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crawler.go
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crawler.go
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package main
import (
"time"
"net/http"
"github.com/yhat/scrape"
"golang.org/x/net/html"
"strconv"
"fmt"
)
type Crawler struct {
timelaps time.Duration
AppContext *AppContext
Listener []*Listener
ServerList ServerList
addListener chan *Listener
//if crawl has started (need at least one listener)
started bool
}
func newCrawler(timelaps time.Duration, context *AppContext) *Crawler {
if timelaps < time.Minute {
context.Logger.Info("Timestamp too short, changed to 1 minute")
timelaps = time.Minute
}
crawler := Crawler{
timelaps: timelaps,
AppContext: context,
started: false,
ServerList: newServerList(),
}
crawler.listenAddListener()
return &crawler
}
// Avoid concurrent write event if low probability
func (c *Crawler) listenAddListener() {
c.addListener = make(chan *Listener)
go func() {
for l := range c.addListener {
c.Listener = append(c.Listener, l)
}
}()
}
func (c *Crawler) AddListener() *Listener {
return c.AddListenerForServer("")
}
func (c *Crawler) AddListenerForServer(serverName string) *Listener {
if !c.started {
c.StartCrawl()
}
l := Listener{
make(chan Server),
serverName,
}
c.addListener <- &l
return &l
}
func (c *Crawler) StartCrawl() {
go func() {
for {
c.checkAvailability()
time.Sleep(c.timelaps)
}
}()
}
func (c *Crawler) checkAvailability() {
resp, err := http.Get(ONLINE_PAGE_SERVER_LIST)
if err != nil {
c.AppContext.Logger.Error(fmt.Sprintf("Fail to get %s : %s", ONLINE_PAGE_SERVER_LIST, err.Error()))
return
}
defer resp.Body.Close()
root, err := html.Parse(resp.Body)
if err != nil {
c.AppContext.Logger.Error(fmt.Sprintf("Fail to get body %s : %s", ONLINE_PAGE_SERVER_LIST, err.Error()))
return
}
serverAnchorNodes := scrape.FindAll(root, scrape.ByClass("Item__link--foot"))
for _, serverAnchorNode := range serverAnchorNodes {
path := scrape.Attr(serverAnchorNode, "href")
c.checkAvailabilityServer(fmt.Sprintf("http://%s%s", resp.Request.Host, path))
}
}
func (c *Crawler) checkAvailabilityServer(url string) {
resp, err := http.Get(url)
if err != nil {
c.AppContext.Logger.Crit(fmt.Sprintf("Fail to get %s : %s", url, err.Error()))
return
}
root, err := html.Parse(resp.Body)
defer resp.Body.Close()
if err != nil {
c.AppContext.Logger.Error(fmt.Sprintf("Fail to get body %s : %s", url, err.Error()))
return
}
serverNumberNodes := scrape.FindAll(root, scrape.ByClass("typenumber--total"))
totalAvailable := 0
for _, serverNumberNode := range serverNumberNodes {
i, err := strconv.Atoi(scrape.Text(serverNumberNode))
if err != nil {
c.AppContext.Logger.Error(fmt.Sprintf("Fail to get availables server for url %s", url))
} else {
totalAvailable += i
}
}
matcher := func(n *html.Node) bool {
// must check for nil values
if n.Parent != nil && scrape.Attr(n.Parent, "class") == "Dedidetails__maintitle Common__title Common__title--main beta--low text-center" {
return scrape.Attr(n, "itemprop") == "name"
}
return false
}
serverNameNode, ok := scrape.Find(root, matcher)
if !ok {
c.AppContext.Logger.Error(fmt.Sprintf("Fail to get server name for url %s", url))
return
}
serverName := scrape.Text(serverNameNode)
c.updateAvailability(serverName, totalAvailable)
}
func (c *Crawler) updateAvailability(serverName string, totalAvailable int) {
server, ok := c.ServerList.GetServerByName(serverName)
if ok {
if server.ServerAvailable != totalAvailable {
prev := server.ServerAvailable
server.ServerAvailable = totalAvailable
server.PreviousAvailability = prev
c.notifyForServer(*server)
}
} else {
server := c.ServerList.AddServer(serverName, "", totalAvailable)
c.notifyForServer(*server)
}
}
func (c *Crawler) notifyForServer(server Server) {
for _, listener := range c.Listener {
if listener.ServerTypeFilter == "" || listener.ServerTypeFilter == server.Name {
listener.Chan <- server
}
}
}
type Listener struct {
Chan chan Server
ServerTypeFilter string
}