Develop a Trigger
Here is how you can develop a Trigger.
You need to extend PollingTriggerInterface and implement the Optional<Execution> evaluate(ConditionContext conditionContext, TriggerContext context) method.
You can have any properties you want, like for any task (validation, documentation, ...), and everything works the same way.
The evaluate method will receive these arguments:
ConditionContext conditionContext: a ConditionContext which includes various properties such as the RunContext in order to render your properties.TriggerContext context: to have the context of this call (flow, execution, trigger, date, ...).
In this method, you add any logic you want: connect to a database, connect to remote file systems, ... You don't have to take care of resources, Kestra will run this method in its own thread.
This method must return an Optional<Execution> with:
Optional.empty(): if the condition is not validated.Optional.of(execution): with the execution created if the condition is validated.
You have to provide a Output for any output needed (result of query, result of file system listing, ...) that will be available for the flow tasks within the {{ trigger.* }} variables.
Take care that the trigger must free the resource for the next evaluation. For each interval, this method will be called and if the conditions are met, an execution will be created.
To avoid this, move the file or remove the record from the database; take an action to avoid an infinite triggering.
Documentation
Remember to document your triggers. For this, we provide a set of annotations explained in the Document each plugin section.
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