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package loop
import (
"context"
"fmt"
"sync"
"sync/atomic"
"time"
"github.com/lightninglabs/lndclient"
"github.com/lightninglabs/loop/loopdb"
"github.com/lightninglabs/loop/sweep"
"github.com/lightningnetwork/lnd/queue"
)
// executorConfig contains executor configuration data.
type executorConfig struct {
lnd *lndclient.LndServices
sweeper *sweep.Sweeper
store loopdb.SwapStore
createExpiryTimer func(expiry time.Duration) <-chan time.Time
loopOutMaxParts uint32
}
// executor is responsible for executing swaps.
//
// TODO(roasbeef): rename to SubSwapper
type executor struct {
wg sync.WaitGroup
newSwaps chan genericSwap
currentHeight uint32
ready chan struct{}
executorConfig
}
// newExecutor returns a new swap executor instance.
func newExecutor(cfg *executorConfig) *executor {
return &executor{
executorConfig: *cfg,
newSwaps: make(chan genericSwap),
ready: make(chan struct{}),
}
}
// run starts the executor event loop. It accepts and executes new swaps,
// providing them with required config data.
func (s *executor) run(mainCtx context.Context,
statusChan chan<- SwapInfo) error {
blockEpochChan, blockErrorChan, err :=
s.lnd.ChainNotifier.RegisterBlockEpochNtfn(mainCtx)
if err != nil {
return err
}
// Before starting, make sure we have an up to date block height.
// Otherwise we might reveal a preimage for a swap that is already
// expired.
log.Infof("Wait for first block ntfn")
var height int32
setHeight := func(h int32) {
height = h
atomic.StoreUint32(&s.currentHeight, uint32(h))
}
select {
case h := <-blockEpochChan:
setHeight(h)
case err := <-blockErrorChan:
return err
case <-mainCtx.Done():
return mainCtx.Err()
}
// Start main event loop.
log.Infof("Starting event loop at height %v", height)
// Signal that executor being ready with an up to date block height.
close(s.ready)
// Use a map to administer the individual notification queues for the
// swaps.
blockEpochQueues := make(map[int]*queue.ConcurrentQueue)
// On exit, stop all queue goroutines.
defer func() {
for _, queue := range blockEpochQueues {
queue.Stop()
}
}()
swapDoneChan := make(chan int)
nextSwapID := 0
for {
select {
case newSwap := <-s.newSwaps:
queue := queue.NewConcurrentQueue(10)
queue.Start()
swapID := nextSwapID
blockEpochQueues[swapID] = queue
s.wg.Add(1)
go func() {
defer s.wg.Done()
newSwap.execute(mainCtx, &executeConfig{
statusChan: statusChan,
sweeper: s.sweeper,
blockEpochChan: queue.ChanOut(),
timerFactory: s.executorConfig.createExpiryTimer,
loopOutMaxParts: s.executorConfig.loopOutMaxParts,
}, height)
select {
case swapDoneChan <- swapID:
case <-mainCtx.Done():
}
}()
nextSwapID++
case doneID := <-swapDoneChan:
queue, ok := blockEpochQueues[doneID]
if !ok {
return fmt.Errorf(
"swap id %v not found in queues",
doneID)
}
queue.Stop()
delete(blockEpochQueues, doneID)
case h := <-blockEpochChan:
setHeight(h)
for _, queue := range blockEpochQueues {
select {
case queue.ChanIn() <- h:
case <-mainCtx.Done():
return mainCtx.Err()
}
}
case err := <-blockErrorChan:
return fmt.Errorf("block error: %v", err)
case <-mainCtx.Done():
return mainCtx.Err()
}
}
}
// initiateSwap delivers a new swap to the executor main loop.
func (s *executor) initiateSwap(ctx context.Context,
swap genericSwap) {
select {
case s.newSwaps <- swap:
case <-ctx.Done():
return
}
}
// height returns the current height known to the swap server.
func (s *executor) height() int32 {
return int32(atomic.LoadUint32(&s.currentHeight))
}
// waitFinished waits for all swap goroutines to finish.
func (s *executor) waitFinished() {
s.wg.Wait()
}