Move utilitarian/generic packages to utils: lastfm, spotify, gravatar, cache, and pool

utils/pool/pool.go

@@ -0,0 +1,90 @@
+package pool
+
+import (
+	"time"
+
+	"github.com/navidrome/navidrome/log"
+)
+
+type Executor func(workload interface{})
+
+type Pool struct {
+	name    string
+	workers []worker
+	exec    Executor
+	queue   chan work // receives jobs to send to workers
+	done    chan bool // when receives bool stops workers
+	working bool
+}
+
+// TODO This hardcoded value will go away when the queue is persisted in disk
+const bufferSize = 10000
+
+func NewPool(name string, workerCount int, exec Executor) (*Pool, error) {
+	p := &Pool{
+		name:    name,
+		exec:    exec,
+		queue:   make(chan work, bufferSize),
+		done:    make(chan bool),
+		working: false,
+	}
+
+	for i := 0; i < workerCount; i++ {
+		worker := worker{
+			p:  p,
+			id: i,
+		}
+		worker.Start()
+		p.workers = append(p.workers, worker)
+	}
+
+	go func() {
+		ticker := time.NewTicker(10 * time.Second)
+		defer ticker.Stop()
+		for {
+			select {
+			case <-ticker.C:
+				if len(p.queue) > 0 {
+					log.Debug("Queue status", "poolName", p.name, "items", len(p.queue))
+				} else {
+					if p.working {
+						log.Info("Queue is empty, all items processed", "poolName", p.name)
+					}
+					p.working = false
+				}
+			case <-p.done:
+				close(p.queue)
+				return
+			}
+		}
+	}()
+
+	return p, nil
+}
+
+func (p *Pool) Submit(workload interface{}) {
+	p.working = true
+	p.queue <- work{workload}
+}
+
+func (p *Pool) Stop() {
+	p.done <- true
+}
+
+type work struct {
+	workload interface{}
+}
+
+type worker struct {
+	id int
+	p  *Pool
+}
+
+// start worker
+func (w *worker) Start() {
+	go func() {
+		for job := range w.p.queue {
+			w.p.exec(job.workload) // do work
+		}
+	}()
+}