It is assumed that you are familiar with the gRPC concepts found here: https://grpc.io/docs/guides/concepts.html
This page describes various concepts referred to within the gRPC-Web documentation.
A method definition includes the service and method names, request and response types and whether the method is client-streaming and/or server-streaming.
Definitions of the format used by @improbable-eng/grpc-web can be generated using the ts-protoc-gen plugin for protoc. See code generation for instructions.
export namespace BookService {
export class GetBook {
static readonly methodName = "GetBook";
static readonly service = BookService;
static readonly requestStream = false;
static readonly responseStream = false;
static readonly requestType = GetBookRequest;
static readonly responseType = Book;
}
}Metadata is a collection of key-value pairs sent by the client to the server and then from the server to the client both before the response (headers) and after the response (trailers). One use case for metadata is for sending authentication tokens from a client.
@improbable-eng/grpc-web uses the js-browser-headers library to provide a consistent implementation of the Headers class across browsers. The BrowserHeaders class from this library is aliased to grpc.Metadata.
Upon completion a gRPC request will expose a status code indicating how the request ended. This status code can be provided by the server in the Metadata, but if the request failed or the server did not include a status code then the status code is determined by the client.
0 - OK indicates that the request was completed successfully.
0 OK
1 Canceled
2 Unknown
3 InvalidArgument
4 DeadlineExceeded
5 NotFound
6 AlreadyExists
7 PermissionDenied
8 ResourceExhausted
9 FailedPrecondition
10 Aborted
11 OutOfRange
12 Unimplemented
13 Internal
14 Unavailable
15 DataLoss
16 UnauthenticatedAlongside a status code, requests can include a message upon completion. This can be provided by the server in the Metadata, but if the request failed or the server did not include a status message then the status message is determined by the client and is intended to aid debugging.