canic

Facade crate that re-exports the main Canic stack for canister projects:

• endpoint and lifecycle macros
• core runtime/types
• stable-memory helpers under canic::memory

Most downstream canister projects should start here instead of reaching for lower-level crates directly.

Use the explicit module paths for the larger bundled surfaces:

• canic::api::* for runtime APIs
• canic::dto::* for public wire and value types
• canic::memory::* for stable-memory helpers and macros

Crate Boundary

Use canic from configured canister role packages and Canic's host-generated built-in infrastructure wrappers. Each package must declare its own direct, normal runtime dependency on canic.

Shared runtime libraries must not depend on canic. Keep their domain logic framework-independent; role packages and IC adapters depend directly on upstream crates such as candid, ic-cdk, or ic-stable-structures for generic IC types and APIs. This keeps every role package's runtime graph to one direct path to Canic.

Feature Contract

The default feature set is empty. Select every Cargo-gated runtime capability required by the role; generated metrics are derived from role configuration, not selected through a facade feature.

The control-plane feature is the normal root-role selection. The narrower fleet-coordinator-canister and wasm-store-canister features exist for Canic-owned infrastructure packages; neither is an alternate application or root configuration.

Config-Driven Auth Features

Some canic.toml auth settings require matching runtime canic features in the role crate's [dependencies]. Add these to the runtime dependency, not only [build-dependencies].

Run canic medic project --ci for concise fail-only diagnostics, or canic medic project --json for automation-friendly check rows such as role_required_canic_feature_missing.

Typical Use

Use canic in both [dependencies] and [build-dependencies] so the build macros and runtime macros come from the same facade crate.

Each canister crate declares its role in package metadata:

[package.metadata.canic]
app = "demo"
role = "app"

Use canic::build!("../canic.toml") from build.rs and canic::start!() from lib.rs. The app value must match [app].name in the selected canic.toml. role = "root" selects the root lifecycle and root endpoint bundle; ordinary roles select the non-root lifecycle and endpoint bundle.

Inter-Canister Calls

Use the Canic call builder when application code benefits from concise Candid encoding, typed public errors, and Canic's inter-canister call metrics:

use candid::Principal;
use canic::prelude::Call;

async fn read_count(target: Principal) -> Result<u64, canic::Error> {
    Call::bounded_wait(target, "read_count")
        .execute_candid()
        .await
}

Call::unbounded_wait is also available, as are with_arg, with_args, with_raw_args, with_cycles, and execute_candid_tuple. Use execute directly when the response must be retained or decoded later. This is an ordinary IC call builder; it does not replace Canic's protected capability RPC used for framework-owned creation, upgrade, placement, recycling, or cycle operations.

Application Timers

Application canisters depend on the exact workspace-compatible ic-timers release and own their native registrations directly. Canic intentionally provides no timer macro, handle or cancellation facade:

use ic_timers::{
    DeclarationLifetime, OnceContext, TimerCompletion, TimerDirective,
    TimerIdentity, TimerRunResult, TimerSchedule, register_once,
};
use std::time::Duration;

let timer = register_once(
    TimerIdentity::try_new("my-app", "cache", "refresh")?,
    DeclarationLifetime::RemoveWhenStopped,
    |_context: OnceContext| async {
        refresh_cache().await;
        TimerRunResult::new(TimerCompletion::success(1), TimerDirective::Stop)
    },
)?;
timer.ensure_scheduled(TimerSchedule::After(Duration::from_secs(30)))?;

Keep the native registration when later cancellation or reconciliation is required. Dropping it detaches caller control without cancelling the timer. Provider inventory is volatile observation, not durable application demand. Use the paired lifecycle_participant(init = ..., post_upgrade = ...) declaration on canic::start! to reconstruct application-owned volatile registrations synchronously after Canic restoration and before deferred hooks.

Every linked owner must resolve the same exact ic-timers package ID; two versions create two canister-local registries rather than one inventory. Timer performance observations bracket the complete accepted shared-runtime callback path: registry acceptance, consumer work, completion accounting, and successor binding. They are operational callback costs, not isolated application-function benchmarks. A transient RemoveWhenStopped declaration that reaches terminal state is removed from the shared inventory, so no final status or performance sample survives after removal; retained declarations preserve their normally completed samples. Authority snapshots currently reject any timer claim outside Canic custody. See the maintained native timer adoption guide for exact dependency, custody, lifecycle reconstruction and qualification rules. Combined Canic/IcyDB qualification remains a separate 0.104 proof.

This crate lives in the Canic workspace. See the workspace guide at ../../README.md for full setup, topology, and example canisters.