When is Cycles deducted?

Developers
1

I learned that If I end the call using ic_cdk::trap(msg), cycles aren’t deducted.
Is the case same when I’m perform cross canister call, http outcalls before calling the trap?
Will the cycles be deducted?

2

trap rolls everything (including cycles accepted, attached to calls, …) back to the last commit point (read: await).

From the docs (can recommend you read the full page):

In particular, any state changes made by the canister before making the inter-canister call and calling await to wait for the response will not be rolled back (as this was a separate message execution that happened before the callback handler was invoked).

1 Like
3

thank you @Severin for sharing, I read it. still had some confusion.
Can you clear this?

let res = ic_cdk::call(canister, "method", ()).await;
if let Err(e) = res{
  ic_cdk::trap("")
}

In this code, cycles will be deducted right?
If it is deducted will it be cycles for calling update method, cycles for inter canister call. am I right?

4

Yes, that’s right. And if you attach cycles to the call then those will stay with the target canister (assuming it accepts the cycles).