Presentation by Tomaz Cerar (Red Hat), delivered at the London JBoss User Group event on the 12th of February 2014. Watch the video here: http://www.youtube.com/watch?v=eu9K5NLUKBI Join London JBUG: http://www.c2b2.co.uk/jbug

2. Extending WildFly
Tomaž Cerar, Red Hat

3. Agenda
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What are extensions
WildFly core
Write simple extension
Silly deployment detector
Demo

4. What are extensions?
• Entry point for extending WildFly
• Can provide
– new deployment types
– new model
– services
– resources

5. WILDFLY CORE

6. WildFly core
• Really small (< 15 mb)
• Consists of
– JBoss Modules
– Modular Service Controller (MSC)
– Domain management (CLI, rest)
– Deployment manager
– Logging

7. JBoss Modules
• Modular class loader
• Isolated class loader
• Can be a set of many resources (jars)

8. Domain management
• Manages configuration
• Backbone for all extensions
• Accessible via
– Extensions
– CLI
– Admin console
– DMR clients
–…

9. MSC
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Truly concurrent service container
Handles service dependencies
Handles lifecycle
“real” functionality should be in services

10. DMR
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Detyped Model Representation
JSON like
Internal format for all operations
Internal model (ModelNode)

11. Domain model definition
• Attributes
• Resources
• Resource tree
– PathElement
– Single target (key=value)
– Multi target (key=*)
• Resolvers & multi language support

12. Operation handlers
• Defines operations on resources
• Execution stage
– MODEL
– RUNTIME
– VERIFY
– DOMAIN
– DONE
• Can be chained

13. Resource handlers
• Every resource needs add & remove
• In MODEL phase
– validate and set model
• In RUNTIME phase
– Add services
– Add deployment processors

14. Deployment manager
• Deployment repository
• Defines deployment phases
• Provides deployment processor
infrastructure
• Can be used via
– Domain management
– Deployment scanner

15. Deployment processor
• Hooks into deployment lifecycle
• Can modify deployment behavior
• Can define new deployment type

16. Extension point
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Loaded via Service Loader
Can define many subsystems
Packaged as JBoss Module
Referenced in configuration
Can provide any new functionality

17. Extension loading
standalone.xml
<extension module="org.wildfly.extension.sdd"/>
ServiceLoader
org.jboss.as.controller.Extension
org.wildfly.extension.sdd.SDDExtension

18. WRITE SIMPLE EXTENSION

19. Building blocks
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Define Extension point
Define Root Model
Define Add handler
Define XML parser
Define XML marshaller

20. Extension class
public class SDDExtension implements Extension {
@Override
public void initializeParsers(ExtensionParsingContext context) {
}
@Override
public void initialize(ExtensionContext context) {
}
}

21. Service Loader entry
• Point it to implementation class
– org.wildfly.extension.sdd.SDDExtension

22. Define root model
public class SDDRootResource extends PersistentResourceDefinition {
static final SDDRootResource INSTANCE = new SDDRootResource();
private SDDRootResource() {
super(SDDExtension.SUBSYSTEM_PATH,
SDDExtension.getResolver(),
new SDDSubsystemAdd(),
ReloadRequiredRemoveStepHandler.INSTANCE);
}
@Override
public void registerOperations(ManagementResourceRegistration resourceRegistration) {
super.registerOperations(resourceRegistration);
resourceRegistration.registerOperationHandler(GenericSubsystemDescribeHandler.DEFINITION,
GenericSubsystemDescribeHandler.INSTANCE, false);
}
}

23. Define root add handler
public class SDDSubsystemAdd extends AbstractBoottimeAddStepHandler {
{
@Override
protected void populateModel(ModelNode operation, ModelNode model) throws OperationFailedException
}
model.setEmptyObject();

24. Define namespace
enum Namespace {
// must be first
UNKNOWN(null),
SDD_1_0("urn:wildfly:domain:sdd:1.0");
/**
* The current namespace version.
*/
public static final Namespace CURRENT = SDD_1_0;
private final String name;
}
Namespace(final String name) {
this.name = name;
}

25. Define XML model
<subsystem xmlns="urn:wildfly:domain:sdd:1.0"/>

26. Define parser
class SDDSubsystemParser implements XMLStreamConstants,
XMLElementReader<List<ModelNode>> {
static final PersistentResourceXMLDescription xmlDescription =
builder(SDDRootResource.INSTANCE).build();
@Override
public void readElement(XMLExtendedStreamReader reader, List<ModelNode>
list) throws XMLStreamException {
xmlDescription.parse(reader, PathAddress.EMPTY_ADDRESS, list);
}
}

27. Define marshaller
public void writeContent(XMLExtendedStreamWriter writer, SubsystemMarshallingContext context) throws
XMLStreamException {
}
context.startSubsystemElement(Namespace.CURRENT.getUriString(), false);
writer.writeEndElement();

28. Making it all work
@Override
public void initializeParsers(ExtensionParsingContext context) {
context.setSubsystemXmlMapping(SUBSYSTEM_NAME, Namespace.SDD_1_0.getUriString(),
SDDSubsystemParser.INSTANCE);
}
@Override
public void initialize(ExtensionContext context) {
final SubsystemRegistration subsystem =
context.registerSubsystem(SUBSYSTEM_NAME, 1, 0, 0);
final ManagementResourceRegistration registration =
subsystem.registerSubsystemModel(SDDRootResource.INSTANCE);
}
subsystem.registerXMLElementWriter(SDDSubsystemParser.INSTANCE);

29. Module definition
<module xmlns="urn:jboss:module:1.1" name="org.wildfly.extension.sdd">
<resources>
<resource-root path="wildfly-sdd-1.0.0.Alpha1-SNAPSHOT.jar"/>
</resources>
<dependencies>
<module name="javax.annotation.api"/>
<module name="javax.api"/>
<module name="org.jboss.jandex"/>
<module name="org.jboss.staxmapper"/>
<module name="org.jboss.as.controller"/>
<module name="org.jboss.as.server"/>
<module name="org.jboss.modules"/>
<module name="org.jboss.msc"/>
<module name="org.jboss.vfs"/>
<module name="org.jboss.logging"/>
</dependencies>
</module>

30. Module layout

31. What does it do?
Nothing!

32. How to test it?
• Test harness enables you to test
– xml parser
– model consistency
– MSC services
– Compatibility (transformers)
– Localization resources
–…

33. public class SDDSubsystemTestCase extends
AbstractSubsystemBaseTest {
public SDDSubsystemTestCase() {
super(SDDExtension.SUBSYSTEM_NAME, new SDDExtension());
}
}
@Override
protected String getSubsystemXml() throws IOException {
return readResource("sdd-1.0.xml");
}

34. SILLY DEPLOYMENT DETECTOR

35. Let’s have subsystem that will detect
common problems in deployments.

36. Silly deployment detector
• Idea come from forums
• Should be able to detect
– Redundant JARs
– Blacklisted jars
– Bundling provided classes/packages
– Common xml misconfigurations
–…

37. Black listed jar detector
• You configure blacklisted jar names
• Subsystem warns you if they are found

38. What we need
• Domain model
• XML parser to handle new model
• Deployment processor

39. Model definition
class JarBlackListResourceDefinition extends SimpleResourceDefinition {
static final JarBlackListResourceDefinition INSTANCE = new JarBlackListResourceDefinition();
private static final StringListAttributeDefinition JAR_NAMES =
new StringListAttributeDefinition.Builder("jar-names")
.setAllowNull(false)
.setXmlName("jars")
.build();
private JarBlackListResourceDefinition() {
super(SDDExtension.JAR_BLACKLIST_PATH,
SDDExtension.getResolver(),
new JarBlackListAdd(),
ReloadRequiredRemoveStepHandler.INSTANCE);
}
@Override
public void registerAttributes(ManagementResourceRegistration resourceRegistration) {
resourceRegistration.registerReadWriteAttribute(JAR_NAMES, null, new
ReloadRequiredWriteAttributeHandler(JAR_NAMES));
}

40. XML
<subsystem xmlns="urn:wildfly:domain:sdd:1.0">
<blacklist jars="mail-*.jar,activation*.jar,javassist-*.jar,jgroups-*.jar,jboss-logging-*.jar"/>
</subsystem>

41. Deployment processor
• Needs to check all jars in deployment
• Compare them with blacklist

42. Demo

43. • https://github.com/ctomc/wildfly-sdd
• https://github.com/wildfly/wildfly
• http://www.wildfly.org/

44. Questions?