is a remote procedure call (RPC) framework initially developed by Google circa 2015 that has seen growing adoption in recent years. Based on HTTP/2 for transport and Protobuf as Interface Definition Language (IDL), gRPC has several capabilities that traditional REST APIs struggle with, such as bi-directional streaming and efficient binary encoding. gRPC Native gRPC Support What follows is a step-by-step tutorial on how to set up Kong to proxy gRPC services, demonstrating two possible scenarios. In the first scenario, a single Route entry in Kong matches all gRPC methods from a service. In the second one, I have per-method Routes, which allows me to apply different plugins to specific gRPC methods. Before starting, install Kong Gateway , if you haven’t already. As gRPC uses HTTP/2 for transport, it is necessary to enable HTTP/2 proxy listeners in Kong. To do so, add the following property in your Kong configuration: proxy_listen = : http2, : http2 ssl 0.0 .0 .0 9080 0.0 .0 .0 9081 Alternatively, you can also configure the proxy listener with environment variables: KONG_PROXY_LISTEN= bin/kong restart "0.0.0.0:9080 http2, 0.0.0.0:9081 http2 ssl" In this guide, I'll assume Kong is listening for HTTP/2 proxy requests on port 9080 and secure HTTP/2 on port 9081. I'll use the command-line client and the collection of mock gRPC services. gRPCurl grpcbin Case 1: Single Service and Route I'll begin with a simple setup with a single gRPC Service and Route; all gRPC requests sent to Kong’s proxy port will match the same route. Issue the following request to create a gRPC Service (assuming your gRPC server is listening in localhost, port 15002): $ curl -XPOST localhost: /services \
  --data name=grpc \
  --data protocol=grpc \
  --data host=localhost \
  --data port= 8001 15002 Issue the following request to create a gRPC Route: $ curl -XPOST localhost: /services/grpc/routes \
  --data protocols=grpc \
  --data name= -all \
  --data paths= 8001 catch / Using gRPCurl, issue the following gRPC request: $ grpcurl -v -d -plaintext localhost: hello.HelloService.SayHello '{"greeting": "Kong 1.3!"}' 9080 The response should resemble the following: Resolved method descriptor:
rpc SayHello ( .hello.HelloRequest ) returns ( .hello.HelloResponse );
Request metadata to send:
(empty)
Response headers received:
content-type: application/grpc
date: Tue, Jul : : GMT
server: openresty/ via: kong/ x-kong-proxy-latency: x-kong-upstream-latency: Response contents:
{ : }
Response trailers received:
(empty)
Sent request and received response 16 2019 21 37 36 1.15 .8 .1 1.2 .1 0 0 "reply" "hello Kong 1.3!" 1 1 Notice that Kong response headers, such as and , were inserted in the response. via x-kong-proxy-latency Case 2: Single Service, Multiple Routes Now I'll move on to a more complex use-case, where requests to separate gRPC methods map to different Routes in Kong, allowing for more flexible use of Kong plugins. Building on top of the previous example, let’s create a few more routes for individual gRPC methods. The gRPC “HelloService” service being used in this example exposes a few different methods, as you can see in its Protobuf definition (obtained from the gRPCbin ): repository syntax = ; hello; { ; ; ; ;
} { greeting = ;
} { reply = ;
} "proto2" package service HelloService SayHello(HelloRequest) (HelloResponse) rpc returns LotsOfReplies(HelloRequest) (stream HelloResponse) rpc returns LotsOfGreetings(stream HelloRequest) (HelloResponse) rpc returns BidiHello(stream HelloRequest) (stream HelloResponse) rpc returns message HelloRequest optional string 1 message HelloResponse required string 1 I'll create individual routes for its “SayHello” and “LotsOfReplies” methods. Create a Route for “SayHello”: $ curl -XPOST localhost: /services/grpc/routes \
  --data protocols=grpc \
  --data paths= SayHello \
  --data name=say-hello 8001 /hello.HelloService/ Create a Route for “LotsOfReplies”: $ curl -XPOST localhost: /services/grpc/routes \
  --data protocols=grpc \
  --data paths= LotsOfReplies \
  --data name=lots- -replies 8001 /hello.HelloService/ of With this setup, gRPC requests to the “SayHello” method will match the first Route, while requests to “LotsOfReplies” will be routed to the latter. Issue a gRPC request to the “SayHello” method: $ grpcurl -v -d \
  -H -plaintext \
  localhost: hello.HelloService.SayHello '{"greeting": "Kong 1.3!"}' 'kong-debug: 1' 9080 (Notice I'm are sending a header , which causes Kong to insert debugging information as response headers.) kong-debug The response should look like this: Resolved method descriptor:
rpc SayHello ( .hello.HelloRequest ) returns ( .hello.HelloResponse );
Request metadata to send:
kong-debug: Response headers received:
content-type: application/grpc
date: Tue, Jul : : GMT
kong-route-id: ef3d1-d092 ca b4e42453d97
kong-service-id: d82736b7-a4fd -b575-c68d94c3493a
kong-service-name: s1
server: openresty/ via: kong/ x-kong-proxy-latency: x-kong-upstream-latency: Response contents:
{ : }
Response trailers received:
(empty)
Sent request and received response 1 16 2019 21 57 00 390 -4401 -99 -0 -4530 1.15 .8 .1 1.2 .1 0 0 "reply" "hello Kong 1.3!" 1 1 Notice the Route ID refers to the first route I created. Similarly, let’s issue a request to the “LotsOfReplies” gRPC method: $ grpcurl -v -d \
  -H -plaintext \
  localhost: hello.HelloService.LotsOfReplies '{"greeting": "Kong 1.3!"}' 'kong-debug: 1' 9080 The response should look like the following: Resolved method descriptor:
rpc LotsOfReplies ( .hello.HelloRequest ) returns ( stream .hello.HelloResponse );
Request metadata to send:
kong-debug: Response headers received:
content-type: application/grpc
date: Tue, Jul : : GMT
kong-route-id: bb ac5-b177-bc04b3974c87
kong-service-id: a87674-f984 f75 abc da478e204f
kong-service-name: grpc
server: openresty/ via: kong/ x-kong-proxy-latency: x-kong-upstream-latency: Response contents:
{ : }
Response contents:
{ : }
Response contents:
{ : }
Response contents:
{ : }
Response contents:
{ : }
Response contents:
{ : }
Response contents:
{ : }
Response contents:
{ : }
Response contents:
{ : }
Response contents:
{ : }
Response trailers received:
(empty)
Sent request and received responses 1 30 2019 22 21 40 133659 -7e88 -4 31 -4 -8 -85 1.15 .8 .1 1.2 .1 14 0 "reply" "hello Kong 1.3!" "reply" "hello Kong 1.3!" "reply" "hello Kong 1.3!" "reply" "hello Kong 1.3!" "reply" "hello Kong 1.3!" "reply" "hello Kong 1.3!" "reply" "hello Kong 1.3!" "reply" "hello Kong 1.3!" "reply" "hello Kong 1.3!" "reply" "hello Kong 1.3!" 1 10 Notice that the response header now carries a different value and refers to the second Route created on this page. kong-route-id Note: gRPC will still be routed to the first route I created (the “catch-all” route) since the request matches neither nor routes. reflection requests SayHello LotsOfReplies Logging and Observability Plugins As I mentioned earlier, Kong 1.3 gRPC support is compatible with logging and observability plugins. For example, let’s try out the and plugins with gRPC. File Log Zipkin File Log Issue the following request to enable File Log on the “SayHello” route: $ curl -X POST localhost: /routes/say-hello/plugins \
  --data name=file-log \
  --data config.path=grpc-say-hello.log 8001 Follow the output of the log as gRPC requests are made to “SayHello”: $ tail -f grpc-say-hello.log
{ :{ : , : , : }, :{ : , : , : , : , : , : , : , : , : , : , : }, :{ :{}, : , : , : , :{ : , : , : , : , : }, : }, : , :[{ : , : , : , : }], :{ :{ : , : , : , : , : , : , : , : , : }, : , : }, :{ : , : , :[ ], : , :{ : }, : , : , : , : , :[ ], : }, : }
{ :{ : , : , : }, :{ : , : , : , : , : , : , : , : , : , : , : }, :{ :{}, : , : , : , :{ : , : , : , : , : }, : }, : , :[{ : , : , : , : }], :{ :{ : , : , : , : , : , : , : , : , : }, : , : }, :{ : , : , :[ ], : , :{ : }, : , : , : , : , :[ ], : }, : } "latencies" "request" 8 "kong" 5 "proxy" 3 "service" "host" "localhost" "created_at" 1564527408 "connect_timeout" 60000 "id" "74a95d95-fbe4-4ddb-a448-b8faf07ece4c" "protocol" "grpc" "name" "grpc" "read_timeout" 60000 "port" 15002 "updated_at" 1564527408 "write_timeout" 60000 "retries" 5 "request" "querystring" "size" "46" "uri" "/hello.HelloService/SayHello" "url" "http://localhost:9080/hello.HelloService/SayHello" "headers" "host" "localhost:9080" "content-type" "application/grpc" "kong-debug" "1" "user-agent" "grpc-go/1.20.0-dev" "te" "trailers" "method" "POST" "client_ip" "127.0.0.1" "tries" "balancer_latency" 0 "port" 15002 "balancer_start" 1564527732522 "ip" "127.0.0.1" "response" "headers" "kong-route-id" "e49f2df9-3e8e-4bdb-8ce6-2c505eac4ab6" "content-type" "application/grpc" "connection" "close" "kong-service-name" "grpc" "kong-service-id" "74a95d95-fbe4-4ddb-a448-b8faf07ece4c" "kong-route-name" "say-hello" "via" "kong/1.2.1" "x-kong-proxy-latency" "5" "x-kong-upstream-latency" "3" "status" 200 "size" "298" "route" "id" "e49f2df9-3e8e-4bdb-8ce6-2c505eac4ab6" "updated_at" 1564527431 "protocols" "grpc" "created_at" 1564527431 "service" "id" "74a95d95-fbe4-4ddb-a448-b8faf07ece4c" "name" "say-hello" "preserve_host" false "regex_priority" 0 "strip_path" false "paths" "/hello.HelloService/SayHello" "https_redirect_status_code" 426 "started_at" 1564527732516 "latencies" "request" 3 "kong" 1 "proxy" 1 "service" "host" "localhost" "created_at" 1564527408 "connect_timeout" 60000 "id" "74a95d95-fbe4-4ddb-a448-b8faf07ece4c" "protocol" "grpc" "name" "grpc" "read_timeout" 60000 "port" 15002 "updated_at" 1564527408 "write_timeout" 60000 "retries" 5 "request" "querystring" "size" "46" "uri" "/hello.HelloService/SayHello" "url" "http://localhost:9080/hello.HelloService/SayHello" "headers" "host" "localhost:9080" "content-type" "application/grpc" "kong-debug" "1" "user-agent" "grpc-go/1.20.0-dev" "te" "trailers" "method" "POST" "client_ip" "127.0.0.1" "tries" "balancer_latency" 0 "port" 15002 "balancer_start" 1564527733555 "ip" "127.0.0.1" "response" "headers" "kong-route-id" "e49f2df9-3e8e-4bdb-8ce6-2c505eac4ab6" "content-type" "application/grpc" "connection" "close" "kong-service-name" "grpc" "kong-service-id" "74a95d95-fbe4-4ddb-a448-b8faf07ece4c" "kong-route-name" "say-hello" "via" "kong/1.2.1" "x-kong-proxy-latency" "1" "x-kong-upstream-latency" "1" "status" 200 "size" "298" "route" "id" "e49f2df9-3e8e-4bdb-8ce6-2c505eac4ab6" "updated_at" 1564527431 "protocols" "grpc" "created_at" 1564527431 "service" "id" "74a95d95-fbe4-4ddb-a448-b8faf07ece4c" "name" "say-hello" "preserve_host" false "regex_priority" 0 "strip_path" false "paths" "/hello.HelloService/SayHello" "https_redirect_status_code" 426 "started_at" 1564527733554 Notice the gRPC requests were logged, with info such as the URI, HTTP verb, and latencies. Zipkin Start a Zipkin server: $ docker run -d --name zipkin -p 9411:9411 openzipkin/zipkin Enable the Zipkin plugin on the grpc Service: curl -X POST localhost:8001/services/grpc/plugins \
    --data name=zipkin \
    --data config.http_endpoint=http://127.0.0.1:9411/api/v2/spans \
    --data config.sample_ratio=1 As requests are proxied, new spans will be sent to the Zipkin server and can be visualized through the Zipkin Index page, which is, by default, http://localhost:9411/zipkin: To display Traces, click “Find Traces”, as shown above. The following screen will list all traces matching the search criteria: A trace can be expanded by clicking on it: Spans can also be extended, as displayed below: Notice that, in this case, it’s a span for a gRPC reflection request. Previously published at https://konghq.com/blog/manage-grpc-services-kong/

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