forked from mirrors/gotosocial
160 lines
3.6 KiB
Go
160 lines
3.6 KiB
Go
package runners
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import (
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"context"
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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 Done()
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// otherwise stopping the pool may block for large periods of time.
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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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queue chan WorkerFunc
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free chan struct{}
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wait sync.WaitGroup
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svc Service
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}
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// NewWorkerPool returns a new WorkerPool with provided worker count and WorkerFunc queue size.
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// The number of workers represents how many WorkerFuncs can be executed simultaneously, and the
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// queue size represents the max number of WorkerFuncs that can be queued at any one time.
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func NewWorkerPool(workers int, queue int) WorkerPool {
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return WorkerPool{
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queue: make(chan WorkerFunc, queue),
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free: make(chan struct{}, workers),
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}
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}
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// Start will attempt to start the worker pool, asynchronously. Return is success state.
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func (pool *WorkerPool) Start() bool {
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ok := true
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done := make(chan struct{})
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go func() {
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ok = pool.svc.Run(func(ctx context.Context) {
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close(done)
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pool.process(ctx)
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})
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if !ok {
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close(done)
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}
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}()
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<-done
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return ok
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}
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// Stop will attempt to stop the worker pool, this will block until stopped. Return is success state.
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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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// Running returns whether the worker pool is running.
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func (pool *WorkerPool) Running() bool {
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return pool.svc.Running()
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}
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// execute will take a queued function and pass it to a free worker when available.
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func (pool *WorkerPool) execute(ctx context.Context, fn WorkerFunc) {
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// Set as running
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pool.wait.Add(1)
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select {
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// Pool context cancelled
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case <-ctx.Done():
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pool.wait.Done()
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// Free worker acquired
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case pool.free <- struct{}{}:
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}
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go func() {
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defer func() {
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// defer in case panic
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<-pool.free
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pool.wait.Done()
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}()
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// Run queued
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fn(ctx)
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}()
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}
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// process is the background processing routine that passes queued functions to workers.
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func (pool *WorkerPool) process(ctx context.Context) {
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for {
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select {
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// Pool context cancelled
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case <-ctx.Done():
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for {
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select {
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// Pop and execute queued
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case fn := <-pool.queue:
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fn(ctx) // ctx is closed
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// Empty, wait for workers
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default:
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pool.wait.Wait()
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return
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}
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}
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// Queued func received
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case fn := <-pool.queue:
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pool.execute(ctx, fn)
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}
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}
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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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// Note that 'fn' will ALWAYS be executed, and the supplied context will specify whether this 'fn'
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// is being executed during normal pool execution, or if the pool has been stopped with <-ctx.Done().
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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 context cancelled
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case <-pool.svc.Done():
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// Placed fn in queue
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case pool.queue <- fn:
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}
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}
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// EnqueueNoBlock performs Enqueue but returns false if queue size is at max. Else, true.
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func (pool *WorkerPool) EnqueueNoBlock(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 context 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.queue <- 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.queue)
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}
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// Workers returns the number of currently active workers.
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func (pool *WorkerPool) Workers() int {
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return len(pool.free)
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}
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