Precall

Precall is a term used in software engineering to describe the set of operations that are executed immediately before a function call, API request, or service invocation. The precall phase is used to prepare the environment, validate inputs, enforce policies, and collect telemetry so that the subsequent call can execute reliably and securely.

In code, precall logic is typically implemented as pre-call hooks, interceptors, or middleware. These tools wrap the target call and run code in advance, which may modify arguments, perform authentication, check permissions, allocate resources, or emit metrics.

In practice, precall is common in API design and distributed systems. API gateways may perform pre-call checks such as authentication, authorization, rate limiting, and request normalization before routing to backend services. RPC frameworks often use client and server interceptors to insert precall behavior. Web frameworks use middleware to run code before request handlers.

Implementation considerations: precall adds overhead and can affect latency, so the logic is typically kept lightweight and idempotent. The order of precall steps matters, and careful design is needed to avoid duplicating work or leaking state across calls. Testing should cover both successful and failed precall conditions and ensure that failures are handled gracefully and do not cause unintended side effects.

See also: post-call, hooks, interceptors, middleware, decorators, preflight.