X-Git-Url: http://git.indexdata.com/?p=yaz-moved-to-github.git;a=blobdiff_plain;f=doc%2Ffrontend.xml;h=2350af3ef892eda070163d754a273cf5543e165e;hp=297c5f3b06ed17a528fd4f25dee4fad36380e329;hb=d168db0590bc858a1bc9bd5a6ea66abbcd8f7d7d;hpb=d82eeac05d2899fa30704e2c40e9dd603ff2c581 diff --git a/doc/frontend.xml b/doc/frontend.xml index 297c5f3..2350af3 100644 --- a/doc/frontend.xml +++ b/doc/frontend.xml @@ -1,7 +1,7 @@ - + Generic server Introduction - + If you aren't into documentation, a good way to learn how the back end interface works is to look at the backend.h @@ -13,7 +13,7 @@ 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 or 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. @@ -41,6 +41,12 @@ too many structural changes in existing applications. + + + + The &yaz; server does not support XCQL. + + The Database Frontend @@ -52,7 +58,8 @@ The backend API consists of a small number of function handlers and structure definitions. You are required to provide the main() 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 @@ -92,6 +99,10 @@ Result-Set Sort (optional). + + Return Explain for SRU (optional). + + @@ -225,7 +236,7 @@ statserv_options_block *statserv_getcontrol(void); int idle_timeout; Maximum session idle-time, in minutes. Zero indicates - no (infinite) timeout. Default is 120 minutes. + no (infinite) timeout. Default is 15 minutes. @@ -323,6 +334,13 @@ bend_initresult (*bend_init)(bend_initrequest *r); bend_init handler is passed in the call to statserv_start. + + + This handler is also called when operating in SRU mode - when + a connection has been made (even though SRU does not offer + this service). + + Unlike previous versions of YAZ, the bend_init also serves as a handler that defines the Z39.50 services that the backend @@ -353,6 +371,13 @@ 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); + + 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 @@ -397,7 +422,8 @@ typedef struct bend_initresult The members peer_name, implementation_id, implementation_name and - implementation_version holds DNS of client, ID of implementor, name + implementation_version holds + DNS of client, ID of implementor, name of client (Z39.50) implementation - and version. @@ -438,13 +464,13 @@ typedef struct { int hits; /* number of hits */ int errcode; /* 0==OK */ char *errstring; /* system error string or NULL */ + Z_OtherInformation *search_info; } bend_search_rr; - The bend_search 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 setname 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 +501,24 @@ typedef struct { defined error codes, and the suggested uses of the addinfo field. + + The bend_search handler is also called when + the frontend server receives a SRU SearchRetrieveRequest. + For SRU, a CQL query is usually provided by the client. + The CQL query is available as part of Z_Query + 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 + here. + + + To maintain backwards compatibility, the frontend server + of yaz always assume that error codes are BIB-1 diagnostics. + For SRU operation, a Bib-1 diagnostic code is mapped to + SRU diagnostic. + + int (*bend_fetch) (void *handle, bend_fetch_rr *rr); @@ -498,21 +541,22 @@ typedef struct bend_fetch_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; The frontend server calls the bend_fetch 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 SRU SearchRetrieveRequest. The setname is simply the name of the result set that holds the reference to the desired record. The number is the offset into the set (with 1 being the first record in the set). The format field - is the record format requested by the client (See section - Object Identifiers). The value - VAL_NONE indicates that the client did not - request a specific format. The stream argument + is the record format requested by the client (See + ). + The value VAL_NONE indicates that the client did + not request a specific format. The stream 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 @@ -522,11 +566,21 @@ typedef struct bend_fetch_rr { + If a SRU SearchRetrieveRequest is received by the frontend server, + the referenceId is NULL and the + request_format (transfer syntax) is XML (OID name + VAL_TEXT_XML). + The schema for SRU is stored in both the + Z_RecordComposition + structure and schema (simple string). + + + In the structure, the basename is the name of the database that holds the record. len is the length of the record returned, in bytes, and record is a pointer to the record. - Last_in_set should be nonzero only if the record + last_in_set should be nonzero only if the record returned is the last one in the given result set. errcode and errstring, if given, will be interpreted as a global error pertaining to the @@ -586,7 +640,8 @@ typedef struct { The bend_present handler is called when - the server receives a Present Request. The setname, + the server receives a Z39.50 Present Request. + The setname, start and number is the name of the result set - start position - and number of records to be retrieved respectively. format and @@ -667,8 +722,21 @@ typedef struct bend_scan_rr { bend_scan_status status; int errcode; char *errstring; + char *scanClause; /* CQL scan clause */ } bend_scan_rr; + + This backend server handles both Z39.50 scan + and SRU scan. In order for a handler to distinguish between SRU (CQL) scan + Z39.50 Scan , it must check for a non-NULL value of + scanClause. + + + + if designed today, it would be a choice using a union or similar, + but that would break binary compatibility with existing servers. + + @@ -679,131 +747,13 @@ typedef struct bend_scan_rr { invocation syntax (by way of statserv_main()): - - appname [-szSiT1 -u uid -a apdufile -l logfile -v loglevel -c config] - [listener ...] - - + &gfs-synopsis; + - The options are - - - - -a - apdufile - - Specify a file for dumping PDUs (for diagnostic purposes). - The special name "-" sends output to - stderr. - - - -S - - 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. - - - -1 - - Like -S but after one session the server - exits. This mode is for debugging only. - - - -T - - 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. - - - -s - - Use the SR protocol (obsolete). - + The options are: - -z - - 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. - - - -l - file - The logfile. - - - -c - config - 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 - confignameof the - statserv_options_block. - - - -v - level - - The log level. Use a comma-separated list of members of the set - {fatal,debug,warn,log,malloc,all,none}. - - - -u - uid - - 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. - - - -w - dir - - The server changes to this directory during before listening - on incoming connections. This option is useful - when the server is operating from the inetd - daemon (see -i). - + &gfs-options; - -i - - Use this to make the the server run from the - inetd server (UNIX only). - - - -install - - 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. - - - -remove - - Use this to remove the server from the NT services - (Windows 2000/NT only). - - - -t - minutes - - Idle session timeout, in minutes. - - - -k - size - - Maximum record size/message size, in kilobytes. - - - @@ -820,36 +770,74 @@ typedef struct bend_scan_rr { hostname | IP-number [: portnumber] - + The port number defaults to 210 (standard Z39.50 port). - For UNIX local socket the address is the name local file. + For UNIX, the address is the filename of socket. - - - Examples - - - - tcp:dranet.dra.com - - ssl:ssl.enterprise.com:3000 - - unix:/tmp/yaz - - For TCP/IP and SSL, the special hostname "@" is mapped to - the address INADDR_ANY, which causes the - server to listen on any local interface. + For TCP/IP and SSL, the special hostname @ + (at sign) is mapped to the address INADDR_ANY, + which causes the server to listen on any local interface. + Running the GFS on Unix + + Assuming the server application appname is + started as root, the following will make it listen on port 210. + The server will change identity to nobody + and write its log to /var/log/app.log. + + appname -l /var/log/app.log -u nobody tcp:@:210 + + + + The server will accept Z39.50 requests and offer SRU service on port 210. + + + Setting up Apache as SRU Frontend + + If you use Apache + as your public web server and want to offer HTTP port 80 + access to the YAZ server on 210, you can use the + + ProxyPass + directive. + If you have virtual host + srw.mydomain you can use the following directives + in Apache's httpd.conf: + + <VirtualHost *> + ErrorLog /home/srw/logs/error_log + TransferLog /home/srw/logs/access_log + ProxyPass / http://srw.mydomain:210/ + </VirtualHost> + + + + The above for the Apache 1.3 series. + + + Running a server with local access only + + Servers that is only being accessed from the local host should listen + on UNIX file socket rather than a Internet socket. To listen on + /tmp/mysocket start the server as follows: + + appname tcp:/tmp/mysocket + + + + + Virtual Hosts + &gfs-virtual; - +