Merge pull request #172 from micro/func

Function

README.md

@@ -20,14 +20,15 @@ Go Micro abstracts way the details of distributed systems. Here are the main fea
 - **Message Encoding** - Micro services can encode requests in a number of encoding formats and seamlessly decode based on the Content-Type header.
 - **RPC Client/Server** - The client and server leverage the above features and provide a clean simple interface for building microservices.
 
+Go Micro supports both the Service and Function programming models. Read on to learn more.
+
 ## Docs
 
 For more detailed information on the architecture, installation and use of go-micro checkout the [docs](https://micro.mu/docs).
 
 ## Learn By Example
 
-An example service can be found in [**examples/service**](https://github.com/micro/examples/tree/master/service). The [**examples**](https://github.com/micro/examples) directory contains many more examples for using things such as middleware/wrappers, selector filters, pub/sub and code generation. 
-
+An example service can be found in [**examples/service**](https://github.com/micro/examples/tree/master/service) and function in [**examples/function**](https://github.com/micro/examples/tree/master/function). The [**examples**](https://github.com/micro/examples) directory contains many more examples for using things such as middleware/wrappers, selector filters, pub/sub and code generation. 
 For the complete greeter example look at [**examples/greeter**](https://github.com/micro/examples/tree/master/greeter). Other examples can be found throughout the GitHub repository.
 
 Check out the blog post to learn how to write go-micro services [https://micro.mu/blog/2016/03/28/go-micro.html](https://micro.mu/blog/2016/03/28/go-micro.html) or watch the talk from the [Golang UK Conf 2016](https://www.youtube.com/watch?v=xspaDovwk34).
@@ -228,6 +229,48 @@ go run client.go
 Hello John
 ```
 
+## Writing a Function
+
+Go Micro includes the Function programming model. This is the notion of a one time executing Service which operates much like a service except exiting 
+after completing a request. A function is defined much like a service and called in exactly the same way.
+
+### Defining a Function
+
+```go
+package main
+
+import (
+	proto "github.com/micro/examples/function/proto"
+	"github.com/micro/go-micro"
+	"golang.org/x/net/context"
+)
+
+type Greeter struct{}
+
+func (g *Greeter) Hello(ctx context.Context, req *proto.HelloRequest, rsp *proto.HelloResponse) error {
+	rsp.Greeting = "Hello " + req.Name
+	return nil
+}
+
+func main() {
+	// create a new function
+	fnc := micro.NewFunction(
+		micro.Name("go.micro.fnc.greeter"),
+	)
+
+	// init the command line
+	fnc.Init()
+
+	// register a handler
+	fnc.Handle(new(Greeter))
+
+	// run the function
+	fnc.Run()
+}
+```
+
+It's that simple.
+
 ## How does it work?
 
 <p align="center">

function.go

@@ -0,0 +1,81 @@
+package micro
+
+import (
+	"time"
+
+	"github.com/micro/go-micro/server"
+	"golang.org/x/net/context"
+)
+
+type function struct {
+	cancel context.CancelFunc
+	Service
+}
+
+func fnHandlerWrapper(f Function) server.HandlerWrapper {
+	return func(h server.HandlerFunc) server.HandlerFunc {
+		return func(ctx context.Context, req server.Request, rsp interface{}) error {
+			defer f.Done()
+			return h(ctx, req, rsp)
+		}
+	}
+}
+
+func fnSubWrapper(f Function) server.SubscriberWrapper {
+	return func(s server.SubscriberFunc) server.SubscriberFunc {
+		return func(ctx context.Context, msg server.Publication) error {
+			defer f.Done()
+			return s(ctx, msg)
+		}
+	}
+}
+
+func newFunction(opts ...Option) Function {
+	ctx, cancel := context.WithCancel(context.Background())
+
+	// force ttl/interval
+	fopts := []Option{
+		RegisterTTL(time.Minute),
+		RegisterInterval(time.Second * 30),
+	}
+
+	// prepend to opts
+	fopts = append(fopts, opts...)
+
+	// make context the last thing
+	fopts = append(fopts, Context(ctx))
+
+	service := newService(fopts...)
+
+	fn := &function{
+		cancel:  cancel,
+		Service: service,
+	}
+
+	service.Server().Init(
+		// ensure the service waits for requests to finish
+		server.Wait(true),
+		// wrap handlers and subscribers to finish execution
+		server.WrapHandler(fnHandlerWrapper(fn)),
+		server.WrapSubscriber(fnSubWrapper(fn)),
+	)
+
+	return fn
+}
+
+func (f *function) Done() error {
+	f.cancel()
+	return nil
+}
+
+func (f *function) Handle(v interface{}) error {
+	return f.Service.Server().Handle(
+		f.Service.Server().NewHandler(v),
+	)
+}
+
+func (f *function) Subscribe(topic string, v interface{}) error {
+	return f.Service.Server().Subscribe(
+		f.Service.Server().NewSubscriber(topic, v),
+	)
+}

function_test.go

@@ -0,0 +1,55 @@
+package micro
+
+import (
+	"sync"
+	"testing"
+
+	"github.com/micro/go-micro/registry/mock"
+	proto "github.com/micro/go-micro/server/debug/proto"
+
+	"golang.org/x/net/context"
+)
+
+func TestFunction(t *testing.T) {
+	var wg sync.WaitGroup
+	wg.Add(1)
+
+	// create service
+	fn := NewFunction(
+		Name("test.function"),
+		Registry(mock.NewRegistry()),
+		AfterStart(func() error {
+			wg.Done()
+			return nil
+		}),
+	)
+
+	// we can't test fn.Init as it parses the command line
+	// fn.Init()
+
+	go func() {
+		// wait for start
+		wg.Wait()
+
+		// test call debug
+		req := fn.Client().NewRequest(
+			"test.function",
+			"Debug.Health",
+			new(proto.HealthRequest),
+		)
+
+		rsp := new(proto.HealthResponse)
+
+		err := fn.Client().Call(context.TODO(), req, rsp)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if rsp.Status != "ok" {
+			t.Fatalf("function response: %s", rsp.Status)
+		}
+	}()
+
+	// run service
+	fn.Run()
+}

go-micro.go

@@ -22,6 +22,18 @@ type Service interface {
 	String() string
 }
 
+// Function is a one time executing Service
+type Function interface {
+	// Inherits Service interface
+	Service
+	// Done signals to complete execution
+	Done() error
+	// Handle registers an RPC handler
+	Handle(v interface{}) error
+	// Subscribe registers a subscriber
+	Subscribe(topic string, v interface{}) error
+}
+
 // Publisher is syntactic sugar for publishing
 type Publisher interface {
 	Publish(ctx context.Context, msg interface{}, opts ...client.PublishOption) error
@@ -49,6 +61,11 @@ func NewContext(ctx context.Context, s Service) context.Context {
 	return context.WithValue(ctx, serviceKey{}, s)
 }
 
+// NewFunction returns a new Function for a one time executing Service
+func NewFunction(opts ...Option) Function {
+	return newFunction(opts...)
+}
+
 // NewPublisher returns a new Publisher
 func NewPublisher(topic string, c client.Client) Publisher {
 	if c == nil {