[BUG]: Trigger's execution queue is cleared on a new block

[Erigara]

Currently it's not possible to create trigger execution chain.
So that events produced in one trigger would be consumed in another trigger (or in the same trigger) in the next block.

Fix itself is pretty simple we need clone matched_ids in impl Clone at core/src/smartcontracts/isi/triggers/set.rs .

But this fix leads to infinite recursion problem.
If trigger produces >1 event it can consume later it execution would grow exponentially.
This would work not only with the single trigger but with any set of triggers which are "calling" each other.

[Erigara]

As discussed with @Mingela iroha now works in permissioned setups so having recussion problems is OK, it's operator responsibility to control this.

[Mingela]

For the public mode the target solution should be designed thoroughly. I object inability of trigger chain calls, that's a huge flexibility/optimization opportunity. Some points to consider:

• Limiting fuel per block instead/together with per trigger (or cross-trigger 'transaction' in case of a chain of calls) + strategies for overflows (prioritization etc)
  • In the public mode the fuel consumed may be used for the fee calculation though limiting that might make no sense at all, though block capacity is usually limited anyway
• Configuring execution queue event time to live per network/consuming trigger
• Endless recursion prevention analysis?
• Number of events generated to become declining eventually analysis?

[mversic]

this is quite hard to prevent at the time of registering trigger, if not impossible because we don't know what events a trigger will produce when executed. Even if we did we don't know under which conditions an event is produced and whether these conditions will coincide with conditions of another trigger to create positive feedback loop

[mversic]

also, it's possible that positive feedback loop will be self dampening due to changing conditions in the blockchain. So it may only be temporary and not create a problem for blockchain operation