Micronaut has been making waves in the Java ecosystem, and for good reason. Its HTTP/2 and gRPC support are game-changers for developers looking to build high-performance, real-time data processing applications. Let’s dive into how you can leverage these features to take your Micronaut projects to the next level.
First things first, make sure you have Micronaut set up in your development environment. If you haven’t already, grab the latest version from the official website or use your favorite package manager. Once you’re all set, we can start exploring the exciting world of HTTP/2 and gRPC with Micronaut.
HTTP/2 is the next evolution of the HTTP protocol, bringing improved performance and efficiency to web applications. Micronaut makes it a breeze to enable HTTP/2 support in your projects. Simply add the following dependency to your build file:
implementation("io.micronaut:micronaut-http-server-netty")
With this in place, Micronaut will automatically use HTTP/2 when available. But the real magic happens when you combine HTTP/2 with server-sent events (SSE) for real-time data streaming. Here’s a quick example of how you can create an SSE endpoint:
@Controller("/stock-prices")
public class StockPriceController {
@Get(produces = MediaType.TEXT_EVENT_STREAM)
public Flowable<Event<StockPrice>> streamPrices() {
return Flowable.interval(1, TimeUnit.SECONDS)
.map(i -> Event.of(new StockPrice("AAPL", 150.0 + Math.random() * 10)));
}
}
This code creates a stream of stock price events that clients can subscribe to. The beauty of HTTP/2 is that it allows multiple streams over a single connection, reducing latency and improving overall performance.
Now, let’s talk about gRPC. If you’re not familiar with it, gRPC is a high-performance, language-agnostic RPC framework that’s perfect for microservices architecture. Micronaut’s gRPC support is top-notch, making it easy to create both gRPC servers and clients.
To get started with gRPC in Micronaut, you’ll need to add a few dependencies:
implementation("io.micronaut.grpc:micronaut-grpc-runtime")
implementation("io.grpc:grpc-protobuf")
implementation("io.grpc:grpc-stub")
Next, you’ll need to define your service using Protocol Buffers. Create a file named stock-service.proto in your src/main/proto directory:
syntax = "proto3";
option java_multiple_files = true;
option java_package = "com.example.grpc";
service StockService {
rpc GetStockPrice (StockRequest) returns (StockResponse) {}
rpc StreamStockPrices (StockRequest) returns (stream StockResponse) {}
}
message StockRequest {
string symbol = 1;
}
message StockResponse {
string symbol = 1;
double price = 2;
}
This defines a service with two methods: one for getting a single stock price and another for streaming stock prices. Now, let’s implement the service:
@Singleton
public class StockServiceImpl extends StockServiceGrpc.StockServiceImplBase {
@Override
public void getStockPrice(StockRequest request, StreamObserver<StockResponse> responseObserver) {
StockResponse response = StockResponse.newBuilder()
.setSymbol(request.getSymbol())
.setPrice(150.0 + Math.random() * 10)
.build();
responseObserver.onNext(response);
responseObserver.onCompleted();
}
@Override
public void streamStockPrices(StockRequest request, StreamObserver<StockResponse> responseObserver) {
Flowable.interval(1, TimeUnit.SECONDS)
.map(i -> StockResponse.newBuilder()
.setSymbol(request.getSymbol())
.setPrice(150.0 + Math.random() * 10)
.build())
.subscribe(
responseObserver::onNext,
responseObserver::onError,
responseObserver::onCompleted
);
}
}
This implementation provides real-time stock price updates using gRPC streaming. The cool thing about Micronaut’s gRPC support is that it integrates seamlessly with Micronaut’s dependency injection and configuration management.
Now that we have our gRPC service up and running, let’s create a client to consume it. Micronaut makes it super easy to create gRPC clients with its @GrpcClient annotation:
@Singleton
public class StockPriceClient {
@GrpcClient
StockServiceGrpc.StockServiceStub stockServiceStub;
public Flowable<StockResponse> streamStockPrices(String symbol) {
return Flowable.create(emitter -> {
stockServiceStub.streamStockPrices(
StockRequest.newBuilder().setSymbol(symbol).build(),
new StreamObserver<StockResponse>() {
@Override
public void onNext(StockResponse response) {
emitter.onNext(response);
}
@Override
public void onError(Throwable t) {
emitter.onError(t);
}
@Override
public void onCompleted() {
emitter.onComplete();
}
}
);
}, BackpressureStrategy.BUFFER);
}
}
This client allows us to easily consume the gRPC stream of stock prices. We can then use this client in our HTTP controllers to bridge the gap between gRPC and HTTP/2:
@Controller("/grpc-stocks")
public class GrpcStockController {
private final StockPriceClient stockPriceClient;
public GrpcStockController(StockPriceClient stockPriceClient) {
this.stockPriceClient = stockPriceClient;
}
@Get(value = "/{symbol}", produces = MediaType.TEXT_EVENT_STREAM)
public Flowable<Event<StockResponse>> streamStockPrices(String symbol) {
return stockPriceClient.streamStockPrices(symbol)
.map(Event::of);
}
}
This controller exposes our gRPC stock price stream as an HTTP/2 server-sent events endpoint. It’s a perfect example of how Micronaut allows you to seamlessly integrate different protocols and communication patterns.
But wait, there’s more! Micronaut’s support for reactive programming really shines when working with real-time data processing. Let’s create a service that aggregates stock prices from multiple sources:
@Singleton
public class StockAggregatorService {
private final StockPriceClient grpcClient;
private final WebClient httpClient;
public StockAggregatorService(StockPriceClient grpcClient,
@Client("https://api.example.com") WebClient httpClient) {
this.grpcClient = grpcClient;
this.httpClient = httpClient;
}
public Flowable<AggregatedStockPrice> aggregateStockPrices(String symbol) {
Flowable<StockPrice> grpcPrices = grpcClient.streamStockPrices(symbol)
.map(response -> new StockPrice(response.getSymbol(), response.getPrice()));
Flowable<StockPrice> httpPrices = Flowable.interval(1, TimeUnit.SECONDS)
.flatMap(i -> httpClient.get("/stocks/" + symbol)
.retrieve()
.bodyToMono(StockPrice.class)
.toFlowable());
return Flowable.combineLatest(grpcPrices, httpPrices,
(grpcPrice, httpPrice) -> new AggregatedStockPrice(symbol, grpcPrice.getPrice(), httpPrice.getPrice()));
}
}
This service combines stock prices from our gRPC service and an external HTTP API, demonstrating how Micronaut can effortlessly work with multiple data sources and protocols.
Now, let’s talk about error handling and resilience. When dealing with real-time data processing, it’s crucial to handle errors gracefully and ensure your application can recover from failures. Micronaut provides excellent support for this through its integration with libraries like Hystrix and Resilience4j.
Here’s an example of how you can add circuit breaking to our stock price client:
@Singleton
public class ResilientStockPriceClient {
@GrpcClient
StockServiceGrpc.StockServiceStub stockServiceStub;
@CircuitBreaker(name = "stock-price-stream", fallbackMethod = "fallbackStreamStockPrices")
public Flowable<StockResponse> streamStockPrices(String symbol) {
return Flowable.create(emitter -> {
stockServiceStub.streamStockPrices(
StockRequest.newBuilder().setSymbol(symbol).build(),
new StreamObserver<StockResponse>() {
@Override
public void onNext(StockResponse response) {
emitter.onNext(response);
}
@Override
public void onError(Throwable t) {
emitter.onError(t);
}
@Override
public void onCompleted() {
emitter.onComplete();
}
}
);
}, BackpressureStrategy.BUFFER);
}
public Flowable<StockResponse> fallbackStreamStockPrices(String symbol, Throwable t) {
return Flowable.interval(1, TimeUnit.SECONDS)
.map(i -> StockResponse.newBuilder()
.setSymbol(symbol)
.setPrice(100.0) // Default fallback price
.build());
}
}
This implementation adds a circuit breaker to our stock price stream. If the gRPC service becomes unresponsive, the circuit breaker will open, and we’ll fall back to a default price stream. This ensures that our application remains responsive even when external services fail.
As we wrap up our journey through Micronaut’s HTTP/2 and gRPC support, it’s worth mentioning the importance of testing. Micronaut provides excellent testing support, allowing you to write both unit and integration tests for your HTTP/2 and gRPC services.
Here’s a quick example of how you might test our gRPC stock service:
@MicronautTest
class StockServiceTest {
@Inject
EmbeddedServer embeddedServer;
@Inject
@GrpcClient
StockServiceGrpc.StockServiceBlockingStub blockingStub;
@Test
void testGetStockPrice() {
StockResponse response = blockingStub.getStockPrice(StockRequest.newBuilder().setSymbol("AAPL").build());
assertNotNull(response);
assertEquals("AAPL", response.getSymbol());
assertTrue(response.getPrice() > 0);
}
@Test
void testStreamStockPrices() {
Iterator<StockResponse> responseIterator = blockingStub.streamStockPrices(
StockRequest.newBuilder().setSymbol("GOOGL").build());
List<StockResponse> responses = new ArrayList<>();
responseIterator.forEachRemaining(responses::add);
assertFalse(responses.isEmpty());
responses.forEach(response -> {
assertEquals("GOOGL", response.getSymbol());
assertTrue(response.getPrice() > 0);
});
}
}
This test class demonstrates how to test both the single-request and streaming gRPC methods. Micronaut’s testing support makes it easy to spin up an embedded server and create gRPC clients for your tests.