allow backends to be changed via unix socket

bin/shasum

@@ -1 +1 @@
-f875002d695a5726444d6a86644f35449f844d44  ./bin/goaround
+71711d3d03e824ec9a51ac734c94648e9874292f  ./bin/goaround

go.mod

@@ -2,4 +2,8 @@ module github.com/CoderCookE/goaround
 
 go 1.12
 
-require github.com/dgraph-io/ristretto v0.0.0-20191004195602-f823dc4a5031
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/dgraph-io/ristretto v0.0.1
+	github.com/stretchr/testify v1.3.0 // indirect
+)

go.sum

@@ -1,10 +1,18 @@
-github.com/codercooke/goaround v0.0.0-20190726005525-216236838df3 h1:SH0qcVMNgZgsuUM8/xtmBtigM4UBvoCfuCQqsWBMo58=
-github.com/codercooke/goaround v0.0.0-20190726005525-216236838df3/go.mod h1:l53nwp2tMBWyIWF0fHoVLBj5tKcovj0yC4LNp3CrvAY=
+github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
+github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
+github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dgraph-io/ristretto v0.0.0-20191004195602-f823dc4a5031 h1:puinfjvl1jM3YaODRJ63nURwCuY+7r2gaOxE4ON+68E=
 github.com/dgraph-io/ristretto v0.0.0-20191004195602-f823dc4a5031/go.mod h1:jg4yDfbNNmxP2Nq5Z7MbyQrXyl/syIRF2LnbbxqViho=
+github.com/dgraph-io/ristretto v0.0.1 h1:cJwdnj42uV8Jg4+KLrYovLiCgIfz9wtWm6E6KA+1tLs=
+github.com/dgraph-io/ristretto v0.0.1/go.mod h1:T40EBc7CJke8TkpiYfGGKAeFjSaxuFXhuXRyumBd6RE=
+github.com/dgryski/go-farm v0.0.0-20190423205320-6a90982ecee2 h1:tdlZCpZ/P9DhczCTSixgIKmwPv6+wP5DGjqLYw5SUiA=
 github.com/dgryski/go-farm v0.0.0-20190423205320-6a90982ecee2/go.mod h1:SqUrOPUnsFjfmXRMNPybcSiG0BgUW2AuFH8PAnS2iTw=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=

internal/connectionpool/connection.go

@@ -8,9 +8,15 @@ import (
 	"sync"
 )
 
+type message struct {
+	health  bool
+	backend string
+	proxy   *httputil.ReverseProxy
+}
+
 type connection struct {
 	healthy  bool
-	messages chan bool
+	messages chan message
 	backend  string
 	sync.RWMutex
 	proxy *httputil.ReverseProxy
@@ -20,7 +26,7 @@ type connection struct {
 func newConnection(proxy *httputil.ReverseProxy, backend string, cache *ristretto.Cache) (*connection, error) {
 	conn := &connection{
 		backend:  backend,
-		messages: make(chan bool),
+		messages: make(chan message),
 		proxy:    proxy,
 		cache:    cache,
 	}
@@ -56,9 +62,19 @@ func (c *connection) get(w http.ResponseWriter, r *http.Request) error {
 
 func (c *connection) healthCheck() {
 	for {
-		healthy := <-c.messages
+		msg := <-c.messages
+
 		c.Lock()
-		c.healthy = healthy
+
+		backend := msg.backend
+		c.healthy = msg.health
+		proxy := msg.proxy
+
+		if proxy != nil && c.backend != backend {
+			c.backend = backend
+			c.proxy = proxy
+		}
+
 		c.Unlock()
 	}
 }

internal/connectionpool/connection_test.go

@@ -39,15 +39,15 @@ func TestHealthCheck(t *testing.T) {
 		assertion.Equal(err, nil)
 
 		assertion.False(conn.healthy)
-		conn.messages <- true
+		conn.messages <- message{health: true}
 		time.Sleep(200 * time.Millisecond)
 
 		conn.Lock()
 		health := conn.healthy
 		conn.Unlock()
 		assertion.True(health)
 
-		conn.messages <- false
+		conn.messages <- message{health: false}
 		time.Sleep(200 * time.Millisecond)
 
 		conn.Lock()

internal/connectionpool/health-checker.go

@@ -7,6 +7,8 @@ import (
 	"io/ioutil"
 	"log"
 	"net/http"
+	"net/http/httputil"
+	"sync"
 	"time"
 )
 
@@ -16,7 +18,8 @@ type healthCheckReponse struct {
 }
 
 type healthChecker struct {
-	subscribers   []chan bool
+	sync.Mutex
+	subscribers   []chan message
 	currentHealth bool
 	client        *http.Client
 	backend       string
@@ -27,27 +30,44 @@ func (hc *healthChecker) Start() {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
+	hc.Lock()
 	hc.check(ctx)
+	hc.Unlock()
+
 	ticker := time.NewTicker(1000 * time.Millisecond)
 	for {
 		select {
 		case <-ticker.C:
 			cancel()
+			hc.Lock()
 			ctx, cancel = context.WithCancel(context.Background())
 			hc.check(ctx)
+			hc.Unlock()
 		case <-hc.done:
 			ticker.Stop()
 			return
 		}
 	}
 }
 
+func (hc *healthChecker) Reuse(newBackend string, proxy *httputil.ReverseProxy) *healthChecker {
+	hc.Lock()
+	hc.backend = newBackend
+	hc.notifySubscribers(false, hc.backend, proxy)
+	hc.Unlock()
+
+	return hc
+}
+
 func (hc *healthChecker) check(ctx context.Context) {
 	url := fmt.Sprintf("%s%s", hc.backend, "/health")
 	healthy := hc.currentHealth
 
-	req, _ := http.NewRequest(http.MethodGet, url, nil)
-	if resp, err := http.DefaultClient.Do(req.WithContext(ctx)); err != nil {
+	req, err := http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		log.Printf("Error creating request: %s, error %s", hc.backend, err.Error())
+		healthy = false
+	} else if resp, err := http.DefaultClient.Do(req.WithContext(ctx)); err != nil {
 		log.Printf("Error with health check, backend: %s, error %s", hc.backend, err.Error())
 		healthy = false
 	} else {
@@ -67,9 +87,14 @@ func (hc *healthChecker) check(ctx context.Context) {
 
 	if healthy != hc.currentHealth {
 		hc.currentHealth = healthy
-		for _, c := range hc.subscribers {
-			c <- healthy
-		}
+		hc.notifySubscribers(healthy, hc.backend, nil)
+	}
+}
+
+func (hc *healthChecker) notifySubscribers(healthy bool, backend string, proxy *httputil.ReverseProxy) {
+	message := message{health: healthy, backend: backend, proxy: proxy}
+	for _, c := range hc.subscribers {
+		c <- message
 	}
 }
 

internal/connectionpool/health-checker_test.go

@@ -20,7 +20,7 @@ func TestHealthChecker(t *testing.T) {
 	assertion := &assert.Asserter{T: t}
 
 	t.Run("backend returns a healthy state", func(t *testing.T) {
-		resChan := make(chan bool, 1)
+		resChan := make(chan message, 1)
 
 		availableHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			healthReponse := &healthCheckReponse{State: "healthy", Message: ""}
@@ -33,7 +33,7 @@ func TestHealthChecker(t *testing.T) {
 
 		hc := healthChecker{
 			client:        client,
-			subscribers:   []chan bool{resChan},
+			subscribers:   []chan message{resChan},
 			backend:       availableServer.URL,
 			done:          make(chan bool),
 			currentHealth: false,
@@ -44,11 +44,11 @@ func TestHealthChecker(t *testing.T) {
 
 		health := <-resChan
 
-		assertion.True(health)
+		assertion.True(health.health)
 	})
 
 	t.Run("backend returns a degraded state", func(t *testing.T) {
-		resChan := make(chan bool, 1)
+		resChan := make(chan message, 1)
 
 		degradedHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			healthReponse := &healthCheckReponse{State: "degraded", Message: ""}
@@ -61,7 +61,7 @@ func TestHealthChecker(t *testing.T) {
 
 		hc := healthChecker{
 			client:        client,
-			subscribers:   []chan bool{resChan},
+			subscribers:   []chan message{resChan},
 			backend:       degradedServer.URL,
 			done:          make(chan bool),
 			currentHealth: true,
@@ -72,6 +72,6 @@ func TestHealthChecker(t *testing.T) {
 
 		health := <-resChan
 
-		assertion.False(health)
+		assertion.False(health.health)
 	})
 }