lntest: use web fee estimator in itests

lntest/fee_service.go

@@ -0,0 +1,106 @@
+package lntest
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"sync"
+
+	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
+)
+
+const (
+	// feeServiceTarget is the confirmation target for which a fee estimate
+	// is returned. Requests for higher confirmation targets will fall back
+	// to this.
+	feeServiceTarget = 2
+
+	// feeServicePort is the tcp port on which the service runs.
+	feeServicePort = 16534
+)
+
+// feeService runs a web service that provides fee estimation information.
+type feeService struct {
+	feeEstimates
+
+	srv *http.Server
+	wg  sync.WaitGroup
+
+	url string
+
+	lock sync.Mutex
+}
+
+// feeEstimates contains the current fee estimates.
+type feeEstimates struct {
+	Fees map[uint32]uint32 `json:"fee_by_block_target"`
+}
+
+// startFeeService spins up a go-routine to serve fee estimates.
+func startFeeService() *feeService {
+	f := feeService{
+		url: fmt.Sprintf(
+			"http://localhost:%v/fee-estimates.json", feeServicePort,
+		),
+	}
+
+	// Initialize default fee estimate.
+	f.Fees = map[uint32]uint32{feeServiceTarget: 50000}
+
+	listenAddr := fmt.Sprintf(":%v", feeServicePort)
+	f.srv = &http.Server{
+		Addr: listenAddr,
+	}
+
+	http.HandleFunc("/fee-estimates.json", f.handleRequest)
+
+	f.wg.Add(1)
+	go func() {
+		defer f.wg.Done()
+
+		if err := f.srv.ListenAndServe(); err != http.ErrServerClosed {
+			fmt.Printf("error: cannot start fee api: %v", err)
+		}
+	}()
+
+	return &f
+}
+
+// handleRequest handles a client request for fee estimates.
+func (f *feeService) handleRequest(w http.ResponseWriter, r *http.Request) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
+	bytes, err := json.Marshal(f.feeEstimates)
+	if err != nil {
+		fmt.Printf("error: cannot serialize "+
+			"estimates: %v", err)
+
+		return
+	}
+
+	_, err = io.WriteString(w, string(bytes))
+	if err != nil {
+		fmt.Printf("error: cannot send estimates: %v",
+			err)
+	}
+}
+
+// stop stops the web server.
+func (f *feeService) stop() {
+	if err := f.srv.Shutdown(context.Background()); err != nil {
+		fmt.Printf("error: cannot stop fee api: %v", err)
+	}
+
+	f.wg.Wait()
+}
+
+// setFee changes the current fee estimate for the fixed confirmation target.
+func (f *feeService) setFee(fee chainfee.SatPerKWeight) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
+	f.Fees[feeServiceTarget] = uint32(fee.FeePerKVByte())
+}