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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 | <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>7. GFS Configuration and Virtual Hosts</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2"><link rel="home" href="index.html" title="YAZ User's Guide and Reference"><link rel="up" href="server.html" title="Chapter 4. Generic server"><link rel="prev" href="server.invocation.html" title="6. Application Invocation"><link rel="next" href="asn.html" title="Chapter 5. 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">Chapter 4. Generic server</th><td width="20%" align="right"> <a accesskey="n" href="asn.html">Next</a></td></tr></table><hr></div><div class="sect1" title="7. GFS Configuration and Virtual Hosts"><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 frontend server to
support multiple backends. A backend is selected on the basis of
the TCP/IP binding (port+listening adddress) and/or the virtual host.
</p><p>
A backend can be configured to execute in a particular working
directory. Or the YAZ frontend may perform CQL to RPN conversion, thus
allowing traditional Z39.50 backends to be offered as a SRW/SRU
service. SRW/SRU Explain information for a particular backend 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" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
Not all Z39.50 clients allows the VHOST information to be set.
For those the selection of the backend must rely on the
TCP/IP information alone (port and address).
</p></div><p>
The YAZ frontend server uses XML to describe the backend
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><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" title="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><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 listener for this server. If this attribute is not
given, the server is accessible from all listener. In order
for the server to be used for real, howeever, 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
specifid, the YAZ fronend 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">Section 1.3.4, “Specification of CQL to RPN mappings”</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">Section 1.2.2, “CCL Qualifiers”</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 neither this is given, nor
the client specifies one, no stylesheet reference is part of the
SRU HTTP response.
</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 (/ exluded) that matches the value of docpath
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/exl</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
seeem 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 servers as 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 supporting conversions and
specifications of record formats/types.
See <a class="xref" href="tools.retrieval.html" title="6. Retrieval Facility">Section 6, “Retrieval Facility”</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">
<yazgfs>
<listen id="public">tcp:@:9900</listen>
<listen id="internal">unix:/var/tmp/socket</listen>
<server id="server1">
<host>server1.mydomain</host>
<directory>/var/www/s1</directory>
<config>config.cfg</config>
</server>
<server id="server2">
<host>server2.mydomain</host>
<directory>/var/www/s2</directory>
<config>config.cfg</config>
<cql2rpn>../etc/pqf.properties</cql2rpn>
<explain xmlns="http://explain.z3950.org/dtd/2.0/">
<serverInfo>
<host>server2.mydomain</host>
<port>9900</port>
<database>a</database>
</serverInfo>
</explain>
</server>
<server id="server3" listenref="internal">
<directory>/var/www/s3</directory>
<config>config.cfg</config>
</server>
</yazgfs>
</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 - since
no <code class="literal">listenref</code> attribute is specified.
In order to distinguish between the two a virtual host has
been specified for each of 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"> Chapter 5. The Z39.50 ASN.1 Module</td></tr></table></div></body></html>
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