :=
89565ae25f070411b0b32505b798195a9c98a1c2mturk prefix_code 6
89565ae25f070411b0b32505b798195a9c98a1c2mturk requested_length (integer)
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The chunk is basically binary data, and is sent directly back to the
89565ae25f070411b0b32505b798195a9c98a1c2mturk browser.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The status code and message are the usual HTTP things
89565ae25f070411b0b32505b798195a9c98a1c2mturk (e.g. <code>200</code> and <code>OK</code>). The response header names are
89565ae25f070411b0b32505b798195a9c98a1c2mturk encoded the same way the request header names are. See header_encoding above
c20b8f35a22c3a19f0f6390f7aba054ca95dd92eerikabele for details about how the codes are distinguished from the strings.<br />
89565ae25f070411b0b32505b798195a9c98a1c2mturk The codes for common headers are:</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p> After the code or the string header name, the header value is
89565ae25f070411b0b32505b798195a9c98a1c2mturk immediately encoded.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>Signals the end of this request-handling cycle. If the
89565ae25f070411b0b32505b798195a9c98a1c2mturk <code>reuse</code> flag is true <code>(==1)</code>, this TCP connection can
89565ae25f070411b0b32505b798195a9c98a1c2mturk now be used to handle new incoming requests. If <code>reuse</code> is false
89565ae25f070411b0b32505b798195a9c98a1c2mturk (anything other than 1 in the actual C code), the connection should
89565ae25f070411b0b32505b798195a9c98a1c2mturk be closed.</p>
89565ae25f070411b0b32505b798195a9c98a1c2mturk <p>The container asks for more data from the request (If the body was
89565ae25f070411b0b32505b798195a9c98a1c2mturk too large to fit in the first packet sent over or when the request is
89565ae25f070411b0b32505b798195a9c98a1c2mturk chuncked). The server will send a body packet back with an amount of data
89565ae25f070411b0b32505b798195a9c98a1c2mturk which is the minimum of the <code>request_length</code>, the maximum send
89565ae25f070411b0b32505b798195a9c98a1c2mturk body size <code>(8186 (8 Kbytes - 6))</code>, and the number of bytes
89565ae25f070411b0b32505b798195a9c98a1c2mturk actually left to send from the request body.<br />
89565ae25f070411b0b32505b798195a9c98a1c2mturk If there is no more data in the body (i.e. the servlet container is
89565ae25f070411b0b32505b798195a9c98a1c2mturk trying to read past the end of the body), the server will send back an
89565ae25f070411b0b32505b798195a9c98a1c2mturk <em>empty</em> packet, which is a body packet with a payload length of 0.
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