collectors: summarize limbo channel balances to avoid stuck values

This commit changes how we collect limbo balances to calculate summaries
instead of separate series by channel, peer, status etc. Having just the
summaries makes it possible to correctly select the last known total
value which was previously not feasible when summarizing over longer
periods due to values with channel/peer specific labels getting "stuck".

collectors/channels_collector.go

@@ -75,12 +75,12 @@ func NewChannelsCollector(lnd lndclient.LightningClient, errChan chan<- error,
 		pendingForceCloseBalanceDesc: prometheus.NewDesc(
 			"lnd_channels_pending_force_close_balance_sat",
 			"force closed channel balances in satoshis",
-			append(labels, "blocks_until_maturity"), nil,
+			[]string{"status"}, nil,
 		),
 		waitingCloseBalanceDesc: prometheus.NewDesc(
 			"lnd_channels_waiting_close_balance_sat",
 			"waiting to close channel balances in satoshis",
-			labels, nil,
+			nil, nil,
 		),
 		incomingChanSatDesc: prometheus.NewDesc(
 			"lnd_channels_bandwidth_incoming_sat",
@@ -408,32 +408,33 @@ func (c *ChannelsCollector) Collect(ch chan<- prometheus.Metric) {
 		"waiting_close",
 	)
 
+	// Preinitialize the map with all possible anchor state labels to avoid
+	// "stuck" values when selecting a longer time range.
+	forceCloseTotal := map[string]btcutil.Amount{
+		anchorStateToString(lndclient.ForceCloseAnchorStateLimbo):     0,
+		anchorStateToString(lndclient.ForceCloseAnchorStateRecovered): 0,
+		anchorStateToString(lndclient.ForceCloseAnchorStateLost):      0,
+	}
 	for _, forceClose := range pendingChannelsResp.PendingForceClose {
-		// Labels are: "chan_id", "status", "initiator", "peer",
-		// "blocks_until_maturity". We'll use status to hold the anchor
-		// state.
+		forceCloseTotal[anchorStateToString(forceClose.AnchorState)] +=
+			forceClose.RecoveredBalance
+	}
+
+	for anchorState, balance := range forceCloseTotal {
 		ch <- prometheus.MustNewConstMetric(
 			c.pendingForceCloseBalanceDesc, prometheus.GaugeValue,
-			float64(forceClose.RecoveredBalance),
-			forceClose.ChannelPoint.String(),
-			anchorStateToString(forceClose.AnchorState),
-			forceClose.ChannelInitiator.String(),
-			forceClose.PubKeyBytes.String(),
-			fmt.Sprintf("%d", forceClose.BlocksUntilMaturity),
+			float64(balance), anchorState,
 		)
 	}
 
+	var waitingClosetotal btcutil.Amount
 	for _, waitingClose := range pendingChannelsResp.WaitingClose {
-		// Labels are: "chan_id", "status", "initiator", "peer".
-		ch <- prometheus.MustNewConstMetric(
-			c.waitingCloseBalanceDesc, prometheus.GaugeValue,
-			float64(waitingClose.LocalBalance),
-			waitingClose.ChannelPoint.String(),
-			waitingClose.ChanStatusFlags,
-			waitingClose.ChannelInitiator.String(),
-			waitingClose.PubKeyBytes.String(),
-		)
+		waitingClosetotal += waitingClose.LocalBalance
 	}
+	ch <- prometheus.MustNewConstMetric(
+		c.waitingCloseBalanceDesc, prometheus.GaugeValue,
+		float64(waitingClosetotal),
+	)
 
 	// Get the list of closed channels.
 	closedChannelsResp, err := c.lnd.ClosedChannels(context.Background())