Standby Flow Execution
Configuration
An until StandBy node can be inserted into a flow.In the node it is possible to:
- define the conditions that a model must meet,
- optionally indicate a deadline by which these conditions must be met.
If the defined conditions are not met, the flow execution is suspended until they are met or until the deadline is exceeded.
Node configuration
The image shows the node form, which includes the following fields:
- Model: box variable in which to drag the model to be subjected to the check.
- Expression: A condition builder that defines the conditions that the model must meet to resume execution.
- Expression (Script): Alternative or supplement to the condition builder. Allows you to write a custom script that returns true or false, which is useful for defining more complex conditions.
- Use Expiration: A switch that enables or disables an expiration for the audit.
- Hours, Minutes, Seconds: fields (variable box integers) in which to indicate respectively the hours, minutes and seconds within which the conditions must be met.
Note: The conditions defined in the condition builder and in the script are combined with an AND operator, both of which must be met for the node to proceed.
Operation
The node performs a check on the model when the flow runs. Depending on the outcome of the condition, the flow continues or the node enters a waiting state.
If the node enters the waiting state, the next time you save a model change, it is re-evaluated and its status updated accordingly:
- Expiration: If the node has been assigned an expiration and it is met without the conditions being met, the flow execution resumes automatically. In this case, the node’s dedicated output variable (expired) takes on a value of true.
If a condition expires, the flow resumes its execution normally. In this case, the Standby node returns the expired output variable set to true, indicating that execution continued but the condition was not met within the expected timeframe.
- Model Deletion: If the model used in the condition is deleted, the flow execution is stopped and the flow goes into the Aborted state.
Note: Deadline checking is performed by a cron job every minute.
Form output
The node outputs the following data:
- Model: The model being checked.
- Standby At: The DateTime at which the flow was put to standby.
- Restarted At: The DateTime of the node’s last replay.
- Expiration: The DateTime at which the check is expected to expire.
- Expired: A Boolean value that indicates whether the check has expired (true) or not (false).
Examples
In this example, a flow is created that, when a model is created or modified, generates the various stages. Each stage is managed by an Until Standby node, which proceeds to the next stage only when the defined conditions are met.
In the example below, a flow was created to determine the state of an operation.
The flow is divided into 3 stages: Taken in charge, In progress and Concluded.
The transition between stages is handled by two Standby Until, which respectively verify:
- in the first case, that the state is “work in progress”
- in the second case, that the state is “closed”.
By doing so we can obtain in the operation form a situation like this:
