<p>I am currently trying to deploy an Istio Service Mesh in our Kubernetes cluster on GKE. When I inject the Istio sidecar using <code>kubectl apply -f &lt;(istioctl kube-inject -f &lt;service-name&gt;.yaml</code> the downstream services are not able to connect using gRPC. The issue does not present itself when the Istio sidecar is running in an HTTP service.</p>

<p>The configuration file for the gRPC service is as follows:</p>

<pre><code>apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: &lt;service name&gt;
  namespace: default
  labels:
    app: &lt;service-name&gt;
    version: v1
spec:
  minReadySeconds: 30
  replicas: 1
  template:
    metadata:
      labels:
        app: &lt;service-name&gt;
    spec:
      containers:
      - name: &lt;service-name&gt;
        image: gcr.io/project/service-name
        ports:
        - containerPort: 5011
          name: grpc
        resources:
          requests:
            memory: "10Mi"
            cpu: "100m"
          limits:
            memory: "100Mi"
            cpu: "250m"
        readinessProbe:
          tcpSocket:
            port: 5011
          initialDelaySeconds: 5
          periodSeconds: 10
        livenessProbe:
          tcpSocket:
            port: 5011
          initialDelaySeconds: 15
          periodSeconds: 20
---
apiVersion: v1
kind: Service
metadata:
  name: &lt;service-name&gt;
  namespace: default
spec:
  selector:
    app: &lt;service-name&gt;
  ports:
  - port: 5011
    targetPort: 5011
    name: grpc
</code></pre>

<p>Istio is running in the downstream service and does not show any outgoing requests to the upstream service. If I redeploy the upstream service without Istio, the gRPC call succeeds and the logs show an outgoing request.</p>

Brendan Chan
<p>I managed to fix this. The issue was that the upstream gRPC service was making a request to Datastore and Istio wasn't configured to let traffic to Google Cloud services out of the mesh, so the request was timing out. I solved this by running</p>

<pre><code>helm template install/kubernetes/helm/istio &lt;the flags you used to install Istio&gt; 
--set global.proxy.includeIPRanges="&lt;cluster IP ranges&gt;" 
-x templates/sidecar-injector-configmap.yaml | kubectl apply -f -
</code></pre>
