...
| Page properties | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ||||||||||||||||||||
|
...
- 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
- We should limit the granularity of possible timestamps, as network has a limit of how fast it can produce and commit blocks
- 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)
- Example: Periodic rewards, scheduled batch processing
- Block number-based 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
- Might not be needed as there are already time based triggers, and block time is not fixed in Iroha v2.
- Example: Per block rewards, scheduled batch processing
- 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
- Example: Swap with liquidity pool, locking funds (for bridges or stable coins for example)
- 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. - Leader has to produce a block with event based triggers in time, even if it will contain no transactions.
Or the view change will happen and the scenario proceeds similar to time based triggers. - Example: Reacting to currency flow, reacting to system events (events from system level triggers), keeping metadata in sync
...
Instead it is proposed to have either a highly configurable system where fee configuration can be done at runtime, or again do it through a separate WASM plugin (if fee handling logic might be changed at runtime).
Implementation Considerations
The scope of work proposed here is huge. It might be good to approach it iteratively, focusing on use cases needed for permission-ed blockchains at first (e.g. start with System Level triggers that check transactions).