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grpc

gRPC is a communication protocol for services, built on HTTP/2. Unlike REST over HTTP/1, which is based on resources, gRPC is based on Service Definitions. You specify service definitions in a format called protocol buffers (“proto”), which can be serialized into an small binary format for transmission.

With gRPC, you can generate boilerplate code from .proto files into multiple programming languages, making gRPC an ideal choice for polyglot microservices.

While gRPC supports some networking use cases like TLS and client-side load balancing, adding Istio to a gRPC architecture can be useful for collecting telemetry, adding traffic rules, and setting RPC-level authorization. Istio can also provide a useful management layer if your traffic is a mix of HTTP, TCP, gRPC, and database protocols, because you can use the same Istio APIs for all traffic types.

Istio and its data plane proxy, Envoy, both support gRPC. Let’s see how to manage gRPC traffic with Istio.

grpc

Here, we’re running two gRPC Services, client and server. client makes an RPC call to the server’s /SayHello function every 2 seconds.

Adding Istio to gRPC Kubernetes services has one pre-requisite: labeling your Kubernetes Service ports. The server’s port is labeled as follows:

apiVersion: v1
kind: Service
metadata:
  name: server
spec:
  selector:
    app: server
  type: ClusterIP
  ports:
  - name: grpc # important!
    protocol: TCP
    port: 8080

Once we deploy the app, we can see this traffic between client and server in a service graph:

kiali

We can also view the server’s gRPC traffic metrics in Grafana:

server healthy

Then, we can apply an Istio traffic rule to inject a 10-second delay fault into server. You might apply this rule in a chaos testing scenario, to test the resiliency of this application.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: server-fault
spec:
  hosts:
  - server
  http:
  - fault:
      delay:
        percentage:
          value: 100.0
        fixedDelay: 10s
    route:
    - destination:
        host: server
        subset: v1

This causes the client RPC to time out (Outgoing Request Duration):

grafana client fault inject

To learn more about gRPC and Istio: