172 lines
3.6 KiB
Go
172 lines
3.6 KiB
Go
package runners
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import (
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"context"
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"runtime"
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"sync"
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)
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// WorkerFunc represents a function processable by a worker in WorkerPool. Note
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// that implementations absolutely MUST check whether passed context is <-ctx.Done()
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// otherwise stopping the pool may block indefinitely.
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type WorkerFunc func(context.Context)
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// WorkerPool provides a means of enqueuing asynchronous work.
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type WorkerPool struct {
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fns chan WorkerFunc
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svc Service
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}
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// Start will start the main WorkerPool management loop in a new goroutine, along
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// with requested number of child worker goroutines. Returns false if already running.
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func (pool *WorkerPool) Start(workers int, queue int) bool {
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// Attempt to start the svc
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ctx, ok := pool.svc.doStart()
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if !ok {
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return false
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}
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if workers < 1 {
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// Use $GOMAXPROCS as default worker count
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workers = runtime.GOMAXPROCS(0)
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}
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if queue < 0 {
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// Set a reasonable queue default
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queue = workers * 2
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}
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// Allocate pool queue of given size
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fns := make(chan WorkerFunc, queue)
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pool.fns = fns
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go func() {
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defer func() {
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// unlock single wait
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pool.svc.wait.Unlock()
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// ensure stopped
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pool.svc.Stop()
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}()
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var wait sync.WaitGroup
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// Start goroutine worker functions
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for i := 0; i < workers; i++ {
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go func() {
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// Trigger start / stop
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wait.Add(1)
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defer wait.Done()
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// Keep workers running on panic
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for !workerstart(ctx, fns) {
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}
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}()
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}
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// Set GC finalizer to stop pool on dealloc
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runtime.SetFinalizer(pool, func(pool *WorkerPool) {
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pool.svc.Stop()
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})
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// Wait on ctx
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<-ctx.Done()
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// Stop all workers
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close(pool.fns)
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wait.Wait()
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}()
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return true
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}
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// workerstart is the main worker runner routine, accepting functions from 'fns' until it is closed.
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func workerstart(ctx context.Context, fns <-chan WorkerFunc) bool {
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// Recover and drop any panic
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defer func() { recover() }()
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for {
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// Wait on next func
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fn, ok := <-fns
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if !ok {
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return true
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}
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// Run with ctx
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fn(ctx)
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}
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}
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// Stop will stop the WorkerPool management loop, blocking until stopped.
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func (pool *WorkerPool) Stop() bool {
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return pool.svc.Stop()
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}
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// Enqueue will add provided WorkerFunc to the queue to be performed when there is a free worker.
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// This will block until function is queued or pool is stopped. In all cases, the WorkerFunc will be
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// executed, with the state of the pool being indicated by <-ctx.Done() of the passed ctx.
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// WorkerFuncs MUST respect the passed context.
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func (pool *WorkerPool) Enqueue(fn WorkerFunc) {
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// Check valid fn
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if fn == nil {
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return
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}
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select {
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// Pool ctx cancelled
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case <-pool.svc.Done():
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fn(closedctx)
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// Placed fn in queue
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case pool.fns <- fn:
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}
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}
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// EnqueueCtx is functionally identical to WorkerPool.Enqueue() but returns early in the
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// case that caller provided <-ctx.Done() is closed, WITHOUT running the WorkerFunc.
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func (pool *WorkerPool) EnqueueCtx(ctx context.Context, fn WorkerFunc) {
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// Check valid fn
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if fn == nil {
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return
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}
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select {
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// Caller ctx cancelled
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case <-ctx.Done():
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// Pool ctx cancelled
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case <-pool.svc.Done():
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fn(closedctx)
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// Placed fn in queue
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case pool.fns <- fn:
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}
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}
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// EnqueueNow attempts Enqueue but returns false if not executed.
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func (pool *WorkerPool) EnqueueNow(fn WorkerFunc) bool {
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// Check valid fn
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if fn == nil {
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return false
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}
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select {
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// Pool ctx cancelled
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case <-pool.svc.Done():
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return false
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// Placed fn in queue
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case pool.fns <- fn:
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return true
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// Queue is full
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default:
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return false
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}
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}
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// Queue returns the number of currently queued WorkerFuncs.
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func (pool *WorkerPool) Queue() int {
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return len(pool.fns)
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}
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