sweepbatcher: fix race conditions in UseLogger

Author: starius

sweepbatcher/greedy_batch_selection.go

@@ -92,8 +92,8 @@ func (b *Batcher) greedyAddSweep(ctx context.Context, sweep *sweep) error {
 			return nil
 		}
 
-		log.Debugf("Batch selection algorithm returned batch id %d for"+
-			" sweep %x, but acceptance failed.", batchId,
+		log().Debugf("Batch selection algorithm returned batch id %d "+
+			"for sweep %x, but acceptance failed.", batchId,
 			sweep.swapHash[:6])
 	}
 

sweepbatcher/log.go

@@ -2,15 +2,21 @@ package sweepbatcher
 
 import (
 	"fmt"
+	"sync/atomic"
 
 	"github.com/btcsuite/btclog"
 	"github.com/lightningnetwork/lnd/build"
 )
 
-// log is a logger that is initialized with no output filters. This
+// log_ is a logger that is initialized with no output filters. This
 // means the package will not perform any logging by default until the
 // caller requests it.
-var log btclog.Logger
+var log_ atomic.Pointer[btclog.Logger]
+
+// log returns active logger.
+func log() btclog.Logger {
+	return *log_.Load()
+}
 
 // The default amount of logging is none.
 func init() {
@@ -20,12 +26,12 @@ func init() {
 // batchPrefixLogger returns a logger that prefixes all log messages with
 // the ID.
 func batchPrefixLogger(batchID string) btclog.Logger {
-	return build.NewPrefixLog(fmt.Sprintf("[Batch %s]", batchID), log)
+	return build.NewPrefixLog(fmt.Sprintf("[Batch %s]", batchID), log())
 }
 
 // UseLogger uses a specified Logger to output package logging info.
 // This should be used in preference to SetLogWriter if the caller is also
 // using btclog.
 func UseLogger(logger btclog.Logger) {
-	log = logger
+	log_.Store(&logger)
 }

sweepbatcher/sweep_batcher.go

@@ -535,13 +535,15 @@ func (b *Batcher) Run(ctx context.Context) error {
 		case sweepReq := <-b.sweepReqs:
 			sweep, err := b.fetchSweep(runCtx, sweepReq)
 			if err != nil {
-				log.Warnf("fetchSweep failed: %v.", err)
+				log().Warnf("fetchSweep failed: %v.", err)
+
 				return err
 			}
 
 			err = b.handleSweep(runCtx, sweep, sweepReq.Notifier)
 			if err != nil {
-				log.Warnf("handleSweep failed: %v.", err)
+				log().Warnf("handleSweep failed: %v.", err)
+
 				return err
 			}
 
@@ -550,11 +552,13 @@ func (b *Batcher) Run(ctx context.Context) error {
 			close(testReq.quit)
 
 		case err := <-b.errChan:
-			log.Warnf("Batcher received an error: %v.", err)
+			log().Warnf("Batcher received an error: %v.", err)
+
 			return err
 
 		case <-runCtx.Done():
-			log.Infof("Stopping Batcher: run context cancelled.")
+			log().Infof("Stopping Batcher: run context cancelled.")
+
 			return runCtx.Err()
 		}
 	}
@@ -614,8 +618,8 @@ func (b *Batcher) handleSweep(ctx context.Context, sweep *sweep,
 		return err
 	}
 
-	log.Infof("Batcher handling sweep %x, completed=%v", sweep.swapHash[:6],
-		completed)
+	log().Infof("Batcher handling sweep %x, completed=%v",
+		sweep.swapHash[:6], completed)
 
 	// If the sweep has already been completed in a confirmed batch then we
 	// can't attach its notifier to the batch as that is no longer running.
@@ -626,8 +630,8 @@ func (b *Batcher) handleSweep(ctx context.Context, sweep *sweep,
 		// on-chain confirmations to prevent issues caused by reorgs.
 		parentBatch, err := b.store.GetParentBatch(ctx, sweep.swapHash)
 		if err != nil {
-			log.Errorf("unable to get parent batch for sweep %x: "+
-				"%v", sweep.swapHash[:6], err)
+			log().Errorf("unable to get parent batch for sweep %x:"+
+				" %v", sweep.swapHash[:6], err)
 
 			return err
 		}
@@ -679,8 +683,8 @@ func (b *Batcher) handleSweep(ctx context.Context, sweep *sweep,
 		return nil
 	}
 
-	log.Warnf("Greedy batch selection algorithm failed for sweep %x: %v. "+
-		"Falling back to old approach.", sweep.swapHash[:6], err)
+	log().Warnf("Greedy batch selection algorithm failed for sweep %x: %v."+
+		" Falling back to old approach.", sweep.swapHash[:6], err)
 
 	// If one of the batches accepts the sweep, we provide it to that batch.
 	for _, batch := range b.batches {
@@ -785,13 +789,13 @@ func (b *Batcher) spinUpBatchFromDB(ctx context.Context, batch *batch) error {
 	}
 
 	if len(dbSweeps) == 0 {
-		log.Infof("skipping restored batch %d as it has no sweeps",
+		log().Infof("skipping restored batch %d as it has no sweeps",
 			batch.id)
 
 		// It is safe to drop this empty batch as it has no sweeps.
 		err := b.store.DropBatch(ctx, batch.id)
 		if err != nil {
-			log.Warnf("unable to drop empty batch %d: %v",
+			log().Warnf("unable to drop empty batch %d: %v",
 				batch.id, err)
 		}
 
@@ -933,7 +937,7 @@ func (b *Batcher) monitorSpendAndNotify(ctx context.Context, sweep *sweep,
 	b.wg.Add(1)
 	go func() {
 		defer b.wg.Done()
-		log.Infof("Batcher monitoring spend for swap %x",
+		log().Infof("Batcher monitoring spend for swap %x",
 			sweep.swapHash[:6])
 
 		for {
@@ -1112,7 +1116,7 @@ func (b *Batcher) loadSweep(ctx context.Context, swapHash lntypes.Hash,
 		}
 	} else {
 		if s.ConfTarget == 0 {
-			log.Warnf("Fee estimation was requested for zero "+
+			log().Warnf("Fee estimation was requested for zero "+
 				"confTarget for sweep %x.", swapHash[:6])
 		}
 		minFeeRate, err = b.wallet.EstimateFeeRate(ctx, s.ConfTarget)

sweepbatcher/sweep_batcher_test.go

@@ -1373,7 +1373,7 @@ func testMaxSweepsPerBatch(t *testing.T, store testStore,
 	batcherStore testBatcherStore) {
 
 	// Disable logging, because this test is very noisy.
-	oldLogger := log
+	oldLogger := log()
 	UseLogger(build.NewSubLogger("SWEEP", nil))
 	defer UseLogger(oldLogger)