Handling OPTIONS request using gRPC backend

[Vito Tumas]

Good afternoon,


What is the correct way to handle OPTIONS requests, when running a gRPC endpoints?

From the latest release notes https://cloud.google.com/endpoints/docs/release-notes I saw that for ESP to accept these requests, allow_cors must be present in the api_configuration.

My configuration setup looks as follows:

type: google.api.Service
config_version: 3
name: app.endpoints.my-project.cloud.goog

endpoints:
  - name: app.endpoints.my-project.cloud.goog
    allow_cors: true

title: Users
apis:
- name: endpoints.users.User

usage:
  rules:
  - selector: endpoints.users.User.Login
    allow_unregistered_calls: true

And the http mapping is written in the proto file as follows:

syntax = "proto3";
package endpoints.users;

option go_package = "proto";
import "google/api/annotations.proto";

service User {
    rpc Login (LoginRequest) returns (AuthResponse) {
        option (google.api.http).post = "/api/v2/users/login";
    }
}

message LoginRequest {
    string email = 1;
    string password = 2;
}

message AuthResponse {
    string token = 1;
}

However when making a OPTIONS request, I get a 404 response.

This makes sense, as I have not defined an option for this request method, but when I add option (google.api.http).option = "/api/v2/users/login"; to the rpc, during the go code generation I get an error that Option "(google.api.http).options" unknown.
I tried adding it using the custom option, however this did not yield any results either.

Currently, to support CORS I'm intercepting the OPTIONS request in the ESP configuration, but this feels a a very hacky way to do things.

Any pointers to solve this problem will be highly appreciated.



Vito


[Raphael Simon]

I think you have to use a custom verb in your proto file to support OPTIONS requests.

See https://github.com/googleapis/googleapis/blob/master/google/api/http.proto (search for custom).

--

Raphael.

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[qiwz...@google.com]

Sorry, CORS is not supported in Endpoints for gRPC backend yet. 

[qiwz...@google.com]

There is a work around for now. 

If the backend server doesn’t support CORS, for example, your backend server is a gRPC server and you are using ESP for gRPC transcoding from HTTP/JSON to gRPC, you may have to use this work around. 

you have to create a custom Nginx config file with CORS supports. Here is a Nginx config example.

Here is instruction on how to use custom Nginx config for GKE.

Nginx config for ESP should contain ESP specific config, otherwise ESP will not work.  One way is to get the ESP Nginx config ESP, modify it to add CORS options.  ESP Nginx config is generated after ESP deployment.   You can ssh into ESP container and get the nginx config from “/etc/nginx/endpoints/” folder.  Here is the instruction on how to SSH into GKE container for ESP. 

Hope it helps.  Thanks.

-Wayne

[fabr...@passiolife.com]

Sorry to review this old thread but I just stumbled on this issue.

Has there been any change on CORS for gRPC backends from January? Is the custom nginx config file still the only viable way?

on another note is the ESP code opensource?

[Wayne Zhang]

Sorry, there is no change in this aspect.  But we are working on it.  not ETA yet.   ESP is not open sourced 

[Jan Paral]

Hi, is there any update on this?

allow_cors: true still does not work with gRPC backend.

thx, J

[Wayne Zhang]

sorry,  we did not add any new feature for CORS.    -Wayne

[sh...@node.mu]

On Wednesday, 23 August 2017 04:39:32 UTC+8, Wayne Zhang wrote:

sorry,  we did not add any new feature for CORS.    -Wayne

Are there any plans to support CORS for gRPC backends? An ETA would be helpful. 

[Wayne Zhang]

Sorry, so far there is no change in the ways of supporting CORS for gRPC.  Using the custom Nginx config is the only way.  

Thanks

-Wayne

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[sh...@node.mu]

If you have a HAProxy sitting in front, you can use the following configuration: https://gist.github.com/vyshane/ae38a21e3d81b97da0b90606d099346a