Crate 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.

Getting Started

[dependencies]
tonic = <tonic-version>
tonic-types = <tonic-types-version>

Examples

The examples bellow 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.

Re-exports

• pub use pb::Status;

Modules

• pb
  Useful protobuf types

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

• RpcStatusExt
  Used to implement associated functions and methods on pb::Status, that allow the extraction of standard error details. This trait is sealed and not meant to be implemented outside of tonic-types.
• StatusExt
  Used to implement associated functions and methods on tonic::Status, that allow the addition and extraction of standard error details. This trait is sealed and not meant to be implemented outside of tonic-types.