Spring Boot + gRPC Error Handling Example

In this tutorial we will be looking at gRPC Error Handling Hello World Example. In the next tutorial we will be further modifying this example to implement Error Handling using gRPC Trailer Metadata. Also in another tutorial we will be implementing Global Exception Handler Using GrpcAdvice.
Error handling in gRPC client and server involves managing and reacting to errors that may occur during communication between the client and server. In gRPC, there are different types of errors that can occur, such as network errors, server errors, security errors, and protocol errors.
In gRPC, error handling is typically implemented using gRPC status codes and status messages. When an error occurs, the server will send an appropriate status code and message to the client, which can then handle the error accordingly.
In the client, error handling can involve checking the status code of the response and taking appropriate action, such as retrying the request, logging the error, or displaying an error message to the user.
gRPC provides users with well defined status codes as part of the RPC API that can be made use of during error handling.

Code	Number
OK	0
CANCELLED	1
UNKNOWN	2
INVALID_ARGUMENT	3
DEADLINE_EXCEEDED	4
NOT_FOUND	5
ALREADY_EXISTS	6
PERMISSION_DENIED	7
RESOURCE_EXHAUSTED	8
FAILED_PRECONDITION	9
ABORTED	10
OUT_OF_RANGE	11
UNIMPLEMENTED	12
INTERNAL	13
UNAVAILABLE	14
DATA_LOSS	15
UNAUTHENTICATED	16

gRPC - Table of Contents
Spring Boot+ gRPC Hello World Example
Spring Boot gRPC Server + C# gRPC Client Example
Spring Boot 3 + gRPC - Types of gRPC
Spring Boot 3 + gRPC Unary Example
Spring Boot 3 + gRPC Server Streaming Example
Spring Boot 3 + gRPC Client Streaming Example
Spring Boot 3 + gRPC Bidirectional Streaming Example
Spring Boot + gRPC Deadline Example
Spring Boot + gRPC Error Handling Example
Spring Boot + gRPC Error Handling - Using Trailer Metadata
Spring Boot + gRPC Error Handling - Global Exception Handler Using GrpcAdvice

Implementation

We will be modifying the code we implemented in a previous tutorial - Spring Boot 3 + gRPC Unary Example. We will be implementing error handling code to return the gRPC status code and the description from the gRPC server to the client.


To the BankAccountBalanceService we will be adding a conditional statement that checks if the account number retrieved from a request is equal to "account5". If the condition is true, it means that the requested account number cannot be found. In this case, the code generates an error response with the status "NOT_FOUND" and a description stating that the requested account number cannot be found. The error response is then returned to the caller, effectively informing them that the requested account number does not exist.

package com.javainuse.bank.service;

import com.javainuse.banking.AccountBalanceResponse;
import com.javainuse.banking.AccountBalanceServiceGrpc;
import com.javainuse.banking.AccountRequest;

import io.grpc.Status;
import io.grpc.stub.StreamObserver;
import net.devh.boot.grpc.server.service.GrpcService;

@GrpcService
public class BankAccountBalanceService extends AccountBalanceServiceGrpc.AccountBalanceServiceImplBase {

	@Override
	public void getAccountBalance(AccountRequest request,
			StreamObserver<com.javainuse.banking.AccountBalanceResponse> responseObserver) {

		if ((request.getAccountNumber().equals("account5"))) {
			responseObserver.onError((Status.NOT_FOUND.withDescription("The requested Account Number cannot be found."))
					.asRuntimeException());
			return;
		}
		AccountBalanceResponse empResp = AccountBalanceResponse.newBuilder()
				.setAccountNumber(request.getAccountNumber()).setBalance(100).build();

		// set the response object
		responseObserver.onNext(empResp);

		// mark process is completed
		responseObserver.onCompleted();
	}
}

Start the gRPC server.

Now run the gRPC client by passing the account number as "account5". We get the following exception at the client end.

So this needs to be properly handled at the gRPC client side by writing the gRPC server call inside the try catch block.

package com.javainuse.bank.service;

import org.springframework.stereotype.Service;

import com.javainuse.banking.AccountBalanceResponse;
import com.javainuse.banking.AccountBalanceServiceGrpc;
import com.javainuse.banking.AccountRequest;

import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.StatusRuntimeException;

@Service
public class BankService {

	public void getAccountBalance() {

		ManagedChannel channel = ManagedChannelBuilder.forAddress("localhost", 8090).usePlaintext().build();

		AccountBalanceServiceGrpc.AccountBalanceServiceBlockingStub stub = AccountBalanceServiceGrpc
				.newBlockingStub(channel);

		try {
			AccountBalanceResponse bookResponse = stub
					.getAccountBalance(AccountRequest.newBuilder().setAccountNumber("account5").build());

			System.out.println(bookResponse);
		} catch (StatusRuntimeException ex) {
			Status status = ex.getStatus();
			System.out.println("error code -" + status.getCode());
			System.out.println("error description -" + status.getDescription());
		}

		channel.shutdown();

	}
}

If we now run the client again we can see that the client has gracefully handled the exception.

Download Source Code

Download it - Spring Boot + gRPC Error Handling Client Example
Download it - Spring Boot + gRPC Error Handling Server Example