mirror of
https://github.com/golang/go
synced 2024-11-25 05:57:57 -07:00
117 lines
2.7 KiB
Go
117 lines
2.7 KiB
Go
// Copyright 2010 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package main
|
|
|
|
import (
|
|
"log"
|
|
"net/http"
|
|
"time"
|
|
)
|
|
|
|
const (
|
|
numPollers = 2 // number of Poller goroutines to launch
|
|
pollInterval = 60 * time.Second // how often to poll each URL
|
|
statusInterval = 10 * time.Second // how often to log status to stdout
|
|
errTimeout = 10 * time.Second // back-off timeout on error
|
|
)
|
|
|
|
var urls = []string{
|
|
"http://www.google.com/",
|
|
"http://golang.org/",
|
|
"http://blog.golang.org/",
|
|
}
|
|
|
|
// State represents the last-known state of a URL.
|
|
type State struct {
|
|
url string
|
|
status string
|
|
}
|
|
|
|
// StateMonitor maintains a map that stores the state of the URLs being
|
|
// polled, and prints the current state every updateInterval nanoseconds.
|
|
// It returns a chan State to which resource state should be sent.
|
|
func StateMonitor(updateInterval time.Duration) chan<- State {
|
|
updates := make(chan State)
|
|
urlStatus := make(map[string]string)
|
|
ticker := time.NewTicker(updateInterval)
|
|
go func() {
|
|
for {
|
|
select {
|
|
case <-ticker.C:
|
|
logState(urlStatus)
|
|
case s := <-updates:
|
|
urlStatus[s.url] = s.status
|
|
}
|
|
}
|
|
}()
|
|
return updates
|
|
}
|
|
|
|
// logState prints a state map.
|
|
func logState(s map[string]string) {
|
|
log.Println("Current state:")
|
|
for k, v := range s {
|
|
log.Printf(" %s %s", k, v)
|
|
}
|
|
}
|
|
|
|
// Resource represents an HTTP URL to be polled by this program.
|
|
type Resource struct {
|
|
url string
|
|
errCount int
|
|
}
|
|
|
|
// Poll executes an HTTP HEAD request for url
|
|
// and returns the HTTP status string or an error string.
|
|
func (r *Resource) Poll() string {
|
|
resp, err := http.Head(r.url)
|
|
if err != nil {
|
|
log.Println("Error", r.url, err)
|
|
r.errCount++
|
|
return err.Error()
|
|
}
|
|
r.errCount = 0
|
|
return resp.Status
|
|
}
|
|
|
|
// Sleep sleeps for an appropriate interval (dependant on error state)
|
|
// before sending the Resource to done.
|
|
func (r *Resource) Sleep(done chan<- *Resource) {
|
|
time.Sleep(pollInterval + errTimeout*time.Duration(r.errCount))
|
|
done <- r
|
|
}
|
|
|
|
func Poller(in <-chan *Resource, out chan<- *Resource, status chan<- State) {
|
|
for r := range in {
|
|
s := r.Poll()
|
|
status <- State{r.url, s}
|
|
out <- r
|
|
}
|
|
}
|
|
|
|
func main() {
|
|
// Create our input and output channels.
|
|
pending, complete := make(chan *Resource), make(chan *Resource)
|
|
|
|
// Launch the StateMonitor.
|
|
status := StateMonitor(statusInterval)
|
|
|
|
// Launch some Poller goroutines.
|
|
for i := 0; i < numPollers; i++ {
|
|
go Poller(pending, complete, status)
|
|
}
|
|
|
|
// Send some Resources to the pending queue.
|
|
go func() {
|
|
for _, url := range urls {
|
|
pending <- &Resource{url: url}
|
|
}
|
|
}()
|
|
|
|
for r := range complete {
|
|
go r.Sleep(pending)
|
|
}
|
|
}
|