Monorepo for Tangled
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import ( "context" "errors"
"tangled.org/core/spindle/models")
var ErrNoWorkflowSlots = errors.New("no workflow slots available")
type WorkflowSlot interface { Release()}
// governs blocking behaviour when acquiring a slottype AcquireMode int
const ( // blocks until a slot is free Wait AcquireMode = iota // fails immediately if full // executors use this because the mill owns the backlog NoWait)
type WorkflowSlotter interface { AcquireWorkflowSlot(ctx context.Context, wid models.WorkflowId, wf *models.Workflow, mode AcquireMode) (WorkflowSlot, error)}
type releaseFunc func()
func (f releaseFunc) Release() { if f != nil { f() }}
type NoopSlot struct{}
func (NoopSlot) Release() {}
// limit by concurrent workflow counttype SemaphoreSlotter struct { slots chan struct{}}
func NewSemaphoreSlotter(maxConcurrent int) *SemaphoreSlotter { if maxConcurrent <= 0 { return &SemaphoreSlotter{} } return &SemaphoreSlotter{slots: make(chan struct{}, maxConcurrent)}}
func (a *SemaphoreSlotter) AcquireWorkflowSlot(ctx context.Context, wid models.WorkflowId, wf *models.Workflow, mode AcquireMode) (WorkflowSlot, error) { if a == nil || a.slots == nil { return NoopSlot{}, nil } if mode == NoWait { select { case a.slots <- struct{}{}: return releaseFunc(func() { <-a.slots }), nil default: return nil, ErrNoWorkflowSlots } } select { case a.slots <- struct{}{}: return releaseFunc(func() { <-a.slots }), nil case <-ctx.Done(): return nil, ctx.Err() }}