<orderedlist>
<listitem>
<para> If the <literal>InitializeRequest</literal> PDU from the
- client includes an <literal>otherInfo</literal> element with OID
+ client includes an
+ <link linkend="otherinfo-encoding"><literal>otherInfo</literal></link>
+ element with OID
<literal>1.2.840.10003.10.1000.81.1</literal>, then the
contents of that element specify the target to be used, in the
usual YAZ address format (typically
</para>
</section>
<section id="proxy-keepalive">
- <title>Keep-alive Facility for Stateless Clients</title>
+ <title>Keep-alive Facility</title>
<para>
- Stateless clients such as web gateways may generate a cookie for a Z39.50
- session which is sent to the proxy as part of PDUs.
- In this case, the proxy will keep alive its Z39.50 session
- to the backend target even when the connection from the client
- to the proxy is closed. When the client contacts the
- proxy again, and re-issues the same cookie, the proxy reuses the
- Z39.50 connection with the backend target.
+ The keep-alive is a facility where the proxy keeps the connection to the
+ backend - even if the client closes the connection to the proxy.
</para>
<para>
- There is no
- guarantee that the Z39.50 connection to the backend
- target is kept forever: the proxy will shut it down after certain
- idle time.
- <!-- ### How long? Wot no command-line option? -->
- So in effect, the connection from the client's
- point of view should be considered stateless, and the keep-alive
- facility should be treated only as a performance booster.
+ If a new or another client connects to the proxy again and requests the
+ same backend it will be reassigned to this backend. In this case, the
+ proxy sends an initialize response directly to the client and an
+ initialize handshake with the backend is omitted.
</para>
<para>
- Cookies may be passed in an <literal>otherInfo</literal> element
- with OID <literal>1.2.840.10003.10.1000.81.2</literal>.
+ When a client reconnects, query and record caching works better, if the
+ proxy assigns it to the same backend as before. And the result set
+ (if any) is re-used. To achive this, Index Data defined a session
+ cookie which identifies the backend session.
+ </para>
+ <para>
+ The cookie is defined by the client and is sent as part of the
+ Initialize Request and passed in an
+ <link linkend="otherinfo-encoding"><literal>otherInfo</literal></link>
+ element with OID <literal>1.2.840.10003.10.1000.81.2</literal>.
+ </para>
+ <para>
+ Clients that do not send a cookie as part of the initialize request
+ may still better performance, since the init handshake is saved.
</para>
</section>
- <section id="proxy-cache">
+ <section id="query-cache">
<title>Query Caching</title>
<para>
Simple stateless clients often send identical Z39.50 searches
backend target, so that if an identical query is received next, it
is turned into Present Requests rather than new Search Requests.
</para>
- <!-- ### should be generalised to an arbitrary-sized cache -->
+ <note>
+ <para>
+ In a future we release will will probably allows for
+ an arbitrary-sized cache for targets supporting named result sets.
+ </para>
+ </note>
<para>
- This optimization should work for any Z39.50 client and/or
- target. The target does not have to support named result sets.
+ You can enable/disable query caching using option -o.
</para>
- <!-- ### There should be an option to turn this off, as it will
- affect semantics for some searches on some databases:
- e.g. "ten most recent stories" in a newswire database.
- -->
+ </section>
+
+
+ <section id="record-cache">
+ <title>Record Caching</title>
+ <para>
+ As an option, the proxy may also cache result set records for the
+ last search.
+ The proxy takes into account the Record Syntax and CompSpec.
+ The CompSpec includes simple element set names as well.
+ </para>
</section>
- <section id="proxy-optimizations">
+ <section id="query-validation">
+ <title>Query Validation</title>
+ <para>
+ </para>
+ </section>
+
+ <section id="record-validation">
+ <title>Record Syntax Validation</title>
+ <para>
+ </para>
+ </section>
+
+ <section id="other-optimizations">
<title>Other Optimizations</title>
- <para>
- We've had some plans to support caching of result set records,
+ <para>
+ We've had some plans to support global caching of result set records,
but this has not yet been implemented.
</para>
</section>
<para>
</para>
<refentry id="yaz-proxy">
- <refmeta>
- <refentrytitle>yaz-proxy</refentrytitle>
- <manvolnum>8</manvolnum>
- </refmeta>
- <refnamediv>
- <refname>yaz-proxy</refname>
- <refpurpose>The YAZ toolkit's transparent Z39.50 proxy</refpurpose>
- </refnamediv>
- <refsynopsisdiv>
- <cmdsynopsis>
- <command>yaz-proxy</command>
- <arg choice="opt">-a <replaceable>filename</replaceable></arg>
- <arg choice="opt">-c <replaceable>num</replaceable></arg>
- <arg choice="opt">-v <replaceable>level</replaceable></arg>
- <arg choice="opt">-t <replaceable>target</replaceable></arg>
- <arg choice="opt">-u <replaceable>auth</replaceable></arg>
- <arg choice="opt">-o <replaceable>level</replaceable></arg>
- <arg choice="req"><replaceable>host</replaceable>:<replaceable>port</replaceable></arg>
- </cmdsynopsis>
- </refsynopsisdiv>
-
- <refsect1><title>DESCRIPTION</title>
- <para>
- The proxy runs stand-alone (not from
- <literal>inetd</literal>). The
- <replaceable>host</replaceable>:<replaceable>port</replaceable>
- argument specifies host address to listen to, and the port to
- listen on. Use the host <literal>@</literal>
- to listen for connections coming from any address.
- </para>
- </refsect1>
- <refsect1><title>OPTIONS</title>
- <variablelist>
- <varlistentry><term>-a <replaceable>filename</replaceable></term>
- <listitem><para>
- Specifies the name of a file to which to write a log of the
- APDUs (protocol packets) that pass through the proxy. The
- special filename <literal>-</literal> may be used to indicate
- standard output.
- </para></listitem>
- </varlistentry>
- <varlistentry><term>-c <replaceable>num</replaceable></term>
- <listitem><para>
- Specifies the maximum number of connections to be cached
- [default 50].
- </para></listitem>
- </varlistentry>
- <varlistentry><term>-v <replaceable>level</replaceable></term>
- <listitem><para>
- Sets the logging level. <replaceable>level</replaceable> is
- a comma-separated list of members of the set
- {<literal>fatal</literal>,<literal>debug</literal>,<literal>warn</literal>,<literal>log</literal>,<literal>malloc</literal>,<literal>all</literal>,<literal>none</literal>}.
- </para></listitem>
- </varlistentry>
- <varlistentry><term>-t <replaceable>target</replaceable></term>
- <listitem><para>
- Specifies the default backend target to use when a client
- connects that does not explicitly specify a target in its
- <literal>initRequest</literal>.
- </para></listitem>
- </varlistentry>
- <varlistentry><term>-u <replaceable>auth</replaceable></term>
- <listitem><para>
- Specifies authentication info to be sent to the backend target.
- This is useful if you happen to have an internal target that
- requires authentication, or if the client software does not allow
- you to set it.
- </para></listitem>
- </varlistentry>
- <varlistentry><term>-o <replaceable>level</replaceable></term>
- <listitem><para>
- Sets level for optimization. Use zero to disable; non-zero
- to enable. Handling for this is not fully implemented;
- we will probably use a bit mask to enable/disable specific
- features.
- </para></listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
- <refsect1>
- <title>EXAMPLES</title>
- <para>
- The following command starts the proxy, listening on port
- 9000, with its default backend target set to the Library of
- Congress bibliographic server:
- </para>
- <screen>
- $ yaz-proxy -t z3950.loc.gov:7090 @:9000
- </screen>
- <para>
- The LOC target is sometimes very slow. You can connect to
- it using yaz-client as follows:
- </para>
- <screen>
- $ yaz-client localhost:9000/voyager
- Connecting...Ok.
- Sent initrequest.
- Connection accepted by target.
- ID : 34
- Name : Voyager LMS - Z39.50 Server
- Version: 1.13
- Options: search present
- Elapsed: 7.131197
- Z> f computer
- Sent searchRequest.
- Received SearchResponse.
- Search was a success.
- Number of hits: 10000
- records returned: 0
- Elapsed: 6.695174
- Z> f computer
- Sent searchRequest.
- Received SearchResponse.
- Search was a success.
- Number of hits: 10000
- records returned: 0
- Elapsed: 0.001417
- </screen>
- <para>
- In this test, the second search was more than 4000 times faster
- than the first, because the proxy cached the result of the first
- search and noticed that the second was the same.
- </para>
- <para>
- The YAZ command-line client,
- <literal>yaz-client</literal>,
- allows you to set the backend target in
- the <literal>initRequest</literal> using the
- <literal>-p</literal> option. For example, to connect to
- Index Data's target you could use:
- </para>
- <screen>
- yaz-client -p indexdata.dk localhost:9000/gils
- </screen>
- </refsect1>
+ &yaz-proxy-ref;
</refentry>
</section>
+ <section id="otherinfo-encoding"><title>OtherInformation Encoding</title>
+ <para>
+ The proxy uses the OtherInformation definition to carry
+ information about the target address and cookie.
+ </para>
+ <screen>
+ OtherInformation ::= [201] IMPLICIT SEQUENCE OF SEQUENCE{
+ category [1] IMPLICIT InfoCategory OPTIONAL,
+ information CHOICE{
+ characterInfo [2] IMPLICIT InternationalString,
+ binaryInfo [3] IMPLICIT OCTET STRING,
+ externallyDefinedInfo [4] IMPLICIT EXTERNAL,
+ oid [5] IMPLICIT OBJECT IDENTIFIER}}
+--
+ InfoCategory ::= SEQUENCE{
+ categoryTypeId [1] IMPLICIT OBJECT IDENTIFIER OPTIONAL,
+ categoryValue [2] IMPLICIT INTEGER}
+ </screen>
+ <para>
+ The <literal>categoryTypeId</literal> is either
+ OID 1.2.840.10003.10.1000.81.1, 1.2.840.10003.10.1000.81.2
+ for proxy target and proxy cookie respectively. The
+ integer element <literal>category</literal> is set to 0.
+ The value proxy and cookie is stored in element
+ <literal>characterInfo</literal> of the <literal>information</literal>
+ choice.
+ </para>
+ </section>
</chapter>
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