lnd.xprv/lntest/fee_service.go

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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
)
// 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 {
port := nextAvailablePort()
f := feeService{
url: fmt.Sprintf("http://localhost:%v/fee-estimates.json", port),
}
// Initialize default fee estimate.
f.Fees = map[uint32]uint32{feeServiceTarget: 50000}
listenAddr := fmt.Sprintf(":%v", port)
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())
}