Crate tonic_richer_error

Expand description

Assets for implementation of the gRPC Richer Error Model with tonic.

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

§Usage

The WithErrorDetails trait adds associated functions to tonic::Status that can be used on the server side to create a status with error details, that can then be returned to the gRPC client. 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.

§Getting Started

To build this crate you must have the Protocol Buffer Compiler, protoc, installed. Instructions can be found here.

[dependencies]
tonic = "0.8"
tonic-richer-error = "0.3"

§Examples

The examples bellow cover a basic use case. More complete server and client implementations can be found at the github examples directory.

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

use tonic::{Code, Status};
use tonic_richer_error::{ErrorDetails, WithErrorDetails};

// ...
// 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_richer_error::{WithErrorDetails};

// ...

// 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
            }
        }
    };
}

§Send different standard error messages

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 WithErrorDetails 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 WithErrorDetails::with_error_details_vec and WithErrorDetails::get_error_details_vec docs, and also the github examples directory.\

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

Modules§

pb: Compiled google.rpc protos

Structs§

BadRequest: Used to encode/decode the BadRequest standard error message described in error_details.proto. Describes violations in a client request. Focuses on the syntactic aspects of the request.
DebugInfo: Used to encode/decode the DebugInfo standard error message described in error_details.proto. Describes additional debugging info.
ErrorDetails: Groups the standard error messages structs. Provides associated functions and methods to setup and edit each error message independently. Used when extracting error details from tonic::Status, and when creating a tonic::Status with error details.
ErrorInfo: Used to encode/decode the ErrorInfo standard error message described in error_details.proto. Describes the cause of the error with structured details.
FieldViolation: Used at the field_violations field of the BadRequest struct. Describes a single bad request field.
Help: Used to encode/decode the Help standard error message described in error_details.proto. Provides links to documentation or for performing an out-of-band action.
HelpLink: Used at the links field of the Help struct. Describes a URL link.
LocalizedMessage: Used to encode/decode the LocalizedMessage standard error message described in error_details.proto. Provides a localized error message that is safe to return to the user.
PreconditionFailure: Used to encode/decode the PreconditionFailure standard error message described in error_details.proto. Describes what preconditions have failed.
PreconditionViolation: Used at the violations field of the PreconditionFailure struct. Describes a single precondition failure.
QuotaFailure: Used to encode/decode the QuotaFailure standard error message described in error_details.proto. Describes how a quota check failed.
QuotaViolation: Used at the violations field of the QuotaFailure struct. Describes a single quota violation.
RequestInfo: Used to encode/decode the RequestInfo standard error message described in error_details.proto. Contains metadata about the request that clients can attach when providing feedback.
ResourceInfo: Used to encode/decode the ResourceInfo standard error message described in error_details.proto. Describes the resource that is being accessed.
RetryInfo: Used to encode/decode the RetryInfo standard error message described in error_details.proto. Describes when the clients can retry a failed request.
Note: When obtained from decoding RetryInfo messages, negative retry_delay’s become 0.

Enums§

ErrorDetail: Wraps the structs corresponding to the standard error messages, allowing the implementation and handling of vectors containing any of them.

Traits§

WithErrorDetails: Used to implement associated functions and methods on tonic::Status, that allow the addition and extraction of standard error details.