calling celery.send_task() from jython fails when using maven - maven

Question

I have the following Java code that uses Jython to call the celery.send_task() method:
import org.python.util.PythonInterpreter;
public class SendTask {
static final String SEND_TASK_PY =
"from celery import Celery\n"+
"c = Celery('tasks', broker='amqp://', backend='amqp://')\n"+
"c.send_task('tasks.add', args=[2, 2], kwargs={})";
public static void main(String[] args) {
PythonInterpreter interpreter = new PythonInterpreter();
interpreter.exec(SEND_TASK_PY);
}
}
Which results with the following error:
mvn clean package
java -cp target/jython-celery-0.1-SNAPSHOT-jar-with-dependencies.jar SendTask
Exception in thread "MainThread" Traceback (most recent call last):
File "<string>", line 3, in <module>
File "/home/itaif/dev/jython-celery/target/jython-celery-0.1-SNAPSHOT-jar-with-dependencies.jar/Lib/celery/app/base.py", line 245, in send_task
File "/home/itaif/dev/jython-celery/target/jython-celery-0.1-SNAPSHOT-jar-with-dependencies.jar/Lib/celery/app/amqp.py", line 242, in publish_task
File "/home/itaif/dev/jython-celery/target/jython-celery-0.1-SNAPSHOT-jar-with-dependencies.jar/Lib/kombu/messaging.py", line 155, in publish
File "/home/itaif/dev/jython-celery/target/jython-celery-0.1-SNAPSHOT-jar-with-dependencies.jar/Lib/kombu/messaging.py", line 232, in _prepare
File "/home/itaif/dev/jython-celery/target/jython-celery-0.1-SNAPSHOT-jar-with-dependencies.jar/Lib/kombu/serialization.py", line 170, in encode
File "/home/itaif/dev/jython-celery/target/jython-celery-0.1-SNAPSHOT-jar-with-dependencies.jar/Lib/kombu/serialization.py", line 356, in dumps
TypeError: dumps(): takes no keyword arguments
For reference, here is the maven pom.xml that created the jar file:
<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>jython-celery</groupId>
<artifactId>jython-celery</artifactId>
<packaging>jar</packaging>
<version>0.1-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.python</groupId>
<artifactId>jython-standalone</artifactId>
<version>2.7-b1</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>net.sf.mavenjython</groupId>
<artifactId>jython-compile-maven-plugin</artifactId>
<version>1.2</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>jython</goal>
</goals>
</execution>
</executions>
<configuration>
<libraries>
<param>Celery</param>
</libraries>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<id>package-jar-with-dependencies</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
<archive>
<manifest>
<mainClass>SendTask</mainClass>
<addClasspath>true</addClasspath>
</manifest>
</archive>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>

Answer 1

The problem indicated by the error is in the msgpack serializer. By changing the serializer to JSON, the problem disappears.
import org.python.util.PythonInterpreter;
public class SendTask {
static final String SEND_TASK_PY =
"from celery import Celery\n"+
"c = Celery('tasks', broker='amqp://', backend='amqp://')\n"+
"c.conf.CELERY_TASK_SERIALIZER='json'\n"+
"result = c.send_task('tasks.add', args=[2, 2], kwargs={}).get()";
public static void main(String[] args) {
PythonInterpreter interpreter = new PythonInterpreter();
interpreter.exec(SEND_TASK_PY);
System.out.println(interpreter.get("result"));
} }