engine.execute() does not wait all the async service to be resolved

Hi, I have a chart like below, each service will run an async function. I expect they will be run one by one, and then finish. But what I get is it finished before the second service is done. Do I mis-understand something which is basic?

console output

### before execute
### before serviceFn1 await
### after serviceFn1 await
### before serviceFn2 await
### after execute  // I expect this line will be at the last line, but it isn't.
### after serviceFn2 await
### inside execute callback

chart

sample code

const { Engine } = require('bpmn-engine');

const source = `
<?xml version="1.0" encoding="UTF-8"?>
<bpmn:definitions id="Definitions_0cz8kjv" targetNamespace="http://bpmn.io/schema/bpmn"
	xmlns:bpmn="http://www.omg.org/spec/BPMN/20100524/MODEL">
  <bpmn:process id="Process_0x60oya" isExecutable="true">
    <bpmn:startEvent id="StartEvent">
      <bpmn:outgoing>Flow1</bpmn:outgoing>
    </bpmn:startEvent>
    <bpmn:sequenceFlow id="Flow1" sourceRef="StartEvent" targetRef="ServiceTask1" />
    <bpmn:serviceTask id="ServiceTask1" implementation="\${environment.services.serviceFn1}" >
      <bpmn:incoming>Flow1</bpmn:incoming>
      <bpmn:outgoing>Flow2</bpmn:outgoing>
    </bpmn:serviceTask>
    <bpmn:sequenceFlow id="Flow2" sourceRef="ServiceTask1" targetRef="ServiceTask2" />
    <bpmn:serviceTask id="ServiceTask2" implementation="\${environment.services.serviceFn2}" >
      <bpmn:incoming>Flow2</bpmn:incoming>
      <bpmn:outgoing>Flow3</bpmn:outgoing>
    </bpmn:serviceTask>
    <bpmn:endEvent id="EndEvent">
      <bpmn:incoming>Flow3</bpmn:incoming>
    </bpmn:endEvent>
    <bpmn:sequenceFlow id="Flow3" sourceRef="ServiceTask2" targetRef="EndEvent" />
  </bpmn:process>
</bpmn:definitions>
`;

(async () => {
	const engine = Engine({ source });
	console.log('### before execute');
	await engine.execute({
		services: {
			serviceFn1: async (scope, callback) => {
				console.log('### before serviceFn1 await');
				await (async () => {})();
				console.log('### after serviceFn1 await');
				return callback(null, 12345);
			},
			serviceFn2: async (scope, callback) => {
				console.log('### before serviceFn2 await');
				await (async () => {})();
				console.log('### after serviceFn2 await');
				return callback(null, 23456);
			},
		},
	}, () => {
		console.log('### inside execute callback');
	});
	console.log('### after execute');
})();

[paed01]

That was true for an older version of the engine. I have updated the documentation.

[aowakennomai]

Hi, thank you for the advice, I’ll try to think more about event-driven programing 😃

By the way, I found that it says that

Event names are composed by activity event name and activity id, e.g. wait-userTask.

at here Execution listener. Is that mean I can listen like this? (which I’ve tried but not work…)

listener.on('wait-MyTaskId', (eleApi, engApi) => {});