Envoy: REST gateway + multiple GRPC clusters - http

Question

I'm trying to config envoy as rest api gateway with multiple grpc servers and have a problem with routing. The only way to match endpoint to grpc cluster, that i've found is to match via request header (http request /first must be resolved by first cluster, /second - by second):
...
routes:
- match:
prefix: "/"
headers:
- name: x-service
exact_match: "first"
route:
cluster: first
- match:
prefix: "/"
headers:
- name: x-service
exact_match: "second"
route:
cluster: second
...
But, in this case i need to set custom header 'x-service' at the client (frontend). This looks like a bad idea, 'couse frontend shouldn't know anything about backend infrastructure.
Is there any other way to match http route with grpc service? Or, can i set such headers somewhere in envoy?

Answer 1

The Envoy configuration pasted below registers a HTTP listener on port 51051 that proxies to helloworld.Greeter service in the cluster grpc1 on port 50051 and bookstore.Bookstore service in the cluster grpc2 on port 50052 by using the gRPC route as the match prefix.
This ensures clean segregation of responsibilities and isolation since the client will not need to inject custom HTTP headers to make multi-gRPC cluster routing work.
admin:
access_log_path: /tmp/admin_access.log
address:
socket_address: { address: 0.0.0.0, port_value: 9901 }
static_resources:
listeners:
- name: listener1
address:
socket_address: { address: 0.0.0.0, port_value: 51051 }
filter_chains:
- filters:
- name: envoy.filters.network.http_connection_manager
typed_config:
"#type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
access_log:
- name: envoy.access_loggers.file
typed_config:
"#type": type.googleapis.com/envoy.extensions.access_loggers.file.v3.FileAccessLog
path: /dev/stdout
stat_prefix: grpc_json
codec_type: AUTO
route_config:
name: local_route
virtual_hosts:
- name: local_service
domains: ["*"]
routes:
# NOTE: by default, matching happens based on the gRPC route, and not on the incoming request path.
# Reference: https://www.envoyproxy.io/docs/envoy/latest/configuration/http_filters/grpc_json_transcoder_filter#route-configs-for-transcoded-requests
- match: { prefix: "/helloworld.Greeter" }
route: { cluster: grpc1, timeout: 60s }
- match: { prefix: "/bookstore.Bookstore" }
route: { cluster: grpc2, timeout: 60s }
clusters:
- name: grpc1
connect_timeout: 1.25s
type: LOGICAL_DNS
lb_policy: ROUND_ROBIN
dns_lookup_family: V4_ONLY
typed_extension_protocol_options:
envoy.extensions.upstreams.http.v3.HttpProtocolOptions:
"#type": type.googleapis.com/envoy.extensions.upstreams.http.v3.HttpProtocolOptions
explicit_http_config:
http2_protocol_options: {}
load_assignment:
cluster_name: grpc1
endpoints:
- lb_endpoints:
- endpoint:
address:
socket_address:
address: 127.0.0.1
port_value: 50051
- name: grpc2
connect_timeout: 1.25s
type: LOGICAL_DNS
lb_policy: ROUND_ROBIN
dns_lookup_family: V4_ONLY
typed_extension_protocol_options:
envoy.extensions.upstreams.http.v3.HttpProtocolOptions:
"#type": type.googleapis.com/envoy.extensions.upstreams.http.v3.HttpProtocolOptions
explicit_http_config:
http2_protocol_options: {}
load_assignment:
cluster_name: grpc2
endpoints:
- lb_endpoints:
- endpoint:
address:
socket_address:
address: 127.0.0.1
port_value: 50052
https://github.com/envoyproxy/envoy/blob/main/test/proto/helloworld.proto
syntax = "proto3";
package helloworld;
import "google/api/annotations.proto";
// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello(HelloRequest) returns (HelloReply) {
option (google.api.http) = {
get: "/say"
};
}
}
https://github.com/envoyproxy/envoy/blob/main/test/proto/bookstore.proto
syntax = "proto3";
package bookstore;
import "google/api/annotations.proto";
import "google/api/httpbody.proto";
import "google/protobuf/empty.proto";
import "google/protobuf/struct.proto";
// A simple Bookstore API.
//
// The API manages shelves and books resources. Shelves contain books.
service Bookstore {
// Returns a list of all shelves in the bookstore.
rpc ListShelves(google.protobuf.Empty) returns (ListShelvesResponse) {
option (google.api.http) = {
get: "/shelves"
};
}
...