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- Time-based - (System Level and User Level )
- At timestamp
- Each `duration`
- For complex use cases Trigger might register itself again to execute at another timestamp
- Time based Triggers seem to be difficult task for synchronization between peers. The following approach is suggested:
Recommendations to execute them should be added by the leader to the block (even if there are no transactions - leader should generate a block with trigger execution recommendations for them)
They are best effort - Iroha does not guarantee them to be executed at exact time. But it guarantees execution at closest possible time if network is operational.
If a leader does not produce a block with appropriate time based triggers in the defined time period after those trigger's selected timestamps - view change happens - similar to how if leader does not produce block for ordinary transactions
Next leader in this case will need to include the previous time based trigger in a block (when a view change happens it will be given a new time window to do this)
- Block number-based - (System Level and User Level )
- At block
- Each `n_blocks`
- For complex use cases Trigger might register itself again to execute at another height
- Transaction-based (Only System Level)
- Before (transaction execution)
- Before each
- Have the ability to check and fail or allow transaction
- Have access to all transaction data
- Example: Transaction metadata validation, prohibiting particular instructions, permissions based on instruction inspection
- After (transaction execution)
- After each
- Have the ability to check and fail or allow transaction
- Have access to all transaction data and WSV diff after execution
- Example: Transaction fees, permissions based on changes to WSV
- Before (transaction execution)
- Triggers that are triggered by specific ISI call - ExecuteTrigger(Params) - (System Level and User Level )
- Similar to smart contracts as they are in Ethereum blockchain
- Execute as part of the transaction instructions execution
- For System Level - only admin can call the Trigger or through democracy pallet
- Event-based - (System Level and User Level )
- Triggered by events emitted from other triggers or transaction execution.
- The triggers react to the events emitted in the previous block as shown in the `Execution` section.
- If leader does not supply the needed trigger execution recommendations based on events from previous block -
the block will be rejected and the next leader will have to do this.
Persistent State
Complex Triggers (such as Swap triggers managing Liquidity Pools) might need to store data between their invocations. For this purpose Triggers will have following persistent storage:
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