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// Copyright (C) 2019-2024 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
package execpool
import (
"context"
"sync"
)
// A backlog for an execution pool. The typical usage of this is to
// create non-blocking queue which would get executed once the execution pool is ready to accept new
// tasks.
type backlog struct {
pool ExecutionPool
wg sync.WaitGroup
buffer chan backlogItemTask
ctx context.Context
ctxCancel context.CancelFunc
owner interface{}
priority Priority
}
type backlogItemTask struct {
enqueuedTask
priority Priority
}
// BacklogPool supports all the ExecutionPool functions plus few more that tests the pending tasks.
type BacklogPool interface {
ExecutionPool
EnqueueBacklog(enqueueCtx context.Context, t ExecFunc, arg interface{}, out chan interface{}) error
BufferSize() (length, capacity int)
}
// MakeBacklog creates a backlog
func MakeBacklog(execPool ExecutionPool, backlogSize int, priority Priority, owner interface{}) BacklogPool {
if backlogSize < 0 {
return nil
}
bl := &backlog{
pool: execPool,
owner: owner,
priority: priority,
}
bl.ctx, bl.ctxCancel = context.WithCancel(context.Background())
if bl.pool == nil {
// create one internally.
bl.pool = MakePool(bl)
}
if backlogSize == 0 {
// use the number of cpus in the system.
backlogSize = bl.pool.GetParallelism()
}
bl.buffer = make(chan backlogItemTask, backlogSize)
bl.wg.Add(1)
go bl.worker()
return bl
}
func (b *backlog) GetParallelism() int {
return b.pool.GetParallelism()
}
// Enqueue enqueues a single task into the backlog
func (b *backlog) Enqueue(enqueueCtx context.Context, t ExecFunc, arg interface{}, priority Priority, out chan interface{}) error {
select {
case b.buffer <- backlogItemTask{
enqueuedTask: enqueuedTask{
execFunc: t,
arg: arg,
out: out,
},
priority: priority,
}:
return nil
case <-enqueueCtx.Done():
return enqueueCtx.Err()
case <-b.ctx.Done():
return b.ctx.Err()
}
}
// BufferSize returns the length and the capacity of the buffer
func (b *backlog) BufferSize() (length, capacity int) {
return len(b.buffer), cap(b.buffer)
}
// Enqueue enqueues a single task into the backlog
func (b *backlog) EnqueueBacklog(enqueueCtx context.Context, t ExecFunc, arg interface{}, out chan interface{}) error {
select {
case b.buffer <- backlogItemTask{
enqueuedTask: enqueuedTask{
execFunc: t,
arg: arg,
out: out,
},
priority: b.priority,
}:
return nil
case <-enqueueCtx.Done():
return enqueueCtx.Err()
case <-b.ctx.Done():
return b.ctx.Err()
}
}
// Shutdown shuts down the backlog.
func (b *backlog) Shutdown() {
b.ctxCancel()
// NOTE: Do not close(b.buffer) because there's no good way to ensure Enqueue*() won't write to it and panic. Just let it be garbage collected.
b.wg.Wait()
if b.pool.GetOwner() == b {
b.pool.Shutdown()
}
}
func (b *backlog) worker() {
var t backlogItemTask
var ok bool
defer b.wg.Done()
for {
select {
case t, ok = <-b.buffer:
case <-b.ctx.Done():
return
}
if !ok {
return
}
if b.pool.Enqueue(b.ctx, t.execFunc, t.arg, t.priority, t.out) != nil {
break
}
}
}
func (b *backlog) GetOwner() interface{} {
return b.owner
}
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