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Migrating from gRPC

Step-by-step guide to migrating existing gRPC services to Go Micro.

Why Migrate?

Go Micro adds:

You keep:

Migration Strategy

Phase 1: Parallel Running

Run Go Micro alongside existing gRPC services

Phase 2: Gradual Migration

Migrate services one at a time

Phase 3: Complete Migration

All services on Go Micro

Step-by-Step Migration

1. Existing gRPC Service

// proto/hello.proto
syntax = "proto3";

package hello;
option go_package = "./proto;hello";

service Greeter {
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}

// Original gRPC server
package main

import (
    "context"
    "log"
    "net"
    "google.golang.org/grpc"
    pb "myapp/proto"
)

type server struct {
    pb.UnimplementedGreeterServer
}

func (s *server) SayHello(ctx context.Context, req *pb.HelloRequest) (*pb.HelloReply, error) {
    return &pb.HelloReply{Message: "Hello " + req.Name}, nil
}

func main() {
    lis, _ := net.Listen("tcp", ":50051")
    s := grpc.NewServer()
    pb.RegisterGreeterServer(s, &server{})
    log.Fatal(s.Serve(lis))
}

2. Generate Go Micro Code

Update your proto generation:

# Install protoc-gen-micro
go install go-micro.dev/v5/cmd/protoc-gen-micro@latest

# Generate both gRPC and Go Micro code
protoc --proto_path=. \
  --go_out=. --go_opt=paths=source_relative \
  --go-grpc_out=. --go-grpc_opt=paths=source_relative \
  --micro_out=. --micro_opt=paths=source_relative \
  proto/hello.proto

This generates:

3. Migrate Server to Go Micro

// Go Micro server
package main

import (
    "context"
    "go-micro.dev/v5"
    "go-micro.dev/v5/server"
    pb "myapp/proto"
)

type Greeter struct{}

func (s *Greeter) SayHello(ctx context.Context, req *pb.HelloRequest, rsp *pb.HelloReply) error {
    rsp.Message = "Hello " + req.Name
    return nil
}

func main() {
    svc := micro.NewService(
        micro.Name("greeter"),
    )
    svc.Init()

    pb.RegisterGreeterHandler(svc.Server(), new(Greeter))

    if err := svc.Run(); err != nil {
        log.Fatal(err)
    }
}

Key differences:

4. Migrate Client

Original gRPC client:

conn, _ := grpc.Dial("localhost:50051", grpc.WithInsecure())
defer conn.Close()

client := pb.NewGreeterClient(conn)
rsp, err := client.SayHello(context.Background(), &pb.HelloRequest{Name: "John"})

Go Micro client:

svc := micro.NewService(micro.Name("client"))
svc.Init()

client := pb.NewGreeterService("greeter", svc.Client())
rsp, err := client.SayHello(context.Background(), &pb.HelloRequest{Name: "John"})

Benefits:

5. Keep gRPC Transport (Optional)

Use gRPC as the underlying transport:

import (
    "go-micro.dev/v5"
    "go-micro.dev/v5/client"
    "go-micro.dev/v5/server"
    grpcclient "go-micro.dev/v5/client/grpc"
    grpcserver "go-micro.dev/v5/server/grpc"
)

svc := micro.NewService(
    micro.Name("greeter"),
    micro.Client(grpcclient.NewClient()),
    micro.Server(grpcserver.NewServer()),
)

This gives you:

Streaming Migration

Original gRPC Streaming

service Greeter {
  rpc StreamHellos (stream HelloRequest) returns (stream HelloReply) {}
}

func (s *server) StreamHellos(stream pb.Greeter_StreamHellosServer) error {
    for {
        req, err := stream.Recv()
        if err == io.EOF {
            return nil
        }
        if err != nil {
            return err
        }
        
        stream.Send(&pb.HelloReply{Message: "Hello " + req.Name})
    }
}

Go Micro Streaming

func (s *Greeter) StreamHellos(ctx context.Context, stream server.Stream) error {
    for {
        var req pb.HelloRequest
        if err := stream.Recv(&req); err != nil {
            return err
        }
        
        if err := stream.Send(&pb.HelloReply{Message: "Hello " + req.Name}); err != nil {
            return err
        }
    }
}

Service Discovery Migration

Before (gRPC with Consul)

// Manually register with Consul
config := api.DefaultConfig()
config.Address = "consul:8500"
client, _ := api.NewClient(config)

reg := &api.AgentServiceRegistration{
    ID:      "greeter-1",
    Name:    "greeter",
    Address: "localhost",
    Port:    50051,
}
client.Agent().ServiceRegister(reg)

// Cleanup on shutdown
defer client.Agent().ServiceDeregister("greeter-1")

After (Go Micro)

import "go-micro.dev/v5/registry/consul"

reg := consul.NewConsulRegistry()
svc := micro.NewService(
    micro.Name("greeter"),
    micro.Registry(reg),
)

// Registration automatic on Run()
// Deregistration automatic on shutdown
svc.Run()

Load Balancing Migration

Before (gRPC with custom LB)

// Need external load balancer or custom implementation
// Example: round-robin DNS, Envoy, nginx

After (Go Micro)

import "go-micro.dev/v5/selector"

// Client-side load balancing built-in
svc := micro.NewService(
    micro.Selector(selector.NewSelector(
        selector.SetStrategy(selector.RoundRobin),
    )),
)

Gradual Migration Path

1. Start with New Services

New services use Go Micro, existing services stay on gRPC.

// New Go Micro service can call gRPC services
// Configure gRPC endpoints directly
grpcConn, _ := grpc.Dial("old-service:50051", grpc.WithInsecure())
oldClient := pb.NewOldServiceClient(grpcConn)

2. Migrate Read-Heavy Services First

Services with many clients benefit most from service discovery.

3. Migrate Services with Fewest Dependencies

Leaf services are easier to migrate.

4. Add Adapters if Needed

// gRPC adapter for Go Micro service
type GRPCAdapter struct {
    microClient pb.GreeterService
}

func (a *GRPCAdapter) SayHello(ctx context.Context, req *pb.HelloRequest) (*pb.HelloReply, error) {
    return a.microClient.SayHello(ctx, req)
}

// Register adapter as gRPC server
s := grpc.NewServer()
pb.RegisterGreeterServer(s, &GRPCAdapter{microClient: microClient})

Checklist

Common Issues

Port Already in Use

gRPC: Manual port management

lis, _ := net.Listen("tcp", ":50051")

Go Micro: Automatic or explicit

// Let Go Micro choose
svc := micro.NewService(micro.Name("greeter"))

// Or specify
svc := micro.NewService(
    micro.Name("greeter"),
    micro.Address(":50051"),
)

Service Not Found

Check registry:

# Consul
curl http://localhost:8500/v1/catalog/services

# Or use micro CLI
micro services

Different Serialization

gRPC uses protobuf by default. Go Micro supports multiple codecs.

Ensure both use protobuf:

import "go-micro.dev/v5/codec/proto"

svc := micro.NewService(
    micro.Codec("application/protobuf", proto.Marshaler{}),
)

Performance Comparison

Scenario gRPC Go Micro (HTTP) Go Micro (gRPC)
Simple RPC ~25k req/s ~20k req/s ~24k req/s
With Discovery N/A ~18k req/s ~22k req/s
Streaming ~30k msg/s ~15k msg/s ~28k msg/s

Go Micro with gRPC transport performs similarly to pure gRPC

Next Steps

Need Help?