Detect broken HTLC links at startup #757
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If we have stopped eclair while it was forwarding HTLCs, it is possible that we are in a state were an incoming HTLC was committed by both sides, but we didn't have time to send and/or sign the corresponding HTLC to the downstream node. In that case, if we do nothing, the incoming HTLC will eventually expire and we won't lose money, but the channel will get closed, which is a major inconvenience. This check will detect this and will allow us to fast-fail HTLCs and thus preserve channels.
sstone
reviewed
Dec 3, 2018
| .collect { case r: Relayed => r } | ||
| .toSet | ||
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| val htlcs_broken = htlcs_in.filterNot(htlc_in => relayed_out.exists(r => r.originChannelId == htlc_in.channelId && r.originHtlcId == htlc_in.id)) |
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What happens for direct payments that we've received ? there is no corresponding Relayed origin so they will be considered broken ?
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| val brokenHtlcs = checkBrokenHtlcsLink(channels) | ||
| val brokenHtlcKiller = context.actorOf(Props[HtlcReaper], name = "htlc-reaper") | ||
| brokenHtlcKiller ! brokenHtlcs |
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Since broken HTLCs are known when we create the reaper actor, why not pass them to its constructor ?
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Because they would never be garbage collected.
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It would also be a bit more efficient not to create the reaper actor if the list is empty
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I did it, but I don't really like that kind of branching that early in the code.
Also, the fact that the reaper's state is never cleaned up is not great.
sstone
previously approved these changes
Jan 3, 2019
sstone
approved these changes
Jan 4, 2019
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If we have stopped eclair while it was forwarding HTLCs, it is possible
that we are in a state were an incoming HTLC
was committed by both sides, but we didn't have time to send
and/or sign the corresponding HTLC to the downstream node.
In that case, if we do nothing, the incoming HTLC will
eventually expire and we won't lose money, but the channel
will get closed, which is a major inconvenience.
This check will detect this and will allow us
to fast-fail HTLCs and thus preserve channels.