Which RPC Framework is Used in Kubernetes?

DDevOpsGuy · 18 Feb

RajeshKumar1 · 18 Feb

Which RPC Framework is Used in Kubernetes?

Kubernetes uses gRPC as its primary Remote Procedure Call (RPC) framework for internal communication between its components.

Why?

gRPC is fast, efficient, and optimized for microservices
It supports streaming, multiplexing, and automatic code generation
It runs over HTTP/2 and uses Protocol Buffers (ProtoBuf) for binary serialization

Where is RPC (gRPC) Used in Kubernetes?

Kubernetes API Server (`kube-apiserver`)

The Kubernetes API server exposes gRPC-based APIs internally.
External clients communicate with the API Server using REST over HTTP, but internally, Kubernetes components use gRPC.

Kubernetes Control Plane Communication

Components like kubelet, kube-scheduler, and kube-controller-manager communicate via gRPC.
This allows efficient data transfer and low-latency interactions.

Kubernetes CSI (Container Storage Interface)

Kubernetes CSI (Container Storage Interface) uses gRPC to communicate with storage backends (like Amazon EBS, Google Persistent Disk, etc.).
This enables dynamic provisioning of storage in Kubernetes clusters.

Kubernetes CRI (Container Runtime Interface)

Kubernetes CRI (Container Runtime Interface) defines how Kubernetes interacts with container runtimes (like Docker, containerd, CRI-O).
Kubernetes CRI communication is entirely based on gRPC.

Kubernetes Networking & Service Mesh (Istio, Linkerd)

Service mesh tools like Istio and Linkerd use gRPC for high-performance service-to-service communication.
They intercept and manage network traffic between Kubernetes pods using gRPC-based proxies.

Why Does Kubernetes Use gRPC Instead of JSON-RPC or REST?

| Feature | gRPC (Used in Kubernetes) | REST (JSON-RPC, HTTP APIs) |
|------------|--------------------|---------------------------|
| Performance | Faster (Binary data over HTTP/2) | Slower (JSON over HTTP/1.1) |
| Streaming Support | Bidirectional streaming | No built-in streaming |
| Efficiency | Compact, optimized serialization | JSON is heavier, text-based |
| Cross-Language Support | Yes (Auto-generated clients for Go, Python, Java, etc.) | Yes (JSON works everywhere) |
| Multiplexing | Multiple requests on one connection | One request per connection |
| Use Case | Microservices, API server, internal communication | External-facing APIs only |

Real Example: Kubernetes gRPC Communication

Example of Kubernetes CRI gRPC Request to the Container Runtime:

service RuntimeService {
  rpc RunPodSandbox (RunPodSandboxRequest) returns (RunPodSandboxResponse);
  rpc StopPodSandbox (StopPodSandboxRequest) returns (StopPodSandboxResponse);
}

The Kubernetes API Server calls this function to start/stop a pod.
The CRI runtime (e.g., containerd, CRI-O) implements these functions.

Final Thoughts

Kubernetes heavily uses gRPC for efficient, high-performance communication between components.
It is used in the API server, CRI (Container Runtime Interface), CSI (Storage), and Service Mesh.
gRPC is chosen over REST/JSON-RPC because of its speed, streaming capabilities, and compact binary serialization.

Would you like a hands-on example of interacting with Kubernetes using gRPC?

RajeshKumar1 · 18 Feb

What is "gRPC Routing via Kubernetes Native Resources (GRPCRoute)"?

GRPCRoute is a Kubernetes-native resource that allows you to define gRPC routing in Kubernetes. It is part of Kubernetes Gateway API, which provides advanced traffic routing and management for services running inside Kubernetes.

gRPC Routing in Kubernetes means:

Defining rules to route gRPC requests between services.
Using native Kubernetes resources (like GRPCRoute) to configure routing instead of external load balancers.
Applying traffic policies, authentication, and observability to gRPC calls.

How gRPC Routing Works in Kubernetes?

A client makes a gRPC request (e.g., myapp.MyService/SayHello) to an Ingress or Gateway.
The request is forwarded to the correct backend service based on GRPCRoute rules.
gRPC-aware proxies (like Envoy, Istio, or Linkerd) apply routing rules (e.g., version-based routing, retries, timeouts).
The correct microservice receives the request and sends back a response.

What is GRPCRoute in Kubernetes Gateway API?

GRPCRoute is a custom Kubernetes resource that enables native gRPC routing.

Example GRPCRoute Resource:

apiVersion: gateway.networking.k8s.io/v1alpha2
kind: GRPCRoute
metadata:
  name: grpc-route
spec:
  parentRefs:
  - name: my-gateway
  rules:
  - matches:
    - method:
        service: "myapp.MyService"
        method: "SayHello"
    backendRefs:
    - name: grpc-service
      port: 50051

What This Does:

Routes gRPC requests matching myapp.MyService/SayHello to grpc-service running on port 50051.
Works with Gateway API controllers like Istio, Envoy, or Traefik.
Supports advanced gRPC traffic policies (timeouts, retries, version-based routing).

Why Use GRPCRoute Instead of Regular Kubernetes Services?

| Feature | GRPCRoute (Gateway API) | Traditional Kubernetes Service |
|------------|----------------------|----------------------------|
| gRPC-Aware Routing | Yes | No (Only Layer 4 TCP Routing) |
| Per-Method Routing | Yes (Route based on service/method) | No (Routes all traffic to one backend) |
| Retries & Timeouts | Yes | No |
| Traffic Splitting | Yes (Blue-Green, Canary Deployments) | No |
| mTLS (Mutual TLS) & Security | Yes (With Istio, Envoy) | No |

GRPCRoute gives fine-grained control over gRPC traffic, unlike standard Kubernetes Services.

When Should You Use GRPCRoute?

When running gRPC-based microservices in Kubernetes.
When you need gRPC-aware traffic management (e.g., route v1 requests to one service and v2 to another).
When you use a service mesh (Istio, Linkerd, Consul) or API Gateway (Envoy, Traefik).

Summary

GRPCRoute is a Kubernetes-native resource for gRPC routing in Gateway API.
It enables gRPC-aware routing, retries, timeouts, and traffic policies.
Works with Envoy, Istio, Traefik, and Kubernetes Gateway API controllers.
Better than traditional Kubernetes Services for gRPC traffic control.

Would you like a step-by-step tutorial on setting up GRPCRoute in Kubernetes?

RajeshKumar1 · 18 Feb

Is `GRPCRoute` Built-in with Kubernetes or Does It Require Installation?

GRPCRoute is NOT built into Kubernetes by default.
It is part of the Kubernetes Gateway API, which you need to install separately.

How `GRPCRoute` Works in Kubernetes

Kubernetes does NOT include GRPCRoute by default.
You must install Kubernetes Gateway API to use GRPCRoute.
GRPCRoute requires a Gateway Controller (like Istio, Envoy Gateway, or Traefik Proxy).
Once installed, you can define gRPC routing rules using GRPCRoute.

How to Install and Enable `GRPCRoute`

You need to:
Step 1: Install Kubernetes Gateway API
Step 2: Install a Gateway Controller (Envoy, Istio, or Traefik)
Step 3: Apply a GRPCRoute YAML configuration

Step 1: Install Kubernetes Gateway API

First, install Gateway API CRDs in Kubernetes:

kubectl kustomize "github.com/kubernetes-sigs/gateway-api/config/crd?ref=v0.7.0" | kubectl apply -f -

This adds support for GRPCRoute and other Gateway API resources.

Step 2: Install a Gateway Controller

A Gateway Controller is required to handle GRPCRoute. You can use:

Istio Gateway
Envoy Gateway
Traefik Proxy

Example: Install Envoy Gateway as your controller:

kubectl apply -f https://github.com/envoyproxy/gateway/releases/latest/download/install.yaml

Why?

Kubernetes itself does not handle gRPC routing.
A controller (like Envoy, Istio, or Traefik) processes and routes gRPC traffic.

Step 3: Apply `GRPCRoute` YAML

Once Gateway API and a Gateway Controller are installed, you can create a GRPCRoute:

apiVersion: gateway.networking.k8s.io/v1alpha2
kind: GRPCRoute
metadata:
  name: grpc-route
spec:
  parentRefs:
  - name: my-gateway
  rules:
  - matches:
    - method:
        service: "myapp.MyService"
        method: "SayHello"
    backendRefs:
    - name: grpc-service
      port: 50051

What This Does:

Routes gRPC calls matching myapp.MyService/SayHello to grpc-service on port 50051.
Works with your installed Gateway Controller (Istio, Envoy, or Traefik).

Summary

| Question | Answer |
|-------------|-----------|
| Is GRPCRoute built into Kubernetes? | No, you must install it manually. |
| How do I enable GRPCRoute? | Install Kubernetes Gateway API first. |
| Do I need a Gateway Controller? | Yes, use Istio, Envoy, or Traefik. |
| Why use GRPCRoute? | Native gRPC routing, service discovery, retries, load balancing. |

Final Thoughts

Kubernetes alone does NOT support GRPCRoute.
Install the Gateway API and a Gateway Controller (like Envoy or Istio).
Then define your GRPCRoute to manage gRPC traffic efficiently.

Would you like a step-by-step guide to setting up GRPCRoute in Kubernetes?

RajeshKumar1 · 18 Feb

Is This Statement Right or Wrong?

"gRPC routing via k8s native resources (GRPCRoute)"
This statement is CORRECT, but requires clarification.

Why Is It Correct?

GRPCRoute is a Kubernetes-native resource.

It is part of Kubernetes Gateway API, which extends native Kubernetes networking.
It works inside Kubernetes clusters just like Ingress or Service objects.

It enables gRPC routing within Kubernetes.

GRPCRoute allows routing gRPC traffic between services without needing external API gateways.
It can define rules per gRPC method, unlike traditional Ingress.

It integrates with Kubernetes controllers like Envoy, Istio, and Traefik.

These controllers act as proxies that read GRPCRoute configurations.

Why Does It Need Extra Installation?

GRPCRoute is not included in Kubernetes by default.
It is part of the Kubernetes Gateway API, which needs to be installed separately.
You also need a Gateway Controller (like Istio, Envoy, or Traefik) to enforce GRPCRoute rules.

Corrected Statement

Instead of saying:
"gRPC routing via k8s native resources (GRPCRoute)"

It should be:
"gRPC routing using Kubernetes-native Gateway API resource (GRPCRoute), requiring a Gateway Controller (Istio, Envoy, Traefik)."

Final Answer

The statement is not entirely wrong because GRPCRoute is a Kubernetes-native resource.
But Kubernetes does not provide GRPCRoute by default; you must install the Gateway API and a controller (Envoy, Istio, etc.).
If you only install Kubernetes, GRPCRoute will not work.

Would you like a guide on how to set up GRPCRoute in your Kubernetes cluster?

RajeshKumar1 · 18 Feb

How gRPC Routing Works in AWS EKS (Kubernetes on AWS)?

When using Amazon EKS (Elastic Kubernetes Service), gRPC routing does not work out-of-the-box. You need to install additional components to handle gRPC traffic.

How to Enable gRPC Routing in EKS?

Since AWS EKS does not natively support GRPCRoute, you have two main options:

Option : Use Kubernetes Gateway API with `GRPCRoute` (Recommended)

Install Kubernetes Gateway API and a Gateway Controller (e.g., Envoy Gateway, Istio, or Traefik).
Use GRPCRoute to route gRPC traffic within your EKS cluster.

Option : Use AWS Load Balancers (NLB/ALB) for gRPC Routing

Use AWS NLB (Network Load Balancer) or AWS ALB (Application Load Balancer) to route external gRPC traffic.
Inside EKS, use Envoy/Istio as a service mesh to route gRPC between microservices.

Option 1: Using Kubernetes Gateway API for gRPC Routing in EKS

Step 1: Install Kubernetes Gateway API CRDs

Install the Kubernetes Gateway API in your EKS cluster:

kubectl kustomize "github.com/kubernetes-sigs/gateway-api/config/crd?ref=v0.7.0" | kubectl apply -f -

Step 2: Install a Gateway Controller

You need a controller to manage GRPCRoute rules. Install Envoy Gateway:

kubectl apply -f https://github.com/envoyproxy/gateway/releases/latest/download/install.yaml

OR use Istio Ingress Gateway:

istioctl install --set profile=demo

Step 3: Define gRPC Routing in EKS (`grpc-gateway.yaml`)

Apply this GRPCRoute to route gRPC traffic:

apiVersion: gateway.networking.k8s.io/v1alpha2
kind: GRPCRoute
metadata:
  name: grpc-route
spec:
  parentRefs:
  - name: my-gateway
  rules:
  - matches:
    - method:
        service: "myapp.MyService"
        method: "SayHello"
    backendRefs:
    - name: grpc-service
      port: 50051

This routes gRPC requests to myapp.MyService/SayHello inside EKS.

Option 2: Using AWS Load Balancers for gRPC Routing in EKS

If you want AWS-managed routing, use AWS Network Load Balancer (NLB) or Application Load Balancer (ALB).

Step 1: Deploy an AWS NLB for gRPC Traffic

AWS Network Load Balancer (NLB) supports gRPC natively.

apiVersion: v1
kind: Service
metadata:
  name: grpc-service
  annotations:
    service.beta.kubernetes.io/aws-load-balancer-type: "nlb"
spec:
  ports:
    - port: 50051
      targetPort: 50051
      protocol: TCP
  selector:
    app: grpc-service
  type: LoadBalancer

This exposes a gRPC service via AWS NLB.

Step 2: Use AWS ALB for Path-Based gRPC Routing

AWS ALB can route gRPC traffic based on HTTP headers.

Install AWS ALB Controller in your EKS cluster:

helm repo add eks https://aws.github.io/eks-charts
helm install aws-load-balancer-controller eks/aws-load-balancer-controller -n kube-system

Deploy an Ingress resource with ALB:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: grpc-ingress
  annotations:
    alb.ingress.kubernetes.io/load-balancer-type: "external"
    alb.ingress.kubernetes.io/backend-protocol: "grpc"
spec:
  rules:
  - host: grpc.example.com
    http:
      paths:
      - path: /myapp.MyService/SayHello
        backend:
          service:
            name: grpc-service
            port:
              number: 50051

This routes gRPC requests from AWS ALB to your EKS service.

Which Option Should You Use?

| Use Case | Recommended Solution |
|-------------|--------------------------|
| Internal gRPC Routing (EKS Microservices) | Use GRPCRoute with Kubernetes Gateway API |
| External gRPC Requests (Clients Outside EKS) | Use AWS Network Load Balancer (NLB) |
| Need Service Mesh (Security, Observability) | Use Istio with GRPCRoute |
| Want AWS-Managed Routing | Use AWS ALB |

Final Thoughts

If running gRPC inside EKS, use Kubernetes Gateway API + GRPCRoute.
If exposing gRPC outside EKS, use AWS NLB or AWS ALB.
For advanced gRPC traffic control, use Istio or Envoy as a service mesh.

Would you like a full step-by-step tutorial on setting up gRPC routing in EKS?

RajeshKumar1 · 18 Feb

How Do Kubernetes Master and Worker Nodes Communicate Without gRPC?

You're asking a great question! If Kubernetes components communicate without installing Kubernetes Gateway API or GRPCRoute, then how do the Kubernetes control plane and worker nodes talk to each other?

Answer: Kubernetes does NOT use gRPC for its core communication between master and worker nodes.
Instead, Kubernetes mostly uses REST APIs over HTTP/HTTPS for internal communication.

How Kubernetes Components Communicate Internally?

Kubernetes has multiple components that need to talk to each other, such as:

kube-apiserver (API Server)
kubelet (Worker Node Agent)
kube-scheduler (Schedules Pods)
kube-controller-manager (Manages Controllers)
etcd (Key-Value Store)
Container Runtime (CRI, e.g., containerd, CRI-O)
Networking Plugins (CNI)

Communication Between These Components Uses:
| Component Communication | Protocol Used | Uses gRPC? |
|----------------------------|------------------|---------------|
| API Server kubelet (Worker Node) | REST API over HTTPS | No |
| API Server etcd (Database Storage) | gRPC | Yes |
| kube-scheduler API Server | REST API over HTTPS | No |
| kube-controller-manager API Server | REST API over HTTPS | No |
| API Server kubectl (CLI Commands) | REST API over HTTPS | No |
| API Server Admission Controllers | REST API over HTTPS | No |
| API Server CRI (Container Runtime Interface) | gRPC | Yes |
| CNI (Network Plugins, like Calico) API Server | REST API over HTTPS | No |

Where Does Kubernetes Use REST API Instead of gRPC?

Most of Kubernetes’ internal communication happens via REST APIs over HTTP/HTTPS.

API Server as the Central Communication Hub

Kubernetes exposes a RESTful API via kube-apiserver.
Components like kubectl, kubelet, kube-controller-manager, and kube-scheduler communicate using HTTPS REST requests.

Example:
A Kubernetes worker node (kubelet) talks to the API Server using a REST API:

curl -X GET https://kubernetes.default.svc/api/v1/nodes --header "Authorization: Bearer <TOKEN>"

This API call retrieves all worker nodes in the cluster using REST, not gRPC.

Where Does Kubernetes Use gRPC?

While Kubernetes primarily uses REST APIs, there are two major places where gRPC is used internally:

etcd (Key-Value Store) Uses gRPC

etcd, the distributed database that stores cluster state, communicates using gRPC.
Kubernetes API Server interacts with etcd using gRPC, making data storage fast and efficient.

Example:
The API Server sends a GET request to etcd using gRPC to fetch a Kubernetes object (e.g., a Pod definition).

CRI (Container Runtime Interface) Uses gRPC

The Container Runtime Interface (CRI) allows Kubernetes to talk to container runtimes (Docker, containerd, CRI-O) using gRPC.
Instead of using a REST API, Kubernetes uses gRPC-based CRI calls to launch containers.

Example:
Kubelet requests container status from containerd:

crictl ps

This command calls containerd’s gRPC API to list running containers.

Why Doesn’t Kubernetes Use gRPC Everywhere?

gRPC is optimized for performance, but REST is easier to manage.
Kubernetes REST API is easier for external tools (kubectl, CI/CD, monitoring tools) to interact with.
Kubernetes prefers REST APIs for its main components, as REST:

Is human-readable.
Works with web-based tools.
Is easy to integrate with third-party systems.

Summary: gRPC vs REST in Kubernetes

| Component | Communication Type | Protocol Used |
|-------------|------------------|------------------|
| API Server Worker Nodes | Control Communication | REST over HTTPS |
| API Server etcd | Cluster Data Storage | gRPC |
| API Server kube-scheduler | Scheduling | REST over HTTPS |
| API Server kube-controller-manager | Control Loops | REST over HTTPS |
| API Server CRI (containerd, CRI-O) | Container Management | gRPC |

Most Kubernetes components use REST APIs.
Only etcd and CRI (container runtime) use gRPC for speed.
Kubernetes does not need Kubernetes Gateway API for its core functions.
If you want gRPC routing for your applications inside Kubernetes, you need to install GRPCRoute.

Final Thoughts

Kubernetes does not need gRPC everywhere because REST is more flexible and widely supported.
However, Kubernetes does use gRPC where high performance is needed (etcd & CRI).
If you want to use gRPC inside Kubernetes for your own applications, install Kubernetes Gateway API and GRPCRoute.

Would you like a practical demo on how Kubernetes components communicate using REST and gRPC?

RajeshKumar1 · 18 Feb

Do You Really Need Envoy, Istio, or Traefik for Internal gRPC in Kubernetes?

If your gRPC services are running inside Kubernetes, ClusterIP or NodePort is enough for basic internal communication.
However, if you need advanced gRPC features, then you may need Envoy, Istio, or Traefik.

So the answer is:
If you're running a small number of microservices, then ClusterIP or NodePort is fine.
If your services need gRPC-aware routing, retries, timeouts, load balancing, or security, you need something more powerful.

When is `ClusterIP` or `NodePort` Enough for Internal gRPC?

Scenario 1: You have only a few microservices communicating via gRPC.
Scenario 2: You don’t need traffic management, retries, load balancing, or observability.
Scenario 3: Your gRPC calls always go to a single backend service instance.

Example of Basic Internal gRPC Using ClusterIP
If you're using ClusterIP, one gRPC service can reach another via Kubernetes DNS:

grpc://my-grpc-service.default.svc.cluster.local:50051

No extra installations are needed.
All internal traffic stays inside the cluster.
If multiple replicas exist, Kubernetes distributes traffic (L4 round-robin).

This is completely fine for simple gRPC applications!

When Do You Need Envoy Gateway, Istio, or Traefik?

If your microservices architecture grows and you need more control over gRPC traffic, ClusterIP and NodePort become limited. Here’s when you need a service mesh or API gateway:

When You Need gRPC Load Balancing Beyond L4

Kubernetes default load balancing is L4 (TCP-based round-robin).
Envoy, Istio, and Traefik provide L7 (gRPC-aware) load balancing.
This helps when you want to route specific gRPC methods to different services.

Example:
SayHello() gRPC call → Goes to v1 of the service.
GetUserData() gRPC call → Goes to v2 of the service.

With ClusterIP, this isn’t possible. With Envoy, Istio, or Traefik, you can route gRPC traffic intelligently.

When You Need Advanced Traffic Control (Blue-Green, Canary Deployments)

If you want to gradually shift traffic from v1 to v2, Kubernetes services cannot do that.
With Istio or Envoy Gateway, you can route 90% of traffic to v1 and 10% to v2.

Example gRPC Traffic Control (Istio VirtualService):

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: grpc-routing
spec:
  hosts:
  - my-grpc-service
  http:
  - match:
    - uri:
        prefix: "/myapp.MyService/SayHello"
    route:
    - destination:
        host: grpc-service-v1
      weight: 90
    - destination:
        host: grpc-service-v2
      weight: 10

This enables controlled gRPC traffic shifting. Kubernetes ClusterIP cannot do this.

When You Need Retries & Timeouts

Kubernetes does not provide built-in gRPC retries and timeouts.
If a gRPC call fails, Envoy or Istio can automatically retry.

Example: gRPC Retry Policy (Istio VirtualService):

http:
  - retries:
      attempts: 3
      perTryTimeout: 2s

This makes sure gRPC calls retry up to 3 times if they fail. Kubernetes ClusterIP does not have this feature.

When You Need Security (mTLS for gRPC)

Kubernetes does not encrypt internal traffic by default.
Istio and Traefik can enforce mutual TLS (mTLS) between microservices.

Example: Enforcing mTLS for gRPC in Istio

apiVersion: security.istio.io/v1beta1
kind: PeerAuthentication
metadata:
  name: default
spec:
  mtls:
    mode: STRICT

With this, only authenticated gRPC calls are allowed inside Kubernetes.

When You Need Observability & Monitoring

Kubernetes services don’t provide insights into gRPC traffic.
Istio, Envoy, and Traefik provide logs, tracing, and metrics.

Example: gRPC Observability via Prometheus (Istio)

apiVersion: telemetry.istio.io/v1alpha1
kind: Telemetry
metadata:
  name: grpc-metrics
spec:
  metrics:
  - providers:
    - name: prometheus

Now you can see gRPC request counts, response times, and failures in Prometheus and Grafana.

Final Answer: Do You Need a Service Mesh or API Gateway?

| Scenario | Use ClusterIP / NodePort | Use Envoy / Istio / Traefik |
|-------------|--------------------------------|-------------------------------|
| Small app, few services, simple gRPC calls | Yes | No |
| Many gRPC services, complex routing | No | Yes |
| Need L7 (method-level) gRPC routing | No | Yes |
| Need blue-green or canary deployments | No | Yes |
| Need automatic gRPC retries & timeouts | No | Yes |
| Need mTLS security for internal gRPC calls | No | Yes |
| Need detailed gRPC monitoring & tracing | No | Yes |

If your gRPC services are simple, you don’t need anything extra.
If your microservices architecture is growing, use Istio, Envoy, or Traefik.

Would you like a step-by-step tutorial to set up gRPC in Kubernetes with and without a service mesh?