Canister Output Message Queue Limits, and IC Management Canister Throttling Limits

[icme]

@roman-kashitsyn

Is that the exact error message that you get? If so, it tells you that the canister sent too many messages to itself.

I am not sending calls to myself. I’m executing code similar to that mentioned in this post, where I send off a bunch of async calls in parallel, and then after all the async calls are in flight, I collect the awaited results.

Motoko Sharable Generics

I’m trying to perform parallel execution of an async function on each of the elements of a collection (i.e. Buffer<T>) and then to collect the results. This would behave something like Promise.allSettled() in Javascript. The code looks something like this public func mapParallel<A, B>(as: StableBuffer<A>, f: shared (A) -> async B): async StableBuffer<B> { let executingFunctionsBuffer = StableBuffer.init<async B>(); var i = 0; label execute loop { if (i >= as.count) break e…

@roman-kashitsyn

The system keeps track of queues between pairs of canisters. When your canister sends messages to thousands of canisters, the system creates a separate queue for each destination. Each canister also has a queue for messages it sends to itself.

In my specific case, all of these asynchronous calls are hitting the IC Management canister, so then according to your description there is a single queue between my canister and the IC managment canister and that queue is filling up (hitting the 500 limit).

@roman-kashitsyn

If you see could not perform self call, your canister might perform nested self calls exhausting the message queue limit. You might be able to fix the issue by restructuring the code. Is the code public?

I’m currently able to get around the 500 limit by batching the calls (batches of ~300 or so) at a time, but wonder what might happen if I now want to do this same batching but now with a second, third, or nth canister, where canister A is batching calls to both canister B, C … all the way to canister N? At some point, would the message queue to canister A hit a cap due to all of the incoming asynchronous messages from canister B to N?