blob: ab99da81816c859aee00bf88b1c9ba86ffd885a9 (
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|
package main
import (
"fmt"
"net/url"
"sync"
)
/*
main goroutine:
- manages urls channel.
*/
func workers(startURL url.URL, maxConcurrency, maxURLs int) {
worklist := make(chan []url.URL)
// Unseen URLs.
urls := make(chan url.URL)
go func() {
worklist <- []url.URL{startURL}
}()
var wg sync.WaitGroup
// Create maxConcurrency worker goroutines to demultiplex from
// the urls channel (unseen links.)
for range maxConcurrency {
wg.Go(func() {
for u := range urls {
batch := getBatch(u)
go func() { worklist <- batch }()
}
})
}
// The main goroutine deduplicates worklist items and sends
// unseen ones to the crawlers in a fan-out fashion.
seen := make(map[url.URL]bool)
count := 1
for batch := range worklist {
for _, u := range batch {
if !seen[u] {
fmt.Printf("%d. %s\n", count, &u)
count++
seen[u] = true
urls <- u
}
}
}
wg.Wait()
}
|
