Package org.a2aproject.sdk.server.grpc.quarkus

package org.a2aproject.sdk.server.grpc.quarkus
Quarkus gRPC reference implementation for the A2A protocol.

This package provides a production-ready gRPC server implementation built on Quarkus gRPC and Protocol Buffers, demonstrating best practices for A2A protocol integration with CDI, authentication, and interceptor support.

Architecture

gRPC Request (Protocol Buffers)
    ↓
A2AExtensionsInterceptor (metadata extraction)
    ↓
QuarkusGrpcHandler (@GrpcService)
    ├─ Protobuf → Domain conversion
    ├─ Create ServerCallContext
    ├─ Route to GrpcHandler (transport layer)
    └─ Domain → Protobuf conversion
        ↓
GrpcHandler (transport/grpc)
    ↓
RequestHandler (server-common)
    ↓
AgentExecutor (your implementation)

Core Components

gRPC Methods

Unary RPC (blocking):

  • SendMessage - Send message and wait for completion
  • GetTask - Get task by ID
  • ListTasks - List tasks with filtering
  • CancelTask - Cancel task execution
  • CreateTaskPushNotificationConfig - Configure push notifications
  • GetTaskPushNotificationConfig - Get push notification config
  • ListTaskPushNotificationConfigs - List push notification configs
  • DeleteTaskPushNotificationConfig - Delete push notification config
  • GetExtendedAgentCard - Get extended agent card

Server Streaming RPC:

  • SendStreamingMessage - Send message with streaming response
  • SubscribeToTask - Subscribe to task events

CDI Integration

Required CDI Beans:

Optional CDI Beans:

Usage

Add Dependency: 

<dependency>
  <groupId>org.a2aproject.sdk</groupId>
  <artifactId>a2a-java-sdk-reference-grpc</artifactId>
  <version>${a2a.version}</version>
</dependency>

Provide Agent Card: 

@ApplicationScoped
public class MyAgentCardProducer {
    @Produces @PublicAgentCard
    public AgentCard agentCard() {
        return new AgentCard.Builder()
            .name("My gRPC Agent")
            .description("Agent description")
            .url("http://localhost:9090")
            .capabilities(new AgentCapabilities.Builder()
                .streaming(true)
                .build())
            .build();
    }
}

Provide Agent Executor: 

@ApplicationScoped
public class MyAgentExecutorProducer {
    @Produces
    public AgentExecutor agentExecutor() {
        return new MyAgentExecutor();
    }
}

Configuration

gRPC Server: 

quarkus.grpc.server.port=9090
quarkus.grpc.server.host=0.0.0.0

Authentication: 

quarkus.security.users.embedded.enabled=true
quarkus.security.users.embedded.plain-text=true
quarkus.security.users.embedded.users.alice=password

Customization

Custom Context Creation:

Provide a CDI bean implementing CallContextFactory: 

@ApplicationScoped
public class CustomCallContextFactory implements CallContextFactory {
    @Override
    public <V> ServerCallContext create(StreamObserver<V> responseObserver) {
        // Extract custom data from gRPC context
        Context grpcContext = Context.current();
        Metadata metadata = GrpcContextKeys.METADATA_KEY.get(grpcContext);
        String orgId = metadata.get(
            Metadata.Key.of("x-organization-id", Metadata.ASCII_STRING_MARSHALLER)
        );

        Map<String, Object> state = new HashMap<>();
        state.put("organization", orgId);
        state.put("grpc_response_observer", responseObserver);

        return new ServerCallContext(
            extractUser(),
            state,
            extractExtensions(grpcContext),
            extractVersion(grpcContext)
        );
    }
}

Python Equivalence

This implementation provides equivalent functionality to Python's grpc.aio server:

See Also: