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feat: on low wasm memory hook #286

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@ielashi ielashi commented Mar 22, 2024

This proposal is based on this forum post and has already been approved by motion proposal 106146.

Canister developers have to actively monitor their canisters to know if they are low on wasm memory. If detected too late, a canister can be completely stuck and forever un-upgradable.

To address this, we introduce a hook called on_low_wasm_memory. When defined, it is triggered whenever the canister's memory usage exceeds some developer-defined threshold.

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🤖 Here's your preview: https://oov64-qqaaa-aaaak-qcnsa-cai.icp0.io/docs

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github-merge-queue bot pushed a commit to dfinity/ic that referenced this pull request Sep 24, 2024
This PR is part of the OnLowWasmMemoryHook effort. Here we implement
checking for hook condition and propagating hook status to SystemState.
Condition for executing hook, as agreed in interface spec
[discussion](dfinity/interface-spec#286 (comment))
is:

1. In the case with memory_allocation `min(memory_allocation -
used_stable_memory, wasm_memory_limit) - used_wasm_memory`
2. Without memory allocation `wasm_memory_limit - used_wasm_memory` 

Hook status can be one of:

1. Condition is not satisfied
3. Ready for execution
4. Executed

The hook condition is checked whenever additional execution (stable or
Wasm) memory allocation is requested.

After this change, we will have all the required information of
SystemState and it will be necessary only to schedule hook execution in
the following round.

This PR will be followed with:

1. [EXC-1724](https://dfinity.atlassian.net/browse/EXC-1724) In which we
will refactor `SystemState::task_queue` to be new struct with additional
field `on_low_wasm_memory_hook_status`, to ensure that whenever
available first task that will be poped form task queue is
`OnLowWasmMemoryHook` (excluding paused executions). For that reason
`SystemState::on_low_wasm_memory_hook status` is private, and we use
`set` and `get`, so it can be easier encapsulated in the future
`TaskQueue` struct.
2. [EXC-1725](https://dfinity.atlassian.net/browse/EXC-1725) Schedule
and execute `OnLowWasmMemoryHook`


[EXC-1724]:
https://dfinity.atlassian.net/browse/EXC-1724?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ
[EXC-1725]:
https://dfinity.atlassian.net/browse/EXC-1725?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

---------

Co-authored-by: Alin Sinpalean <[email protected]>
frankdavid pushed a commit to dfinity/ic that referenced this pull request Sep 25, 2024
This PR is part of the OnLowWasmMemoryHook effort. Here we implement
checking for hook condition and propagating hook status to SystemState.
Condition for executing hook, as agreed in interface spec
[discussion](dfinity/interface-spec#286 (comment))
is:

1. In the case with memory_allocation `min(memory_allocation -
used_stable_memory, wasm_memory_limit) - used_wasm_memory`
2. Without memory allocation `wasm_memory_limit - used_wasm_memory` 

Hook status can be one of:

1. Condition is not satisfied
3. Ready for execution
4. Executed

The hook condition is checked whenever additional execution (stable or
Wasm) memory allocation is requested.

After this change, we will have all the required information of
SystemState and it will be necessary only to schedule hook execution in
the following round.

This PR will be followed with:

1. [EXC-1724](https://dfinity.atlassian.net/browse/EXC-1724) In which we
will refactor `SystemState::task_queue` to be new struct with additional
field `on_low_wasm_memory_hook_status`, to ensure that whenever
available first task that will be poped form task queue is
`OnLowWasmMemoryHook` (excluding paused executions). For that reason
`SystemState::on_low_wasm_memory_hook status` is private, and we use
`set` and `get`, so it can be easier encapsulated in the future
`TaskQueue` struct.
2. [EXC-1725](https://dfinity.atlassian.net/browse/EXC-1725) Schedule
and execute `OnLowWasmMemoryHook`


[EXC-1724]:
https://dfinity.atlassian.net/browse/EXC-1724?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ
[EXC-1725]:
https://dfinity.atlassian.net/browse/EXC-1725?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

---------

Co-authored-by: Alin Sinpalean <[email protected]>
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:::note

While the above function is scheduled immediately once the condition above is triggered, it may not necessarily be executed immediately if it does not have enough cycles.
If the canister gets frozen immediately after the function is scheduled for execution, the function will run once the canister's unfrozen _if_ the canister's wasm memory remains above the threshold `t`.
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If the canister gets frozen immediately after the function is scheduled for execution, the function will run once the canister's unfrozen if the canister's wasm memory remains above the threshold t.

This property is not established by the implementation.

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mraszyk commented Oct 30, 2024

The implementation only considers stable memory and ignores, e.g., the chunk store and snapshot size, when deriving the wasm memory capacity.

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mraszyk commented Oct 30, 2024

The hook should not run after an upgrade/reinstall/uninstall/install if the condition is not satisfied after the upgrade (although the condition was satisfied before the upgrade and the hook did not execute yet).

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mraszyk commented Nov 15, 2024

Superseded by dfinity/portal#3761

@mraszyk mraszyk closed this Nov 15, 2024
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