RPC Definition
Stands for “Remote Procedure Call.” Most computer programs run procedures, or sets of instructions, using the computer’s CPU. In other words, the instructions are processed locally on the same computer that the software is running from. Remote procedure calls, however, run procedures on other machines or devices connected to a network. Once the instructions have been run, the results of the procedure are usually returned to the local computer.
For example, a computer without a hard drive may use an RPC to access data from a network file system (NFS). When printing to a network printer, a computer might use an RPC to tell the printer what documents to print. A client system connected to a database server may execute an RPC to process data on the server.
Remote procedure calls are based on the client-server model, where multiple client computers may connect to a server and retrieve data from it. RPCs are typically written in a standard format, such as XML, so that the procedures can be understood by multiple computer platforms. For example, an XML-RPC sent by a Windows computer could be recognized by a Macintosh or Unix-based system.
A Remote Procedure Call (RPC) is a protocol that enables a program to execute a procedure (or a subroutine) on a different address space, typically on a remote server or computer, as if it were a local procedure call. This abstraction allows developers to build distributed systems, where components can communicate and invoke functions seamlessly across networks.
Key Aspects of RPC
- Mechanism:
- RPC abstracts the complexities of network communication. When a client makes an RPC call, the following steps generally occur:
- Client Stub: The client program calls a local procedure (the client stub), which prepares the call and the arguments for transmission.
- Marshalling: The arguments are serialized (marshalled) into a format suitable for transmission over the network.
- Transport: The marshalled data is sent over the network to the remote server using a transport protocol (e.g., TCP, UDP).
- Server Stub: Upon receiving the request, the server stub unmarshals the data and invokes the actual procedure on the server.
- Execution: The server executes the procedure and sends the results back to the client stub.
- Response: The client stub receives the response, unmarshals the results, and presents them to the calling program.
- RPC abstracts the complexities of network communication. When a client makes an RPC call, the following steps generally occur:
- Communication:
- RPC can be implemented using various communication protocols, including HTTP, WebSocket, or custom protocols. It can also be designed to support different data formats, such as JSON, XML, or binary.
- Synchronous vs. Asynchronous:
- Synchronous RPC: The client waits for the server to complete the procedure call and return the results before continuing execution.
- Asynchronous RPC: The client initiates the call and can continue processing without waiting for the server to respond, allowing for non-blocking operations.
- Advantages:
- Abstraction: RPC hides the complexities of network communication, making distributed systems easier to develop and manage.
- Interoperability: Different systems and programming languages can communicate through RPC, as long as they adhere to the same protocol and data formats.
- Modularity: RPC promotes modular design by allowing services to be developed and maintained independently.
- Challenges:
- Network Latency: RPC calls may experience delays due to network latency, which can affect performance.
- Error Handling: Handling errors in a distributed environment can be complex, as issues may arise from network failures, timeouts, or server crashes.
- Security: RPC communication can be vulnerable to attacks, necessitating robust security measures like encryption and authentication.
- Examples:
- XML-RPC: A protocol that uses XML to encode procedure calls and HTTP as a transport mechanism.
- JSON-RPC: A lightweight protocol that uses JSON for encoding and can also work over various transport protocols.
- gRPC: A modern RPC framework developed by Google that uses Protocol Buffers for serialization and supports multiple programming languages and streaming.
Conclusion
Remote Procedure Calls facilitate communication between distributed systems, enabling developers to build scalable and modular applications. By abstracting the complexities of network interactions, RPC allows for seamless execution of procedures across different machines, enhancing the interoperability and flexibility of software architectures.