Spring Cloud Stream Source - Not Pulling

I'm trying to develop a customized Source for a proof of concept in Spring Cloud Dataflow.

I managed to deploy it correctly, but it seems that the bean is not pulled.

Here's a part of the parent pom.xml

...
<properties>
  <spring-cloud.version>Hoxton.SR8</spring-cloud.version>
  ...
</properties>

<dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-dependencies</artifactId>
        <version>${spring-cloud.version}</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
</dependencyManagement>
...

Here's the project pom.xml

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-stream</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-stream-binder-kafka</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-cloud-connectors</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.kafka</groupId>
        <artifactId>spring-kafka</artifactId>
        <version>2.3.10.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-configuration-processor</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <version>2.3.4.RELEASE</version>
            <configuration>
                <excludes>
                    <exclude>
                        <groupId>org.springframework.boot</groupId>
                        <artifactId>spring-boot-configuration-processor</artifactId>
                    </exclude>
                </excludes>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-app-starter-metadata-maven-plugin</artifactId>
            <version>2.0.2.RELEASE</version>
            <executions>
                <execution>
                    <id>aggregate-metadata</id>
                    <phase>compile</phase>
                    <goals>
                        <goal>aggregate-metadata</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

SourceApplication.java

@SpringBootApplication
@EnableBinding(Source.class)
@EnableConfigurationProperties(ReportingProperties.class)
public class SourceApplication {

    public static void main(String[] args) {
        SpringApplication.run(SourceApplication.class, args);
    }
}

ReportingProperties.java

@Validated
@ConfigurationProperties("reporting-properties")
public class ReportingProperties {

    /**
     * The starting date of the reporting.
     */
    private LocalDateTime fromDate = LocalDateTime.now().minusDays(1000);

    /**
     * The end date of the reporting.
     */
    private LocalDateTime toDate = LocalDateTime.now();

    public LocalDateTime getFromDate() {
        return fromDate;
    }

    public ReportingProperties setFromDate(LocalDateTime fromDate) {
        this.fromDate = fromDate;
        return this;
    }

    public LocalDateTime getToDate() {
        return toDate;
    }

    public ReportingProperties setToDate(LocalDateTime toDate) {
        this.toDate = toDate;
        return this;
    }
}

And finally the service :

@Configuration
@EnableBinding(Source.class)
public class PullUsersService {

    @Bean
    @Publisher(channel = Source.OUTPUT)
    @SendTo(Source.OUTPUT)
    public Supplier<String> pullUsers() {
        return () -> "Test";
    }

}

I'm wondering how to trigger the pulling mechanism so when deployed I can see "Test" in the logs
(I believe everything is setup correctly on SCDF, if I do "time | log" i can see some results in the log, but if I do "myservice | log" nothing appears.

What am I doing wrong ? (maybe there's some redundancy in my code)

The answer above is correct, you can also do it the following way:

Note: Remove all @EnableBinding(Source.class) anotations

@Component
public class PullUsersService {

    @PollableBean
    public Supplier<String> pullUsers() {
        return () -> "Test";
    }
}

Add the following configurations if you want queue to rabbitMq or kafka based on your binder configuration

spring.cloud.function.definition=pullUsers
spring.cloud.stream.bindings.pullUsers-out-0.destination=users
spring.cloud.stream.bindings.pullUsers-out-0.group=users-service
spring.cloud.stream.bindings.pullUsers-out-0.producer.requiredGroups=users-service

spring.cloud.stream.bindings.pullUsers-out-0.producer.requiredGroups configuration forces producer to create the queues

That's interesting what made you to use this:

@Publisher(channel = Source.OUTPUT)
@SendTo(Source.OUTPUT)

If you take a look into that time source code you mention, you'll see something like this:

@PollableSource
public String publishTime() {
	return new SimpleDateFormat(this.triggerProperties.getDateFormat()).format(new Date());
}

Consider to use that @PollableSource instead and don't use a Supplier.
The point is that all your current annotations do nothing with polling.

The @Publisher works only when we call the method.
The @SendTo is fully ignored here since @Publisher does exactly the same and it "sends to".