Understanding RPC: Principles, Architecture, and Implementation Process

Remote Procedure Call (RPC) has become a fundamental building block for distributed service architectures, enabling different services to invoke each other's methods across network boundaries. The article begins by outlining the need for RPC as web applications scale from single‑application deployments to vertical architectures and finally to distributed service architectures.

In a monolithic setup, all functionality resides in one application to minimize deployment cost. As traffic grows, vertical architectures split the system into independent applications, often using MVC frameworks for front‑end development. When the number of vertical applications increases, inter‑service communication becomes unavoidable, prompting the extraction of core business logic into independent services managed by an RPC framework.

The implementation of RPC involves several key steps: (1) establishing a communication channel (typically a TCP connection), (2) service addressing (discovering the target host and port, often via a registry such as Zookeeper or Redis), (3) network transmission, which includes serialization of request data on the client side and deserialization on the server side, (4) invoking the actual service method on the server, and (5) returning the result through the reverse process of serialization, transmission, and deserialization.

A basic RPC architecture consists of four components: the client (service consumer), the client stub (packages the request and handles network transmission), the server stub (decodes the request and calls the local service), and the server (the actual service provider). The article also outlines the lifecycle of services in a registry, including registration, heartbeat, and deregistration.

Finally, the article presents a complete RPC call flow: the client invokes a local method, the client stub serializes the call, sends it to the server stub, which deserializes, invokes the local service, serializes the response, and sends it back to the client stub for deserialization and delivery to the original caller.