java - Apache Nifi 属性描述符的 dynamicallyModifiesClasspath() 的 Hello world 程序不起作用

Question

我有一个处理器，它依赖于一些 jar 作为依赖项。然而，依赖 jar 的更改非常频繁。所以我希望能够将 jar 路径指定为处理器的属性，并让 nifi 在每次修改属性中的路径并重新启动处理器时加载 jar。这应该可以使用 dynamicallyModifiesClasspath 来实现如 this article 中所述.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:

(在下文中，Djl 代表“动态 jar 加载”，我猜是为这个 hello world 程序命名的随机前缀。)

DjlDependencyClass.java

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

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。

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());
    }
}

这就是 pom 内部的依赖项被标记为具有 provided 范围的方式，这样依赖项 jar 就不会嵌入到 nar 中:

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

我正在测试这个处理器如下:

处理器配置:

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)

我是不是在做什么蠢事？

请下载两个项目(nifi 和依赖jar)here .

Answer 1

PropertyDescriptor 的 API 文档提到以下注释:

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“无效”部分是否仍然适用，但是是的，在更新您的处理器代码以使用 @RequiresInstanceClassloading 对其进行注释之后，我能够让它工作。