v0.0.103

API Updates

• This release is almost entirely focused on a new API in the
  lightning-invoice crate - the InvoicePayer. InvoicePayer is a
  struct which takes a reference to a ChannelManager and a Router
  and retries payments as paths fail. It limits retries to a configurable
  number, but is not serialized to disk and may retry additional times across
  a serialization/load. In order to learn about failed payments, it must
  receive Events directly from the ChannelManager, wrapping a
  user-provided EventHandler which it provides all unhandled events to
  (#1059).
• get_route has been renamed find_route (#1059) and now takes a
  RouteParameters struct in replacement of a number of its long list of
  arguments (#1134). The Payee in the RouteParameters is stored in the
  Route object returned and provided in the RouteParameters contained in
  Event::PaymentPathFailed (#1059).
• ChannelMonitors must now be persisted after calls that provide new block
  data, prior to MonitorEvents being passed back to ChannelManager for
  processing. If you are using a ChainMonitor this is handled for you.
  The Persist API has been updated to Optionally take the
  ChannelMonitorUpdate as persistence events that result from chain data no
  longer have a corresponding update (#1108).
• routing::Score now has a payment_path_failed method which it can use to
  learn which channels often fail payments. It is automatically called by
  InvoicePayer for failed payment paths (#1144).
• The default Scorer implementation is now a type alias to a type generic
  across different clocks and supports serialization to persist scoring data
  across restarts (#1146).
• Event::PaymentSent now includes the full fee which was spent across all
  payment paths which were fulfilled or pending when the payment was fulfilled
  (#1142).
• Event::PaymentSent and Event::PaymentPathFailed now include the
  PaymentId which matches the PaymentId returned from
  ChannelManager::send_payment or InvoicePayer::pay_invoice (#1059).
• NetGraphMsgHandler now takes a Deref to the NetworkGraph, allowing for
  shared references to the graph data to make serialization and references to
  the graph data in the InvoicePayer's Router simpler (#1149).
• routing::Score::channel_penalty_msat has been updated to provide the
  NodeId of both the source and destination nodes of a channel (#1133).

Bug Fixes

• Previous versions would often disconnect peers during initial graph sync due
  to ping timeouts while processing large numbers of gossip messages. We now
  delay disconnecting peers if we receive messages from them even if it takes
  a while to receive a pong from them. Further, we avoid sending too many
  gossip messages between pings to ensure we should always receive pongs in a
  timely manner (#1137).
• If a payment was sent, creating an outbound HTLC and sending it to our
  counterparty (implying the ChannelMonitor was persisted on disk), but the
  ChannelManager was not persisted prior to shutdown/crash, no
  Event::PaymentPathFailed event was generated if the HTLC was eventually
  failed on chain. Events are now consistent irrespective of ChannelManager
  persistence or non-persistence (#1104).

Serialization Compatibility

• All above new Events/fields are ignored by prior clients. All above new
  Events/fields are not present when reading objects serialized by prior
  versions of the library.
• Payments for which a Route was generated using a previous version or for
  which the payment was originally sent by a previous version of the library
  will not be retried by an InvoicePayer.

This release was singularly focused and some contributions by third parties
were delayed.
In total, this release features 38 files changed, 4414 insertions, and 969
deletions in 71 commits from 2 authors, in alphabetical order:

• Jeffrey Czyz
• Matt Corallo