WildFly Swarm Get Start Tips

System Properties


Add -Dswarm.debug.bootstrap=true before start swarm Container will enable bootstrap modules related detailed log.


Add -Dswarm.project.stage.file=/path/to/stage-file before start swarm Container will use a pre-configured stage file, more details about Project Stages refer to Configuration overlays using stage properties.


Add -Dswarm.http.eager=true to enable eagerly Open


Add -Dswarm.node.id={node id} define the swarm node id, alternatively.


Add -Dswarm.bind.address={ip addr} to bind servers, defaults to


Add -Dswarm.port.offset={number} to set a global port adjustment, defaults to 0


Add -Dswarm.http.port={port} to set he HTTP port to be used, defaults to 8080.

Develop Tips

How to enable more log

System properties with the prefix swarm.log. can enable more log, eg: -Dswarm.log.org.wildfly.swarm=DEBUG

All available log levels are:


How to debug swarm jar

Add -agentlib:jdwp=transport=dt_socket,address=8787,server=y,suspend=y before run -swarm.jar

java -agentlib:jdwp=transport=dt_socket,address=8787,server=y,suspend=y -jar NAME-swarm.jar

Maven plugins in swarm


A fraction in wildfly-swarm-fraction-plugin represent a maven assets, which consisted by groupId, artifactId and version. wildfly-swarm-fraction-plugin has defined several mojo goals, including:

how fraction-list works

If configu fraction plugin as below


then the plugin mainly do 2 apsects work:

Firstly, the plugin

  1. collect all dependencies which defined in dependencyManagement
  2. filter all dependencies which groupId start with org.wildfly.swarm
  3. convert all dependencies to MavenProjects
  4. filter all MavenProjects which project has defined any of these 3 properties(swarm.fraction.stability, swarm.fraction.tags, swarm.fraction.internal).
  5. convert all MavenProjects to fractions and keep in a map(groupId:artifactId -> fraction)
  6. create a org.wildfly.swarm, container fraction, and put it to map, and set all fractions dependent on container fraction.

Secondly, generate fractions descriptors

  • generate a fraction-list.txt under classspath, a example line in fraction-list.txt:
org.wildfly.swarm:jaxrs:2016.7-SNAPSHOT = org.wildfly.swarm:ee:2016.7-SNAPSHOT, org.wildfly.swarm:request-controller:2016.7-SNAPSHOT, org.wildfly.swarm:security:2016.7-SNAPSHOT, org.wildfly.swarm:naming:2016.7-SNAPSHOT, org.wildfly.swarm:undertow:2016.7-SNAPSHOT, org.wildfly.swarm:io:2016.7-SNAPSHOT, org.wildfly.swarm:logging:2016.7-SNAPSHOT, org.wildfly.swarm:container:2016.7-SNAPSHOT
org.wildfly.swarm:connector:2016.7-SNAPSHOT = org.wildfly.swarm:container:2016.7-SNAPSHOT

NOTE: fraction-list.txt contain all fractions and it’s depdencies, in above, jaxrs depend on ee, request-controller, security, naming, undertow, io, logging, container. and connector only depend on container.

  • generate a fraction-list.json under classpath, a example line in fraction-list.json:
  "groupId" : "org.wildfly.swarm",
  "artifactId" : "jaxrs",
  "version" : "2016.7-SNAPSHOT",
  "name" : "JAX-RS",
  "description" : "RESTful Web Services with RESTEasy",
  "tags" : "JavaEE,Web",
  "internal" : false,
  "stabilityIndex" : 3,
  "stabilityDescription" : "stable"
  "groupId" : "org.wildfly.swarm",
  "artifactId" : "connector",
  "version" : "2016.7-SNAPSHOT",
  "name" : "Connector",
  "description" : "Connector",
  "tags" : "",
  "internal" : true,
  "stabilityIndex" : 3,
  "stabilityDescription" : "stable"

NOTE: fraction-list.json contains all fractions, as above are jaxrs and connector fractions.

  • generate a fraction-list.js under classpath, this file only contain one line, as below
fractionList = [{"groupId":"org.wildfly.swarm","artifactId":"jaxrs","version":"2016.7-SNAPSHOT","name"    :"JAX-RS","description":"RESTful Web Services with RESTEasy","tags":"JavaEE,Web","internal":false,"stabilityIndex":3,"stabilityDescription":"stable"},{"groupId":"org.wildfly.swarm","artifactId":"connector","version":"2016.7-SNAPSHOT"    ,"name":"Connector","description":"Connector","tags":"","internal":true,"stabilityIndex":3,"stabilityDescription":"stable"}]

NOTE: fractionList in fraction-list.js contains all fractions, in above only contain jaxrs and connector fractions.

how process works

If configu fraction plugin as below


then the process task do the following:

1. Generate modules

This step against on compiled project’s source code, usually under target/classes path, these code are categorized by path and add into one module with 3 slots, in other words, in this section, 3 module.xml will generate

  1. main - the parent follder of a *Fraction.java, eg, org.wildfly.swarm.teiid
  2. api - under the main module
  3. runtime - under the main module

NOTE: This step depend on a module.conf file which under project base directory. In this file, every line define a module, eg, org.jboss.teiid. All this lines of modules be added as new created modules’ dependencies.

An example of generated module.xml

  • target/classes/modules/org/wildfly/swarm/teiid/main/module.xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<module xmlns="urn:jboss:module:1.5" name="org.wildfly.swarm.teiid" slot="main">
    <system export="true">
        <path name="org/wildfly/swarm/config"/>
        <path name="org/wildfly/swarm/teiid/internal"/>
        <path name="org/wildfly/swarm/teiid"/>
    <module export="true" name="org.wildfly.swarm.teiid" services="export" slot="api"/>
  • target/classes/modules/org/wildfly/swarm/teiid/api/module.xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<module xmlns="urn:jboss:module:1.5" name="org.wildfly.swarm.teiid" slot="api">
    <artifact name="org.wildfly.swarm:teiid:2016.7-SNAPSHOT">
          <path name="org/wildfly/swarm/config"/>
          <path name="org/wildfly/swarm/teiid/internal"/>
          <path name="org/wildfly/swarm/teiid"/>
    <module name="org.wildfly.swarm.container"/>
    <module name="org.jboss.teiid" slot="main"/>
  • target/classes/modules/org/wildfly/swarm/teiid/runtime/module.xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<module xmlns="urn:jboss:module:1.5" name="org.wildfly.swarm.teiid" slot="runtime">
    <artifact name="org.wildfly.swarm:teiid:2016.7-SNAPSHOT">
          <path name="org/wildfly/swarm/config"/>
          <path name="org/wildfly/swarm/teiid/internal"/>
          <path name="org/wildfly/swarm/teiid"/>
    <module name="org.wildfly.swarm.teiid" slot="main"/>
    <module name="org.wildfly.swarm.bootstrap" optional="true"/>
    <module name="org.wildfly.swarm.container" slot="runtime"/>
    <module name="org.jboss.teiid" slot="main"/>

2. create bootstrap conf

Set up bootstrap means create a wildfly-swarm-bootstrap.conf file under classpath, which contain the bootstrap module name, there are 3 ways to do this:

  1. Pre-packaged wildfly-swarm-bootstrap.conf file under src/main/resources
  2. Use system proeprties swarm.fraction.bootstrap define the bootstrap module name, eg -Dswarm.fraction.bootstrap=org.wildfly.swarm.teiid
  3. Walk through src, if file path end with Fraction.java, then this java’s package as bootstrap module name, eg org.wildfly.swarm.teiid.TeiidFraction referenced bootstrap module name is org.wildfly.swarm.teiid

NOTE: Both step 2 and 3 will create a wildfly-swarm-bootstrap.conf under classpath, which comtain the bootstrap module name.

3. Generate Dependencies

Firstly, collect the dependencies in provided-dependencies.txt.

The dependencies can be defined in provided-dependencies.txt filem which under src/main/resources/, which define the provided dependencies. Each line in provided-dependencies.txt represent a dependency, a format like :.

An example of provided-dependencies.txt:


Secondly, dump the collected dependencies to META-INF/wildfly-swarm-classpath.conf.

An example of META-INF/wildfly-swarm-classpath.conf:

  1 package(org.wildfly.swarm.container) replace(org.wildfly.swarm.container:main)
  2 package(org.wildfly.swarm.container) replace(org.wildfly.swarm.container:runtime)
  4 maven(org.wildfly.swarm:config-api) remove
  5 maven(org.wildfly.swarm:config-api-runtime) remove
  6 maven(org.ow2.asm:asm-all) remove
  7 maven(org.jboss.shrinkwrap:shrinkwrap-api) remove
  8 maven(org.jboss.shrinkwrap:shrinkwrap-spi) remove
  9 maven(org.jboss.shrinkwrap:shrinkwrap-impl-base) remove
 10 maven(org.jboss.shrinkwrap.descriptors:shrinkwrap-descriptors-spi) remove
 11 maven(org.jboss.shrinkwrap.descriptors:shrinkwrap-descriptors-api-base) remove
 12 maven(org.jboss.shrinkwrap.descriptors:shrinkwrap-descriptors-api-jboss) remove
 13 maven(org.jboss.shrinkwrap.descriptors:shrinkwrap-descriptors-api-javaee) remove
 14 maven(org.jboss.shrinkwrap.descriptors:shrinkwrap-descriptors-impl-base) remove
 15 maven(org.jboss.shrinkwrap.descriptors:shrinkwrap-descriptors-impl-jboss) remove
 16 maven(org.jboss.shrinkwrap.descriptors:shrinkwrap-descriptors-impl-javaee) remove
 17 maven(org.yaml:snakeyaml) remove
 18 maven(org.wildfly:wildfly-naming) remove
 19 maven(org.ow2.asm:asm-all) remove
 20 maven(org.yaml:snakeyaml) remove

4. Filter Modules

The Sequence diagram as below

Filter Modules

4- loadRewriteRules(): This step depend on module-rewrite.conf under base dir
5- walkProjectModules()
  1) requiredModules - keep all module's name both from class path and generated
  2) availableModules - keep all modules's dependency module's name both from class path and generated
  3) Both module.xml contained under resources/modules and target/classes/modules will be analyzed, each module's name add to availableModules, each module's dependencies module as requiredModules  
7- walkDependencyModules(): find all dependencies' modules definition, add each of them as availableModules
11- locateFillModules(): filter requiredModules which not exist in availableModules,
12- addFillModules()
  1) find the wildfly-feature-pack.xml, process feature pack xml
  2) addFillModule, generate modules to class path, analyze module xml, add module's name add to availableModules, it's dependencies module as requiredModules  
 3) addResources, if module define resources, like deployment, etc, generate to classpath  

This steps including the following procedures:

  • Load module rewrite rules

This step depend on module-rewrite.conf under base dir, which defines module rewrite rules. An example of module-rewrite.conf:

module: org.jboss.as.server
  optional: org.jboss.as.domain-http-interface
  • Walk Project Modules

Modules can be pre configured and packaged under resources/modules, walk Project Modules will load each module as a availableModules and each module’s dependencies module as requiredModules.

  • Walk Dependency Modules

Walk through all project dependencies, if a jar dependency has define the modules, then get all these modules as availableModules.

NOTE: org.wildfly.swarm:container has defined lots of modules(more than 50), which supply the base evn of running wildfly self container, completed list refer to modules list.

  • Index Potential Modules

Walk through all project dependencies, if a feature pack zip dependency has define, then index all zip file, if there are any modules defined, the add it as potentialModules


NOTE: so far, there are 3 kinds of modules: availableModules, requiredModules, potentialModules.

  • locate Fill Modules

5. execute Jandexer


The wildfly-swarm-plugin use a BuildTool to a build swarm jar, the BuildTool mainly has 2 aspects task:

Firstly, initialization.

  1. init projectArtifact - create a projectAsset base on project’s groupId, artifactId, version, etc.
  2. init fractionList - the fractions predefined by fraction-list project, which contains all wildfly-swarm fractions
  3. init properties - properties passed from mvn build
  4. set main class - main class name come from plugin config
  5. set bundleDependencies - bundleDependencies come from plugin config
  6. set executable - executable come from plugin config
  7. set executableScript - executableScript come from plugin config
  8. set fractionDetectMode - fractionDetectMode come from plugin config, default value is when_missing
  9. init ArtifactResolvingHelper - a MavenArtifactResolvingHelper be created
  10. set logger - BuildTool.SimpleLogger be create
  11. set additionalFractions - additionalFractions come from plugin config, BuildTool’s fraction method be used to set additionalFractions
  12. set dependency - any dependency of project will be set to BuildTool
  13. set Resources - any resource of project will be set to BuildTool
  14. set additionalModules - additionalModules come from plugin config

Secondly, build the -swarm.jar.

  1. analyze Dependencies - scan modules dependencies, scan bootstrap dependencies, analyze module dependencies, analyze provided dependencies
  2. add Wildfly Swarm Bootstrap Jar - move swarm bootstrap.jar to target archive.
  3. add WildFly Bootstrap Conf - META-INF/wildfly-swarm-bootstrap.conf
  4. add Manifest - mainClass be used
  5. add WildFly Swarm Properties - wildfly-swarm.properties
  6. add WildFly Swarm Application Conf - META-INF/wildfly-swarm-application.conf
  7. add WildFly Swarm Dependencies Conf - META-INF/wildfly-swarm-dependencies.conf
  8. add Additional Modules
  9. add Project Asset
  10. populate UberJar Maven Repository

A traditional config:


A simplest -swarm.jar

In this section, a project with a simple Main class and no dependency, then we focus on how -swam.jar be build.

WildFly-Swarm container

A WildFly-Swarm container is the topest interface for Micro-Service WildFly Swarm, it use to start a simple JBoss MSC container, a tradition usag is

Swarm swarm = new Swarm();

Fractions can be add to Container before container start, or Archives be deloyed after container start.

A WildFly-Swarm container represented by org.wildfly.swarm.container.Container, it contains the following private fileds represents the fractions, socketBindingGroups, socketBindings, server, deployer, etc.

Pre Container construction - bootstrap

java -jar X-swarm.jar can start the lightweight container and fragment, how does this implemented? If look at the META-INF/MANIFEST.MF uder the unberjar,

Manifest-Version: 1.0
Main-Class: org.wildfly.swarm.bootstrap.Main
WildFly-Swarm-Main-Class: org.teiid.test.swarm.Main

NOTE: org.wildfly.swarm.bootstrap.Main is the entrence of run uberjar, this Main be run before Container construction. WildFly-Swarm-Main-Class come from wildfly-swarm-plugin’s configuration.

Pre Container construction

The bootstrap Main first set boot.module.loader, then invoke the WildFly-Swarm-Main-Class. The getMainClass() code looks

String mainClassName = getMainClassName();
Module module = Module.getBootModuleLoader().loadModule(ModuleIdentifier.create("swarm.application"));

NOTE: How to set JBoss modules’s BootModuleLoader? - system properties boot.module.loader can be used set BootModuleLoader, for example, System.setProperty("boot.module.loader", BootModuleLoader.class.getName()).


Pre Container construction bootstrap mainly extended the jboss modules, made jboss modules can load zip file’s internal modules, this due to the implementation of org.wildfly.swarm.bootstrap.modules.BootModuleLoader.

The boot module loader is the initial loader that is established by the module framework. It typically is based off of the environmental module path unless it is overridden by specifying a different class name for the boot.module.loader system property.`

BootModuleLoader defines a series of Module Finders:

public class BootModuleLoader extends ModuleLoader {

    public BootModuleLoader() throws IOException {
        super(new ModuleFinder[]{
                new BootstrapClasspathModuleFinder(),
                new BootstrapModuleFinder(),
                new ClasspathModuleFinder(),
                new ContainerModuleFinder(),
                new ApplicationModuleFinder(),
                new FlattishApplicationModuleFinder(),

As UML diagram:

UML of ModuleFinder

  • BootstrapClasspathModuleFinder - Used only for loading dependencies of org.wildfly.bootstrap:main from its own jar. The classpath modules in bootstrap including: javax.api, javax.sql.api, org.jboss.msc, etc
  • BootstrapModuleFinder - Module-finder used only for loading the first set of jars when run in an fat-jar scenario.
  • ClasspathModuleFinder
  • BootstrapModuleFinder
  • ApplicationModuleFinder
  • FlattishApplicationModuleFinder

Container construction

Container construction

As figure, Container construction mainly do the following:

  1. Check the ‘swarm.debug.bootstrap’ system property, if true enable bootstrap debug
  2. init ‘userComponentClasses’, ‘explicitlyInstalledFractions’, ‘stageConfig’, ‘xmlConfig’, ‘stageConfigUrl’
  3. init main method ‘args’
  4. JBoss logger be initialized, used to as logging system for container
  5. create ShrinkWrap Domain, a domain encapsulates a shared Configuration to be used by all Archives
  6. configure command-line base on passed arguments,’Container(boolean debugBootstrap, String… args)’, args are command-line arguments
  7. If stageFile not null, load stage configuration

Once Swarm be constructed, usually, it’s start method be invoked, refer below section for more details.

Swarm start

The main procedure of Swarm start including:

  1. Swarm RuntimeServer as a bean instance be registered in Weld SE Container, all extentions be inject via Weld SE Container
  2. untimeServer statr invoke SelfContainedContainer’s start() method
  3. MSC container start and install services.

Swarm start

bootstrapOperations initilization

JBoss SelfContainedContainer start

A sample code to start MSC and install services via bootstrapOptions

import org.jboss.as.server.SelfContainedContainer;
import org.jboss.dmr.ModelNode;
import org.jboss.msc.service.ServiceActivator;
import org.jboss.msc.service.ServiceContainer;

SelfContainedContainer container = new SelfContainedContainer();
List<ModelNode> bootstrapOperations = new ArrayList<>();
SimpleContentProvider contentProvider = new SimpleContentProvider();
List<ServiceActivator> activators = new ArrayList<>();
ServiceContainer serviceContainer = container.start(bootstrapOperations, contentProvider, activators);