Error

Error handling is an important aspect of ensuring the smooth operation of services. gRPCity provides convenient error handling mechanisms. In general, it is recommended to use try/catch for error catching and throw to expose errors.

Client-Side Error Handling

When a client calls a server, if the server encounters an error, it will return an ERROR object with the following four fields:

name: The value is GrpcClientError, which can be used to determine if it is a client-side RPC error.
code: gRPC Status Code.
message: The error message emitted by the gRPC server.
stack: The error trace stack from the server.

The expanded ERROR object looks like this:

{
    "name": "GrpcClientError",
    "code": 2,
    "message": "/test.helloworld.Greeter/SayHello (2 UNKNOWN: Error: throw error because x-throw-error [Error Message From Server, stack: at Greeter.SayHello (/Users/lau/Documents/GitHub/grpcity/test/server.js:27:13)])",
    "stack": "
        at start (/Users/lau/Documents/GitHub/grpcity/test/client.js:36:72)
        ...
        at callErrorFromStatus (/Users/lau/Documents/GitHub/grpcity/node_modules/@grpc/grpc-js/build/src/call.js:31:19)
        at Object.onReceiveStatus (/Users/lau/Documents/GitHub/grpcity/node_modules/@grpc/grpc-js/build/src/client.js:192:76)
    "
}

Server-Side Error Triggering

The following example shows how the server can proactively trigger an error when the client sends x-throw-error metadata, and the sayHello() method on the server checks for this metadata:

async sayHello(call) {
    const metadata = call.metadata.clone()
    metadata.add('x-timestamp-server', 'received=' + new Date().toISOString())
    call.sendMetadata(metadata)
 
    if (metadata.get('x-throw-error').length > 0) {
        throw new Error('throw error because x-throw-error')
    }
 
    return { message: `hello, ${call.request.name || 'world'}` }
}

When the server proactively triggers an error, the error is caught by the client and reported as shown in the client-side error handling example above.

Status Advanced