Notify node operator on low fee bumping reserve (#2104)

With anchor outputs, we need to keep utxos available for fee bumping. Having enough on-chain funds to claim HTLCs in case channels force-close is necessary to guarantee funds safety. There is no perfect formula to estimate how much we should reserve: it depends on the feerate when the channels force-close, the number of impacted HTLCs and their amount. We use a very rough estimation, to avoid needlessly spamming node operators while still notifying them when the situation becomes risky.
ACINQ · Dec 14, 2021 · 4ebc8b5 · 4ebc8b5
1 parent 535daec
commit 4ebc8b5
Show file tree

Hide file tree

Showing 4 changed files with 35 additions and 31 deletions.
diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/balance/BalanceActor.scala b/eclair-core/src/main/scala/fr/acinq/eclair/balance/BalanceActor.scala
@@ -3,7 +3,7 @@ package fr.acinq.eclair.balance
 import akka.actor.typed.eventstream.EventStream
 import akka.actor.typed.scaladsl.{ActorContext, Behaviors}
 import akka.actor.typed.{ActorRef, Behavior}
-import fr.acinq.bitcoin.{ByteVector32, MilliBtcDouble}
+import fr.acinq.bitcoin.{ByteVector32, SatoshiLong}
 import fr.acinq.eclair.NotificationsLogger
 import fr.acinq.eclair.NotificationsLogger.NotifyNodeOperator
 import fr.acinq.eclair.balance.BalanceActor._
@@ -27,7 +27,7 @@ object BalanceActor {
   private final case object TickBalance extends Command
   final case class GetGlobalBalance(replyTo: ActorRef[Try[GlobalBalance]], channels: Map[ByteVector32, HasCommitments]) extends Command
   private final case class WrappedChannels(wrapped: ChannelsListener.GetChannelsResponse) extends Command
-  private final case class WrappedGlobalBalance(wrapped: Try[GlobalBalance]) extends Command
+  private final case class WrappedGlobalBalanceWithChannels(wrapped: Try[GlobalBalance], channelsCount: Int) extends Command
   private final case class WrappedUtxoInfo(wrapped: Try[UtxoInfo]) extends Command
   // @formatter:on
 
@@ -79,15 +79,27 @@ private class BalanceActor(context: ActorContext[Command],
       context.pipeToSelf(checkUtxos(bitcoinClient))(WrappedUtxoInfo)
       Behaviors.same
     case WrappedChannels(res) =>
-      context.pipeToSelf(CheckBalance.computeGlobalBalance(res.channels, db, bitcoinClient))(WrappedGlobalBalance)
+      val channelsCount = res.channels.size
+      context.pipeToSelf(CheckBalance.computeGlobalBalance(res.channels, db, bitcoinClient))(b => WrappedGlobalBalanceWithChannels(b, channelsCount))
       Behaviors.same
-    case WrappedGlobalBalance(res) =>
+    case WrappedGlobalBalanceWithChannels(res, channelsCount) =>
       res match {
         case Success(result) =>
           log.info("current balance: total={} onchain.confirmed={} onchain.unconfirmed={} offchain={}", result.total.toDouble, result.onChain.confirmed.toDouble, result.onChain.unconfirmed.toDouble, result.offChain.total.toDouble)
-          log.debug("current balance details : {}", result)
-          if (result.onChain.confirmed < 1.millibtc) {
-            context.system.eventStream ! EventStream.Publish(NotifyNodeOperator(NotificationsLogger.Warning, s"on-chain confirmed balance is low (${result.onChain.confirmed.toMilliBtc}), eclair may not be able to guarantee funds safety in case channels force-close: you should add some utxos to your bitcoin wallet"))
+          log.debug("current balance details: {}", result)
+          // This is a very rough estimation of the fee we would need to pay for a force-close with 5 pending HTLCs at 100 sat/byte.
+          val perChannelFeeBumpingReserve = 50_000.sat
+          // Instead of scaling this linearly with the number of channels we have, we use sqrt(channelsCount) to reflect
+          // the fact that if you have channels with many peers, only a subset of these peers will likely be malicious.
+          val estimatedFeeBumpingReserve = perChannelFeeBumpingReserve * Math.sqrt(channelsCount)
+          if (result.onChain.confirmed < estimatedFeeBumpingReserve) {
+            val message =
+              s"""On-chain confirmed balance is low (${result.onChain.confirmed.toMilliBtc}): eclair may not be able to guarantee funds safety in case channels force-close.
+                 |You have $channelsCount channels, which could cost $estimatedFeeBumpingReserve in fees if some of these channels are malicious.
+                 |Please note that the value above is a very arbitrary estimation: the real cost depends on the feerate and the number of malicious channels.
+                 |You should add more utxos to your bitcoin wallet to guarantee funds safety.
+                 |""".stripMargin
+            context.system.eventStream ! EventStream.Publish(NotifyNodeOperator(NotificationsLogger.Warning, message))
           }
           Metrics.GlobalBalance.withoutTags().update(result.total.toMilliBtc.toDouble)
           Metrics.GlobalBalanceDetailed.withTag(Tags.BalanceType, Tags.BalanceTypes.OnchainConfirmed).update(result.onChain.confirmed.toMilliBtc.toDouble)

diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/balance/CheckBalance.scala b/eclair-core/src/main/scala/fr/acinq/eclair/balance/CheckBalance.scala
@@ -289,7 +289,7 @@ object CheckBalance {
     }
   } yield CorrectedOnChainBalance(detailed.confirmed, detailed.unconfirmed)
 
-  case class GlobalBalance (onChain: CorrectedOnChainBalance, offChain: OffChainBalance) {
+  case class GlobalBalance(onChain: CorrectedOnChainBalance, offChain: OffChainBalance) {
     val total: Btc = onChain.total + offChain.total
   }
 

diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/json/JsonSerializers.scala b/eclair-core/src/main/scala/fr/acinq/eclair/json/JsonSerializers.scala
@@ -19,7 +19,7 @@ package fr.acinq.eclair.json
 import com.google.common.net.HostAndPort
 import fr.acinq.bitcoin.Crypto.{PrivateKey, PublicKey}
 import fr.acinq.bitcoin.{Btc, ByteVector32, ByteVector64, OutPoint, Satoshi, Transaction}
-import fr.acinq.eclair.balance.CheckBalance.GlobalBalance
+import fr.acinq.eclair.balance.CheckBalance.{CorrectedOnChainBalance, GlobalBalance, OffChainBalance}
 import fr.acinq.eclair.blockchain.fee.FeeratePerKw
 import fr.acinq.eclair.channel._
 import fr.acinq.eclair.crypto.Sphinx.RouteBlinding.BlindedRoute
@@ -399,22 +399,15 @@ object OriginSerializer extends MinimalSerializer({
   })
 })
 
-object GlobalBalanceSerializer extends MinimalSerializer({
-  case o: GlobalBalance =>
-    val formats = DefaultFormats + ByteVector32KeySerializer + BtcSerializer + SatoshiSerializer
-    JObject(JField("total", JDecimal(o.total.toDouble))) merge Extraction.decompose(o)(formats)
-})
-
 // @formatter:off
+private case class GlobalBalanceJson(total: Btc, onChain: CorrectedOnChainBalance, offChain: OffChainBalance)
+object GlobalBalanceSerializer extends ConvertClassSerializer[GlobalBalance](b => GlobalBalanceJson(b.total, b.onChain, b.offChain))
+
 private case class PeerInfoJson(nodeId: PublicKey, state: String, address: Option[InetSocketAddress], channels: Int)
 object PeerInfoSerializer extends ConvertClassSerializer[Peer.PeerInfo](peerInfo => PeerInfoJson(peerInfo.nodeId, peerInfo.state.toString, peerInfo.address, peerInfo.channels))
-// @formatter:on
 
-// @formatter:off
 private[json] case class MessageReceivedJson(pathId: Option[ByteVector], replyPath: Option[BlindedRoute], unknownTlvs: Map[String, ByteVector])
-object OnionMessageReceivedSerializer extends ConvertClassSerializer[OnionMessages.ReceiveMessage]({ m: OnionMessages.ReceiveMessage =>
-  MessageReceivedJson(m.pathId, m.finalPayload.replyPath.map(_.blindedRoute), m.finalPayload.records.unknown.map(tlv => (tlv.tag.toString -> tlv.value)).toMap)
-})
+object OnionMessageReceivedSerializer extends ConvertClassSerializer[OnionMessages.ReceiveMessage](m => MessageReceivedJson(m.pathId, m.finalPayload.replyPath.map(_.blindedRoute), m.finalPayload.records.unknown.map(tlv => tlv.tag.toString -> tlv.value).toMap))
 // @formatter:on
 
 case class CustomTypeHints(custom: Map[Class[_], String]) extends TypeHints {
@@ -524,6 +517,7 @@ object JsonSerializers {
     PaymentRequestSerializer +
     JavaUUIDSerializer +
     OriginSerializer +
+    ByteVector32KeySerializer +
     GlobalBalanceSerializer +
     PeerInfoSerializer +
     PaymentFailedSummarySerializer +

diff --git a/eclair-core/src/test/scala/fr/acinq/eclair/json/JsonSerializersSpec.scala b/eclair-core/src/test/scala/fr/acinq/eclair/json/JsonSerializersSpec.scala
@@ -22,7 +22,7 @@ import fr.acinq.bitcoin.{Btc, ByteVector32, OutPoint, Satoshi, SatoshiLong, Tran
 import fr.acinq.eclair._
 import fr.acinq.eclair.balance.CheckBalance
 import fr.acinq.eclair.balance.CheckBalance.{ClosingBalance, GlobalBalance, MainAndHtlcBalance, PossiblyPublishedMainAndHtlcBalance, PossiblyPublishedMainBalance}
-import fr.acinq.eclair.channel.{CMD_UPDATE_RELAY_FEE, CommandResponse, CommandUnavailableInThisState, Origin, RES_FAILURE, RES_SUCCESS}
+import fr.acinq.eclair.channel._
 import fr.acinq.eclair.io.Peer
 import fr.acinq.eclair.io.Peer.PeerInfo
 import fr.acinq.eclair.payment.{PaymentRequest, PaymentSettlingOnChain}
@@ -185,16 +185,14 @@ class JsonSerializersSpec extends AnyFunSuite with Matchers {
       offChain = CheckBalance.OffChainBalance(normal = MainAndHtlcBalance(
         toLocal = Btc(0.2),
         htlcs = Btc(0.05)
-      ),
-        closing = ClosingBalance(
-          localCloseBalance = PossiblyPublishedMainAndHtlcBalance(
-            toLocal = Map(ByteVector32(hex"4d176ad844c363bed59edf81962b008faa6194c3b3757ffcd26ba60f95716db2") -> Btc(0.1)),
-            htlcs = Map(ByteVector32(hex"94b70cec5a98d67d17c6e3de5c7697f8a6cab4f698df91e633ce35efa3574d71") -> Btc(0.03), ByteVector32(hex"a844edd41ce8503864f3c95d89d850b177a09d7d35e950a7d27c14abb63adb13") -> Btc(0.06)),
-            htlcsUnpublished = Btc(0.01)),
-          mutualCloseBalance = PossiblyPublishedMainBalance(
-            toLocal = Map(ByteVector32(hex"7e3b012534afe0bb8d1f2f09c724b1a10a813ce704e5b9c217ccfdffffff0247") -> Btc(0.1)))
-        )
-      )
+      ), closing = ClosingBalance(
+        localCloseBalance = PossiblyPublishedMainAndHtlcBalance(
+          toLocal = Map(ByteVector32(hex"4d176ad844c363bed59edf81962b008faa6194c3b3757ffcd26ba60f95716db2") -> Btc(0.1)),
+          htlcs = Map(ByteVector32(hex"94b70cec5a98d67d17c6e3de5c7697f8a6cab4f698df91e633ce35efa3574d71") -> Btc(0.03), ByteVector32(hex"a844edd41ce8503864f3c95d89d850b177a09d7d35e950a7d27c14abb63adb13") -> Btc(0.06)),
+          htlcsUnpublished = Btc(0.01)),
+        mutualCloseBalance = PossiblyPublishedMainBalance(
+          toLocal = Map(ByteVector32(hex"7e3b012534afe0bb8d1f2f09c724b1a10a813ce704e5b9c217ccfdffffff0247") -> Btc(0.1)))
+      ))
     )
     JsonSerializers.serialization.write(gb)(JsonSerializers.formats) shouldBe """{"total":1.0,"onChain":{"confirmed":0.4,"unconfirmed":0.05},"offChain":{"waitForFundingConfirmed":0.0,"waitForFundingLocked":0.0,"normal":{"toLocal":0.2,"htlcs":0.05},"shutdown":{"toLocal":0.0,"htlcs":0.0},"negotiating":0.0,"closing":{"localCloseBalance":{"toLocal":{"4d176ad844c363bed59edf81962b008faa6194c3b3757ffcd26ba60f95716db2":0.1},"htlcs":{"94b70cec5a98d67d17c6e3de5c7697f8a6cab4f698df91e633ce35efa3574d71":0.03,"a844edd41ce8503864f3c95d89d850b177a09d7d35e950a7d27c14abb63adb13":0.06},"htlcsUnpublished":0.01},"remoteCloseBalance":{"toLocal":{},"htlcs":{},"htlcsUnpublished":0.0},"mutualCloseBalance":{"toLocal":{"7e3b012534afe0bb8d1f2f09c724b1a10a813ce704e5b9c217ccfdffffff0247":0.1}},"unknownCloseBalance":{"toLocal":0.0,"htlcs":0.0}},"waitForPublishFutureCommitment":0.0}}"""
   }