DFINITY Foundation

Synapse.vote (formerly ICP Maximalist Network)

ICDevs.org

CryptoIsGood

Anvil

ICPL.app

ysyms

The Accumulators’ Neuron

RawTech Venture

Paul Young

ICPMANUAL

8yeargangDAO

Isaac Valadez

Krzysztof Żelazko

Nicolas.ic

Smaug’s Neuron for Retail Investors

Internet Computer Association

Arthur’s Neuron (used to be cycle_dao)

The Fools' Court

Always Rejects

John Wiegley



# Background

Currently, developers have to actively monitor their canisters by periodically
polling the cycle balance and the memory usage of the canisters. Periodic polling
is inefficient in terms of resource usage and difficult to maintain for dapps
with many canisters.

This proposal aims to improve the monitoring and observability of canisters by
introducing a push model, where the canister is automatically notified when it
is low on cycles and memory.

# Proposal

The proposal is to introduce new canister settings and new end-point functions.
If a canister exports an end-point function, then the Internet Computer will
invoke it when the corresponding event occurs:

- `canister_on_low_cycles(threshold)`: this end-point is invoked when the cycle balance becomes lower than the new cycle threshold in the canister settings.
- `canister_on_low_heap_memory(threshold)`: this end-point is invoked when the heap usage exceeds the new heap threshold in the canister settings.


# Use cases

The `canister_on_low_cycles()` hook is useful for dapps with many canisters.
When a canister becomes low on cycles, it can send a message to the main
canister to request more cycles.


The `canister_on_low_heap_memory()` allows the canister to free memory to avoid
out-of-memory errors by dropping caches and unused memory. The canister can also
send a message to alert the developer about the potential out-of-memory issue. 


# Future work

More hooks may be added in the future such as, for example, `canister_on_error()`, `canister_post_upgrade()`.

# What are we asking the community
- Vote accept or reject on NNS Motion
- Participate in technical discussions as the motion moves forward

# Acknowledgment

This proposal is based on the forum post by @icme.




Motion for Canister Lifecycle Hooks