In this commit, we fix an existing bug that could cause lnd to crash if
we sent a payment, and the *destination* sent a temp channel failure
error message. When handling such a message, we’ll look in the nextHop
map to see which channel was *after* the node that sent the payment.
However, if the destination sends this error, then there’ll be no entry
in this map.
To address this case, we now add a prevHop map. If we attempt to lookup
a node in the nextHop map, and they don’t have an entry, then we’ll
consult the prevHop map.
We also update the set of tests to ensure that we’re properly setting
both the prevHop map and the nextHop map.
In this commit, we modify the pruning semantics of the missionControl
struct. Before this commit, on each payment attempt, we would fetch a
new graph pruned view each time. This served to instantly propagate any
detected failures to all outstanding payment attempts. However, this
meant that we could at times get stuck in a retry loop if sends take a
few second, then we may prune an edge, try another, then the original
edge is now unpruned.
To remedy this, we now introduce the concept of a paymentSession. The
session will start out as a snapshot of the latest graph prune view.
Any payment failures are now reported directly to the paymentSession
rather than missionControl. The rationale for this is that
edges/vertexes pruned as result of failures will never decay for a
local payment session, only for the global prune view. With this in
place, we ensure that our set of prune view only grows for a session.
Fixes#536.
For Part 1 of Issue #275. Create isolated private struct in
networkHandler goroutine that will de-duplicate
announcements added to the batch. The struct contains maps
for each of channel announcements, channel updates, and
node announcements to keep track of unique announcements.
The struct has a Reset method to reset stored announcements, an
AddMsg(lnwire.Message) method to add a new message to the current
batch, and a Batch method to return the set of de-duplicated
announcements.
Also fix a few minor typos.
In this commit, from the PoV of the SendPayment method we now delegate
all path finding+verification to missionControl. This change doesn’t
materially affect anything, it simply expands the abstraction to make
way for future features that more heavily utilize mission control.
This commit adds a new system within the ChannelRouter: missionControl.
The purpose of this system to is to act as a shared memory of sorts
between payment sending attempts, recording which edges/vertexes word
or didn’t work. Allowing execution attempts to pass on their iterative
knowledge of the graph to later attempts will reduce the number of
failures encountered, and generally lead to a better UX when sending
payments.
The current capabilities of missionControl are rather limited just to
introduce the new abstraction. Later follow up commits will also add
preferential treatment for reliable nodes, knowledge the impact that
target payments have on unbalancing the payment graph, etc.
Olaoluwa Osuntokun
practicalswift
Laura Cressman