Logging (id_effect_logger)

Workspace crate id_effect_logger provides an injectable EffectLogger service: log lines are effect steps that read EffectLogKey from R, so formatting and sinks stay composable and testable.

Usage shape

• ~EffectLogger inside effect! (or explicit Get) to obtain the handle, then info, warn, … on static or dynamic messages (impl Into<Cow<'static, str>>).
• layer_effect_logger (and related constructors) build the Service<EffectLogKey, EffectLogger> cell you Cons into Context.

Backends

The crate ships pipeline pieces such as structured JSON, tracing integration, and composite backends—see cargo doc -p id_effect_logger for LogBackend, JsonLogBackend, TracingLogBackend, CompositeLogBackend.

Relation to the rest of Part II

Logging is just another tagged service: same mental model as Tags and Context and Providing Services via Layers. Swap backends in tests instead of silencing println!.

Further reading

• cargo doc --open -p id_effect_logger