Building Streaming API with gRPC

Building resilient real-time applications with gRPC streaming in Java: A practical guide

In this article, I’ll guide you through implementing streaming APIs using gRPC in Java. We’ll look at various types of streaming. Then, we’ll create a practical example to show real-time flow.

Introduction

Many developers know about traditional request-response APIs. Yet, modern apps often need real-time data streaming. gRPC provides powerful streaming capabilities that can transform how your services communicate. Whether you’re making chat apps, real-time analytics, or IoT systems, knowing gRPC streaming is key.

Let’s create a weather monitoring service. It will stream temperature updates to clients.

Types of gRPC streaming

Before we start coding, let’s understand the three types of streaming gRPC offers:

• Server streaming: the server sends multiple response to a single client request.
• Client streaming: the client sends many messages to the server.
• Bidirectional streaming: both the server and multiple messages at the same time.

We’ll use server streaming for our weather monitoring service. This method suits our needs well. The client sends one request to start monitoring. Then, the server provides continuous temperature updates.

Implementation

Firtst, let’s define our service contract in protocol buffers:

syntax = "proto3";
package io.vrnsky.weather;

option java_multiple_files = true;
option java_package = "io.vrnsky.weather";
option java_outer_classname = "WeatherServiceProto";

service WeatherService {
  rpc monitorTemperature (Location) returns (stream Temperature) {}
}

message Location {
  double latitude = 1;
  double longitude = 2;
}

message Temperature {
  double celsius = 1;
  string timestamp = 2;
}

Now let’s implement our service

package io.vrnsky.grpc.streaming.service;

import io.grpc.stub.StreamObserver;
import io.vrnsky.weather.Location;
import io.vrnsky.weather.Temperature;
import io.vrnsky.weather.WeatherServiceGrpc;
import…