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Monorepo for Tangled
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Go
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import ( "slices" "sync"
"github.com/bluesky-social/indigo/atproto/syntax")
type Job struct { Run func() error OnFail func(error)}
type ownedJob struct { owner syntax.DID job Job}
// prefers users with fewer running jobs, otherwise it's FIFOtype Queue struct { mu sync.Mutex cond *sync.Cond queue []ownedJob running map[syntax.DID]int maxSize int workers int stopped bool wg sync.WaitGroup}
func NewQueue(queueSize, numWorkers int) *Queue { q := &Queue{ maxSize: queueSize, workers: numWorkers, running: make(map[syntax.DID]int), } q.cond = sync.NewCond(&q.mu) return q}
// todo(dawn): add a per-user cap so a single user can't fill the queuefunc (q *Queue) Enqueue(owner syntax.DID, job Job) bool { q.mu.Lock() defer q.mu.Unlock() if q.stopped || len(q.queue) >= q.maxSize { return false } q.queue = append(q.queue, ownedJob{owner: owner, job: job}) q.cond.Signal() return true}
func (q *Queue) Start() { for range q.workers { q.wg.Add(1) go q.worker() }}
func (q *Queue) worker() { defer q.wg.Done() for { picked, ok := q.takeNext() if !ok { return }
err := picked.job.Run() if err != nil && picked.job.OnFail != nil { picked.job.OnFail(err) }
q.finish(picked.owner) }}
// get or wait for the next jobfunc (q *Queue) takeNext() (ownedJob, bool) { q.mu.Lock() defer q.mu.Unlock()
for len(q.queue) == 0 && !q.stopped { q.cond.Wait() // waiting for jobs } if q.stopped && len(q.queue) == 0 { return ownedJob{}, false // no jobs are left and the queue is stopped }
idx := q.pickBest() picked := q.queue[idx] q.queue = slices.Delete(q.queue, idx, idx+1) q.running[picked.owner]++
return picked, true}
// index of the queued job whose owner has the fewest currently-running jobs,// tiebreaking by arrival order.func (q *Queue) pickBest() int { best := 0 for idx, job := range q.queue { if q.running[job.owner] < q.running[q.queue[best].owner] { best = idx } } return best}
// called when finishing a jobfunc (q *Queue) finish(owner syntax.DID) { q.mu.Lock() defer q.mu.Unlock()
q.running[owner]-- if q.running[owner] <= 0 { delete(q.running, owner) }}
func (q *Queue) Stop() { q.mu.Lock() q.stopped = true q.cond.Broadcast() q.mu.Unlock() q.wg.Wait()}