tonic-types

A collection of useful protobuf types that can be used with tonic.

This crate also introduces the StatusExt trait and implements it in tonic::Status, allowing the implementation of the gRPC Richer Error Model with tonic in a convenient way.

Usage

Useful protobuf types are available through the pb module. They can be imported and worked with directly.

The StatusExt trait adds associated functions to tonic::Status that can be used on the server side to create a status with error details, which can then be returned to gRPC clients. Moreover, the trait also adds methods to tonic::Status that can be used by a tonic client to extract error details, and handle them with ease.

Examples

The examples below cover a basic use case of the gRPC Richer Error Model. More complete server and client implementations are provided in the Richer Error example, located in the main repo examples directory.

Server Side: Generating tonic::Status with an ErrorDetails struct

use tonic::{Code, Status};
use tonic_types::{ErrorDetails, StatusExt};

// ...
// Inside a gRPC server endpoint that returns `Result<Response<T>, Status>`

// Create empty `ErrorDetails` struct
let mut err_details = ErrorDetails::new();

// Add error details conditionally
if some_condition {
    err_details.add_bad_request_violation(
        "field_a",
        "description of why the field_a is invalid"
    );
}

if other_condition {
    err_details.add_bad_request_violation(
        "field_b",
        "description of why the field_b is invalid",
    );
}

// Check if any error details were set and return error status if so
if err_details.has_bad_request_violations() {
    // Add additional error details if necessary
    err_details
        .add_help_link("description of link", "https://resource.example.local")
        .set_localized_message("en-US", "message for the user");

    let status = Status::with_error_details(
        Code::InvalidArgument,
        "bad request",
        err_details,
    );
    return Err(status);
}

// Handle valid request
// ...

Client Side: Extracting an ErrorDetails struct from tonic::Status

use tonic::{Response, Status};
use tonic_types::StatusExt;

// ...
// Where `req_result` was returned by a gRPC client endpoint method
fn handle_request_result<T>(req_result: Result<Response<T>, Status>) {
    match req_result {
        Ok(response) => {
            // Handle successful response
        },
        Err(status) => {
            let err_details = status.get_error_details();
            if let Some(bad_request) = err_details.bad_request() {
                // Handle bad_request details
            }
            if let Some(help) = err_details.help() {
                // Handle help details
            }
            if let Some(localized_message) = err_details.localized_message() {
                // Handle localized_message details
            }
        }
    };
}

Working with different error message types

Multiple examples are provided at the ErrorDetails doc. Instructions about how to use the fields of the standard error message types correctly are provided at error_details.proto.

Alternative tonic::Status associated functions and methods

In the StatusExt doc, an alternative way of interacting with tonic::Status is presented, using vectors of error details structs wrapped with the ErrorDetail enum. This approach can provide more control over the vector of standard error messages that will be generated or that was received, if necessary. To see how to adopt this approach, please check the StatusExt::with_error_details_vec and StatusExt::get_error_details_vec docs, and also the main repo's Richer Error example directory.

Besides that, multiple examples with alternative error details extraction methods are provided in the StatusExt doc, which can be specially useful if only one type of standard error message is being handled by the client. For example, using StatusExt::get_details_bad_request is a more direct way of extracting a BadRequest error message from tonic::Status.