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Receive tasks

Receive tasks are tasks which reference a message; these are used to wait until a proper message is received.

Receive Tasks

When a receive task is entered, a corresponding message subscription is created. The process instance stops at this point and waits until the message is correlated.

A message can be published using one of the Zeebe clients. When the message is correlated, the receive task is completed and the process instance continues.

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An alternative way to receive tasks are message intermediate catch events, which behave the same but can be used together with event-based gateways.

Messages#

A message can be referenced by one or more receive tasks. It must define the name of the message (e.g. Money collected) and the correlationKey expression (e.g. = orderId).

Usually, the name of the message is defined as a static value (e.g. order canceled), but it can also be defined as expression (e.g. = "order " + awaitingAction). The expression is evaluated on activating the receive task and must result in a string.

The correlationKey is an expression that usually accesses a variable of the process instance that holds the correlation key of the message. The expression is evaluated on activating the receive task and must result either in a string or number.

To correlate a message to the receive task, the message is published with the defined name (e.g. Money collected) and the value of the correlationKey expression. For example, if the process instance has a variable orderId with value "order-123", the message is published with the correlation key "order-123".

Variable mappings#

By default, all message variables are merged into the process instance. This behavior can be customized by defining an output mapping at the receive task.

Additional resources#

XML representation#

A receive task with message definition:

<bpmn:message id="Message_1iz5qtq" name="Money collected">   <bpmn:extensionElements>     <zeebe:subscription correlationKey="orderId" />   </bpmn:extensionElements></bpmn:message>
<bpmn:receiveTask id="money-collected" name="Money collected"  messageRef="Message_1iz5qtq"></bpmn:receiveTask>

References#