reaper/reaper.go
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package reaper
import (
"log"
"sort"
"sync"
"time"
"git.j3s.sh/vore/rss"
"git.j3s.sh/vore/sqlite"
)
type Reaper struct {
// internal list of all rss feeds where the map
// key represents the url of the feed (which should be unique)
feeds map[string]*rss.Feed
db *sqlite.DB
}
func New(db *sqlite.DB) *Reaper {
r := &Reaper{
feeds: make(map[string]*rss.Feed),
db: db,
}
go r.start()
return r
}
// Start initializes the reaper by populating a list of feeds from the database
// and periodically refreshes all feeds every 15 minutes, if the feeds are
// stale.
// reaper should only ever be started once (in New)
func (r *Reaper) start() {
urls := r.db.GetAllFeedURLs()
for _, url := range urls {
// Setting UpdateURL lets us defer fetching
feed := &rss.Feed{
UpdateURL: url,
}
r.feeds[url] = feed
}
for {
log.Println("reaper start: refresh all feeds")
r.refreshAllFeeds()
log.Println("reaper end: completed all feeds, sleeping")
time.Sleep(15 * time.Minute)
}
}
// Add the given rss feed to Reaper for maintenance.
func (r *Reaper) addFeed(f *rss.Feed) {
r.feeds[f.UpdateURL] = f
}
// UpdateAll fetches every feed & attempts updating them
// asynchronously, then prints the duration of the sync
func (r *Reaper) refreshAllFeeds() {
ch := make(chan *rss.Feed)
var wg sync.WaitGroup
for i := 20; i > 0; i-- {
wg.Add(1)
go func() {
defer wg.Done()
for f := range ch {
start := time.Now()
log.Printf("refreshing %s\n", f.UpdateURL)
r.refreshFeed(f)
log.Printf("%s refreshed in %s\n", f.UpdateURL, time.Since(start))
}
}()
}
for i := range r.feeds {
if r.feeds[i].Stale() {
ch <- r.feeds[i]
}
}
close(ch)
wg.Wait()
}
// refreshFeed triggers a fetch on the given feed,
// and sets a fetch error in the db if there is one.
func (r *Reaper) refreshFeed(f *rss.Feed) {
err := f.Update()
if err != nil {
r.handleFeedFetchFailure(f.UpdateURL, err)
}
}
func (r *Reaper) handleFeedFetchFailure(url string, err error) {
log.Printf("[err] reaper: fetch failure '%s': %s\n", url, err)
err = r.db.SetFeedFetchError(url, err.Error())
if err != nil {
log.Printf("[err] reaper: could not set feed fetch error '%s'\n", err)
}
}
// HasFeed checks whether a given url is represented
// in the reaper cache.
func (r *Reaper) HasFeed(url string) bool {
if _, ok := r.feeds[url]; ok {
return true
}
return false
}
func (r *Reaper) GetFeed(url string) *rss.Feed {
return r.feeds[url]
}
// GetUserFeeds returns a list of feeds
func (r *Reaper) GetUserFeeds(username string) []*rss.Feed {
urls := r.db.GetUserFeedURLs(username)
var result []*rss.Feed
for _, u := range urls {
// feeds in the db are guaranteed to be in reaper
result = append(result, r.feeds[u])
}
r.SortFeeds(result)
return result
}
func (r *Reaper) SortFeeds(f []*rss.Feed) {
sort.Slice(f, func(i, j int) bool {
return f[i].UpdateURL < f[j].UpdateURL
})
}
func (r *Reaper) SortFeedItemsByDate(feeds []*rss.Feed) []*rss.Item {
var posts []*rss.Item
for _, f := range feeds {
for _, i := range f.Items {
posts = append(posts, i)
}
}
sort.Slice(posts, func(i, j int) bool {
return posts[i].Date.After(posts[j].Date)
})
return posts
}
// Fetch attempts to fetch a feed from a given url, marshal
// it into a feed object, and manage it via reaper.
func (r *Reaper) Fetch(url string) error {
feed, err := rss.Fetch(url)
if err != nil {
return err
}
r.addFeed(feed)
return nil
}