NATS Docker blog post/HTTP Server

api-server.go

package main

import (
	"fmt"
	"log"
	"net/http"
	"os"
	"time"

	"github.com/nats-io/nats"
)

type server struct {
	nc *nats.Conn
}

func (s server) baseRoot(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintln(w, "Basic NATS based microservice example v0.0.1")
}

func (s server) createTask(w http.ResponseWriter, r *http.Request) {
	requestAt := time.Now()
	response, err := s.nc.Request("tasks", []byte("help please"), 5*time.Second)
	if err != nil {
		log.Println("Error making NATS request:", err)
	}
	duration := time.Since(requestAt)

	fmt.Fprintf(w, "Task scheduled in %+v\nResponse: %v\n", duration, string(response.Data))
}

func (s server) healthz(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintln(w, "OK")
}

func main() {
	var s server
	var err error
	uri := os.Getenv("NATS_URI")
	
	for i := 0; i < 5; i++ {
		nc, err := nats.Connect(uri)
		if err == nil {
			s.nc = nc
			break
		}

		fmt.Println("Waiting before connecting to NATS at:", uri)
		time.Sleep(1 * time.Second)	
	}
	if err != nil {
		log.Fatal("Error establishing connection to NATS:", err)
	}

	fmt.Println("Connected to NATS at:", s.nc.ConnectedUrl())
	http.HandleFunc("/", s.baseRoot)
	http.HandleFunc("/createTask", s.createTask)
	http.HandleFunc("/healthz", s.healthz)

	fmt.Println("Server listening on port 8080...")
	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatal(err)
	}
}

build

$ docker-compose -f build.yml up
nats uses an image, skipping
Building api
Step 1 : FROM golang:1.6.2
 ---> 5850add7ecc2
Step 2 : COPY . /go
 ---> 188fa03a7cf5
Removing intermediate container 37ee6fd35e0d
Step 3 : RUN go build api-server.go
 ---> Running in 048e4010e539
 ---> 21dbaf567bbb
Removing intermediate container 048e4010e539
Step 4 : EXPOSE 8080
 ---> Running in b07dde665ad2
 ---> 3a6a59102f81
Removing intermediate container b07dde665ad2
Step 5 : ENTRYPOINT /go/api-server
 ---> Running in e3c5de88d6d4
 ---> faf4d12797f3
Removing intermediate container e3c5de88d6d4
Successfully built faf4d12797f3
Building worker
Step 1 : FROM golang:1.6.2
 ---> 5850add7ecc2
Step 2 : COPY . /go
 ---> Using cache
 ---> 0376e8a54e9d
Step 3 : RUN go build worker.go
 ---> Using cache
 ---> 1a53e068ad91
Step 4 : EXPOSE 8080
 ---> Using cache
 ---> 77b8a0e0ab4f
Step 5 : ENTRYPOINT /go/worker
 ---> Using cache
 ---> 7d23b0d4e846
Successfully built 7d23b0d4e846

build.yml

version: "2"

services:
  nats:
    image: 'nats:0.8.0'
    entrypoint: "/gnatsd -DV"
    expose:
      - "4222"
    ports:
      - "8222:8222"
    hostname: nats-server
  api:
    build:
      context: "./api"
    entrypoint: /go/api-server
    links:
      - nats
    environment:
      - "NATS_URI=nats://nats:4222"
    depends_on:
      - nats
    ports:
      - "8080:8080"
  worker:
    build:
      context: "./worker"
    entrypoint: /go/worker
    links:
      - nats
    environment:
      - "NATS_URI=nats://nats:4222"
    depends_on:
      - nats
    ports:
      - "8181:8181"

Docker Compose + NATS example

FROM golang:1.6.2

COPY . /go

RUN go get github.com/nats-io/nats
RUN go build api-server.go

EXPOSE 8080
ENTRYPOINT ["/go/api-server"]

docker-compose up

$ docker-compose -f build.yml up
nats_1    | [1] 2016/06/14 01:30:25.563332 [INF] Starting nats-server version 0.8.0
nats_1    | [1] 2016/06/14 01:30:25.564371 [DBG] Go build version go1.6.2
nats_1    | [1] 2016/06/14 01:30:25.564392 [INF] Listening for client connections on 0.0.0.0:4222
nats_1    | [1] 2016/06/14 01:30:25.564444 [DBG] Server id is VYcRrgxx6c097Tq62NIIVp
nats_1    | [1] 2016/06/14 01:30:25.564451 [INF] Server is ready
nats_1    | [1] 2016/06/14 01:30:25.799723 [DBG] 172.18.0.3:32999 - cid:1 - Client connection created
nats_1    | [1] 2016/06/14 01:30:25.800213 [TRC] 172.18.0.3:32999 - cid:1 - ->> [CONNECT {"verbose":false,"pedantic":false,"tls_required":false,"name":"","lang":"go","version":"1.2.0"}]
nats_1    | [1] 2016/06/14 01:30:25.800308 [TRC] 172.18.0.3:32999 - cid:1 - ->> [PING]
nats_1    | [1] 2016/06/14 01:30:25.800311 [TRC] 172.18.0.3:32999 - cid:1 - <<- [PONG]
nats_1    | [1] 2016/06/14 01:30:25.800703 [TRC] 172.18.0.3:32999 - cid:1 - ->> [SUB tasks  1]
worker_1  | 2016/06/14 01:30:25 Connected to NATS at nats://nats:4222
worker_1  | 2016/06/14 01:30:25 Worker subscribed to 'tasks' for processing requests...
worker_1  | 2016/06/14 01:30:25 Server listening on port 8181...
nats_1    | [1] 2016/06/14 01:30:26.009136 [DBG] 172.18.0.4:47156 - cid:2 - Client connection created
nats_1    | [1] 2016/06/14 01:30:26.009536 [TRC] 172.18.0.4:47156 - cid:2 - ->> [CONNECT {"verbose":false,"pedantic":false,"tls_required":false,"name":"","lang":"go","version":"1.2.0"}]
nats_1    | [1] 2016/06/14 01:30:26.009562 [TRC] 172.18.0.4:47156 - cid:2 - ->> [PING]
nats_1    | [1] 2016/06/14 01:30:26.009566 [TRC] 172.18.0.4:47156 - cid:2 - <<- [PONG]
api_1     | 2016/06/14 01:30:26 Connected to NATS at nats://nats:4222
api_1     | 2016/06/14 01:30:26 Server listening on port 8080...

Dockerfile Example Worker

FROM golang:1.6.2

COPY . /go

RUN go get github.com/nats-io/nats
RUN go build worker.go

EXPOSE 8080
ENTRYPOINT ["/go/worker"]

worker.go

package main

import (
	"fmt"
	"log"
	"net/http"
	"os"
	"time"

	"github.com/nats-io/nats"
)

func healthz(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintln(w, "OK")
}

func main() {
	uri := os.Getenv("NATS_URI")
	var err error
	var nc *nats.Conn

	for i := 0; i < 5; i++ {
		nc, err = nats.Connect(uri)
		if err == nil {
			break
		}

		fmt.Println("Waiting before connecting to NATS at:", uri)
		time.Sleep(1 * time.Second)
	}
	if err != nil {
		log.Fatal("Error establishing connection to NATS:", err)
	}
	fmt.Println("Connected to NATS at:", nc.ConnectedUrl())
	nc.Subscribe("tasks", func(m *nats.Msg) {
		fmt.Println("Got task request on:", m.Subject)
		nc.Publish(m.Reply, []byte("Done!"))
	})

	fmt.Println("Worker subscribed to 'tasks' for processing requests...")
	fmt.Println("Server listening on port 8181...")

	http.HandleFunc("/healthz", healthz)
	if err := http.ListenAndServe(":8181", nil); err != nil {
		log.Fatal(err)
	}
}