The instructions for `ChannelManagerReadArgs` indicate that you need
to connect blocks on a newly-deserialized `ChannelManager` in a
separate pass from the newly-deserialized `ChannelMontiors` as the
`ChannelManager` assumes the ability to update the monitors during
block [dis]connected events, saying that users need to:
```
4) Reconnect blocks on your ChannelMonitors
5) Move the ChannelMonitors into your local chain::Watch.
6) Disconnect/connect blocks on the ChannelManager.
```
This is fine for `ChannelManager`'s purpose, but is very awkward
for users. Notably, our new `lightning-block-sync` implemented
on-load reconnection in the most obvious (and performant) way -
connecting the blocks all at once, violating the
`ChannelManagerReadArgs` API.
Luckily, the events in question really don't need to be processed
with the same urgency as most channel monitor updates. The only two
monitor updates which can occur in block_[dis]connected is either
a) in block_connected, we identify a now-confirmed commitment
transaction, closing one of our channels, or
b) in block_disconnected, the funding transaction is reorganized
out of the chain, making our channel no longer funded.
In the case of (a), sending a monitor update which broadcasts a
conflicting holder commitment transaction is far from
time-critical, though we should still ensure we do it. In the case
of (b), we should try to broadcast our holder commitment transaction
when we can, but within a few minutes is fine on the scale of
block mining anyway.
Note that in both cases cannot simply move the logic to
ChannelMonitor::block[dis]_connected, as this could result in us
broadcasting a commitment transaction from ChannelMonitor, then
revoking the now-broadcasted state, and only then receiving the
block_[dis]connected event in the ChannelManager.
Thus, we move both events into an internal invent queue and process
them in timer_chan_freshness_every_min().
The return value from Channel::force_shutdown previously always
returned a `ChannelMonitorUpdate`, but expected it to only be
applied in the case that it *also* returned a Some for the funding
transaction output.
This is confusing, instead we move the `ChannelMontiorUpdate`
inside the Option, making it hold a tuple instead.
functional_tests.rs is huge, so anything we can do to split it up
some is helpful. This also exposes a somewhat glaring lack of
reorgs in our existing tests.
We could have possibly constructed a slightly inconsistent
path: since we reduce value being transferred all the way, we
could have violated htlc_minimum_msat on some channels
we already passed (assuming dest->source direction). Here,
we recompute the fees again, so that if that's the case, we
match the currently underpaid htlc_minimum_msat with fees.
If the ChannelManager never receives any blocks, it'll return a default blockhash
on deserialization. It's preferable for this to be an Option instead.
Refactor synchronize_listeners by pulling out a function returning the
validated block header of a BlockSource's best chain tip. This is needed
when a node is started from scratch and has no listeners to sync.
The implementation of chain::Listen for ChannelMonitor required using a
RefCell since its block_connected method required a mutable borrow. This
is no longer the case since ChannelMonitor now uses interior mutability
via a Mutex. So the RefCell is no longer needed.
Now that ChannelMonitor uses an internal Mutex to support interior
mutability, ChainMonitor can use a RwLock to manage its ChannelMonitor
map. This allows parallelization of update_channel operations since an
exclusive lock only needs to be held when adding to the map in
watch_channel.
ChainMonitor accesses a set of ChannelMonitors behind a single Mutex.
As a result, update_channel operations cannot be parallelized. It also
requires using a RefCell around a ChannelMonitor when implementing
chain::Listen.
Moving the Mutex into ChannelMonitor avoids these problems and aligns it
better with other interfaces. Note, however, that get_funding_txo and
get_outputs_to_watch now clone the underlying data rather than returning
references.
We currently "support" not having a router or channel in memory by
forcing users to implement the same, but its trivial to provide our
own dummy implementations.
This will switch to use the clang/C WASM ABI instead of the
wasm_bindgen WASM ABI as of rustc 1.51 (or nightly since [1]),
allowing us to link C and Rust code in a single wasm binary.
[1] https://github.com/rust-lang/rust/pull/79998
For ChannelManager, at least, we have two separate functions called
block_connected, one in the Listen trait, one in the struct, we
need to be explicit with which one we're trying to call.
