Function triggerAsyncFetch

pkg/faviconcache/faviconcache.go:90–123

triggerAsyncFetch starts a goroutine to update the favicon cache for the given domain if one isn’t already in progress.

(domain string)

// triggerAsyncFetch starts a goroutine to update the favicon cache
// for the given domain if one isn’t already in progress.
func triggerAsyncFetch(domain string) {
	fetchLock.Lock()
	if fetching[domain] {
		// Already fetching this domain; nothing to do.
		fetchLock.Unlock()
		return
	}
	// Mark this domain as in-flight.
	fetching[domain] = true
	fetchLock.Unlock()

	go func() {
		defer func() {
			panichandler.PanicHandler("Favicon:triggerAsyncFetch", recover())
		}()

		// Acquire a slot in the semaphore.
		fetchSemaphore <- true

		// When done, ensure that we clear the “fetching” flag.
		defer func() {
			<-fetchSemaphore
			fetchLock.Lock()
			delete(fetching, domain)
			fetchLock.Unlock()
		}()

		iconStr, err := fetchFavicon(domain)
		if err != nil {
			log.Printf("triggerAsyncFetch: error fetching favicon for %s: %v", domain, err)
		}
		SetInCache(domain, FaviconCacheItem{Data: iconStr, LastFetched: time.Now()})
	}()
}

func fetchFavicon(domain string) (string, error) {
	// Create a context that times out after 5 seconds.