Add program

.gitignore

@@ -22,3 +22,7 @@ _testmain.go
 *.exe
 *.test
 *.prof
+
+counter
+results.bin
+*.retry

.travis.yml

@@ -0,0 +1,10 @@
+language: go
+go:
+  - 1.6
+  - 1.7
+  - tip
+before_install:
+  - go get github.com/mattn/goveralls
+  - go get golang.org/x/tools/cmd/cover
+script:
+  - $HOME/gopath/bin/goveralls -service=travis-ci

Dockerfile

@@ -0,0 +1 @@
+FROM golang:onbuild

README.md

@@ -1 +1,27 @@
-# counter
+# counter [![Build Status](https://travis-ci.org/phedoreanu/counter.svg?branch=master)](https://travis-ci.org/phedoreanu/counter) [![Coverage Status](https://coveralls.io/repos/github/phedoreanu/counter/badge.svg)](https://coveralls.io/github/phedoreanu/counter) [![Go Report Card](https://goreportcard.com/badge/github.com/phedoreanu/counter)](https://goreportcard.com/report/github.com/phedoreanu/counter)
+
+[![License](http://img.shields.io/:license-mit-blue.svg)](http://doge.mit-license.org) [![GoDoc](https://godoc.org/github.com/phedoreanu/counter?status.svg)](https://godoc.org/github.com/phedoreanu/counter)
+
+###Installation
+Counter requires Go 1.5 or later.
+
+###Usage
+```
+docker-compose up
+```
+
+###Unit tests
+```
+go test -v -race -cover -parallel 8 -cpu 8
+```
+
+###Smoke tests
+```
+ansible-playbook smoke-tests.yml 
+```
+
+###Load tests
+Start the app and execute:
+```
+HOSTNAME=localhost:8080 ./load-tests.sh 
+```

db/db.go

@@ -0,0 +1,115 @@
+package db
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"github.com/garyburd/redigo/redis"
+	"github.com/youtube/vitess/go/pools"
+	"golang.org/x/net/context"
+)
+
+// Datastore is an interface helper that allows mocking a test database
+type Datastore interface {
+	ReadCounter() int64
+	IncrementCounter()
+	DecrementCounter()
+	FlushDB()
+}
+
+// DB is a wrapper over the connection pool
+type DB struct {
+	*pools.ResourcePool
+}
+
+// ResourceConn adapts a Redigo connection to a Vitess Resource
+type ResourceConn struct {
+	redis.Conn
+}
+
+// Close closes a connection owned by a Vitess Resource
+func (r ResourceConn) Close() {
+	r.Conn.Close()
+}
+
+// NewPool creates a new Redis connection pool
+func NewPool() *DB {
+	p := pools.NewResourcePool(func() (pools.Resource, error) {
+		c, err := redis.Dial("tcp", fmt.Sprintf("%s:6379", os.Getenv("REDIS_HOST")))
+		return ResourceConn{c}, err
+	}, 4, 100, time.Minute)
+	//defer p.Close()
+	return &DB{p}
+}
+
+// ReadCounter returns the current contents of the counter in the database
+func (p *DB) ReadCounter() int64 {
+	ctx := context.TODO()
+	r, err := p.Get(ctx)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer p.Put(r)
+	c := r.(ResourceConn)
+	i64, err := redis.Int64(c.Do("GET", "counter"))
+	if err != nil {
+		fmt.Println(err)
+	}
+	return i64
+}
+
+// IncrementCounter increments the counter by 1
+func (p *DB) IncrementCounter() {
+	ctx := context.TODO()
+	r, err := p.Get(ctx)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer p.Put(r)
+	c := r.(ResourceConn)
+	c.Send("MULTI")
+	c.Send("INCR", "counter")
+	//c.Send("EXEC")
+	_, err = c.Do("EXEC")
+	if err != nil {
+		fmt.Println(err)
+	}
+}
+
+// DecrementCounter decrements the counter by 1
+func (p *DB) DecrementCounter() {
+	ctx := context.TODO()
+	r, err := p.Get(ctx)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer p.Put(r)
+	c := r.(ResourceConn)
+	c.Send("MULTI")
+	c.Send("DECR", "counter")
+	//c.Send("EXEC")
+	_, err = c.Do("EXEC")
+	if err != nil {
+		fmt.Println(err)
+	}
+}
+
+// FlushDB flushed the DB
+func (p *DB) FlushDB() {
+	ctx := context.TODO()
+	r, err := p.Get(ctx)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer p.Put(r)
+	c := r.(ResourceConn)
+	c.Send("MULTI")
+	c.Send("FLUSHDB")
+	rep, err := c.Do("EXEC")
+	if err != nil {
+		fmt.Println(err)
+	}
+	fmt.Println(rep)
+}

docker-compose.yml

@@ -0,0 +1,12 @@
+version: '2'
+services:
+  counter:
+    environment:
+      - REDIS_HOST=redis
+    ports:
+      - 8080:8080
+    image: 'phedoreanu/counter:latest'
+    links:
+      - redis
+  redis:
+    image: 'redis:latest'

load-tests.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+if [ ! -d "$DIRECTORY" ]; then
+  go get -u github.com/tsenart/vegeta
+fi
+
+echo "GET http://${HOSTNAME}/get" | vegeta attack -duration=30s | tee results.bin | vegeta report

main.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/phedoreanu/counter/db"
+	"github.com/phedoreanu/counter/synced"
+)
+
+// Env is a dependency injection helper
+type Env struct {
+	db     db.Datastore
+	c      chan int64
+	synced *synced.Synced
+}
+
+// GetHandler returns the number of hits to /get endpoint
+func (env *Env) handleGet(w http.ResponseWriter, _ *http.Request) {
+	go func() {
+		env.c <- env.synced.Increment()
+	}()
+	fmt.Fprint(w, env.synced.Read())
+}
+
+// StatusHandler returns the current contents of the counter in the database
+func (env *Env) handleStatus(w http.ResponseWriter, _ *http.Request) {
+	fmt.Fprint(w, env.db.ReadCounter())
+}
+
+// SyncCounter increments the counter in the database
+// and every 10 requests to /get flips and decrements the counter
+func (env *Env) SyncCounter(hits int64) {
+	switch env.synced.GetDirection() {
+	case true:
+		env.db.DecrementCounter()
+	case false:
+		env.db.IncrementCounter()
+	}
+	if hits%10 == 0 {
+		env.synced.Reverse()
+	}
+}
+
+func main() {
+	env := Env{
+		db:     db.NewPool(),
+		c:      make(chan int64),
+		synced: synced.NewSynced(),
+	}
+	env.db.FlushDB()
+
+	go func() {
+		for {
+			env.SyncCounter(<-env.c)
+		}
+	}()
+
+	http.HandleFunc("/get", env.handleGet)
+	http.HandleFunc("/status", env.handleStatus)
+
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}