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Configuring a gRPC Service
Note: This guide assumes familiarity with gRPC. For learning how to set up Kong with an upstream REST API, check out the Configuring a service guide.
gRPC proxying is natively supported in Kong. In this guide, you’ll learn how
to configure Kong to manage your gRPC services. For the
purpose of this guide, we’ll use grpcurl
and grpcbin
- they
provide a gRPC client and gRPC services, respectively.
The guide sets up two examples:
- A single gRPC service and route, with a single catch-all route that proxies all matching gRPC traffic to an upstream gRPC service.
- A single gRPC service with multiple routes, demonstrating how to use a route per gRPC method.
In Kong, gRPC support assumes gRPC over HTTP/2 framing. Make sure you have at least one HTTP/2 proxy listener.
The following examples assume that Kong is running and listening for HTTP/2 proxy requests on port 9080.
Single gRPC service and route
-
Issue the following request to create a gRPC service. For example, if your gRPC server is listening on
localhost
, port15002
:curl -XPOST localhost:8001/services \ --data name=grpc \ --data protocol=grpc \ --data host=localhost \ --data port=15002
-
Issue the following request to create a gRPC route:
curl -XPOST localhost:8001/services/grpc/routes \ --data protocols=grpc \ --data name=catch-all \ --data paths=/
-
Using the
grpcurl
command line client, issue the following gRPC request:grpcurl -v -d '{"greeting": "Kong!"}' \ -plaintext localhost:9080 hello.HelloService.SayHello
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, 16 Jul 2019 21:37:36 GMT server: openresty/1.15.8.1 via: kong/1.2.1 x-kong-proxy-latency: 0 x-kong-upstream-latency: 0 Response contents: { "reply": "hello Kong!" } Response trailers received: (empty) Sent 1 request and received 1 response
Notice that Kong response headers, such as via
and x-kong-proxy-latency
, were
inserted in the response.
Single gRPC service with multiple routes
Building on top of the previous example, let’s create a few more routes for individual gRPC methods.
In this example, the gRPC HelloService
service exposes a few different
methods, as can be seen in its protocol buffer file.
-
Create individual routes for its
SayHello
andLotsOfReplies
methods.-
Create a route for
SayHello
:curl -X POST localhost:8001/services/grpc/routes \ --data protocols=grpc \ --data paths=/hello.HelloService/SayHello \ --data name=say-hello
-
Create a route for
LotsOfReplies
:curl -X POST localhost:8001/services/grpc/routes \ --data protocols=grpc \ --data paths=/hello.HelloService/LotsOfReplies \ --data name=lots-of-replies
With this setup, gRPC requests to the
SayHello
method will match the first route, while requests toLotsOfReplies
will be routed to the latter. -
-
In
kong.conf
, setallow_debug_header: on
. -
Issue a gRPC request to the
SayHello
method:grpcurl -v -d '{"greeting": "Kong!"}' \ -H 'kong-debug: 1' -plaintext \ localhost:9080 hello.HelloService.SayHello
Notice that the example sends the header
kong-debug
, which causes Kong to insert debugging information in response headers.The response should look like:
Resolved method descriptor: rpc SayHello ( .hello.HelloRequest ) returns ( .hello.HelloResponse ); Request metadata to send: kong-debug: 1 Response headers received: content-type: application/grpc date: Tue, 16 Jul 2019 21:57:00 GMT kong-route-id: 390ef3d1-d092-4401-99ca-0b4e42453d97 kong-service-id: d82736b7-a4fd-4530-b575-c68d94c3493a kong-service-name: s1 server: openresty/1.15.8.1 via: kong/1.2.1 x-kong-proxy-latency: 0 x-kong-upstream-latency: 0 Response contents: { "reply": "hello Kong!" } Response trailers received: (empty) Sent 1 request and received 1 response
Notice the route ID should refer to the first route we created.
-
Similarly, let’s issue a request to the
LotsOfReplies
gRPC method:grpcurl -v -d '{"greeting": "Kong!"}' \ -H 'kong-debug: 1' -plaintext \ localhost:9080 hello.HelloService.LotsOfReplies
The response should look like the following:
Resolved method descriptor: rpc LotsOfReplies ( .hello.HelloRequest ) returns ( stream .hello.HelloResponse ); Request metadata to send: kong-debug: 1 Response headers received: content-type: application/grpc date: Tue, 30 Jul 2019 22:21:40 GMT kong-route-id: 133659bb-7e88-4ac5-b177-bc04b3974c87 kong-service-id: 31a87674-f984-4f75-8abc-85da478e204f kong-service-name: grpc server: openresty/1.15.8.1 via: kong/1.2.1 x-kong-proxy-latency: 14 x-kong-upstream-latency: 0 Response contents: { "reply": "hello Kong!" } Response contents: { "reply": "hello Kong!" } Response contents: { "reply": "hello Kong!" } Response contents: { "reply": "hello Kong!" } Response contents: { "reply": "hello Kong!" } Response contents: { "reply": "hello Kong!" } Response contents: { "reply": "hello Kong!" } Response contents: { "reply": "hello Kong!" } Response contents: { "reply": "hello Kong!" } Response contents: { "reply": "hello Kong!" } Response trailers received: (empty) Sent 1 request and received 10 responses
Notice that the
kong-route-id
response header now carries a different value and refers to the second Route created in this page.
Note: Some gRPC clients (typically CLI clients) issue “gRPC Reflection Requests” as a means of determining what methods a server exports and how those methods are called. These requests have a particular path. For example,
/grpc.reflection.v1alpha.ServerReflection/ServerReflectionInfo
is a valid reflection path. As with any proxy request, Kong needs to know how to route these requests. In the current example, they would be routed to the catch-all route whose path is/
, matching any path. If no route matches the gRPC reflection request, Kong will respond, as expected, with a404 Not Found
response.
Enabling plugins
Let’s try out the File Log plugin with gRPC.
-
Issue the following request to enable the File Log plugin on the
SayHello
route:curl -X POST localhost:8001/routes/say-hello/plugins \ --data name=file-log \ --data config.path=grpc-say-hello.log
-
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}