Most APIs today are accessed over the ubiquitous HTTP protocol and the framework to create these APIs is known as REpresentational State Transfer (REST). These APIs are known as RESTful APIs.

However, if you've been working in API development over the last several years, then you have likely heard of gRPC. gRPC is a robust, newer framework for developing APIs and implementing their communication. It's a CNCF incubation project that aims to provide a modern, open-source framework modeled after Remote Procedure Calls (RPC) that can run anywhere.

Developed by Google and released as an open-source project in 2015, gRPC is gaining popularity in the microservices world as it offers a simpler and more efficient alternative to REST. It's based on the work done on Stubby (Google's internal RPC framework). Many of the world's largest companies, including Netflix, Cisco, Twitter, and Uber, use gRPC in their systems.

What makes up gRPC?

To understand gRPC, let's first talk about RPC. RPC is a method of inter-process communication used by software applications to communicate over the network. gRPC is RPC-based and uses HTTP/2 as its transport layer protocol for communication. Being RPC-based, clients can call any service method of the gRPC whether it's running on the local machine or a remote server. This makes it a versatile tool that goes beyond simple GET and PUT requests.

For the API interface, gRPC uses Protocol Buffers (protobuf) instead of JSON or XML as the interface definition language. Developers define a data structure to specify the message format between the client and the server, and the protobuf compiler converts them into a binary format, the protobuf.

Key Components of gRPC

• Protocol Buffers: A language-agnostic mechanism for serializing structured data.
• HTTP/2: The underlying transport protocol that provides features like multiplexing and header compression.
• Channel: A connection to a gRPC server on a specified host and port.
• Stub: A client-side object that implements the same methods as the gRPC server.

How does gRPC work?

To implement gRPC APIs, you create gRPC services with methods that clients can call. You then define a contract between a client and a server. This contract stipulates the procedures the clients can call from the service, the parameters that can be passed to those procedures, and the types of data that will be returned. The client and the server then use this contract to generate code in their respective languages for calling the procedures and exchanging data. This generated code covers all communication details like message serialization, network calls, and error handling.

As mentioned above, gRPC uses HTTP/2 for transport and Protocol Buffers for message serialization. The client creates local objects or stubs for the API methods and calls those methods locally. The gRPC runtime sends the client requests to the remote server and receives the responses from it.

gRPC API Service Methods

gRPC supports four types of service methods:

1. Unary RPC: A unary service method takes one input and returns one output.
2. Server Streaming RPC: A server streaming service method receives one input from the client and sends a stream of outputs. It can also send back multiple outputs as data becomes available.
3. Client Streaming RPC: Client streaming service methods open a connection to a server, and then when the server acknowledges the stream can begin, the client side can begin sending data until it terminates the stream.
4. Bidirectional Streaming RPC: Bidirectional streaming service methods simultaneously send and receive data streams in both directions.

Each type of method has its unique benefits and use cases. For example, unary methods are ideal for simple RPCs, while server streaming methods are perfect for tasks requiring heavy data processing. Client streaming methods can be used when latency is a concern, while bidirectional streaming methods are perfect for real-time communication.

Advanced Features of gRPC

gRPC also offers several advanced features that make developing and debugging distributed systems easier:

• Synchronous and Asynchronous Calls: gRPC supports both synchronous and asynchronous RPC calls. Synchronous calls wait for the remote server to return a response before continuing. Asynchronous calls return immediately and the response is handled as a separate task.
• Metadata: gRPC allows you to attach metadata to calls. This metadata can be used to describe services and methods, helping clients find the right services and their methods. Developers can also use metadata to validate calls.
• Channels: gRPC channels allow simultaneously sending and receiving multiple calls. This can improve performance by enabling the server to handle multiple requests simultaneously.
• Interceptors: gRPC supports interceptors, which are a powerful mechanism for extending gRPC functionality. They can be used for logging, authentication, monitoring, and more.
• Deadlines/Timeouts: gRPC allows clients to specify how long they are willing to wait for an RPC to complete. The gRPC framework will automatically cancel the RPC if it exceeds this deadline.

Why use gRPC?

There are several reasons you may want to use the gRPC framework for developing your APIs.

1. Broad language support

gRPC has broad language support. It's widely supported in most modern languages and frameworks, including Java, Ruby, Go, Node.js, Python, C#, and PHP. As mentioned above, gRPC clients can invoke any function just GET and making it more versatile than traditional APIs.

2. Smaller message size

gRPC messages are smaller than traditional RESTful API messages because the binary message formats—Protocol Buffers—are smaller and faster to parse than text-based formats like JSON. This results in faster transmission between the client and the server.

3. Faster communication

HTTP/2 is more efficient than older protocols like HTTP/1.1—allowing gRPC to reduce network bandwidth usage and decrease latency. Also, since the messages are smaller, they can be transferred more quickly between servers and clients. This also helps to reduce the load on the network and provides a smoother user experience.

4. Streaming Connection

Another advantage of gRPC is its support for streaming connection mode. Streaming mode sends or receives data in chunks, which can improve performance when the data is too large to send or receive at once. This allows clients to continuously receive data from the server without waiting for the entire response to arrive. As a result, users don't have to wait until all the data transfer is complete.

During streaming, the connection between the client and the server is maintained, meaning no data is lost or corrupted while transmitted. gRPC streaming is ideal for real-time applications like chat or gaming.

5. Pluggable Support

gRPC supports plugging in load balancing, tracing, health checking, and authentication. This makes it easy to set up and manage high-performance systems. gRPC is modular, so it's simple to set up and configure its different feature sets.

6. Strong Typing

gRPC uses Protocol Buffers, which provide strong typing for messages. This can help catch errors at compile-time rather than runtime, leading to more robust and reliable systems.

7. Code Generation

gRPC automatically generates client and server code from your service definitions. This can significantly reduce the amount of boilerplate code you need to write and maintain.

What are the drawbacks of gRPC?

Overall, gRPC is a powerful tool that offers many benefits for your applications. However, there are some drawbacks as well:

• Debugging Complexity: Application errors can be difficult to debug in gRPC systems, especially for developers who are new to the framework.
• Limited Browser Support: gRPC relies on HTTP/2, which is not fully supported in all web browsers. This can make it challenging to use gRPC directly in web applications.
• Learning Curve: For teams familiar with REST, there can be a significant learning curve when adopting gRPC.
• Limited Tooling: While the situation is improving, there are still fewer tools available for working with gRPC compared to REST APIs.
• Firewall Issues: Some firewalls may have issues with HTTP/2, which can cause problems for gRPC in certain network environments.

However, the advantages can far outweigh such drawbacks for many use cases, particularly in microservices architectures and high-performance systems.

gRPC vs REST: When to Use Which?

While gRPC offers many advantages, it's not always the best choice for every situation. Here's a comparison to help you decide:

Use gRPC when:

• You need high performance, especially for systems with many RPCs.
• You're working in a microservices architecture where low latency is crucial.
• You need to support streaming.
• You're working in a polyglot environment with multiple programming languages.
• You need strong typing and contract-based development.

Use REST when:

• You need wide client support, especially for web browsers.
• You want your API to be easily explorable by humans.
• You need to support caching on the client side or intermediary servers.
• You're building a public API that needs to be easily accessible to a wide range of clients.

Implementing gRPC: Best Practices

When implementing gRPC in your system, consider the following best practices:

1. Design Your Protocol Buffers Carefully: Your .proto files define your API contract. Design them thoughtfully, considering versioning and backward compatibility.
2. Use Streaming Judiciously: While gRPC's streaming capabilities are powerful, they're not always necessary. Use them when you have a clear use case for streaming.
3. Implement Error Handling: gRPC has a rich set of error codes. Use them appropriately to provide meaningful error messages to clients.
4. Secure Your gRPC Services: Use TLS/SSL to encrypt communications and implement proper authentication and authorization mechanisms.
5. Monitor Your gRPC Services: Implement proper logging and monitoring to track the performance and health of your gRPC services.
6. Consider Using Interceptors: Interceptors can help you implement cross-cutting concerns like logging, authentication, and monitoring in a clean, reusable way.

The Future of gRPC

As microservices architectures continue to gain popularity and the need for efficient, high-performance communication between services grows, gRPC is likely to see increased adoption. Some trends to watch in the gRPC space include:

• Improved Web Browser Support: Efforts are underway to make gRPC more accessible in web browsers, which could significantly expand its use cases.
• Integration with Service Mesh: As service mesh technologies like Istio mature, we're likely to see tighter integration with gRPC for features like load balancing and security.
• Serverless gRPC: Cloud providers are starting to offer better support for running gRPC in serverless environments, which could lead to new patterns of use.
• gRPC-Web: This project aims to bring gRPC to web applications, allowing them to benefit from gRPC's performance advantages.
• Enhanced Tooling: As gRPC adoption grows, we can expect to see more robust tooling for debugging, testing, and monitoring gRPC services.

Conclusion

Today, you learned about the core components of the gRPC framework and saw how it works. Overall, gRPC offers a fast, reliable, and efficient way to handle remote procedure calls. If you're looking for a faster and more efficient way to build web services, especially in a microservices architecture, then consider gRPC.

Kong, the world's most popular API Gateway, has native support for gRPC, making it an excellent choice for modern organizations that want to try newer API technologies. As a robust API Gateway, Kong provides many features, including authentication, rate limiting, logging, and monitoring. It can secure, manage, and extend gRPC-based APIs, and its rich set of plugins allows custom operations like gRPC service access via REST or browser-based clients.

As you evaluate whether gRPC is the right choice for your next project, consider factors like your performance requirements, your target clients, your team's expertise, and your overall system architecture. While gRPC isn't a one-size-fits-all solution, its powerful features make it a compelling choice for many modern API development scenarios.

To see how Kong can help manage your gRPC API fleet, request a personalized demo. Whether you're just starting with gRPC or looking to optimize your existing gRPC implementation, Kong can provide the tools and support you need to succeed in your API development journey.

gRPC FAQs

Q: What is gRPC and how does it differ from traditional REST APIs?

A: gRPC is a modern, open-source framework for developing APIs, based on Remote Procedure Calls (RPC). Unlike REST APIs which typically use HTTP/1.1 and JSON, gRPC uses HTTP/2 for transport and Protocol Buffers for message serialization, resulting in faster and more efficient communication.

Q: What are the main advantages of using gRPC?

A: The main advantages of gRPC include: broad language support, smaller message size due to Protocol Buffers, faster communication thanks to HTTP/2, support for streaming connections, strong typing, and automatic code generation. These features make gRPC particularly suitable for microservices architectures and high-performance systems.

Q: What types of service methods does gRPC support?

A: gRPC supports four types of service methods:

• Unary RPC (one request, one response)
• Server Streaming RPC (one request, multiple responses)
• Client Streaming RPC (multiple requests, one response)
• Bidirectional Streaming RPC (multiple requests and responses in any order)

Q: What are some drawbacks or challenges of using gRPC?

A: Some drawbacks of gRPC include: difficulty in debugging application errors, limited browser support due to HTTP/2 requirements, a steeper learning curve compared to REST, fewer available tools compared to REST APIs, and potential firewall issues with HTTP/2.

Q: When should I use gRPC instead of REST?

A: Consider using gRPC when you need high performance, especially in systems with many RPCs; when working in a microservices architecture where low latency is crucial; when you need to support streaming; in polyglot environments with multiple programming languages; or when you need strong typing and contract-based development.

Q: How does gRPC handle security and authentication?

A: gRPC supports various security features. It uses TLS/SSL for encryption of communications. For authentication, gRPC can be integrated with different authentication mechanisms such as OAuth 2.0, JSON Web Tokens (JWT), or custom authentication methods through the use of interceptors. It's also designed to work well with API gateways like Kong, which can provide additional security features.