Installing the Open Source Xavier XML/A client on the Jedox Premium OLAP Suite

Jedox is a software vendor that specializes in OLAP services and solutions. The company has been around quite a while and is probably best known for their PALO MOLAP engine and the matching add-in for Microsoft Excel.

Jedox' flagship product, Jedox Premium comprises the Palo MOLAP engine, API's, a REST server, and ETL server, and client tools. It also comes with a MDX interpreter and a XML for Analysis server. An interesting tidbit is that the MDX layer is not considered native, and Jedox' own clients use a lower level API, or address it via the REST service.

In this blog post I will explain how to install and configure the Open Source browser-based ad-hoc query and analysis tool Xavier to use it with Jedox. A video of the process is embedded below:


Here's a written list of instructions to get up and running with Xavier and Jedox:

1. Download Jedox Premium. Run the downloaded installer to actually install the product. By default, it will be installed in C:\Program Files (x86)\Jedox\Jedox Suite. In the remainder of this post, I will refer to this directory as "the Jedox Suite directory".
2. Download xavier.zip. Unpack the zip. A xavier directory will be extracted.
3. Stop the JedoxSuiteHttpdService. If you don't know about windows services, then look here.
4. Copy the xavier directory that you extracted from xavier.zip into the Jedox Suite\httpd\app\docroot directory.
5. Open the Jedox Suite/httpd/conf/httpd.conf file in a text editor. You should probably make a backup copy of the httpd.conf file before editing it so you can always revert your changes.
6. Add a line to load the HTTP proxy module. To do that, search the httpd.conf file for a bunch of lines that start with LoadModule. Look for a line that reads:
   
   LoadModule proxy_http_module modules/mod_proxy_http.so
   
   In my installation, the line is already present, like this:

   <IfDefine JDX_DEV>
   LoadModule log_config_module modules/mod_log_config.so
   LoadModule proxy_http_module modules/mod_proxy_http.so
   LoadModule setenvif_module modules/mod_setenvif.so
   </IfDefine>
       

   Now, what you'll want to do is to cut this line out of the <IfDefine JDX_DEV> block, and put it outside that block, for example, right before it, like this:

   LoadModule proxy_http_module modules/mod_proxy_http.so
   <IfDefine JDX_DEV>
   LoadModule log_config_module modules/mod_log_config.so
   LoadModule setenvif_module modules/mod_setenvif.so
   </IfDefine>
       

7. Add a proxy configuration so that web applications deployed on the Apache HTTP server can access the Jedox XML/A service as if it lives in the same domain as the web application. To do that, add a Location directive at the end of the httpd.conf file, like this:

   <Location /xavier/Xmla>
     ProxyPass http://localhost:4242/xmla/
     ProxyPassReverse http://localhost:4242/xmla/
     SetEnv proxy-chain-auth
   </Location>
       

   This allows a web application on the Apache HTTP server to access the XML/A service via the URL /xavier/Xmla. By default, the place where the Jedox XML/A service lives is http://localhost:4242/xmla. You can verify this by crosscecking this with the configation in Jedox Suite\odbo\config.ini: the values for the MDXAddress and MDXPort should match the server and port in the URLs configured for ProxyPass and ProxyPassReverse
8. Save the changes to your httpd.conf file, and start the JedoxSuiteHttpdService. If the service starts, you should be good to go. If it doesn't, check the Jedox Suite/log/apache_error.log file and see if you can find some information there that can help you troubleshoot your problem.

If all went well, you should now be able to navigate to http://localhost/xavier/resources/html/index.html and you should see the xavier welcome screen. Note that this assumes the Jedox HTTP server is running on its default port (80). If you chose another port for the HTTP server when installing Jedox, the URL for xavier would have to be amended respectively. For example, I chose port 8181, and hence my URL would be http://localhost/xavier/resources/html/index.html instead.

If you're in doubt what port you chose for your Jedox HTTP server, you can look it up in the Jedox Suite/httpd/conf/httpd.conf file. Look for a line that starts with Define JDX_PORT_HTTP. The port is specified right after that, enclosed in double quotes.

Running Pentaho BI Server behind a proxy

To whom it may concern - a quick hands-on guide for running the Pentaho BI server behind a proxy

Prerequisites

This post assumes you're running Ubuntu linux (or at least a Debian) and that you have both the apache Httpd server as well as the Pentaho BI server installed.

Apache HTTP Server

If you haven't got apache installed, this is your line:

$ sudo apt-get install apache2

You can then control the apache2 Http server using the apaceh2ctl script. For instance, to start it, do:

$ sudo apache2ctl start

Once it's started you can navigate to its homepage to verify that it is running:

http://localhost/

You can stop it by running

$ sudo apache2ctl stop

If you're changing apache's configuration, you need to restart it to allow changes to take effect using this command:

$ sudo apache2ctl restart

.

Java

Pentaho relies on Java. If not installed already you can get it like this:

$ sudo apt-get install openjdk-6-jdk

Pentaho BI Server

If you haven't got the Pentaho BI Server, download the latest version from sourceforge, and unpack the archive in some location you find convenient. (For development purposes I simply keep and run it in a subdirectory of my home directory)

You can start the pentaho BI Server by cd-ing into the biserver-ce directory and then run:

$ ./start-pentaho.sh

You can then navigate to its homepage:

http://localhost:8080/pentaho/Home

(Simply navigating to http://localhost:8080 will automatically redirect you there too).

It can be useful to monitor the log while it's running:

$ tail -f tomcat/logs/catalina.out

If you want to change something in Pentaho's configuration, you need to stop the server and then restart it. This is done by running:

$ ./stop-pentaho.sh

Configuring Proxy support for Apache

Boris Kuzmanovic wrote an excellent post to setting up proxy support for Apache. My summary (and adjustment) follows below.

First, change the apache configuration to load the required proxy modules:

$ sudo a2enmod proxy
$ sudo a2enmod proxy_http

Then, edit any site definitions to use the proxy. I just modified the default site definition:

$ sudo geany /etc/apache2/sites-enabled/000-default

Inside the <VirtualHost> section, I added these snippets immediately above the </VirtualHost> that ends the section:

    <Location /pentaho/>
      ProxyPass http://localhost:8080/pentaho/
      ProxyPassReverse http://localhost:8080/pentaho/
      SetEnv proxy-chain-auth
    </Location>

    <Location /pentaho-style/>
      ProxyPass http://localhost:8080/pentaho-style/
      ProxyPassReverse http://localhost:8080/pentaho-style/
      SetEnv proxy-chain-auth
    </Location>

After making these changes, we need to restart apache:

$ sudo apache2ctl restart

.

These two <Location> directives are now effectively tunneled to the respective locations on the Pentaho BI Server, and vice versa, the response is passed back.

Using mod_proxy_ajp instead of proxy_http

While the regular HTTP proxy simply works, there is a better, more thightly integrated solution. The regular HTTP proxy basically handles HTTP requests received by the Apache Httpd server by sending a new, equivalent HTTP request, through to the tomcat server. Likewise, Tomcat's HTTP response is then send back as a new equivalent HTTP response to the source of the original, initial request.

So, that's twice a transport over HTTP.

Things can be improved by routing the incoming HTTP request to the tomcat server using a binary protocol called the AJP (Apache JServ) protocol. (For a detailed comparison, see this excellent comparison between HTTP/HTTPS and AJP.)

Fortunately, the steps to setup an AJP proxy are almost identical to those for setting up a regular HTTP proxy. First, enable the ajp proxy module:

$ sudo a2enmod proxy
$ sudo a2enmod proxy_ajp

(Note that the proxy module was already enabled as part of setting up the regular http proxy. The line is repeated here for completeness, but not necessary if you completed the steps for setting up support for the regular http proxy. You can enable either or both the proxy_http and the proxy_ajp modules, and both require the proxy module.)

Then, we edit again the site configuration to use the proxy. Since the locations /pentaho/ and /pentaho-style/ were already used, we first comment those out:

    #<Location /pentaho/>
    #  ProxyPass http://localhost:8080/pentaho/
    #  ProxyPassReverse http://localhost:8080/pentaho/
    #  SetEnv proxy-chain-auth
    #</Location>

    #<Location /pentaho-style/>
    #  ProxyPass http://localhost:8080/pentaho-style/
    #  ProxyPassReverse http://localhost:8080/pentaho-style/
    #  SetEnv proxy-chain-auth
    #</Location>

Then we add equivalent lines going via the AJP proxy:

    ProxyPass /pentaho ajp://localhost:8009/pentaho
    ProxyPassReverse /pentaho ajp://localhost:8009/pentaho

    ProxyPass /pentaho-style ajp://localhost:8009/pentaho-style
    ProxyPassReverse /pentaho-style ajp://localhost:8009/pentaho-style

(The bit that goes ajp://localhost:8009 refers to the ajp service that is running on port 8009 of tomcat by default.)

Again we have to restart the apache service for the changes to take effect:

$ sudo apache2ctl restart

.

Acknowledgements

Thanks to Paul Stöllberger, Pedro Alves and Tom Barber for valuable feedback and background information regarding AJP.