lnwallet: add no cache option to web api estimator

chainregistry.go

@@ -257,6 +257,7 @@ func newChainControlFromConfig(cfg *Config, localDB, remoteDB *channeldb.DB,
 				chainfee.SparseConfFeeSource{
 					URL: cfg.NeutrinoMode.FeeURL,
 				},
+				false,
 			)
 
 			if err := estimator.Start(); err != nil {

lnwallet/chainfee/estimator.go

@@ -540,16 +540,21 @@ type WebAPIEstimator struct {
 	feesMtx          sync.Mutex
 	feeByBlockTarget map[uint32]uint32
 
+	// noCache determines whether the web estimator should cache fee
+	// estimates.
+	noCache bool
+
 	quit chan struct{}
 	wg   sync.WaitGroup
 }
 
 // NewWebAPIEstimator creates a new WebAPIEstimator from a given URL and a
 // fallback default fee. The fees are updated whenever a new block is mined.
-func NewWebAPIEstimator(api WebAPIFeeSource) *WebAPIEstimator {
+func NewWebAPIEstimator(api WebAPIFeeSource, noCache bool) *WebAPIEstimator {
 	return &WebAPIEstimator{
 		apiSource:        api,
 		feeByBlockTarget: make(map[uint32]uint32),
+		noCache:          noCache,
 		quit:             make(chan struct{}),
 	}
 }
@@ -566,6 +571,11 @@ func (w *WebAPIEstimator) EstimateFeePerKW(numBlocks uint32) (SatPerKWeight, err
 			"accepted is %v", numBlocks, minBlockTarget)
 	}
 
+	// Get fee estimates now if we don't refresh periodically.
+	if w.noCache {
+		w.updateFeeEstimates()
+	}
+
 	feePerKb, err := w.getCachedFee(numBlocks)
 	if err != nil {
 		return 0, err
@@ -589,6 +599,11 @@ func (w *WebAPIEstimator) EstimateFeePerKW(numBlocks uint32) (SatPerKWeight, err
 //
 // NOTE: This method is part of the Estimator interface.
 func (w *WebAPIEstimator) Start() error {
+	// No update loop is needed when we don't cache.
+	if w.noCache {
+		return nil
+	}
+
 	var err error
 	w.started.Do(func() {
 		log.Infof("Starting web API fee estimator")
@@ -608,6 +623,11 @@ func (w *WebAPIEstimator) Start() error {
 //
 // NOTE: This method is part of the Estimator interface.
 func (w *WebAPIEstimator) Stop() error {
+	// Update loop is not running when we don't cache.
+	if w.noCache {
+		return nil
+	}
+
 	w.stopped.Do(func() {
 		log.Infof("Stopping web API fee estimator")
 

lnwallet/chainfee/estimator_test.go

@@ -192,7 +192,7 @@ func TestWebAPIFeeEstimator(t *testing.T) {
 		fees: testFees,
 	}
 
-	estimator := NewWebAPIEstimator(feeSource)
+	estimator := NewWebAPIEstimator(feeSource, false)
 
 	// Test that requesting a fee when no fees have been cached fails.
 	_, err := estimator.EstimateFeePerKW(5)