NIFI: No controller service types found that are applicable for this property

Question

I am developing a Milo OPCUA Processor and Service for Apache NiFi. The Processor and Service compile fine, and I am able to start NiFi with them. However, when trying to configure the service for the processor that I just added, it just says "No controller service types found that are applicable for this property.".

Here are my POMs:

Processor JAR

<parent>
    <groupId>com.tcon</groupId>
    <artifactId>pubsub</artifactId>
    <version>0.1</version>
</parent>

<artifactId>nifi-pubsub-processors</artifactId>
<packaging>jar</packaging>

<dependencies>
    <dependency>
        <groupId>org.apache.nifi</groupId>
        <artifactId>nifi-api</artifactId>
    </dependency>
    <dependency>
        <groupId>org.apache.nifi</groupId>
        <artifactId>nifi-utils</artifactId>
    </dependency>
    <dependency>
        <groupId>org.apache.nifi</groupId>
        <artifactId>nifi-mock</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-simple</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>tcon</groupId>
        <artifactId>nifi-miloservice-api</artifactId>
        <version>0.1</version>
    </dependency>
</dependencies>

Processor NAR

<parent>
    <groupId>com.tcon</groupId>
    <artifactId>pubsub</artifactId>
    <version>0.1</version>
</parent>

<artifactId>nifi-pubsub-nar</artifactId>
<version>0.1</version>
<packaging>nar</packaging>
<properties>
    <maven.javadoc.skip>true</maven.javadoc.skip>
    <source.skip>true</source.skip>
</properties>

<dependencies>
    <dependency>
        <groupId>com.tcon</groupId>
        <artifactId>nifi-pubsub-processors</artifactId>
        <version>0.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.nifi</groupId>
        <artifactId>nifi-standard-services-api-nar</artifactId>
        <version>1.2.0</version>
        <type>nar</type>
    </dependency>
</dependencies>

The service POMs shouldn't matter, afaik. They haven't been modified, save for a few Milo dependencies.

As you can see, the processor JAR POM has the custom service API dependency from my custom service and the processor NAR POM has the standard API dependency from nifi.

The docs say that that is all I need to do to "link" my processor to my service.

What am I missing?

Answer 1

You also need to register your controller service with the ServiceLoader by including a file in the src/main/resources folder of your processor JAR project. You'll need a META-INF/services folder under your resources folder, with a file called org.apache.nifi.controller.ControllerService with a line containing the fully qualified name of the class implementing the ControllerService interface.