Message Start Event

Message Start Event (Start Catch Message) node represents the starting point for a process instance based on the receipt of a specific message or an incoming email. When this event is triggered, it initiates the execution of the associated process.

Why it is important? The Message Start Event is important because it allows a process to be triggered and initiated based on the reception of a specific message or external event like an incoming email.

Configuring a message start event

A Message Start Event is a special event in a process that initiates the start of a process instance upon receiving a specific trigger. It acts as the entry point for the process, waiting for the designated trigger to occur. Once triggered, the process instance is created and begins its execution, following the defined process flow from that point onwards.

It is mandatory that in order to use this type of node together with task management plugin, to have a service account defined in your identity solution. For more information, check our documentation in how to create service accounts using Keycloak, here.

General config

Node name · string

The name of the node.

Process Stage · dropdown

Assign a stage to the node, if needed.

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Process trigger

The Trigger Type determines how the process instance is started. Two options are available:

Internal Throw Message

Use this trigger type when you want to start a process instance from another process using a Message Throw Event. This is the classic approach for inter-process communication.

Trigger Type · enum · required

Select Internal Throw Message to enable message-based triggering from other processes.

Correlate with throwing message events · dropdown

The message event name that this start event listens for. This must match the event name configured in the corresponding Message Throw Event from the sending process.

Process Key · string

The process key / variable name where incoming message data will be mapped in the started process. The data sent from the throwing process will be available under this key.

Note: The correlation key field is not available for Message Start Events. Correlation keys are only used for intermediate catch events where a running process instance needs to be identified. For start events, a new process instance is always created.

Email Trigger

Use this trigger type when you want to automatically start a process instance when an email is received. This requires an Email Trigger data source to be configured in Integration Designer.

Trigger Type · enum · required

Select Email Trigger to enable email-based process triggering.

Select Email Trigger · dropdown · required

Choose the Email Trigger data source that will initiate this process. The dropdown displays all Email Trigger resources configured in your application.

Before using Email Trigger, you must configure an Email Trigger data source in Integration Designer. See Email Trigger for complete setup instructions.

When an email arrives and triggers the process, the email data (sender, subject, body, attachments, etc.) is automatically mapped to the process instance data. See the Email Trigger documentation for the complete data structure.

When switching between trigger types in the Designer UI, the configuration fields are automatically cleared to prevent invalid configurations. Ensure you reconfigure all required fields after changing the trigger type.

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Example: Interprocess communication with internal throw message

This section demonstrates how to use the Internal Throw Message trigger type to start a process from another process.

Throwing process (sender)

The throwing process contains a Message Throw Event that sends a message to start the target process.

Configuring the throw intermediate event

Correlate with catch events · dropdown · required

The message event name. This must match the Correlate with throwing message events value configured in the target Message Start Event.

Send data · string

Define a JSON structure with the data to be sent along with the message. For example:

{"test": "docs"}

Process Stage · dropdown

Assign a stage to the node if needed.

Catching process (receiver)

The catching process uses a Message Start Event configured with the Internal Throw Message trigger type.

Configuring the Message Start Event (Start Catch Message) node

Remember, it’s mandatory to have a service account defined in your identity solution to have the necessary rights to start a process using the message catch start event. Refer to our documentation on how to create service accounts using Keycloak, here.

Result

After running the throw process, the process containing the Message Start Event (Start Catch Message) node is triggered automatically. The data sent from the throwing process is available in the new process instance: