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Example Fn Java FDK : Service Connector Hub - Logging

This example provides a Function to use as a service connector hub target. The function accepts a typed event containing a batch of source events.

Source

LoggingData.java

Dependencies

  • [fn-events] for ConnectorHubFunction classes.
  • [fn-events-testing] for ConnectorHubFunction testing library.

Demonstrated FDK features

This example showcases how to use the fn-event ConnectorHubFunction to use a Function as the target for Logging source.

Step by step

Set up the connector hub with Logging source and Function target:

The Function entrypoint extends the ConnectorHubFunction abstract class. Note: the func.yaml entrypoint remains the class which extends ConnectorHubFunction e.g. cmd: com.fnproject.fn.examples.Function::handler

Function.java

package com.fnproject.fn.examples;

import com.fnproject.events.ConnectorHubFunction;
import com.fnproject.events.input.ConnectorHubBatch;
import com.fnproject.events.input.sch.LoggingData;

public class Function extends ConnectorHubFunction<LoggingData> {

    public LogService logService;

    public Function() {
        this.logService = new LogService();
    }

    @Override
    public void handler(ConnectorHubBatch<LoggingData> batch) {
        for (LoggingData log : batch.getBatch()) {
            logService.readLog(log);
        }
    }
}

The ConnectorHubBatch.java batch contains a list of events from Logging as specified in Batch Settings.

The class LoggingData.java is each logging event.

Function.java public class Function extends ConnectorHubFunction<LoggingData>.

To return an error response, throw RuntimeException.class. Doing so will cause the Function to return a 502 Retry policy

Test walkthrough

Unit testing ConnectorHubFunction is supported with the ConnectorHubTestFeature and FnTestingRule.

First of all, the class initializes the FnTestingRule harness, as explained in Testing Functions.

FunctionTest.java

@Rule
public FnTestingRule fn = FnTestingRule.createDefault();

private final ConnectorHubTestFeature connectorHubTestFeature = ConnectorHubTestFeature.createDefault(fn);

@Test
public void testInvokeFunctionWithLoggingData() throws Exception {

    ConnectorHubBatch<LoggingData> event = createMinimalRequest();
    connectorHubTestFeature.givenEvent(event).enqueue();

    fn.thenRun(Function.class, "handler");

    FnResult result = fn.getOnlyResult();
    assertEquals(200, result.getStatus().getCode());
}

Use connectorHubTestFeature.givenEvent(event).enqueue(); to queue the request event and invoke the Function with fn.thenRun(Function.class, "handler");.