Remote Procedure Call (RPC)

In distributed computing, Remote Procedure Call (RPC) is a powerful protocol that enables a program to execute a procedure (function or subroutine) on another address space—typically on a remote server—without the programmer needing to code the details for this remote interaction explicitly.

RPC abstracts the complexity of network communication, making it appear as though the remote procedures are local, allowing developers to focus on application logic rather than the intricacies of network programming.

What is RPC?

Definition

Remote Procedure Call (RPC) is a protocol that allows a client to invoke procedures or functions on a remote server as if they were local functions. The communication between client and server is handled transparently in the background.

Basic Workflow

Client makes a request to execute a function.
RPC Stub serializes (marshals) the function call and parameters.
Client-side RPC Runtime sends the request over the network.
Server-side RPC Runtime receives the request.
Server Stub deserializes (unmarshals) the request and calls the appropriate function.
Function executes and returns a response.
Server-side RPC Runtime sends the response back.
Client-side RPC Runtime receives and returns the result to the client.

Why Use RPC?

Abstraction: Makes remote calls look like local calls.
Productivity: Simplifies distributed application development.
Interoperability: Enables cross-platform communication (e.g., Python client, Java server).
Scalability: Used in microservices architecture for decoupled communication.

Types of RPC

Synchronous RPC: The client sends a request and waits for the response before continuing.

Asynchronous RPC: The client sends a request and proceeds without waiting. The response may be handled via callback, polling, or future/promise patterns.

RPC vs REST

Feature	RPC	REST
Interface	Procedure/function-based	Resource-based
Communication	Typically binary (efficient)	Typically HTTP/JSON or XML
Flexibility	More tightly coupled	Loosely coupled
Performance	Faster due to binary format	Slower due to text parsing

Popular RPC Frameworks

gRPC

Developed by Google
Uses HTTP/2 and Protocol Buffers
Strongly typed contracts
Supports many languages
Ideal for microservices

Apache Thrift

Developed at Facebook
Cross-language support
Efficient binary serialization

JSON-RPC / XML-RPC

Lightweight alternatives
Use JSON or XML over HTTP
Simpler than gRPC, but less performant

Java RMI

Java-specific RPC framework
Allows calling Java objects on remote JVMs

RPC Components in Detail

Client Stub: Handles request serialization and sending to the server.

Server Stub (Skeleton): Receives request, deserializes, and invokes actual procedure.

Transport Layer: Carries the serialized data over the network (e.g., TCP, HTTP/2).

Serialization: Transforms data structures into a format suitable for transmission (e.g., JSON, XML, Protobuf).

Challenges of RPC

Tight Coupling: RPC interfaces are often tightly coupled to server implementations.
Versioning: Changing function signatures can break clients.
Error Handling: Remote errors must be gracefully handled.
Latency and Failures: Network-related delays and failures must be accounted for.
Security: Authentication, encryption, and authorization must be handled manually or via frameworks.

Best Practices

Use strongly typed interfaces (like Protobuf in gRPC).
Handle timeouts and retries gracefully.
Monitor and log RPC traffic.
Version APIs to prevent breaking changes.
Secure communication using TLS.

Use Cases

Microservices communication (e.g., gRPC in Kubernetes).
IoT device-to-cloud communication.
Cross-language service communication.
High-performance internal APIs.

Why Choose RPC Over REST API?

Performance & Efficiency

RPC (especially with binary serialization like gRPC + Protocol Buffers) is significantly faster and more compact than text-based REST APIs (which use JSON or XML).
Ideal for low-latency or high-throughput scenarios (e.g., real-time systems, microservices).
Use RPC when performance is critical.

Tight Coupling with Strong Typing

RPC frameworks like gRPC enforce strongly-typed contracts via .proto files.
This ensures that both client and server adhere strictly to the defined interface.
Helps catch bugs early at compile time.

Streaming Support

RPC protocols like gRPC support:
- Client streaming
- Server streaming
- Bidirectional streaming
Perfect for chat apps, video streaming, live feeds—something REST doesn’t handle well.

Automatic Code Generation

Tools like protoc in gRPC auto-generate client/server code in multiple languages.
Saves development time and reduces boilerplate code.
Great for polyglot systems (e.g., Python client, Go server)

Better for Internal Microservices

In internal microservices architecture (e.g., in Kubernetes), services often:
- Know each other’s interface.
- Need fast, reliable communication.
RPC fits better than REST, which is more generic and resource-focused.
Use RPC behind the scenes; expose REST to the outside world.

When NOT to Use RPC

Public APIs: REST is more human-readable, debuggable, and accessible with browsers or tools like Postman.
Loose Coupling Needed: REST’s resource-based design is more flexible for evolving services.
Simple CRUD Services: REST is ideal for basic data manipulation apps.

Use RPC When:

You need performance.
You want strong contracts.
You’re building internal microservices.
You need streaming.
You want to auto-generate clients/servers.

Stick to REST When:

You’re building public APIs.
You prioritize simplicity and flexibility.
You want URL-based, resource-focused design.

Conclusion

Remote Procedure Calls simplify the complexity of distributed computing by abstracting network communication behind familiar function calls. Modern frameworks like gRPC and Thrift have made RPC more efficient, scalable, and language-agnostic. While it offers immense benefits in performance and productivity, proper design, and handling of edge cases like failures and compatibility are crucial for robust RPC systems.

Whether you’re building microservices, cross-platform systems, or high-performance APIs, RPC is a valuable tool in your architectural toolkit.

Resources

API Guide