From: Mike Taylor Date: Wed, 19 Apr 2006 15:43:40 +0000 (+0000) Subject: Much new material, lots of cleaning up, etc. X-Git-Tag: METAPROXY.1.0.0~21 X-Git-Url: http://lists.indexdata.com/cgi-bin?a=commitdiff_plain;h=4b5158c40900ee67ec56fc6933fb5cd2dcca72b9;p=metaproxy-moved-to-github.git Much new material, lots of cleaning up, etc. --- diff --git a/doc/book.xml b/doc/book.xml index 74bd70d..ad11c21 100644 --- a/doc/book.xml +++ b/doc/book.xml @@ -1,4 +1,4 @@ - + Metaproxy - User's Guide and Reference @@ -13,7 +13,24 @@ - Metaproxy - universal Z39.50/SRU router, proxy and encapsulated metasearcher + Metaproxy is a universal Z39.50/SRU router, proxy and encapsulated + metasearcher. It accepts, processes, interprets and redirects + requests from IR clients using standard protocols such as + ANSI/NISO Z39.50, SRU and SRW, as well as functioning as a limited + HTTP server. Metaproxy is configured by an XML file which + specifies how the software should function in terms of routes that + the request packets can take through the proxy, each step on a + route being an instantiation of a filter. Filters come in many + types, one for each operation: accepting Z39.50 packets, logging, + query transformation, multiplexing, etc. Further filter-types can + be added as loadable modules to extend Metaproxy functionality, + using the filter API. + + + The terms under which Metaproxy will be distributed have yet to be + established, but it will not necessarily be open source; so users + should not at this stage redistribute the code without explicit + written permission from the copyright holders, Index Data ApS. @@ -22,8 +39,6 @@ Introduction -
- Overview Metaproxy is a standalone program that acts as a universal router, proxy and @@ -34,8 +49,17 @@ retrieves records from them, etc. it satisfies its clients' requests by transforming them, multiplexing them, forwarding them on to zero or more servers, merging the results, transforming - them, and delivering them back to the client. + them, and delivering them back to the client. In addition, it + acts as a simple HTTP server; support for further protocols can be + added in a module fashion, through the creation of new filters. + + Anything goes in! + Anything goes out! + Cold bananas, fish, pyjamas, + Mutton, beef and trout! + - attributed to Cole Porter. + Metaproxy is a more capable alternative to YAZ Proxy, @@ -47,7 +71,6 @@ facilitites the creation of pluggable modules implementing further functionality. -
@@ -65,6 +88,8 @@ made and a public statement made, then, and unless it has been delivered to you other specific terms, please treat Metaproxy as though it were proprietary software. + The code should not be redistributed without explicit + written permission from the copyright holders, Index Data ApS. @@ -137,9 +162,10 @@ different ways: it may be used to mean a particular type of filter, as when we speak of ``the auth_simplefilter'' or ``the multi filter''; or it may be used - to be a specific instance of a filter within a Metaproxy - configuration. For example, a single configuration will often - contain multiple instances of the z3950_client filter. In + to be a specific instance of a filter + within a Metaproxy configuration. For example, a single + configuration will often contain multiple instances of the + z3950_client filter. In operational terms, of these is a separate filter. In practice, context always make it clear which sense of the word ``filter'' is being used. @@ -189,7 +215,7 @@ There are many kinds of filter: some that are defined statically - as part of Metaproxy, and other that may be provided by third parties + as part of Metaproxy, and others may be provided by third parties and dynamically loaded. They all conform to the same simple API of essentially two methods: configure() is called at startup time, and is passed a DOM tree representing that @@ -221,13 +247,25 @@
- Individual filters + Overview of filter types + + We now briefly consider each of the types of filter supported by + the core Metaproxy binary. This overview is intended to give a + flavour of the available functionality; more detailed information + about each type of filter is included below in the Module + Reference. + The filters are here named by the string that is used as the type attribute of a <filter> element in the configuration file to request them, with the name of the class that implements - them in parentheses. + them in parentheses. (The classname is not needed for normal + configuration and use of Metaproxy; it is useful only to + developers.) + + + The filters are here listed in alphabetical order:
@@ -239,10 +277,13 @@ lists username:password pairs, one per line, colon separated. When a session begins, it is rejected unless username and passsword are supplied, and match - a pair in the register. - - - ### discuss authorisation phase + a pair in the register. The configuration file may also specific + the name of another file that is the target register: this lists + lists username:dbname,dbname... + sets, one per line, with multiple database names separated by + commas. When a search is processed, it is rejected unless the + database to be searched is one of those listed as available to + the user.
@@ -252,7 +293,8 @@ A sink that provides dummy responses in the manner of the yaz-ztest Z39.50 server. This is useful only - for testing. + for testing. Seriously, you don't need this. Pretend you didn't + even read this section.
@@ -262,8 +304,8 @@ A source that accepts Z39.50 and SRW connections from a port specified in the configuration, reads protocol units, and - feeds them into the next filter, eventually returning the - result to the origin. + feeds them into the next filter in the route. When the result is + revceived, it is returned to the original origin. @@ -292,8 +334,23 @@ <literal>multi</literal> (mp::filter::Multi) - Performs multicast searching. See the extended discussion of - multi-database searching below. + Performs multicast searching. + See + the extended discussion + of virtual databases and multi-database searching below. + + + +
+ <literal>query_rewrite</literal> + (mp::filter::QueryRewrite) + + Rewrites Z39.50 Type-1 and Type-101 (``RPN'') queries by a + three-step process: the query is transliterated from Z39.50 + packet structures into an XML representation; that XML + representation is transformed by an XSLT stylesheet; and the + resulting XML is transliterated back into the Z39.50 packet + structure.
@@ -303,8 +360,16 @@ When this is finished, it will implement global sharing of result sets (i.e. between threads and therefore between - clients), but it's not yet done. + clients), yielding performance improvements especially when + incoming requests are from a stateless environment such as a + web-server, in which the client process representing a session + might be any one of many. However: + + + This filter is not yet completed. + +
@@ -315,7 +380,8 @@ should be called nop or passthrough?) This exists not to be used, but to be copied - to become the skeleton of new filters as they are - written. + written. As with backend_test, this is not + intended for civilians.
@@ -323,8 +389,14 @@ <literal>virt_db</literal> (mp::filter::Virt_db) - Performs virtual database selection. See the extended discussion - of virtual databases below. + Performs virtual database selection: based on the name of the + database in the search request, a server is selected, and its + address added to the request in a VAL_PROXY + otherInfo packet. It will subsequently be used by a + z3950_client filter. + See + the extended discussion + of virtual databases and multi-database searching below. @@ -349,7 +421,8 @@ Some other filters that do not yet exist, but which would be useful, are briefly described. These may be added in future - releases. + releases (or may be created by third parties, as loadable + modules). @@ -399,6 +472,32 @@ + + Virtual databases and multi-database searching + + +
+ Introductory notes + + Two of Metaproxy's filters are concerned with multiple-database + operations. Of these, virt_db can work alone + to control the routing of searches to one of a number of servers, + while multi can work with the output of + virt_db to perform multicast searching, merging + the results into a unified result-set. The interaction between + these two filters is necessarily complex, reflecting the real + complexity of multicast searching in a protocol such as Z39.50 + that separates initialisation from searching, with the database to + search known only during the latter operation. + + + ### Much, much more to say! + +
+ + + + Configuration: the Metaproxy configuration file format @@ -559,6 +658,15 @@
+ <literal>query_rewrite</literal> + + <filter type="query_rewrite"> + <xslt>pqf2pqf.xsl</xslt> + </filter> + +
+ +
<literal>session_shared</literal> <filter type="session_shared"> @@ -603,30 +711,6 @@ - - Virtual database as multi-database searching - - -
- Introductory notes - - Two of Metaproxy's filters are concerned with multiple-database - operations. Of these, virt_db can work alone - to control the routing of searches to one of a number of servers, - while multi can work with the output of - virt_db to perform multicast searching, merging - the results into a unified result-set. The interaction between - these two filters is necessarily complex, reflecting the real - complexity of multicast searching in a protocol such as Z39.50 - that separates initialisation from searching, with the database to - search known only during the latter operation. - - - ### Much, much more to say! - -
- - Module Reference