channels.md•11.4 kB
# Channel Management
## Overview
This guide covers Lightning channel lifecycle management using LDK, including opening, monitoring, and closing channels.
## Channel Opening
### Basic Channel Opening
```swift
import LightningDevKit
class ChannelOpener {
let channelManager: Bindings.ChannelManager
let peerManager: Bindings.PeerManager
func openChannel(
nodeId: [UInt8],
channelValue: UInt64,
pushMsat: UInt64 = 0,
isPublic: Bool = false
) async throws -> [UInt8; 32] {
// Create user channel ID
let userChannelId = try generateUserChannelId()
// Configure channel
let channelConfig = Bindings.ChannelConfig()
channelConfig.setMaxDustHtlcExposure(
.feeRateMultiplier(multiplier: 5000)
)
channelConfig.setForceCloseAvoidanceMaxFeeSatoshis(1000)
// Open channel
let result = channelManager.createChannel(
theirNetworkKey: nodeId,
channelValueSatoshis: channelValue,
pushMsat: pushMsat,
userChannelId: userChannelId,
overrideConfig: channelConfig
)
switch result {
case .ok(let temporaryChannelId):
return temporaryChannelId
case .err(let error):
throw ChannelError.openFailed(error)
}
}
}
```
### Batch Channel Opening
```swift
class BatchChannelOpener {
func openMultipleChannels(_ requests: [ChannelRequest]) async throws {
// Group by target fee rate
let groupedRequests = Dictionary(grouping: requests) { $0.targetFeeRate }
for (feeRate, channels) in groupedRequests {
// Create batch funding transaction
let fundingTx = try await createBatchFundingTransaction(
channels: channels,
feeRate: feeRate
)
// Open all channels in batch
for channel in channels {
try await openChannelWithFunding(
channel: channel,
fundingTx: fundingTx
)
}
}
}
}
```
## Channel Monitoring
### Real-time Channel Status
```swift
class ChannelMonitor {
let channelManager: Bindings.ChannelManager
func getChannelStatus() -> [ChannelInfo] {
let channels = channelManager.listChannels()
return channels.map { details in
ChannelInfo(
channelId: details.getChannelId(),
counterpartyNodeId: details.getCounterparty().getNodeId(),
channelValueSats: details.getChannelValueSatoshis(),
balanceMsat: details.getBalanceMsat(),
inboundCapacityMsat: details.getInboundCapacityMsat(),
outboundCapacityMsat: details.getOutboundCapacityMsat(),
isUsable: details.getIsUsable(),
isPublic: details.getIsPublic(),
state: parseChannelState(details)
)
}
}
func parseChannelState(_ details: Bindings.ChannelDetails) -> ChannelState {
if !details.getIsChannelReady() {
return .pending
} else if details.getIsUsable() {
return .active
} else {
return .inactive
}
}
}
```
### Channel Health Monitoring
```swift
class ChannelHealthMonitor {
struct ChannelHealth {
let channelId: [UInt8; 32]
let healthScore: Double
let issues: [HealthIssue]
}
func assessChannelHealth(_ channel: ChannelDetails) -> ChannelHealth {
var issues: [HealthIssue] = []
var score = 1.0
// Check liquidity balance
let totalCapacity = channel.getChannelValueSatoshis() * 1000 // to msat
let outboundRatio = Double(channel.getOutboundCapacityMsat()) / Double(totalCapacity)
if outboundRatio < 0.1 {
issues.append(.lowOutboundLiquidity)
score -= 0.3
} else if outboundRatio > 0.9 {
issues.append(.lowInboundLiquidity)
score -= 0.3
}
// Check channel age and activity
if let lastActivity = getLastChannelActivity(channel.getChannelId()) {
let daysSinceActivity = Date().timeIntervalSince(lastActivity) / 86400
if daysSinceActivity > 30 {
issues.append(.inactive)
score -= 0.2
}
}
// Check fee rates
if let feeRate = channel.getConfig()?.getForwardingFeeBaseMsat() {
if feeRate > marketAverageFee * 2 {
issues.append(.highFees)
score -= 0.1
}
}
return ChannelHealth(
channelId: channel.getChannelId()!,
healthScore: max(0, score),
issues: issues
)
}
}
```
## Channel Operations
### Fee Management
```swift
class ChannelFeeManager {
func updateChannelFees(
channelId: [UInt8; 32],
baseFee: UInt32,
proportionalFee: UInt32
) throws {
let config = Bindings.ChannelConfig()
config.setForwardingFeeBaseMsat(baseFee)
config.setForwardingFeeProportionalMillionths(proportionalFee)
let result = channelManager.updateChannelConfig(
counterpartyNodeId: getCounterpartyForChannel(channelId),
channelIds: [channelId],
config: config
)
guard result.isOk() else {
throw ChannelError.feeUpdateFailed
}
}
// Dynamic fee adjustment based on channel usage
func optimizeFees() {
for channel in channelManager.listChannels() {
let usage = calculateChannelUsage(channel)
let optimalFees = calculateOptimalFees(
usage: usage,
capacity: channel.getChannelValueSatoshis(),
marketConditions: getCurrentMarketConditions()
)
try? updateChannelFees(
channelId: channel.getChannelId()!,
baseFee: optimalFees.base,
proportionalFee: optimalFees.proportional
)
}
}
}
```
### Channel Rebalancing
```swift
class ChannelRebalancer {
func rebalanceChannels(
from: [UInt8; 32],
to: [UInt8; 32],
amountMsat: UInt64
) async throws {
// Create circular payment to rebalance
let invoice = try await createRebalanceInvoice(
amountMsat: amountMsat,
targetChannel: to
)
// Route payment through specific channel
let routeParams = Bindings.RouteParameters(
paymentParamsArg: paymentParams,
finalValueMsatArg: amountMsat,
maxTotalRoutingFeeMsatArg: amountMsat / 100 // 1% max fee
)
// Force first hop through source channel
let firstHop = getFirstHopForChannel(from)
let route = try router.findRouteWithFirstHop(
firstHop: firstHop,
routeParams: routeParams
)
// Send payment
try await sendPaymentAlongRoute(route: route, invoice: invoice)
}
}
```
## Channel Closing
### Cooperative Close
```swift
class ChannelCloser {
func closeChannelCooperatively(
channelId: [UInt8; 32],
targetFeeSatsPerVbyte: UInt32? = nil
) throws {
let result = channelManager.closeChannel(
channelId: channelId,
counterpartyNodeId: getCounterpartyForChannel(channelId),
targetFeeSatoshisPerVirtualByte: targetFeeSatsPerVbyte
)
switch result {
case .ok:
Logger.info("Initiated cooperative close for channel \(channelId.toHex())")
case .err(let error):
throw ChannelError.closeFailed(error)
}
}
}
```
### Force Close
```swift
extension ChannelCloser {
func forceCloseChannel(
channelId: [UInt8; 32],
broadcastImmediately: Bool = true
) throws {
let result = channelManager.forceCloseBroadcastingLatestTxn(
channelId: channelId,
counterpartyNodeId: getCounterpartyForChannel(channelId)
)
switch result {
case .ok:
Logger.warning("Force closed channel \(channelId.toHex())")
if broadcastImmediately {
try broadcastPendingTransactions()
}
case .err(let error):
throw ChannelError.forceCloseFailed(error)
}
}
// Monitor force close resolution
func monitorForceClose(channelId: [UInt8; 32]) {
let monitor = chainMonitor.getMonitor(channelId)
monitor.onEvent = { event in
switch event {
case .commitmentTxConfirmed(let height):
Logger.info("Commitment tx confirmed at height \(height)")
case .htlcResolved(let htlcId, let amount):
Logger.info("HTLC \(htlcId) resolved for \(amount) sats")
case .fundsRecovered(let amount):
Logger.info("Recovered \(amount) sats from force close")
notifyUserFundsRecovered(amount)
}
}
}
}
```
## Advanced Channel Features
### Splicing Support
```swift
class ChannelSplicer {
func spliceIn(
channelId: [UInt8; 32],
additionalSats: UInt64
) async throws {
// Check if peer supports splicing
let peerFeatures = getPeerFeatures(channelId)
guard peerFeatures.supportsChannelSplicing() else {
throw ChannelError.splicingNotSupported
}
// Initiate splice
let spliceRequest = Bindings.SpliceRequest(
channelId: channelId,
satsDelta: Int64(additionalSats),
feerate: getCurrentFeeRate()
)
try await performSplice(spliceRequest)
}
}
```
### Zero-Conf Channels
```swift
class ZeroConfChannelManager {
func acceptZeroConfChannel(
temporaryChannelId: [UInt8; 32],
counterparty: [UInt8]
) -> Bool {
// Check if we trust this peer for zero-conf
let trustLevel = evaluatePeerTrust(counterparty)
guard trustLevel >= .high else {
return false
}
// Check channel size is within acceptable range
let channelValue = getProposedChannelValue(temporaryChannelId)
guard channelValue <= maxZeroConfChannelSize else {
return false
}
// Accept zero-conf
channelManager.acceptInboundChannelFromTrustedPeer(
temporaryChannelId: temporaryChannelId,
counterpartyNodeId: counterparty,
userChannelId: generateUserChannelId()
)
return true
}
}
```
## Best Practices
1. **Channel Sizing**: Open channels with sufficient capacity for expected payment volume
2. **Peer Selection**: Choose well-connected, reliable peers
3. **Fee Management**: Regularly adjust fees based on channel usage
4. **Liquidity Management**: Maintain balanced channels for routing
5. **Monitoring**: Set up alerts for channel issues
6. **Backup**: Always backup channel state after changes
7. **Security**: Validate all channel operations
8. **Documentation**: Keep records of all channel events