Service Tasks

workflow

A service task represents a work item in the workflow with a specific type. When the workflow instance arrives a service task then it creates a corresponding job. The token flow stops at this point.

A worker can subscribe to these jobs and complete them when the work is done. When a job is completed, the token flow continues.

XML representation:

<bpmn:serviceTask id="collect-money" name="Collect Money">
  <bpmn:extensionElements>
    <zeebe:taskDefinition type="payment-service" />
    <zeebe:taskHeaders>
      <zeebe:header key="method" value="VISA" />
    </zeebe:taskHeaders>
  </bpmn:extensionElements>
</bpmn:serviceTask>

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Task Definition

Each service task must have a task definition. It specifies the type of job which workers can subscribe to.

Optionally, a task definition can specify the number of times the job is retried when a worker signals failure (default = 3).

<zeebe:taskDefinition type="payment-service" retries="5" />

Task Headers

A service task can define an arbitrary number of task headers. Task headers are metadata that are handed to workers along with the job. They can be used as configuration parameters for the worker.

<zeebe:taskHeaders>
  <zeebe:header key="method" value="VISA" />
</zeebe:taskHeaders>

Variable Mappings

By default, all job variables are merged into the workflow instance. This behavior can be customized by defining an output mapping at the service task. Input mappings can be used to transform the variables into a format that is accepted by the job worker.

XML representation:

<serviceTask id="collectMoney">
  <extensionElements>
    <zeebe:ioMapping>
      <zeebe:input source="price" target="total"/>
      <zeebe:output source="method" target="paymentMethod"/>
     </zeebe:ioMapping>
  </extensionElements>
</serviceTask>

Additional Resources