protecting log rotation with a mutex

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

diff --git a/doc/frontend.xml b/doc/frontend.xml
index 297c5f3..2ff6ed9 100644 (file)
--- a/doc/frontend.xml
+++ b/doc/frontend.xml
@@ -1,7 +1,7 @@
-<!-- $Id: frontend.xml,v 1.13 2002-08-17 07:55:51 adam Exp $ -->
+<!-- $Id: frontend.xml,v 1.23 2004-06-15 09:33:12 adam Exp $ -->

  <chapter id="server"><title>Generic server</title>
   <sect1><title>Introduction</title>
  <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 aren't into documentation, a good way to learn how the
     back end interface works is to look at the <filename>backend.h</filename>

@@ -13,7 +13,7 @@
 
    <para>
     If you have a database system that you would like to make available by
 
    <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.
     can use the APIs provided by the &asn;, &odr;, and &comstack;
     modules to
     create and decode PDUs, and exchange them with a client.

@@ -41,6 +41,12 @@
      too many structural changes in existing applications.
     </para>
    </note>
      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>
   </sect1>
   
   <sect1 id="server.frontend"><title>The Database Frontend</title>

@@ -52,7 +58,8 @@
     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
     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
     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

@@ -225,7 +232,7 @@ statserv_options_block *statserv_getcontrol(void);
      <varlistentry><term>
        <literal>int idle_timeout;</literal></term>
       <listitem><para>Maximum session idle-time, in minutes. Zero indicates
      <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>
        </para></listitem></varlistentry>
      
      <varlistentry><term>

@@ -323,6 +330,13 @@ bend_initresult (*bend_init)(bend_initrequest *r);
      <function>bend_init</function> handler is passed in the call to
      <function>statserv_start</function>.
     </para>
      <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
     <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

@@ -353,6 +367,11 @@ typedef struct bend_initrequest
     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);
     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;

 } bend_initrequest;
 
 typedef struct bend_initresult
 } bend_initrequest;
 
 typedef struct bend_initresult

@@ -397,7 +416,8 @@ typedef struct bend_initresult
      The members <literal>peer_name</literal>,
      <literal>implementation_id</literal>,
      <literal>implementation_name</literal> and
      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>
 
      of client (Z39.50) implementation - and version.
     </para>
 

@@ -439,12 +459,11 @@ typedef struct {
     int errcode;               /* 0==OK */
     char *errstring;           /* system error string or NULL */
 } bend_search_rr;
     int errcode;               /* 0==OK */
     char *errstring;           /* system error string or NULL */
 } bend_search_rr;

-

     </synopsis>
 
     <para>
      The <function>bend_search</function> handler is a fairly close
     </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.
      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.

@@ -475,7 +494,24 @@ typedef struct {
      defined error codes, and the suggested uses of the addinfo field.
     </para>
 
      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);
 
     <synopsis>
 int (*bend_fetch) (void *handle, bend_fetch_rr *rr);
 

@@ -498,21 +534,22 @@ typedef struct bend_fetch_rr {
     int errcode;               /* 0==success */
     char *errstring;           /* system error string or NULL */
     int surrogate_flag;        /* surrogate diagnostic */
     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
 } 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
      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
      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

@@ -522,11 +559,21 @@ typedef struct bend_fetch_rr {
     </para>
 
     <para>
     </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.
      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
      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

@@ -586,7 +633,8 @@ typedef struct {
 
     <para>
      The <function>bend_present</function> handler is called when
 
     <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
      <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

@@ -678,132 +726,32 @@ typedef struct bend_scan_rr {
     The finished application has the following
     invocation syntax (by way of <function>statserv_main()</function>):
    </para>
     The finished application has the following
     invocation syntax (by way of <function>statserv_main()</function>):
    </para>

-
-   <synopsis>
-    <replaceable>appname</replaceable> &lsqb;-szSiT1 -u <replaceable>uid</replaceable> -a <replaceable>apdufile</replaceable> -l <replaceable>logfile</replaceable> -v <replaceable>loglevel</replaceable> -c <replaceable>config</replaceable>&rsqb;
-    &lsqb;listener ...&rsqb;
-   </synopsis>
-
+   
+   <cmdsynopsis>
+    <command>appname</command>
+    <arg choice="opt"><option>-install</option></arg>
+    <arg choice="opt"><option>-installa</option></arg>
+    <arg choice="opt"><option>-remove</option></arg>
+    <arg choice="opt"><option>-a <replaceable>file</replaceable></option></arg>
+    <arg choice="opt"><option>-v <replaceable>level</replaceable></option></arg>
+    <arg choice="opt"><option>-l <replaceable>file</replaceable></option></arg>
+    <arg choice="opt"><option>-u <replaceable>uid</replaceable></option></arg>
+    <arg choice="opt"><option>-c <replaceable>config</replaceable></option></arg>
+    <arg choice="opt"><option>-t <replaceable>minutes</replaceable></option></arg>
+    <sbr/>
+    <arg choice="opt"><option>-k <replaceable>kilobytes</replaceable></option></arg>
+    <arg choice="opt"><option>-d <replaceable>daemon</replaceable></option></arg>
+    <arg choice="opt"><option>-w <replaceable>dir</replaceable></option></arg>
+    <arg choice="opt"><option>-p <replaceable>pidfile</replaceable></option></arg>
+    <arg choice="opt"><option>-ziDST1</option></arg>
+    <arg choice="opt" rep="repeat">listener-spec</arg>
+   </cmdsynopsis>
+   

    <para>
    <para>

-    The options are
-
-    <variablelist>
-
-     <varlistentry><term><literal>-a </literal>
-       <replaceable>apdufile</replaceable></term>
-      <listitem><para>
-       Specify a file for dumping PDUs (for diagnostic purposes).
-       The special name &quot;-&quot; 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>-1</literal></term>
-      <listitem><para>
-        Like <literal>-S</literal> but after one session the server
-        exits. This mode is for debugging <emphasis>only</emphasis>.
-       </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>
+    The options are:

 
 

-     <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,malloc,all,none}.
-       </para></listitem></varlistentry>
-
-     <varlistentry><term><literal>-u </literal>
-       <replaceable>uid</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>
-       The server changes to this directory during before listening 
-        on incoming connections. This option is useful
-        when the server is operating from the <application>inetd</application>
-         daemon (see <literal>-i</literal>).
-       </para></listitem></varlistentry>
+    &ztest-options;

 
 

-     <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>
    </para>
    
    <para>

@@ -820,36 +768,72 @@ typedef struct bend_scan_rr {
    <synopsis>
     hostname | IP-number &lsqb;: portnumber&rsqb;
    </synopsis>
    <synopsis>
     hostname | IP-number &lsqb;: portnumber&rsqb;
    </synopsis>

-
+   

    <para>
     The port number defaults to 210 (standard Z39.50 port).
    </para>
 
    <para>
    <para>
     The port number defaults to 210 (standard Z39.50 port).
    </para>
 
    <para>

-    For UNIX local socket the address is the name local file.
+    For UNIX, the address is the filename of socket.

    </para>
    </para>

-   
-   <para>
-    Examples
-   </para>
-
-   <screen>
-    tcp:dranet.dra.com
-
-    ssl:ssl.enterprise.com:3000
-
-    unix:/tmp/yaz
-   </screen>

 
    <para>
 
    <para>

-    For TCP/IP and SSL, the special hostname &quot;@&quot; 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>
 
    </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="http://httpd.apache.org/">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="http://httpd.apache.org/docs/mod/mod_proxy.html#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>
+      &lt;VirtualHost *>
+       ErrorLog /home/srw/logs/error_log
+       TransferLog /home/srw/logs/access_log
+       ProxyPass / http://srw.mydomain:210/
+      &lt;/VirualHost>
+     </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>
  </chapter>
   </sect1>
  </chapter>

-
+ 

  <!-- Keep this comment at the end of the file
  Local variables:
  mode: sgml
  <!-- Keep this comment at the end of the file
  Local variables:
  mode: sgml