GFS: Allow multiple listenrefs YAZ-554

[yaz-moved-to-github.git] / doc / gfs-virtual.xml

diff --git a/doc/gfs-virtual.xml b/doc/gfs-virtual.xml
index d307f62..1250331 100644 (file)
--- a/doc/gfs-virtual.xml
+++ b/doc/gfs-virtual.xml
@@ -1,6 +1,5 @@
-<!-- 
-   $Id: gfs-virtual.xml,v 1.1 2005-03-13 21:43:00 adam Exp $
-   Description of the virtual hosts mechanism in YAZ GFS
+<!--
+   Description of the virtual host mechanism in YAZ GFS

    Included in both manual and man page for yaz-ztest
 -->
 
    Included in both manual and man page for yaz-ztest
 -->
 

@@ -10,6 +9,13 @@
  the TCP/IP binding (port+listening adddress) and/or the virtual host.
 </para>
 <para>
  the TCP/IP binding (port+listening adddress) and/or the virtual host.
 </para>
 <para>

+ 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.
+</para>
+<para>

  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.
  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.

@@ -23,7 +29,7 @@
 </note>
 <para>
  The YAZ frontend server uses XML to describe the backend
 </note>
 <para>
  The YAZ frontend server uses XML to describe the backend

- configurations. Command-line option <literal>-f</literal> 
+ configurations. Command-line option <literal>-f</literal>

  specifies filename of the XML configuration.
 </para>
 <para>
  specifies filename of the XML configuration.
 </para>
 <para>

@@ -33,44 +39,227 @@
 </para>
 <para>
  The <literal>listen</literal> describes listener (transport end point),
 </para>
 <para>
  The <literal>listen</literal> describes listener (transport end point),

- such as TCP/IP, Unix file socket or SSL server.
+ such as TCP/IP, Unix file socket or SSL server. Content for
+ a listener:
+ <variablelist>
+  <varlistentry><term>CDATA (required)</term>
+   <listitem>
+    <para>
+     The CDATA for the <literal>listen</literal> element holds the
+     listener string, such as <literal>tcp:@:210</literal>,
+     <literal>tcp:server1:2100</literal>,
+     etc.
+    </para>
+   </listitem>
+  </varlistentry>
+  <varlistentry><term>attribute <literal>id</literal> (optional)</term>
+    <listitem>
+     <para>
+      identifier for this listener. This may be referred to from
+      server sections.
+     </para>
+    </listitem>
+   </varlistentry>
+ </variablelist>
+ <note>
+  <para>
+   We expect more information to be added for the listen section in
+   a future version, such as CERT file for SSL servers.
+  </para>
+ </note>

 </para>
 <para>
 </para>
 <para>

- The <literal>server</literal> describes a server and includes sub
- elements which servers as parameters for this server.
+ The <literal>server</literal> describes a server and the parameters
+ for this server type. Content for a server:
+ <variablelist>
+  <varlistentry><term>attribute <literal>id</literal> (optional)</term>
+   <listitem>
+    <para>
+     Identifier for this server. Currently not used for anything,
+     but it might be for logging purposes.
+   </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>attribute <literal>listenref</literal> (optional)</term>
+   <listitem>
+    <para>
+     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.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>element <literal>config</literal> (optional)</term>
+   <listitem>
+    <para>
+     Specifies the server configuration. This is equivalent
+     to the config specified using command line option
+     <literal>-c</literal>.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>element <literal>directory</literal> (optional)</term>
+   <listitem>
+    <para>
+     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).
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>element <literal>host</literal> (optional)</term>
+   <listitem>
+    <para>
+     Specifies the virtual host for this server. If this is specified
+     a client <emphasis>must</emphasis> specify this host string in
+     order to use this backend.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>element <literal>cql2rpn</literal> (optional)</term>
+   <listitem>
+    <para>
+     Specifies a filename that includes CQL to RPN conversion for this
+     backend server. See &reference-tools-cql-map;
+     If given, the backend server will only "see" a Type-1/RPN query.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>element <literal>ccl2rpn</literal> (optional)</term>
+   <listitem>
+    <para>
+     Specifies a filename that includes CCL to RPN conversion for this
+     backend server. See &reference-tools-ccl-qualifiers;
+     If given, the backend server will only "see" a Type-1/RPN query.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>element <literal>stylesheet</literal> (optional)</term>
+   <listitem>
+    <para>
+     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.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>element <literal>docpath</literal> (optional)</term>
+   <listitem>
+    <para>
+     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 <literal>xsl</literal>, the docpath would be
+     <literal>xsl</literal> and all URLs of the form
+     <literal>http://host/exl</literal> will result in a local file access.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>element <literal>explain</literal> (optional)</term>
+   <listitem>
+    <para>
+     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.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>element <literal>maximumrecordsize</literal> (optional)</term>
+   <listitem>
+    <para>
+     Specifies maximum record size/message size, in bytes. This
+     value also servers as maximum size of <emphasis>incoming</emphasis>
+     packages (for Record Updates etc). It's the same value as that
+     given by the <literal>-k</literal> option.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry><term>element <literal>retrievalinfo</literal> (optional)</term>
+   <listitem>
+    <para>
+     Enables the retrieval facility supporting conversions and
+     specifications of record formats/types.
+     See <xref linkend="tools.retrieval"/> for
+     more information.
+    </para>
+   </listitem>
+  </varlistentry>
+
+ </variablelist>

 </para>
 </para>

-<para>
- The XML below configures a server with 2 listeners and 3 backend
- servers. The server listens on port 9900 and 9901 identified 
- with references "public9900" and "public9901".

 
 

- [More to be written]
+<para>
+ 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 <literal>public</literal> and the
+ other server <literal>internal</literal>.
+ </para>

  <screen>
   <![CDATA[
  <screen>
   <![CDATA[

-<yazgfs>
-  <listen id="public9900">tcp:@:9900</listen>
-  <listen id="public9901">tcp:@:9901</listen>
-  <server>
-    <host>host1</host>
+ <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>
     <directory>/var/www/s1</directory>

-    <config>zebra1.cfg</config>
+    <config>config.cfg</config>

   </server>
   </server>

-  <server>
-    <host>host2</host>
+  <server id="server2" listenref="public,internal">
+    <host>server2.mydomain</host>

     <directory>/var/www/s2</directory>
     <directory>/var/www/s2</directory>

-    <config>zebra2.cfg</config>
-  </server>
-  <server listenref="public9901">
-    <directory>/var/www/s3</directory>
-    <config>zebra3.cfg</config>
+    <config>config.cfg</config>

     <cql2rpn>../etc/pqf.properties</cql2rpn>
     <cql2rpn>../etc/pqf.properties</cql2rpn>

-    <explain>
-      <my>explain</my>
+    <explain xmlns="http://explain.z3950.org/dtd/2.0/">
+      <serverInfo>
+        <host>server2.mydomain</host>
+        <port>9900</port>
+        <database>a</database>
+      </serverInfo>

     </explain>
   </server>
     </explain>
   </server>

+  <server id="server3" listenref="internal">
+    <directory>/var/www/s3</directory>
+    <config>config.cfg</config>
+  </server>

  </yazgfs>
 ]]>
  </screen>
  </yazgfs>
 ]]>
  </screen>

+<para>
+ There are three configured backend servers. The first two
+ servers, <literal>"server1"</literal> and <literal>"server2"</literal>,
+ can be reached by both listener addresses.
+ <literal>"server1"</literal> is reached by all (two) since no
+  <literal>listenref</literal> attribute is specified.
+ <literal>"server2"</literal> is reached by the two listeners specified.
+ In order to distinguish between the two, a virtual host has
+ been specified for each of server in the <literal>host</literal>
+ elements.
+</para>
+<para>
+ For <literal>"server2"</literal> elements for CQL to RPN conversion
+ is supported and explain information has been added (a short one here
+ to keep the example small).
+</para>
+<para>
+ The third server, <literal>"server3"</literal> can only be reached
+ via listener <literal>"internal"</literal>.

 </para>
 
 <!-- Keep this comment at the end of the file
 </para>
 
 <!-- Keep this comment at the end of the file