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<html><head><meta charset="ISO-8859-1"><title>7.GFS Configuration and Virtual Hosts</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot"><link rel="home" href="index.html" title="YAZ User's Guide and Reference"><link rel="up" href="server.html" title="Chapter4.Generic server"><link rel="prev" href="server.invocation.html" title="6.Application Invocation"><link rel="next" href="asn.html" title="Chapter5.The Z39.50 ASN.1 Module"></head><body><link rel="stylesheet" type="text/css" href="common/style1.css"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">7.GFS Configuration and Virtual Hosts</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="server.invocation.html">Prev</a></td><th width="60%" align="center">Chapter4.Generic server</th><td width="20%" align="right"><a accesskey="n" href="asn.html">Next</a></td></tr></table><hr></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="server.vhosts"></a>7.GFS Configuration and Virtual Hosts</h2></div></div></div><p>
 The Virtual hosts mechanism allows a YAZ front-end server to
 support multiple back-ends. A back-end is selected on the basis of
 the TCP/IP binding (port+listening address) and/or the virtual host.
</p><p>
 A back-end can be configured to execute in a particular working
 directory. Or the YAZ front-end may perform CQL to RPN conversion, thus
 allowing traditional Z39.50 back-ends to be offered as a SRW/SRU
 service. SRW/SRU Explain information for a particular back-end may also
 be specified.
</p><p>
 For the HTTP protocol, the virtual host is specified in the Host header.
 For the Z39.50 protocol, the virtual host is specified as in the
 Initialize Request in the OtherInfo, OID 1.2.840.10003.10.1000.81.1.
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
  Not all Z39.50 clients allow the VHOST information to be set.
  For those, the selection of the back-end must rely on the
  TCP/IP information alone (port and address).
 </p></div><p>
 The YAZ front-end server uses XML to describe the back-end
 configurations. Command-line option <code class="literal">-f</code>
 specifies filename of the XML configuration.
</p><p>
 The configuration uses the root element <code class="literal">yazgfs</code>.
 This element includes a list of <code class="literal">listen</code> elements,
 followed by one or more <code class="literal">server</code> elements.
</p><p>
 The <code class="literal">listen</code> describes listener (transport end point),
 such as TCP/IP, Unix file socket or SSL server. Content for
 a listener:
 </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">CDATA (required)</span></dt><dd><p>
     The CDATA for the <code class="literal">listen</code> element holds the
     listener string, such as <code class="literal">tcp:@:210</code>,
     <code class="literal">tcp:server1:2100</code>,
     etc.
    </p></dd><dt><span class="term">attribute <code class="literal">id</code> (optional)</span></dt><dd><p>
      Identifier for this listener. This may be referred to from
      server sections.
     </p></dd></dl></div><p>
 </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
   We expect more information to be added for the listen section in
   a future version, such as CERT file for SSL servers.
  </p></div><p>
</p><p>
 The <code class="literal">server</code> describes a server and the parameters
 for this server type. Content for a server:
 </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">attribute <code class="literal">id</code> (optional)</span></dt><dd><p>
     Identifier for this server. Currently not used for anything,
     but it might be for logging purposes.
   </p></dd><dt><span class="term">attribute <code class="literal">listenref</code> (optional)</span></dt><dd><p>
     Specifies one or more listeners for this server. Each server ID is
     separated by a comma.
     If this attribute is not given, the server is accessible from all
     listeners. In order for the server to be used for real, however, the
     virtual host must match if specified in the configuration.
    </p></dd><dt><span class="term">element <code class="literal">config</code> (optional)</span></dt><dd><p>
     Specifies the server configuration. This is equivalent
     to the config specified using command line option
     <code class="literal">-c</code>.
    </p></dd><dt><span class="term">element <code class="literal">directory</code> (optional)</span></dt><dd><p>
     Specifies a working directory for this backend server. If
     specified, the YAZ frontend changes current working directory
     to this directory whenever a backend of this type is
     started (backend handler bend_start), stopped (backend handler hand_stop)
     and initialized (bend_init).
    </p></dd><dt><span class="term">element <code class="literal">host</code> (optional)</span></dt><dd><p>
     Specifies the virtual host for this server. If this is specified
     a client <span class="emphasis"><em>must</em></span> specify this host string in
     order to use this backend.
    </p></dd><dt><span class="term">element <code class="literal">cql2rpn</code> (optional)</span></dt><dd><p>
     Specifies a filename that includes CQL to RPN conversion for this
     backend server. See <a class="xref" href="tools.html#cql.to.rpn" title="1.3.4.Specification of CQL to RPN mappings">Section1.3.4, &#8220;Specification of CQL to RPN mappings&#8221;</a>.
     If given, the backend server will only "see" a Type-1/RPN query.
    </p></dd><dt><span class="term">element <code class="literal">ccl2rpn</code> (optional)</span></dt><dd><p>
     Specifies a filename that includes CCL to RPN conversion for this
     backend server. See <a class="xref" href="tools.html#ccl.qualifiers" title="1.2.2.CCL Qualifiers">Section1.2.2, &#8220;CCL Qualifiers&#8221;</a>.
     If given, the backend server will only "see" a Type-1/RPN query.
    </p></dd><dt><span class="term">element <code class="literal">stylesheet</code> (optional)</span></dt><dd><p>
     Specifies the stylesheet reference to be part of SRU HTTP responses
     when the client does not specify one. If none is given, then if
     the client does not specify one, then no stylesheet reference is part of the
     SRU HTTP response.
    </p></dd><dt><span class="term">element <code class="literal">client_query_charset</code> (optional)</span></dt><dd><p>
     If specified, a conversion from the character set given to UTF-8 is
     performed by the generic frontend server. It is only executed for
     Z39.50 search requests (SRU/Solr are assumed to be UTF-8 encoded already).
    </p></dd><dt><span class="term">element <code class="literal">docpath</code> (optional)</span></dt><dd><p>
     Specifies a path for local file access using HTTP. All URLs with
     a leading prefix (/ excluded) that matches the value of <code class="literal">docpath</code>
     are used for file access. For example, if the server is to offer
     access in directory <code class="literal">xsl</code>, the docpath would be
     <code class="literal">xsl</code> and all URLs of the form
     <code class="literal">http://host/xsl</code> will result in a local file access.
    </p></dd><dt><span class="term">element <code class="literal">explain</code> (optional)</span></dt><dd><p>
     Specifies SRW/SRU ZeeRex content for this server. Copied verbatim
     to the client. As things are now, some of the Explain content
     seem redundant because host information, etc. is also stored
     elsewhere.
    </p></dd><dt><span class="term">element <code class="literal">maximumrecordsize</code> (optional)</span></dt><dd><p>
     Specifies maximum record size/message size, in bytes. This
     value also serves as the maximum size of <span class="emphasis"><em>incoming</em></span>
     packages (for Record Updates etc). It's the same value as that
     given by the <code class="literal">-k</code> option.
    </p></dd><dt><span class="term">element <code class="literal">retrievalinfo</code> (optional)</span></dt><dd><p>
     Enables the retrieval facility to support conversions and
     specifications of record formats/types.
     See <a class="xref" href="tools.retrieval.html" title="6.Retrieval Facility">Section6, &#8220;Retrieval Facility&#8221;</a> for
     more information.
    </p></dd></dl></div><p>
</p><p>
 The XML below configures a server that accepts connections from
 two ports, TCP/IP port 9900 and a local UNIX file socket.
 We name the TCP/IP server <code class="literal">public</code> and the
 other server <code class="literal">internal</code>.
 </p><pre class="screen">
  
 &lt;yazgfs&gt;
  &lt;listen id="public"&gt;tcp:@:9900&lt;/listen&gt;
  &lt;listen id="internal"&gt;unix:/var/tmp/socket&lt;/listen&gt;
  &lt;server id="server1"&gt;
    &lt;host&gt;server1.mydomain&lt;/host&gt;
    &lt;directory&gt;/var/www/s1&lt;/directory&gt;
    &lt;config&gt;config.cfg&lt;/config&gt;
  &lt;/server&gt;
  &lt;server id="server2" listenref="public,internal"&gt;
    &lt;host&gt;server2.mydomain&lt;/host&gt;
    &lt;directory&gt;/var/www/s2&lt;/directory&gt;
    &lt;config&gt;config.cfg&lt;/config&gt;
    &lt;cql2rpn&gt;../etc/pqf.properties&lt;/cql2rpn&gt;
    &lt;explain xmlns="http://explain.z3950.org/dtd/2.0/"&gt;
      &lt;serverInfo&gt;
        &lt;host&gt;server2.mydomain&lt;/host&gt;
        &lt;port&gt;9900&lt;/port&gt;
        &lt;database&gt;a&lt;/database&gt;
      &lt;/serverInfo&gt;
    &lt;/explain&gt;
  &lt;/server&gt;
  &lt;server id="server3" listenref="internal"&gt;
    &lt;directory&gt;/var/www/s3&lt;/directory&gt;
    &lt;config&gt;config.cfg&lt;/config&gt;
  &lt;/server&gt;
 &lt;/yazgfs&gt;

 </pre><p>
 There are three configured backend servers. The first two
 servers, <code class="literal">"server1"</code> and <code class="literal">"server2"</code>,
 can be reached by both listener addresses.
 <code class="literal">"server1"</code> is reached by all (two) since no
  <code class="literal">listenref</code> attribute is specified.
 <code class="literal">"server2"</code> is reached by the two listeners specified.
 In order to distinguish between the two, a virtual host has
 been specified for each server in the <code class="literal">host</code>
 elements.
</p><p>
 For <code class="literal">"server2"</code> elements for CQL to RPN conversion
 is supported and explain information has been added (a short one here
 to keep the example small).
</p><p>
 The third server, <code class="literal">"server3"</code> can only be reached
 via listener <code class="literal">"internal"</code>.
</p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="server.invocation.html">Prev</a></td><td width="20%" align="center"><a accesskey="u" href="server.html">Up</a></td><td width="40%" align="right"><a accesskey="n" href="asn.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">6.Application Invocation</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">Chapter5.The Z39.50 ASN.1 Module</td></tr></table></div></body></html>