This commit partially reverts bf27d05a.
To avoid creating multiple database transactions during a single path
finding operation, we create an explicit transaction when the cached
graph is instantiated.
We cache the source node to avoid needing to look that up for every path
finding session.
The database transaction will be nil in case of the in-memory graph.
To further separate the channel graph from the channel state, we
refactor the AddrsForNode method to use the graphs's public methods
instead of directly accessing any buckets. This makes sure that we can
have the channel state cached with just its buckets while not using a
kvdb level cache for the graph.
At the same time we refactor the graph's test to also be less dependent
upon the channel state DB.
This commit overhauls the routing package significantly to simplify the
code, conform to the rest of the coding style within the package, and
observe the new authenticated gossiping scheme outlined in BOLT07.
As a major step towards a more realistic path finding algorithm, fees
are properly calculated and observed during path finding. If a path has
sufficient capacity _before_ fees are applied, but afterwards the
finalized route would exceed the capacity of a single link, the route
is marked as invalid.
Currently a naive weighting algorithm is used which only factors in the
time-lock delta at each hop, thereby optimizing for the lowest time
lock. Fee calculation also isn’t finalized since we aren’t yet using
milli-satoshi throughout the daemon. The final TODO item within the PR
is to properly perform a multi-path search and rank the results based
on a summation heuristic rather than just return the first (out of
many) route found.
On the server side, once nodes are initially connected to the daemon,
our routing table will be synced with the peer’s using a naive “just
send everything scheme” to hold us over until I spec out some a
efficient graph reconciliation protocol. Additionally, the routing
table is now pruned by the channel router itself once new blocks arrive
rather than depending on peers to tell us when a channel flaps or is
closed.
Finally, the validation of peer announcements aren’t yet fully
implemented as they’ll be implemented within the pending discovery
package that was blocking on the completion of this package. Most off
the routing message processing will be moved out of this package and
into the discovery package where full validation will be carried out.
