Automate a process

The following tutorial shows the automation of an example process.

The process consists of an exclusive gateway and 2 service tasks. A decision must be made, if either service task doX or doY should be executed. After the gateway is evaluated, one service task must be executed to end an instance of the example process.

Example process

example.bpmn

<definitions>
  <process id="example" isExecutable="true">
    <startEvent id="startEvent" name="Start">
      <outgoing>f1</outgoing>
    </startEvent>
    <sequenceFlow id="f1" sourceRef="startEvent" targetRef="fork" />
    <exclusiveGateway id="fork" name="X or Y?">
      <incoming>f1</incoming>
      <outgoing>f2</outgoing>
      <outgoing>f3</outgoing>
    </exclusiveGateway>
    <sequenceFlow id="f2" sourceRef="fork" targetRef="doX" />
    <serviceTask id="doX" name="Do X">
      <incoming>f2</incoming>
      <outgoing>f4</outgoing>
    </serviceTask>
    <sequenceFlow id="f4" sourceRef="doX" targetRef="join" />
    <sequenceFlow id="f3" sourceRef="fork" targetRef="doY" />
    <serviceTask id="doY" name="Do Y">
      <incoming>f3</incoming>
      <outgoing>f5</outgoing>
    </serviceTask>
    <sequenceFlow id="f5" sourceRef="doY" targetRef="join" />
    <exclusiveGateway id="join">
      <incoming>f4</incoming>
      <incoming>f5</incoming>
      <outgoing>f6</outgoing>
    </exclusiveGateway>
    <sequenceFlow id="f6" sourceRef="join" targetRef="endEvent" />
    <endEvent id="endEvent" name="End">
      <incoming>f6</incoming>
    </endEvent>
  </process>
</definitions>

Caution

To reproduce this example, a running process engine and an API key is required - please have a look at the guides on how to install and run a process engine.

Create process

To execute an instance of the example process, the process must first be created at the engine, using the BPMN 2.0 XML (see file example.bpmn).

curl

curl -v \
-H "Authorization: ${GO_BPMN_AUTHORIZATION}" \
-H "Content-Type: application/json" \
-X POST http://127.0.0.1:8080/processes \
-d "$(jq -n --arg bpmnXml "$(cat example.bpmn)" '{"bpmnProcessId": "example", "bpmnXml": $bpmnXml, "version": "1", "workerId": "curl"}')"

CLI

go-bpmn process create \
--bpmn-file example.bpmn \
--bpmn-process-id example \
--version 1

Go

Create a process engine, using a PostgreSQL database URL:

e, err := pg.New("postgres://usernam:password@127.0.0.1:5432/database?search_path=schema")
if err != nil {
  log.Fatalf("failed to create process engine: %v", err)
}

defer e.Shutdown()

Read the BPMN XML from file example.bpmn and create a process:

bpmnFile, err := os.Open("example.bpmn")
if err != nil {
  log.Fatalf("failed to open BPMN file: %v", err)
}

defer bpmnFile.Close()

bpmnXml, err := io.ReadAll(bpmnFile)
if err != nil {
  log.Fatalf("failed to read BPMN XML: %v", err)
}

process, err := e.CreateProcess(engine.CreateProcessCmd{
  BpmnProcessId: "example",
  BpmnXml:       bpmnXml,
  Version:       "1",
  WorkerId:      "go",
})
if err != nil {
  log.Fatalf("failed to create process: %v", err)
}

Create process instance

Based on an existing process, identified by BPMN process ID and version, instances can be created. A process instance can hold any data in form of string encoded process variables.

In this example, the initial process data is provided as variable xory, a JSON encoded string with value x.

curl

curl -v \
-H "Authorization: ${GO_BPMN_AUTHORIZATION}" \
-H "Content-Type: application/json" \
-X POST http://127.0.0.1:8080/process-instances \
-d '{"bpmnProcessId": "example", "variables": {"xory": {"encoding": "json", "value": "x"}}, "version": "1", "workerId": "curl"}'

CLI

go-bpmn process-instance create \
--bpmn-process-id example \
--variable xory='{"encoding": "json", "value": "x"}' \
--version 1

Go

processInstance, err := e.CreateProcessInstance(engine.CreateProcessInstanceCmd{
  BpmnProcessId: "example",
  Variables: map[string]*engine.Data{
    "xory": {
      Encoding: "json",
      Value:    "x",
    },
  },
  Version:  "1",
  WorkerId: "go",
})
if err != nil {
  log.Fatalf("failed to create process instance: %v", err)
}

Evaluate exclusive gateway

When the process engine reaches an exclusive gateway, a job of type EVALUATE_EXCLUSIVE_GATEWAY is created. It must be locked, executed and completed to continue the execution.

In case of an exclusive gateway, a job needs to be completed with a decision that provides the ID of an BPMN element to continue with after the gateway.

curl

Lock job:

curl -v \
-H "Authorization: ${GO_BPMN_AUTHORIZATION}" \
-H "Content-Type: application/json" \
-X POST http://127.0.0.1:8080/jobs/lock \
-d '{"limit": 1, "workerId": "curl"}'

Get variables of process instance (to make an decision):

curl -v \
-H "Authorization: ${GO_BPMN_AUTHORIZATION}" \
"http://127.0.0.1:8080/process-instances/$(date -I)/1/variables"

Complete job with an exclusive gateway decision:

curl -v \
-H "Authorization: ${GO_BPMN_AUTHORIZATION}" \
-H "Content-Type: application/json" \
-X PATCH http://127.0.0.1:8080/jobs/$(date -I)/1/complete \
-d '{"completion": {"exclusiveGatewayDecision": "doX"}, "workerId": "curl"}'

CLI

Lock job:

go-bpmn job lock

Get variables of process instance (to make an decision):

go-bpmn process-instance get-variables --partition $(date -I) --id 1

Complete job with an exclusive gateway decision:

go-bpmn job complete \
--exclusive-gateway-decision doX \
--partition $(date -I) \
--id 1

Go

Lock job:

lockedJobs, err := e.LockJobs(engine.LockJobsCmd{
  WorkerId:  "go",
})
if err != nil {
  log.Fatalf("failed to lock job: %v", err)
}
if len(lockedJobs) == 0 {
  log.Fatal("no job locked")
}

Get variables of process instance (to make an decision):

variables, err := e.GetProcessVariables(engine.GetProcessVariablesCmd{
  Partition:         engine.Partition{},
  ProcessInstanceId: 1,
})
if err != nil {
  t.Fatalf("failed to get process variables: %v", err)
}

Complete job with an exclusive gateway decision:

completedJob, err := e.CompleteJob(engine.CompleteJobCmd{
  Partition: lockedJobs[0].Partition,
  Id:        lockedJobs[0].Id,
  Completion: &engine.JobCompletion{
    ExclusiveGatewayDecision: "doX",
  },
  WorkerId: "go",
})
if err != nil {
  log.Fatalf("failed to complete job: %v", err)
}

Execute service task

When the process engine reaches a service task, a job of type EXECUTE is created. It must be locked, executed and completed to continue the execution.

In case of a service task, no type-specific completion is required.

curl

Lock job:

curl -v \
-H "Authorization: ${GO_BPMN_AUTHORIZATION}" \
-H "Content-Type: application/json" \
-X POST http://127.0.0.1:8080/jobs/lock \
-d '{"limit": 1, "workerId": "curl"}'

Complete job, which confirms the execution of service task doX:

curl -v \
-H "Authorization: ${GO_BPMN_AUTHORIZATION}" \
-H "Content-Type: application/json" \
-X PATCH http://127.0.0.1:8080/jobs/$(date -I)/2/complete \
-d '{"processVariables": {"result": {"encoding": "json", "value": "x done"}}, "workerId": "curl"}'

Verify that process instance is in state ENDED:

curl -v \
-H "Authorization: ${GO_BPMN_AUTHORIZATION}" \
-H "Content-Type: application/json" \
-X POST http://127.0.0.1:8080/process-instances/query \
-d '{}'

CLI

Lock job:

go-bpmn job lock

Complete job, which confirms the execution of service task doX:

go-bpmn job complete \
--exclusive-gateway-decision doX \
--partition $(date -I) \
--process-variable result='{"encoding": "json", "value": "x done"}' \
--id 2

Verify that process instance is in state ENDED:

go-bpmn process-instance query

Go

Lock job:

lockedJobs, err := e.LockJobs(engine.LockJobsCmd{
  WorkerId:  "go",
})
if err != nil {
  log.Fatalf("failed to lock job: %v", err)
}
if len(lockedJobs) == 0 {
  log.Fatal("no job locked")
}

Complete job, which confirms the execution of service task doX:

completedJob, err := e.CompleteJob(engine.CompleteJobCmd{
  Partition: lockedJobs[0].Partition,
  Id:        lockedJobs[0].Id,
  WorkerId: "go",
})
if err != nil {
  log.Fatalf("failed to complete job: %v", err)
}

Verify that process instance is in state ENDED:

results, err := e.Query(engine.ProcessInstanceCriteria{
  Partition: engine.Partition{},
  Id:        1,
})
if err != nil {
  log.Fatalf("failed to query process instance: %v", err)
}

if len(results) != 1 {
  log.Fatalf("expected one process instance, but got %d", len(results))
}

processInstance := results[0].(engine.ProcessInstance)
if !processInstance.IsEnded() {
  log.Fatalf("expected process instance to be ended, but is not ended")
}