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()) }