Exception Child services have no parent when starting Optaplanner application - drools

Question

I have a test program that uses optaplanner. There is no direct use of KIE API's but it looks like they are being invoked behind the scenes. This may be related to the fact that I am using DROOLS for the score calculation. The program works from the IDE or through maven, but I want to create a standalone jar that will not require maven.
I used the maven assembly plugin to build a fat jar with all dependencies included to be run standalone.
When I run java -jar target/OptaPlannerTest-1.4-SNAPSHOT-jar-with-dependencies.jar I get :
Exception in thread "main" java.lang.ExceptionInInitializerError
at org.kie.api.internal.utils.ServiceRegistry.getInstance(ServiceRegistry.java:27)
at org.kie.api.KieServices$Factory$LazyHolder.<clinit>(KieServices.java:332)
at org.kie.api.KieServices$Factory.get(KieServices.java:339)
at org.optaplanner.core.config.score.director.ScoreDirectorFactoryConfig.buildDroolsScoreDirectorFactory(ScoreDirectorFactoryConfig.java:460)
at org.optaplanner.core.config.score.director.ScoreDirectorFactoryConfig.buildScoreDirectorFactory(ScoreDirectorFactoryConfig.java:331)
at org.optaplanner.core.config.solver.SolverConfig.buildSolver(SolverConfig.java:220)
at org.optaplanner.core.impl.solver.AbstractSolverFactory.buildSolver(AbstractSolverFactory.java:61)
at com.github.wshackle.optaplannertest.Main.main(Main.java:38)
Caused by: java.lang.RuntimeException: Child services [org.kie.api.internal.assembler.KieAssemblers] have no parent
at org.kie.api.internal.utils.ServiceDiscoveryImpl.buildMap(ServiceDiscoveryImpl.java:186)
at org.kie.api.internal.utils.ServiceDiscoveryImpl.getServices(ServiceDiscoveryImpl.java:97)
at org.kie.api.internal.utils.ServiceRegistryImpl.<init>(ServiceRegistryImpl.java:36)
at org.kie.api.internal.utils.ServiceRegistryImpl$LazyHolder.<clinit>(ServiceRegistryImpl.java:32)
Line 38 of Main.java is only two lines into the application, so all it has done is load the config file and try to build the solver.
SolverFactory<Plan> solverFactory = SolverFactory.createFromXmlResource(
"com/github/wshackle/optaplannertest/solverConfig.xml");
Solver<Plan> solver = solverFactory.buildSolver();
solverConfig.xml is:
<solver>
<!-- Domain model configuration -->
<scanAnnotatedClasses>
<packageInclude>com.github.wshackle.optaplannertest.model</packageInclude>
</scanAnnotatedClasses>
<!-- Score configuration -->
<scoreDirectorFactory>
<scoreDrl>com/github/wshackle/optaplannertest/scoreRules.drl</scoreDrl>
</scoreDirectorFactory>
<!-- Optimization algorithms configuration -->
<termination>
<secondsSpentLimit>5</secondsSpentLimit>
</termination>
</solver>
In cast it is relevant my pom is this:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.github.wshackle</groupId>
<artifactId>OptaPlannerTest</artifactId>
<version>1.4-SNAPSHOT</version>
<packaging>jar</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<optiplanner.version>7.3.0.Final</optiplanner.version>
<main.class>com.github.wshackle.optaplannertest.Main</main.class>
</properties>
<dependencies>
<dependency>
<groupId>org.optaplanner</groupId>
<artifactId>optaplanner-core</artifactId>
<version>${optiplanner.version}</version>
</dependency>
<dependency>
<groupId>org.kie</groupId>
<artifactId>kie-api</artifactId>
<version>${optiplanner.version}</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.25</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<scope>runtime</scope>
<version>1.2.3</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.5.5</version>
<configuration>
<archive>
<manifest>
<mainClass>${main.class}</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
<executions>
<execution>
<id>make-assembly</id> <!-- this is used for inheritance merges -->
<phase>package</phase> <!-- bind to the packaging phase -->
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
The complete list of files in the jar is shown at
https://gist.github.com/wshackle/8887aac8a10e8c4b1f862a4bda288e41
I used grep to verify they seem to include the expected classes for each jar dependancy:
> grep -c org/kie/api jarlisting.txt
391
> grep -c org/kie/internal jarlisting.txt
364
> grep -c org/optaplanner/core jarlisting.txt
841
> grep -c org/drools/core jarlisting.txt
2175
> grep -c org/drools/compiler jarlisting.txt
832

Answer 1

The problem is that the following jar files all contain different versions of META-INF/kie.conf:
optaplanner-core-7.3.0.Final.jar
kie-internal/7.3.0.Final/kie-internal-7.3.0.Final.jar
drools-core-7.3.0.Final.jar
drools-compiler-7.3.0.Final.jar
When the maven-assembly-plugin puts them together only one version of the META-INF/kie.conf can be included. When building the solver the Optaplanner library will indirectly call getResources("META-INF/kie.conf") on the current Thread context classloader. If there are multiple jars on the classpath then all of them will be found and the resulting configuration will be the product of parsing all of them. In order to make this work in a single fat uber jar the kie.conf files need to be moved to different file names and a classloader overloaded to direct the library to use them at the new names. (It might also be possible to combine them into a single kie.conf file)
Extract and move the kie.conf files:
jar -xf ~/.m2/repository/org/optaplanner/optaplanner-core/7.3.0.Final/optaplanner-core-7.3.0.Final.jar META-INF/kie.conf
mv META-INF/kie.conf src/main/resources/optaplanner-core-kie.conf
jar -xf ~/.m2/repository/org/kie/kie-internal/7.3.0.Final/kie-internal-7.3.0.Final.jar META-INF/kie.conf
mv META-INF/kie.conf src/main/resources/kie-internal-kie.conf
jar -xf ~/.m2/repository/org/drools/drools-core/7.3.0.Final/drools-core-7.3.0.Final.jar META-INF/kie.conf
mv META-INF/kie.conf src/main/resources/drools-core-kie.conf
jar -xf ~/.m2/repository/org/drools/drools-compiler/7.3.0.Final/drools-compiler-7.3.0.Final.jar META-INF/kie.conf
mv META-INF/kie.conf src/main/resources/drools-compiler-kie.conf
Then overload and set the thread context loader.
ClassLoader oldClassLoader = Thread.currentThread().getContextClassLoader();
URL[] localKieConfUrls = new URL[]{
ClassLoader.getSystemResource("optaplanner-core-kie.conf"),
ClassLoader.getSystemResource("kie-internal-kie.conf"),
ClassLoader.getSystemResource("drools-core-kie.conf"),
ClassLoader.getSystemResource("drools-compiler-kie.conf")
};
ClassLoader newClassLoader = new ClassLoader(oldClassLoader) {
private final URL[] kieConfUrls = localKieConfUrls;
#Override
public Enumeration<URL> getResources(String name) throws IOException {
if ("META-INF/kie.conf".equals(name)) {
return new Enumeration<URL>() {
int index;
#Override
public boolean hasMoreElements() {
return index < kieConfUrls.length;
}
#Override
public URL nextElement() {
return kieConfUrls[index++];
}
};
}
return super.getResources(name);
}
};
Thread.currentThread().setContextClassLoader(newClassLoader);

Answer 2

I agree that the problem is as #WillSchackleford describes:
The problem is that the following jar files all contain different versions of META-INF/kie.conf:
optaplanner-core-7.3.0.Final.jar
kie-internal/7.3.0.Final/kie-internal-7.3.0.Final.jar
drools-core-7.3.0.Final.jar
drools-compiler-7.3.0.Final.jar
When the maven-assembly-plugin puts them together only one version of the META-INF/kie.conf can be included.
The best trick to combine all of these kie.conf files is to use a transformer in your maven config, like so:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<!-- get all project dependencies -->
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
<!-- MainClass in mainfest make a executable jar -->
<archive>
<manifest>
<mainClass>com.paconsulting.powerpeers.PowerPeersDemo</mainClass>
</manifest>
</archive>
<transformers>
<transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
<resource>META-INF/kie.conf</resource>
</transformer>
</transformers>
</configuration>
<executions>
<execution>
<id>make-assembly</id>
<!-- bind to the packaging phase -->
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
This creates one META-INF/kie.conf file with the content of any of the kie.conf files it finds.

Answer 3

Run "mvn dependency:tree" and you'll see that optaplanner-core depends on kie-api, kie-internal-api, drools-core and drools-compiler. One of those will be missing in your fat jar.

Answer 4

I was having the same problem with the following pom
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
..
<dependencies>
<dependency>
<groupId>org.optaplanner</groupId>
<artifactId>optaplanner-core</artifactId>
<version>${optaPlanner.version}</version>
</dependency>
...
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>${jar.plugin.version}</version>
<configuration>
<archive>
<addMavenDescriptor>false</addMavenDescriptor>
<compress>false</compress>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>libs/</classpathPrefix>
<mainClass>${mainClass}</mainClass>
</manifest>
<index>true</index>
<manifestEntries>
<impl-version>${project.version}</impl-version>
</manifestEntries>
</archive>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>${dependency.plugin.version}</version>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>${project.build.directory}/libs</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<version>${assembly.plugin.version}</version>
<configuration>
<descriptors>
<descriptor>assembly/release.xml</descriptor>
</descriptors>
<finalName>${distribution.file.name}</finalName>
<outputDirectory>${project.build.directory}/dist</outputDirectory>
<workDirectory>${project.build.directory}/assembly/work</workDirectory>
</configuration>
<executions>
<execution>
<id>make-assembly</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
Removing
<index>true</index>
solved my problem. Hope this helps others as well.

Answer 5

For people using maven-shade-plugin, here is a proposed fix that is going to merge the META-INF/kie.conf that are duplicated into a single file using the AppendingTransformer https://stackoverflow.com/a/53273253/5903731

Answer 6

I have also met this error but i found a solution with different way. Instead of generating a jar file with all dependencies, generating jar file with library folder of dependencies is easier way for getting runnable jar file. To produce jar file with lib folder modify your pom.xml file as indicated below.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>prepare-package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>${project.build.directory}/lib</outputDirectory>
<overWriteReleases>false</overWriteReleases>
<overWriteSnapshots>false</overWriteSnapshots>
<overWriteIfNewer>true</overWriteIfNewer>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
<mainClassMain-Class</mainClass>
</manifest>
</archive>
</configuration>
</plugin>