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Using StrixDB with httpd (Apache HTTP Server)

Apache httpd module for SPARQL and SPARQL/Update 

Copyright © 2010 StrixDB. Freely available under the terms of the StrixDB license.

Overview

This document explains how to configure httpd (Apache HTTP Server) to use the StrixDB RDF store. Configured Apache Server could :

  • download and upload RDF graphs into the RDF store (in XML or turtle format),
  • respond to SPARQL and SPARQL/Update HTTP requests with the SPARQL protocol
  • respond to HTTP requests with dynamic Lua pages
    • created from Lua scripts or
    • created from files with embedded Lua code.

Status and License

Current version of StrixStore is 0.92
The current version is a beta release and could be used free of charges for any purpose. The current version is ruled by the terms of the StrixDB license for beta releases.

Lua API is not final: it could be extended.

History

  • 14-07-2010    Initial release v 0.9
  • 02-09-2010    release 0.91: improved XML/RDF and RFC 2396 compliance
  • 06-11-2010    release 0.92: could be used with APACHE http server.  StrixServer no more maintained.

Download and installation (for Windows)

Install an httpd (Apache HTTP Server) of version 2.2.  The standard Windows installation at http://httpd.apache.org/  could be used.

Download a StrixStore from http://opoirel.free.fr/strixDB/download.html (minimum version 0.92). Installation is easy : just unzip files into a folder.

Copy the file mod_strixdb.so into the modules folder of Apache Server (with standard installation, this folder is  C:\Program Files\Apache Software Foundation\Apache2.2\modules )

Configuration

You have to modify the Apache server configuration file : the default configuration file with standard installation is C:/Program Files/Apache Software Foundation/Apache2.2/conf/httpd.conf

Example of configuration :

LoadModule	strixdb_module	modules/mod_strixdb.so

<IfModule strixdb_module>
StrixRoot	"C:/Program Files/StrixDB/"
StrixFilename 	"D:/RDF/strix.db"
StrixInitfile 	"D:/RDF/initDatabase.lua"
StrixDefaultURI "http://mydefault/graph/uri/"
StrixTruncate	true
</IfModule>

<Location /strixdb>
   SetHandler strix-db-handler
</Location>

AddHandler strix-luapage-handler .hlua
AddHandler strix-lua-handler .lua

Explanations :

LoadModule	strixdb_module	modules/mod_strixdb.so

REQUIRED: load the strixdb module

StrixRoot	"C:/Program Files/StrixDB/"

REQUIRED: defines location of StrixDB installation (where are StrixStore.dll, etc...)

StrixFilename 	"D:/RDF/strix.db"

Defines the path of the persistence file used to store graphs.
NOTES: this parameter is not required (by default it is "./strix.db"). If not specified, file will be located in the directory of Apache httpd.

StrixInitfile 	"D:/RDF/initDatabase.lua"

Use this parameter to specify a file to run at creation (first opening) of the database file (specified with parameter StrixFilename).

StrixDefaultURI "http://www.myfoaf.com/"

Defines the default graph URI. If not specified, use URI returned by gethostname C function.

StrixTruncate	true

If this parameter is set to true, the database file is deleted at the server start.

AddHandler strix-luapage-handler .hlua

Associate an extension file (here .hlua) to the dynamic pages (containing embedded lua code inside <?lua ?> tags).

AddHandler strix-lua-handler .lua

Associate an extension file (here .lua) to full interpreted Lua pages.

Advanced parameters (be carefull)

StrixPoolsize <integer> the number of pages cached in the poolSize. Each page has 4K. Big poolSize improves speed but consumes memory. default=100*1024
StrixInitindex <integer> Size of the inital index (bitmap). default=8*1024*1024
StrixQuantum <integer> Size of the new allocated quantum (bitmap) when the allocated file is full. default=512*1024*1024
StrixSafe <boolean>   default=false
StrixNobuffer <boolean>   default=false
StrixWritethrough <boolean> if true, wait disk write acknowledge event for each write transaction (safer but slower with SPARQL/Update transactions). default=false

 

Dynamic Lua Pages

With StrixDB, Lua can be used as a nice alternative to php. We propose 2 uses of Lua:

  • as script generating the HTTP response with print function.
  • as embedded Lua code inside a file (code is inside <?lua  ?> tags).

First we have to configure Apache httpd.conf :

AddHandler strix-luapage-handler .hlua
AddHandler strix-lua-handler .lua

Explanations: the strix-luapage-handler handler associate file with a .hlua extension with the embedded Lua code execution. The strix-lua-handler handler associate .lua extension with the script generation. You could change the extensions as needed. These association are available for all Apache accessible files.

To test, just copy the folder tests/scripts from the StrixDB distribution into your DocumentRoot folder specified in httpd.conf.

Embedded Lua code

Lua code must be included inside <?lua  ?> . See test.hlua for an example. The MIME type of the file is set by the Lua function apache.setContent

apache.setContent('text/html')

In the sample testCreatedRdf.hlua, the content type is set to application/rdf+xml; charset=utf-8 so that the browser will interpret the response as RDF/XML.

Script generated responses

In this case, all the file is generated by the Lua script. The sample test.lua shows how to generate an HTML file. The sample testCreateRdf.lua shows how to generate a RDF/turtle file.

As for embedded code, the Lua function apache.setContent set the MIME type of the response.

Lua functions reference

With dynamic Lua pages, a Lua table named 'apache' make the bindings with apache.

apache.host

returns the hostname of the request.

apache.filename

returns the filename requested (this file is the current file executed as a script for  strix-lua-handler handler and sended for the  strix-luapage-handler handler)

apache.method

 "GET" for a HTTP GET request, "POST" for a HTTP POST request.

apache.uri

 the uri of the request.

apache.authentication

returns 2 values : the user and authentication type.

apache.root ()

returns the root folder of Apache (specified with DocumentRoot in the Apache configuration file).

apache.datas ()

returns a table of the content datas (only avalaible with a POST request).

apache.headers ()

returns a table of the apache headers_i.

apache.args ()

returns a table of the arguments of the request. NOTE: with a POST request, use apache.datas() to get the content.

apache.setStatus ( <int> )

Set the status of the response (for example, apache.setStatus( 404 ) ....)

apache.setContent ( <string> )

Set the MIME type of the response.