Fuseki webapp does not load FusekiAutoModules

[Ostrzyciel]

Version

5.2.0

What happened?

I wrote an implementation of FusekiAutoModule and registered it via the service loader. However, I can't get this to work when using the Fuseki web app (FusekiWebappCmd). It seems like the module is never discovered, called, anything.

I did some probing with a debugger and it seems that the FusekiAutoModules class is not called when starting via this main class. In FusekiMain there is this code that does it:

jena/jena-fuseki2/jena-fuseki-main/src/main/java/org/apache/jena/fuseki/main/cmds/FusekiMain.java

Lines 508 to 515 in f6a4f3a

	if ( withModules ) {
	// Use the discovered ones.
	FusekiAutoModules.enable(true);
	// Allows for external setting of serverConfig.fusekiModules
	if ( serverConfig.fusekiModules == null ) {
	FusekiAutoModules.setup();
	serverConfig.fusekiModules = FusekiAutoModules.load();
	}

But I can't find it in FusekiWebappCmd. There is also no parameter for enabling/disabling modules, which makes me guess that this was omitted by mistake when the module system was introduced.

I think this can be fixed by basically copy-pasting the module initialization part from FusekiMain to FusekiWebappCmd, along with the command-line argument. Assuming I'm correct in the assessment that this is really the issue 😆

Relevant output and stacktrace

No response

Are you interested in making a pull request?

Yes, but I'm not sure how to build Fuseki so that I can test the fix.

[Ostrzyciel]

In the meantime I've finally figured out where to find the FusekiMain JAR and how to run it. Fuseki module loading works there just fine, but it's disabled by default. I'm not sure if this is the intended behavior, I thought this says it should be enabled:

jena/jena-fuseki2/jena-fuseki-main/src/main/java/org/apache/jena/fuseki/main/sys/FusekiAutoModules.java

Lines 59 to 63 in f6a4f3a

	/**
	* Enable/disable discovery of modules using the service loader.
	* The default is 'enabled'.
	*/
	public static void enable(boolean setting) {

[afs]

Correct - the whole Fuseki module system is part of Fuseki main, not Fuseki webapp.

To add custom functionality to Fusekiwebap, you'll need to add the jar and repackage the server (see the current jena-fuseki-fulljar).

Webapps start up differently and can be run in environments that preclude additional jar files by design. They are supposed to be portable to different web application containers (Tomcat, Jetty, Resin, ...), A webapp is targetted at business logic,
middle tier functionality, originally running in a shared environment; not databases.

See #2775 for discussion about moving all development to the Fuskei main as base, and leaving the WAR file as fixed functionality.

[Ostrzyciel]

Ahhh, now I get it! Thank you for the detailed explanation and the context in #2775.

In that case, I will close this. For my module, I will switch to the Jena initialization system instead, because what I want to do is simple enough to work in this way as well.