RPCs

RPC stands for Remote Procedure Call, a method for invoking procedures on a remote machine as if they were local. It enables a program to request a service from another address space, typically across a network, without embedding explicit network communication logic into the caller.

In a typical RPC, the interface is defined in an interface definition language. Client and server stubs are generated from this definition. The client calls a local stub, which marshals the arguments and sends a request to the server. The server unmarshals parameters, executes the procedure, and returns the result to the client through the stub.

RPC implementations vary in data encoding and transport. Classic systems use compact binary protocols; newer variants include JSON-RPC and XML-RPC over HTTP, and gRPC over HTTP/2 using Protocol Buffers. Others include Apache Thrift and DCE/RPC. Some support unary calls only, others offer streaming and bidirectional communication.

Key considerations include call semantics (synchronous vs asynchronous), error handling, retries, and idempotency. Security concerns cover authentication, authorization, and encryption, typically via TLS. Performance aspects include serialization efficiency, multiplexing, and connection management.

RPC is often contrasted with RESTful APIs, which emphasize resource manipulation over remote procedure invocation. RPC can provide strong typing, compact payloads, and efficient communication for tightly coupled services. It is widely used in microservices, distributed systems, and high-performance computing contexts.

Notable families and implementations include ONC RPC, DCE/RPC, XML-RPC, JSON-RPC, Apache Thrift, and Google gRPC, reflecting a long history of RPC design across different ecosystems.