-<!-- $Id: frontend.xml,v 1.12 2002-05-30 20:57:38 adam Exp $ -->
+<!-- $Id: frontend.xml,v 1.29 2006-04-25 11:25:08 marc Exp $ -->
<chapter id="server"><title>Generic server</title>
<sect1><title>Introduction</title>
-
+
<para>
If you aren't into documentation, a good way to learn how the
back end interface works is to look at the <filename>backend.h</filename>
<para>
If you have a database system that you would like to make available by
- means of Z39.50, &yaz; basically offers your two options. You
+ means of Z39.50, SRW o SRU, &yaz; basically offers your two options. You
can use the APIs provided by the &asn;, &odr;, and &comstack;
modules to
create and decode PDUs, and exchange them with a client.
too many structural changes in existing applications.
</para>
</note>
+
+ <note>
+ <para>
+ The &yaz; server does not support XCQL.
+ </para>
+ </note>
</sect1>
<sect1 id="server.frontend"><title>The Database Frontend</title>
The backend API consists of a small number of function handlers and
structure definitions. You are required to provide the
<function>main()</function> routine for the server (which can be
- quite simple), as well as a set of handlers to match each of the prototypes.
+ quite simple), as well as a set of handlers to match each of the
+ prototypes.
The interface functions that you write can use any mechanism you like
to communicate with your database system: You might link the whole
thing together with your database application and access it by
Result-Set Sort (optional).
</para></listitem>
+ <listitem><para>
+ Return Explain for SRW/SRU (optional).
+ </para></listitem>
+
</itemizedlist>
<para>
<varlistentry><term>
<literal>int idle_timeout;</literal></term>
<listitem><para>Maximum session idle-time, in minutes. Zero indicates
- no (infinite) timeout. Default is 120 minutes.
+ no (infinite) timeout. Default is 15 minutes.
</para></listitem></varlistentry>
<varlistentry><term>
<function>bend_init</function> handler is passed in the call to
<function>statserv_start</function>.
</para>
+
+ <para>
+ This handler is also called when operating in SRW/SRU mode - when
+ a connection has been made (even though SRW/SRU does not offer
+ this service).
+ </para>
+
<para>
Unlike previous versions of YAZ, the <function>bend_init</function> also
serves as a handler that defines the Z39.50 services that the backend
int (*bend_delete)(void *handle, bend_delete_rr *rr);
int (*bend_scan)(void *handle, bend_scan_rr *rr);
int (*bend_segment)(void *handle, bend_segment_rr *rr);
+
+ ODR decode; /* decoding stream */
+ /* character set and language negotiation - see include/yaz/z-charneg.h */
+ Z_CharSetandLanguageNegotiation *charneg_request;
+ Z_External *charneg_response;
+ int (*bend_srw_explain)(void *handle, bend_explain_rr *rr);
+ int (*bend_srw_scan)(void *handle, bend_scan_rr *rr);
} bend_initrequest;
typedef struct bend_initresult
The members <literal>peer_name</literal>,
<literal>implementation_id</literal>,
<literal>implementation_name</literal> and
- <literal>implementation_version</literal> holds DNS of client, ID of implementor, name
+ <literal>implementation_version</literal> holds
+ DNS of client, ID of implementor, name
of client (Z39.50) implementation - and version.
</para>
int hits; /* number of hits */
int errcode; /* 0==OK */
char *errstring; /* system error string or NULL */
+ Z_OtherInformation *search_info;
} bend_search_rr;
-
</synopsis>
<para>
The <function>bend_search</function> handler is a fairly close
- approximation of a protocol Search Request - and Response PDUs
+ approximation of a protocol Z39.50 Search Request - and Response PDUs
The <literal>setname</literal> is the resultSetName from the protocol.
You are required to establish a mapping between the set name and whatever
your backend database likes to use.
defined error codes, and the suggested uses of the addinfo field.
</para>
+ <para>
+ The <function>bend_search</function> handler is also called when
+ the frontend server receives a SRW/SRU SearchRetrieveRequest.
+ For SRW/SRU, a CQL query is usually provided by the client.
+ The CQL query is available as part of <literal>Z_Query</literal>
+ structure (note that CQL is now part of Z39.50 via an external).
+ To support CQL in existing implementations that only do Type-1,
+ we refer to the CQL-to-PQF tool described
+ <link linkend="tools.cql.pqf">here</link>.
+ </para>
+ <para>
+ To maintain backwards compatibility, the frontend server
+ of yaz always assume that error codes are BIB-1 diagnostics.
+ For SRW/SRU operation, a Bib-1 diagnostic code is mapped to
+ SRW/SRU diagnostic.
+ </para>
+
<synopsis>
int (*bend_fetch) (void *handle, bend_fetch_rr *rr);
int errcode; /* 0==success */
char *errstring; /* system error string or NULL */
int surrogate_flag; /* surrogate diagnostic */
+ char *schema; /* string record schema input/output */
} bend_fetch_rr;
</synopsis>
<para>
The frontend server calls the <function>bend_fetch</function> handler
- when it needs database records to fulfill a Search Request or a Present
- Request.
+ when it needs database records to fulfill a Z39.50 Search Request, a
+ Z39.50 Present Request or a SRW SearchRetrieveRequest.
The <literal>setname</literal> is simply the name of the result set
that holds the reference to the desired record.
The <literal>number</literal> is the offset into the set (with 1
being the first record in the set). The <literal>format</literal> field
- is the record format requested by the client (See section
- <link linkend="oid">Object Identifiers</link>). The value
- <literal>VAL_NONE</literal> indicates that the client did not
- request a specific format. The <literal>stream</literal> argument
+ is the record format requested by the client (See
+ <xref linkend="asn.oid"/>).
+ The value <literal>VAL_NONE</literal> indicates that the client did
+ not request a specific format. The <literal>stream</literal> argument
is an &odr; stream which should be used for
allocating space for structured data records.
The stream will be reset when all records have been assembled, and
</para>
<para>
+ If a SRW/SRU SearchRetrieveRequest is received by the frontend server,
+ the <literal>referenceId</literal> is NULL and the
+ <literal>request_format</literal> (transfer syntax) is XML (OID name
+ <literal>VAL_TEXT_XML</literal>).
+ The schema for SRW/SRU is stored in both the
+ <literal>Z_RecordComposition</literal>
+ structure and <literal>schema</literal> (simple string).
+ </para>
+
+ <para>
In the structure, the <literal>basename</literal> is the name of the
database that holds the
record. <literal>len</literal> is the length of the record returned, in
bytes, and <literal>record</literal> is a pointer to the record.
- <literal>Last_in_set</literal> should be nonzero only if the record
+ <literal>last_in_set</literal> should be nonzero only if the record
returned is the last one in the given result set.
<literal>errcode</literal> and <literal>errstring</literal>, if
given, will be interpreted as a global error pertaining to the
<para>
The <function>bend_present</function> handler is called when
- the server receives a Present Request. The <literal>setname</literal>,
+ the server receives a Z39.50 Present Request.
+ The <literal>setname</literal>,
<literal>start</literal> and <literal>number</literal> is the
name of the result set - start position - and number of records to
be retrieved respectively. <literal>format</literal> and
bend_scan_status status;
int errcode;
char *errstring;
+ char *scanClause; /* CQL scan clause */
} bend_scan_rr;
</synopsis>
+ <para>
+ This backend server handles both Z39.50 scan
+ and SRW/SRU scan. In order for a
+ handler to distinguish between SRW/SRU (CQL) scan
+ Z39.50 Scan , it must check for a non-NULL value of
+ <literal>scanClause</literal>.
+ </para>
+ <note>
+ <para>
+ if designed today, it would be a choice using a union or similar,
+ but that would break binary compatibility with existing servers.
+ </para>
+ </note>
</sect2>
</sect1>
invocation syntax (by way of <function>statserv_main()</function>):
</para>
- <synopsis>
- <replaceable>appname</replaceable> [-szSiTu -a <replaceable>apdufile</replaceable> -l <replaceable>logfile</replaceable> -v <replaceable>loglevel</replaceable> -c <replaceable>config</replaceable>]
- [listener ...]
- </synopsis>
-
+ &gfs-synopsis;
+
<para>
- The options are
-
- <variablelist>
+ The options are:
- <varlistentry><term><literal>-a </literal>
- <replaceable>file</replaceable></term>
- <listitem><para>
- Specify a file for dumping PDUs (for diagnostic purposes).
- The special name "-" sends output to
- <literal>stderr</literal>.
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-S</literal></term>
- <listitem><para>
- Don't fork or make threads on connection requests. This is good for
- debugging, but not recommended for real operation: Although the
- server is asynchronous and non-blocking, it can be nice to keep
- a software malfunction (okay then, a crash) from affecting all
- current users.
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-T</literal></term>
- <listitem><para>
- Operate the server in threaded mode. The server creates a thread
- for each connection rather than a fork a process. Only available
- on UNIX systems that offers POSIX threads.
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-s</literal></term>
- <listitem><para>
- Use the SR protocol (obsolete).
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-z</literal></term>
- <listitem><para>
- Use the Z39.50 protocol (default). These two options complement
- each other. You can use both multiple times on the same command
- line, between listener-specifications (see below). This way, you
- can set up the server to listen for connections in both protocols
- concurrently, on different local ports.
- </para></listitem></varlistentry>
+ &gfs-options;
- <varlistentry><term><literal>-l </literal>
- <replaceable>file</replaceable></term>
- <listitem><para>The logfile.
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-c </literal>
- <replaceable>config</replaceable></term>
- <listitem><para>A user option that serves as a specifier for some
- sort of configuration, e.g. a filename.
- The argument to this option is transferred to member
- <literal>configname</literal>of the
- <literal>statserv_options_block</literal>.
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-v </literal>
- <replaceable>level</replaceable></term>
- <listitem><para>
- The log level. Use a comma-separated list of members of the set
- {fatal,debug,warn,log,all,none}.
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-u </literal>
- <replaceable>userid</replaceable></term>
- <listitem><para>
- Set user ID. Sets the real UID of the server process to that of the
- given user. It's useful if you aren't comfortable with having the
- server run as root, but you need to start it as such to bind a
- privileged port.
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-w </literal>
- <replaceable>dir</replaceable></term>
- <listitem><para>
- Working directory.
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-i</literal></term>
- <listitem><para>
- Use this to make the the server run from the
- <application>inetd</application> server (UNIX only).
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-install</literal></term>
- <listitem><para>
- Use this to install the server as an NT service (Windows 2000/NT only).
- Control the server by going to the Services in the Control Panel.
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-remove</literal></term>
- <listitem><para>
- Use this to remove the server from the NT services (Windows 2000/NT only).
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-t </literal>
- <replaceable>minutes</replaceable></term>
- <listitem><para>
- Idle session timeout, in minutes.
- </para></listitem></varlistentry>
-
- <varlistentry><term><literal>-k </literal>
- <replaceable>size</replaceable></term>
- <listitem><para>
- Maximum record size/message size, in kilobytes.
- </para></listitem></varlistentry>
-
- </variablelist>
</para>
-
+
<para>
A listener specification consists of a transport mode followed by a
colon (:) followed by a listener address. The transport mode is
- either <literal>tcp</literal> or <literal>ssl</literal>.
+ either <literal>tcp</literal>, <literal>unix:</literal> or
+ <literal>ssl</literal>.
</para>
-
+
<para>
For TCP and SSL, an address has the form
</para>
<synopsis>
hostname | IP-number [: portnumber]
</synopsis>
-
+
<para>
The port number defaults to 210 (standard Z39.50 port).
</para>
<para>
- Examples
+ For UNIX, the address is the filename of socket.
</para>
- <screen>
- tcp:dranet.dra.com
-
- ssl:ssl.enterprise.com:3000
- </screen>
-
<para>
- In both cases, the special hostname "@" is mapped to
- the address <literal>INADDR_ANY</literal>, which causes the
- server to listen on any local interface.
+ For TCP/IP and SSL, the special hostname <literal>@</literal>
+ (at sign) is mapped to the address <literal>INADDR_ANY</literal>,
+ which causes the server to listen on any local interface.
</para>
+ <example><title>Running the GFS on Unix</title>
+ <para>
+ Assuming the server application <replaceable>appname</replaceable> is
+ started as root, the following will make it listen on port 210.
+ The server will change identity to <literal>nobody</literal>
+ and write its log to <filename>/var/log/app.log</filename>.
+ <screen>
+ <replaceable>appname</replaceable> -l /var/log/app.log -u nobody tcp:@:210
+ </screen>
+ </para>
+ <para>
+ The server will accept Z39.50 requests and offer SRW/SRU service
+ on port 210.
+ </para>
+ </example>
+ <example><title>Setting up Apache as SRW/SRU Frontend</title>
+ <para>
+ If you use <ulink url="&url.apache;">Apache</ulink>
+ as your public web server and want to offer HTTP port 80
+ access to the YAZ server on 210, you can use the
+ <ulink url="&url.apache.directive.proxypass;">
+ <literal>ProxyPass</literal></ulink>
+ directive.
+ If you have virtual host
+ <literal>srw.mydomain</literal> you can use the following directives
+ in Apache's httpd.conf:
+ <screen>
+ <VirtualHost *>
+ ErrorLog /home/srw/logs/error_log
+ TransferLog /home/srw/logs/access_log
+ ProxyPass / http://srw.mydomain:210/
+ </VirtualHost>
+ </screen>
+ </para>
+ <para>
+ The above for the Apache 1.3 series.
+ </para>
+ </example>
+ <example><title>Running a server with local access only</title>
+ <para>
+ Servers that is only being accessed from the local host should listen
+ on UNIX file socket rather than a Internet socket. To listen on
+ <filename>/tmp/mysocket</filename> start the server as follows:
+ <screen>
+ <replaceable>appname</replaceable> tcp:/tmp/mysocket
+ </screen>
+ </para>
+ </example>
+ </sect1>
+ <sect1 id="server.vhosts"><title>Virtual Hosts</title>
+ &gfs-virtual;
</sect1>
</chapter>
-
+
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