RPC Remote Procedure Call
Remote Procedure Call (RPC) is a communication protocol that allows a computer program running on one device to call a subroutine or procedure on a remote device, as if it were a local procedure. It enables distributed systems to communicate and interact with each other transparently, hiding the underlying complexities of network communication.
RPC provides a high-level abstraction that makes it easier for developers to build distributed applications. It allows them to invoke procedures on remote systems without having to deal with the low-level details of network communication, such as socket programming and message serialization.
The basic concept behind RPC is similar to a traditional procedure call in a programming language. However, instead of invoking a procedure within the same address space, RPC allows the invocation of a procedure on a different device over a network. This enables the distributed system to act as if the remote procedure is a local one, abstracting away the network communication aspect.
Here's a step-by-step breakdown of how RPC works:
- Client requests a remote procedure call: The client program initiates an RPC by calling a local procedure that appears to be local but is actually a proxy for the remote procedure. The client provides the necessary arguments to the procedure call.
- Client stub marshaling: The client stub (a client-side library) receives the procedure call and marshals (serializes) the arguments into a format suitable for transmission over the network. This typically involves converting the arguments into a standardized binary or textual representation.
- Client network communication: The client stub sends the marshaled arguments to the server over the network. It uses a transport protocol (such as TCP/IP) to establish a connection with the server and transmit the data.
- Server network communication: The server's RPC runtime receives the incoming request from the client and passes it to the appropriate server stub (server-side library). The transport protocol handles the network communication details, such as packet routing and data integrity.
- Server stub unmarshaling: The server stub unmarshals (deserializes) the received data, extracting the arguments of the remote procedure call. It converts the arguments back into a format usable by the server program.
- Server procedure execution: The server stub invokes the actual procedure or subroutine in the server program, passing the unmarshaled arguments. The procedure executes as if it were a local call.
- Server result marshaling: Once the procedure execution is complete, the server stub marshals the return value (if any) and any output arguments back into a format suitable for transmission.
- Server network communication: The server stub sends the marshaled return value and output arguments back to the client over the network using the established connection.
- Client network communication: The client's RPC runtime receives the response from the server and passes it to the client stub.
- Client stub unmarshaling: The client stub unmarshals the received data, extracting the return value and any output arguments. It converts them back into a format usable by the client program.
- Client procedure call completion: The client stub returns the unmarshaled result to the client program as if it were the result of a local procedure call. The client program can continue its execution, processing the result or performing further actions.
The RPC process encapsulates the complexity of network communication, data serialization, and marshaling/unmarshaling, allowing developers to focus on the logic of their applications. It provides a convenient and efficient way to build distributed systems by enabling seamless interaction between remote components.