Concepts
The trigger module allows users to delay the execution of a message until an event is detected. Users should have a strong understanding of what a Trigger, Event, Queued Trigger are, and how Payment works before using this module.
Trigger
A Trigger is an address owned object that registers to a Block Event, and then proceeds to fire off its Actions when that Block Event has been detected by the system. A Trigger is single-shot, and it will automatically be destroyed after its Block Event has been detected.
Actions
Actions are one or more messages that should be invoked. Every Action follows the same rules as a sdk message and requires purchased gas to run. See the Gas Payment section for more information.
Gas Payment
Gas is vital in running the Actions, and in order to simplify the system as much as possible we leave it up to the user to calculate gas usage. When a user creates a Trigger they are required to purchase gas for the transaction AND the Actions. The remaining gas that is not used by the creation transaction will be rolled into a gas meter for the Actions. These Actions will only run and update state if their is enough allocated gas.
Block Event
A Block Event is a blanket term that refers to events that occur during the creation of a block. The Trigger module currently supports Transaction Events, Block Height Events, and Block Time Events.
Transaction Event
These type of events refer to the ABCI Events that are emitted by the DeliverTx transactions. An ABCI Event must have the same Type and Attributes as the user defined Transaction Event for the event criteria to be met. A user defined Attribute with an empty Value will always match as long as the Attribute Name field matches.
Block Height Events
These type of events refer to the Block Height on a newly created block. The Block Height must be greater than or equal to the defined value for the event criteria to be met.
Block Time Event
These type of events refer to the Block Time on a newly created block. The Block Time must be greater than or equal to the defined value for the event criteria to be met.
Queued Trigger
The Queued Trigger is a Trigger that is ready to have its actions be executed at a future block.