Scaling (#109)

Make PWD scalable

.gitignore

@@ -1,3 +1,3 @@
 play-with-docker
 node_modules
-
+pwd/*

config/config.go

@@ -2,12 +2,17 @@ package config
 
 import "flag"
 
-var SSLPortNumber, PortNumber, Key, Cert string
+var SSLPortNumber, PortNumber, Key, Cert, SessionsFile, PWDContainerName, PWDCName string
+var MaxLoadAvg float64
 
 func ParseFlags() {
 	flag.StringVar(&PortNumber, "port", "3000", "Give a TCP port to run the application")
 	flag.StringVar(&SSLPortNumber, "sslPort", "3001", "Give a SSL TCP port")
 	flag.StringVar(&Key, "key", "./pwd/server-key.pem", "Server key for SSL")
 	flag.StringVar(&Cert, "cert", "./pwd/server.pem", "Give a SSL cert")
+	flag.StringVar(&SessionsFile, "save", "./pwd/sessions", "Tell where to store sessions file")
+	flag.StringVar(&PWDContainerName, "name", "pwd", "Container name used to run PWD (used to be able to connect it to the networks it creates)")
+	flag.StringVar(&PWDCName, "cname", "host1", "CNAME given to this host")
+	flag.Float64Var(&MaxLoadAvg, "maxload", 100, "Maximum allowed load average before failing ping requests")
 	flag.Parse()
 }

docker-compose.yml

@@ -1,16 +1,35 @@
 version: '2'
 services:
-    pwd:
+    haproxy:
+        container_name: proxy
+        image: haproxy
+        ports:
+            - "80:8080"
+            - "443:8443"
+
+        volumes:
+            - ./haproxy:/usr/local/etc/haproxy
+    pwd1:
         # pwd daemon container always needs to be named this way
-        container_name: pwd
+        container_name: pwd1
         # use the latest golang image
         image: golang
         # go to the right place and starts the app
-        command: /bin/sh -c 'cd /go/src/github.com/franela/play-with-docker; go run api.go'
-        ports:
-            # app exposes port 3000
-            - "80:3000"
-            - "443:3001"
+        command: /bin/sh -c 'cd /go/src/github.com/franela/play-with-docker; go run api.go -save ./pwd/sessions1 -name pwd1 -cname host1'
+        volumes:
+            # since this app creates networks and launches containers, we need to talk to docker daemon
+            - /var/run/docker.sock:/var/run/docker.sock
+            # mount the box mounted shared folder to the container
+            - $GOPATH/src:/go/src
+        environment:
+            GOOGLE_RECAPTCHA_DISABLED: "true"
+    pwd2:
+        # pwd daemon container always needs to be named this way
+        container_name: pwd2
+        # use the latest golang image
+        image: golang
+        # go to the right place and starts the app
+        command: /bin/sh -c 'cd /go/src/github.com/franela/play-with-docker; go run api.go -save ./pwd/sessions2 -name pwd2 -cname host2'
         volumes:
             # since this app creates networks and launches containers, we need to talk to docker daemon
             - /var/run/docker.sock:/var/run/docker.sock

handlers/get_session.go

@@ -2,7 +2,6 @@ package handlers
 
 import (
 	"encoding/json"
-	"log"
 	"net/http"
 
 	"github.com/franela/play-with-docker/services"
@@ -12,7 +11,6 @@ import (
 func GetSession(rw http.ResponseWriter, req *http.Request) {
 	vars := mux.Vars(req)
 	sessionId := vars["sessionId"]
-	log.Println(sessionId)
 
 	session := services.GetSession(sessionId)
 

handlers/new_session.go

@@ -1,13 +1,20 @@
 package handlers
 
 import (
+	"encoding/json"
 	"fmt"
 	"log"
 	"net/http"
 
+	"github.com/franela/play-with-docker/config"
 	"github.com/franela/play-with-docker/services"
 )
 
+type NewSessionResponse struct {
+	SessionId string `json:"session_id"`
+	Hostname  string `json:"hostname"`
+}
+
 func NewSession(rw http.ResponseWriter, req *http.Request) {
 	req.ParseForm()
 	if !services.IsHuman(req) {
@@ -25,11 +32,15 @@ func NewSession(rw http.ResponseWriter, req *http.Request) {
 		log.Println(err)
 		//TODO: Return some error code
 	} else {
+
+		hostname := fmt.Sprintf("%s.%s", config.PWDCName, req.Host)
 		// If request is not a form, return sessionId in the body
 		if req.Header.Get("X-Requested-With") == "XMLHttpRequest" {
-			rw.Write([]byte(s.Id))
+			resp := NewSessionResponse{SessionId: s.Id, Hostname: hostname}
+			rw.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(rw).Encode(resp)
 			return
 		}
-		http.Redirect(rw, req, fmt.Sprintf("/p/%s", s.Id), http.StatusFound)
+		http.Redirect(rw, req, fmt.Sprintf("http://%s/p/%s", hostname, s.Id), http.StatusFound)
 	}
 }

handlers/ping.go

@@ -1,6 +1,23 @@
 package handlers
 
-import "net/http"
+import (
+	"log"
+	"net/http"
+
+	"github.com/franela/play-with-docker/config"
+	"github.com/shirou/gopsutil/load"
+)
 
 func Ping(rw http.ResponseWriter, req *http.Request) {
+	// Get system load average of the last 5 minutes and compare it against a threashold.
+
+	a, err := load.Avg()
+	if err != nil {
+		log.Println("Cannot get system load average!", err)
+	} else {
+		if a.Load5 > config.MaxLoadAvg {
+			log.Printf("System load average is too high [%f]\n", a.Load5)
+			rw.WriteHeader(http.StatusInsufficientStorage)
+		}
+	}
 }

haproxy/haproxy.cfg

@@ -0,0 +1,32 @@
+defaults
+    mode http
+    timeout connect 5000ms
+    timeout client 50000ms
+    timeout server 50000ms
+
+frontend http-in
+    bind *:8080
+
+    acl host_localhost hdr(host) localhost
+    acl host_pwd1 hdr_reg(host) -i ^.*\.?host1\.localhost$
+    acl host_pwd2 hdr_reg(host) -i ^.*\.?host2\.localhost$
+
+    use_backend all if host_localhost
+    use_backend pwd1 if host_pwd1
+    use_backend pwd2 if host_pwd2
+
+backend all
+    balance roundrobin
+
+    option httpchk GET /ping HTTP/1.0
+    http-check expect rstatus 200
+    default-server inter 3s fall 3 rise 2
+
+    server node1 pwd1:3000 check
+    server node2 pwd2:3000 check
+
+backend pwd1
+    server node1 pwd1:3000
+
+backend pwd2
+    server node2 pwd2:3000

pwd/.gitignore

@@ -1 +0,0 @@
-sessions.gob

services/session.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/docker/docker/api"
 	"github.com/docker/docker/client"
+	"github.com/franela/play-with-docker/config"
 	"github.com/googollee/go-socket.io"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/twinj/uuid"
@@ -241,13 +242,13 @@ func NewSession(duration time.Duration) (*Session, error) {
 	log.Printf("Network [%s] created for session [%s]\n", s.Id, s.Id)
 
 	// Connect PWD daemon to the new network
-	ip, err := ConnectNetwork("pwd", s.Id, "")
+	ip, err := ConnectNetwork(config.PWDContainerName, s.Id, "")
 	if err != nil {
 		log.Println("ERROR NETWORKING")
 		return nil, err
 	}
 	s.PwdIpAddress = ip
-	log.Printf("Connected pwd to network [%s]\n", s.Id)
+	log.Printf("Connected %s to network [%s]\n", config.PWDContainerName, s.Id)
 
 	// Schedule peridic tasks execution
 	s.SchedulePeriodicTasks()
@@ -290,7 +291,7 @@ func setGauges() {
 }
 
 func LoadSessionsFromDisk() error {
-	file, err := os.Open("./pwd/sessions.gob")
+	file, err := os.Open(config.SessionsFile)
 	if err == nil {
 		decoder := gob.NewDecoder(file)
 		err = decoder.Decode(&sessions)
@@ -322,7 +323,7 @@ func LoadSessionsFromDisk() error {
 			if s.PwdIpAddress == "" {
 				log.Fatal("Cannot load stored sessions as they don't have the pwd ip address stored with them")
 			}
-			if _, err := ConnectNetwork("pwd", s.Id, s.PwdIpAddress); err != nil {
+			if _, err := ConnectNetwork(config.PWDContainerName, s.Id, s.PwdIpAddress); err != nil {
 				if strings.Contains(err.Error(), "Could not attach to network") {
 					log.Printf("Network for session [%s] doesn't exist. Removing all instances and session.", s.Id)
 					CloseSession(s)
@@ -331,7 +332,7 @@ func LoadSessionsFromDisk() error {
 					return err
 				}
 			} else {
-				log.Printf("Connected pwd to network [%s]\n", s.Id)
+				log.Printf("Connected %s to network [%s]\n", config.PWDContainerName, s.Id)
 
 				// Schedule peridic tasks execution
 				s.SchedulePeriodicTasks()
@@ -346,7 +347,7 @@ func LoadSessionsFromDisk() error {
 func saveSessionsToDisk() error {
 	rw.Lock()
 	defer rw.Unlock()
-	file, err := os.Create("./pwd/sessions.gob")
+	file, err := os.Create(config.SessionsFile)
 	if err == nil {
 		encoder := gob.NewEncoder(file)
 		err = encoder.Encode(&sessions)