# gRPC and gRPC-Web

> A gRPC service behind Flexway reads three ways: native gRPC, gRPC-Web from a browser, and REST/JSON at its annotations' routes. It is one operation per…

Guide - Since version 1.1.0 - Flexway v1.6.3 - https://flexway.io/en/docs/developer-grpc/

> A gRPC service behind Flexway reads three ways: native gRPC, gRPC-Web from a browser, and REST/JSON at its annotations' routes. It is **one** operation per method.
>
> Product side: [gRPC](https://flexway.io/en/docs/product-grpc/); operations side: [A gRPC upstream](https://flexway.io/en/docs/operations-grpc/).

## gRPC

The gateway's traffic port serves gRPC (HTTP/2, in clear inside a mesh or over TLS). Metadata carries
the identity:

```bash
grpcurl -protoset orders.binpb -H "authorization: Bearer $TOKEN" \
  -d '{"id":"42"}' api.example.com:443 shop.v1.Orders/GetOrder
```

```go
conn, _ := grpc.NewClient("api.example.com:443", grpc.WithTransportCredentials(credentials.NewTLS(nil)))
ctx := metadata.AppendToOutgoingContext(ctx, "authorization", "Bearer "+token)
order, err := shopv1.NewOrdersClient(conn).GetOrder(ctx, &shopv1.GetOrderRequest{Id: "42"})
```

## REST on the same method

```bash
curl -H "Authorization: Bearer $TOKEN" https://api.example.com/v1/shop/orders/42
```

A server stream arrives as `text/event-stream`. Client and bidirectional streams are served in gRPC
only.

## gRPC-Web from a browser

Use a standard gRPC-Web client (`grpc-web`, Connect in gRPC-Web mode). The operator must allow your
origin and expose `grpc-status`, `grpc-message` and `grpc-status-details-bin`: without them, the
browser cannot read a refusal.

## Errors

| You call over | You get |
| --- | --- |
| gRPC, gRPC-Web | `google.rpc.Status`; the problem code in `ErrorInfo.reason` |
| REST | RFC 9457; an error of the gRPC upstream becomes `upstream_status`, its gRPC status in the `grpc` extension |

| Gateway code | gRPC status |
| --- | --- |
| `unauthenticated` | `UNAUTHENTICATED` |
| `forbidden` | `PERMISSION_DENIED` |
| `invalid_request`, `malformed_request` | `INVALID_ARGUMENT` |
| `rate_limited`, `quota_exceeded` | `RESOURCE_EXHAUSTED` |
| `upstream_unavailable`, `overloaded` | `UNAVAILABLE` |
| `upstream_timeout` | `DEADLINE_EXCEEDED` |