Apache Nifi属性描述符的dynamicModifyClasspath()的Hello World程序不起作用 [英] Hello world program of dynamicallyModifiesClasspath() of Apache Nifi properties descriptor not working

问题描述

我有一个依赖于某些jar的处理器.但是，相当频繁地对依赖项jar进行了更改.因此，我希望能够将jar路径指定为处理器的属性，并在每次我修改属性中的路径并重新启动处理器时让nifi加载jar.使用这篇文章.但是，我无法做到这一点.下面是我使用dynamicallyModifiesClasspath属性的hello world程序代码:

I have a processor which depends on some jar as a dependency. However changes are made to the dependency jar quite frequenctly. So I want to be able to specify the jar path as a property of processor and let the nifi load the jar each time I modify the path in the property and restart the processor. This is supposed to be doable using dynamicallyModifiesClasspath as explained in this article. However I am unable to do this. Below is my code of hello world program using dynamicallyModifiesClasspath property:

(下面，Djl代表动态jar加载"，我猜这是一个您好叫这个世界程序的随机前缀.)

(Below, Djl stands for "dynamic jar loading", a random prefix I guessed to name this hello world program.)

DjlDependencyClass.java

这是我的nifi处理器所依赖的类，我想在我的nifi处理器中动态更改其jar路径.

This is the class on which my nifi processor depends and I want to dynamically change its jar path in my nifi processor.

public class DjlDependencyClass {

    public static String getMessage()
    {
        return "DJL-DEPENDENCY VERSION-1";
    }
}

MyDjlProcessor.java

这是依赖于DjlDependencyClass的nifi处理器.

This is the nifi processor which depends on DjlDependencyClass.

import org.apache.nifi.annotation.lifecycle.OnScheduled;
import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.processor.exception.ProcessException;    
import org.apache.nifi.processor.AbstractProcessor;
import org.apache.nifi.processor.ProcessContext;
import org.apache.nifi.processor.ProcessSession;
import org.apache.nifi.processor.ProcessorInitializationContext;
import org.apache.nifi.processor.Relationship;
import org.apache.nifi.processor.util.StandardValidators;

import com.mycompany.djldependency.DjlDependencyClass;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class MyDjlProcessor extends AbstractProcessor {

    public static final Relationship MY_RELATIONSHIP = new Relationship.Builder()
            .name("MY_RELATIONSHIP")
            .description("Example relationship")
            .build();

    public static final PropertyDescriptor pathToDjlDependencyJar = new PropertyDescriptor.Builder()
            .name("Djl Dependency JAR")
            .description("Djl Dependency JAR")
            .required(true)
            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
            .dynamicallyModifiesClasspath(true)
            .expressionLanguageSupported(true)
            .build();

    private List<PropertyDescriptor> descriptors;

    private Set<Relationship> relationships;

    @Override
    protected void init(final ProcessorInitializationContext context) {
        final List<PropertyDescriptor> descriptors = new ArrayList<PropertyDescriptor>();
        descriptors.add(pathToDjlDependencyJar);
        this.descriptors = Collections.unmodifiableList(descriptors);

        final Set<Relationship> relationships = new HashSet<Relationship>();
        relationships.add(MY_RELATIONSHIP);
        this.relationships = Collections.unmodifiableSet(relationships);
    }

    @Override
    public Set<Relationship> getRelationships() {
        return this.relationships;
    }

    @Override
    public final List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        return descriptors;
    }

    @OnScheduled
    public void onScheduled(final ProcessContext context) {

    }

    @Override
    public void onTrigger(final ProcessContext context, final ProcessSession session) throws ProcessException {
        System.out.println(DjlDependencyClass.getMessage());
    }
}

这是将pom内的依赖项标记为具有provided范围的方式，这样依赖项jar将不会嵌入nar中:

This is how dependency inside pom is marked to have provided scope, so that the dependency jar will not be embedded inside nar:

   <dependency>
        <groupId>com.mycompany</groupId>
        <artifactId>djl-dependency</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <scope>provided </scope>
    </dependency>

我正在如下测试该处理器:

I am testing this processor as follows:

处理器的配置:

我遇到以下异常:

2019-05-27 17:01:54,536 ERROR [Timer-Driven Process Thread-1] com.mycompany.djl.MyDjlProcessor MyDjlProcessor[id=f8fa5750-016a-1000-ecc3-c19732119332] MyDjlProcessor[id=f8fa5750-016a-1000-ecc3-c19732119332] failed to process due to java.lang.NoClassDefFoundError: com/mycompany/djldependency/DjlDependencyClass; rolling back session: {}
java.lang.NoClassDefFoundError: com/mycompany/djldependency/DjlDependencyClass
    at com.mycompany.djl.MyDjlProcessor.onTrigger(MyDjlProcessor.java:76)
    at org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:27)
    at org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1122)
    at org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:147)
    at org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:47)
    at org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:128)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

我在这里做蠢事吗?

请下载两个项目(nifi和依赖项jar)此处.

Please download both projects (nifi and dependency jar) here.

推荐答案

PropertyDescriptor的API文档提到以下注释:

The API document for PropertyDescriptor mentions the following note:

如果组件包含一个PropertyDescriptor，并且dynamicModifyClasspath设置为true，则该组件还必须使用@RequiresInstanceClassloading进行注释，否则该组件将被视为无效.

If a component contains a PropertyDescriptor where dynamicallyModifiesClasspath is set to true, the component must also be annotated with @RequiresInstanceClassloading, otherwise the component will be considered invalid.

我不确定那个无效"部分是否仍然成立，但是，是的，在更新了处理器代码并用@RequiresInstanceClassloading进行注释之后，我能够使其正常工作.

I'm not sure whether that 'invalid' part still holds true but yeah, after updating your processor code to have it annotated with @RequiresInstanceClassloading, I was able to get it working.

这篇关于Apache Nifi属性描述符的dynamicModifyClasspath()的Hello World程序不起作用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！