Merge pull request #1228 from halseth/fee-estimation-rpc

Fee estimation RPC

Author: Roasbeef

cmd/lncli/commands.go

@@ -144,6 +144,52 @@ func newAddress(ctx *cli.Context) error {
 	return nil
 }
 
+var estimateFeeCommand = cli.Command{
+	Name:      "estimatefee",
+	Category:  "On-chain",
+	Usage:     "Get fee estimates for sending bitcoin on-chain to multiple addresses.",
+	ArgsUsage: "send-json-string [--conf_target=N]",
+	Description: `
+	Get fee estimates for sending a transaction paying the specified amount(s) to the passed address(es).
+
+	The send-json-string' param decodes addresses and the amount to send respectively in the following format:
+
+	    '{"ExampleAddr": NumCoinsInSatoshis, "SecondAddr": NumCoins}'
+	`,
+	Flags: []cli.Flag{
+		cli.Int64Flag{
+			Name: "conf_target",
+			Usage: "(optional) the number of blocks that the transaction *should* " +
+				"confirm in",
+		},
+	},
+	Action: actionDecorator(estimateFees),
+}
+
+func estimateFees(ctx *cli.Context) error {
+	var amountToAddr map[string]int64
+
+	jsonMap := ctx.Args().First()
+	if err := json.Unmarshal([]byte(jsonMap), &amountToAddr); err != nil {
+		return err
+	}
+
+	ctxb := context.Background()
+	client, cleanUp := getClient(ctx)
+	defer cleanUp()
+
+	resp, err := client.EstimateFee(ctxb, &lnrpc.EstimateFeeRequest{
+		AddrToAmount: amountToAddr,
+		TargetConf:   int32(ctx.Int64("conf_target")),
+	})
+	if err != nil {
+		return err
+	}
+
+	printRespJSON(resp)
+	return nil
+}
+
 var sendCoinsCommand = cli.Command{
 	Name:      "sendcoins",
 	Category:  "On-chain",

cmd/lncli/main.go

@@ -257,6 +257,7 @@ func main() {
 		unlockCommand,
 		changePasswordCommand,
 		newAddressCommand,
+		estimateFeeCommand,
 		sendManyCommand,
 		sendCoinsCommand,
 		listUnspentCommand,

lnrpc/rpc.pb.go

@@ -220,6 +220,16 @@ service Lightning {
         };
     }
 
+    /** lncli: `estimatefee`
+    EstimateFee asks the chain backend to estimate the fee rate and total fees
+    for a transaction that pays to multiple specified outputs.
+    */
+    rpc EstimateFee (EstimateFeeRequest) returns (EstimateFeeResponse) {
+        option (google.api.http) = {
+            get: "/v1/transactions/fee"
+        };
+    }
+
     /** lncli: `sendcoins`
     SendCoins executes a request to send coins to a particular address. Unlike
     SendMany, this RPC call only allows creating a single output at a time. If
@@ -839,6 +849,22 @@ message LightningAddress {
     string host = 2 [json_name = "host"];
 }
 
+message EstimateFeeRequest {
+    /// The map from addresses to amounts for the transaction.
+    map<string, int64> AddrToAmount = 1;
+
+    /// The target number of blocks that this transaction should be confirmed by.
+    int32 target_conf = 2;
+}
+
+message EstimateFeeResponse {
+    /// The total fee in satoshis.
+    int64 fee_sat = 1 [json_name = "fee_sat"];
+
+    /// The fee rate in satoshi/byte.
+    int64 feerate_sat_per_byte = 2 [json_name = "feerate_sat_per_byte"];
+}
+
 message SendManyRequest {
     /// The map from addresses to amounts
     map<string, int64> AddrToAmount = 1;

lnrpc/rpc.pb.gw.go

@@ -1044,6 +1044,33 @@
         ]
       }
     },
+    "/v1/transactions/fee": {
+      "get": {
+        "summary": "* lncli: `estimatefee`\nEstimateFee asks the chain backend to estimate the fee rate and total fees\nfor a transaction that pays to multiple specified outputs.",
+        "operationId": "EstimateFee",
+        "responses": {
+          "200": {
+            "description": "",
+            "schema": {
+              "$ref": "#/definitions/lnrpcEstimateFeeResponse"
+            }
+          }
+        },
+        "parameters": [
+          {
+            "name": "target_conf",
+            "description": "/ The target number of blocks that this transaction should be confirmed by.",
+            "in": "query",
+            "required": false,
+            "type": "integer",
+            "format": "int32"
+          }
+        ],
+        "tags": [
+          "Lightning"
+        ]
+      }
+    },
     "/v1/unlockwallet": {
       "post": {
         "summary": "* lncli: `unlock`\nUnlockWallet is used at startup of lnd to provide a password to unlock\nthe wallet database.",
@@ -1747,6 +1774,21 @@
     "lnrpcDisconnectPeerResponse": {
       "type": "object"
     },
+    "lnrpcEstimateFeeResponse": {
+      "type": "object",
+      "properties": {
+        "fee_sat": {
+          "type": "string",
+          "format": "int64",
+          "description": "/ The total fee in satoshis."
+        },
+        "feerate_sat_per_byte": {
+          "type": "string",
+          "format": "int64",
+          "description": "/ The fee rate in satoshi/byte."
+        }
+      }
+    },
     "lnrpcFeeLimit": {
       "type": "object",
       "properties": {

lnrpc/rpc.proto

@@ -17,6 +17,8 @@ import (
 	"github.com/btcsuite/btcwallet/chain"
 	"github.com/btcsuite/btcwallet/waddrmgr"
 	base "github.com/btcsuite/btcwallet/wallet"
+	"github.com/btcsuite/btcwallet/wallet/txauthor"
+	"github.com/btcsuite/btcwallet/wallet/txrules"
 	"github.com/btcsuite/btcwallet/walletdb"
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
@@ -297,9 +299,45 @@ func (b *BtcWallet) SendOutputs(outputs []*wire.TxOut,
 	// SendOutputs.
 	feeSatPerKB := btcutil.Amount(feeRate.FeePerKVByte())
 
+	// Sanity check outputs.
+	if len(outputs) < 1 {
+		return nil, lnwallet.ErrNoOutputs
+	}
 	return b.wallet.SendOutputs(outputs, defaultAccount, 1, feeSatPerKB)
 }
 
+// CreateSimpleTx creates a Bitcoin transaction paying to the specified
+// outputs. The transaction is not broadcasted to the network, but a new change
+// address might be created in the wallet database. In the case the wallet has
+// insufficient funds, or the outputs are non-standard, an error should be
+// returned. This method also takes the target fee expressed in sat/kw that
+// should be used when crafting the transaction.
+//
+// NOTE: The dryRun argument can be set true to create a tx that doesn't alter
+// the database. A tx created with this set to true SHOULD NOT be broadcasted.
+//
+// This is a part of the WalletController interface.
+func (b *BtcWallet) CreateSimpleTx(outputs []*wire.TxOut,
+	feeRate lnwallet.SatPerKWeight, dryRun bool) (*txauthor.AuthoredTx, error) {
+
+	// The fee rate is passed in using units of sat/kw, so we'll convert
+	// this to sat/KB as the CreateSimpleTx method requires this unit.
+	feeSatPerKB := btcutil.Amount(feeRate.FeePerKVByte())
+
+	// Sanity check outputs.
+	if len(outputs) < 1 {
+		return nil, lnwallet.ErrNoOutputs
+	}
+	for _, output := range outputs {
+		err := txrules.CheckOutput(output, feeSatPerKB)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return b.wallet.CreateSimpleTx(defaultAccount, outputs, 1, feeSatPerKB, dryRun)
+}
+
 // LockOutpoint marks an outpoint as locked meaning it will no longer be deemed
 // as eligible for coin selection. Locking outputs are utilized in order to
 // avoid race conditions when selecting inputs for usage when funding a

lnrpc/rpc.swagger.json

@@ -9,6 +9,7 @@ import (
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
+	"github.com/btcsuite/btcwallet/wallet/txauthor"
 	"github.com/lightningnetwork/lnd/lntypes"
 )
 
@@ -48,6 +49,10 @@ var (
 	ErrNotMine = errors.New("the passed output doesn't belong to the wallet")
 )
 
+// ErrNoOutputs is returned if we try to create a transaction with no outputs
+// or send coins to a set of outputs that is empty.
+var ErrNoOutputs = errors.New("no outputs")
+
 // Utxo is an unspent output denoted by its outpoint, and output value of the
 // original output.
 type Utxo struct {
@@ -169,6 +174,19 @@ type WalletController interface {
 	SendOutputs(outputs []*wire.TxOut,
 		feeRate SatPerKWeight) (*wire.MsgTx, error)
 
+	// CreateSimpleTx creates a Bitcoin transaction paying to the specified
+	// outputs. The transaction is not broadcasted to the network. In the
+	// case the wallet has insufficient funds, or the outputs are
+	// non-standard, an error should be returned. This method also takes
+	// the target fee expressed in sat/kw that should be used when crafting
+	// the transaction.
+	//
+	// NOTE: The dryRun argument can be set true to create a tx that
+	// doesn't alter the database. A tx created with this set to true
+	// SHOULD NOT be broadcasted.
+	CreateSimpleTx(outputs []*wire.TxOut, feeRate SatPerKWeight,
+		dryRun bool) (*txauthor.AuthoredTx, error)
+
 	// ListUnspentWitness returns all unspent outputs which are version 0
 	// witness programs. The 'minconfirms' and 'maxconfirms' parameters
 	// indicate the minimum and maximum number of confirmations an output